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Find video protocols related to scientific articles indexed in Pubmed.
Temporal constraints on predation risk assessment in a changing world.
Sci. Total Environ.
PUBLISHED: 06-27-2014
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Habitat degradation takes various forms and likely represents the most significant threat to our global biodiversity. Recently, we have seen considerable attention paid to increasing global CO2 emissions which lead to ocean acidification (OA). Other stressors, such as changing levels of ultraviolet radiation (UVR), also impact biodiversity but have received much less attention in the recent past. Here we examine fundamental questions about temporal aspects of risk assessment by coral reef damselfish and provide critical insights into how OA and UVR influence this assessment. Chemical cues released during a predator attack provide a rich source of information that other prey animals use to mediate their risk of predation and are the basis of the majority of trait-mediated indirect interactions in aquatic communities. However, we have surprisingly limited information about temporal aspects of risk assessment because we lack knowledge about how long chemical cues persist after they are released into the environment. Here, we showed that under ambient CO2 conditions (~385?atm), alarm cues of ambon damselfish (Pomacentrus amboinensis) did not degrade within 30min in the absence of ultraviolet radiation (UVR), but were degraded within 15min when the CO2 was increased to ~905?atm. In experiments that used filters to eliminate UVR, we found minimal degradation of alarm cues within 30min, whereas under ambient UVR conditions, alarm cues were completely degraded within 15min. Moreover, in the presence of both UVR and elevated CO2, alarm cues were broken down within 5min. Our results highlight that alarm cues degrade surprisingly quickly under natural conditions and that anthropogenic changes have the potential to dramatically change rates of cue degradation in the wild. This has considerable implications for risk assessment and consequently the importance of trait-mediated indirect interactions in coral-reef communities.
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Background level of risk determines how prey categorize predators and non-predators.
Proc. Biol. Sci.
PUBLISHED: 06-06-2014
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Much of the plasticity that prey exhibit in response to predators is linked to the prey's immediate background level of risk. However, we know almost nothing of how background risk influences how prey learn to categorize predators and non-predators. Learning non-predators probably represents one of the most underappreciated aspects of anti-predator decision-making. Here, we provide larval damselfish (Pomacentrus chrysurus) with a high or low background risk and then try to teach them to recognize a cue as non-threatening through the process of latent inhibition. Prey from the low-risk background that were pre-exposed to the novel odour cues in the absence of negative reinforcement for 3 days, and then provided the opportunity to learn to recognize the odour as threatening, failed to subsequently respond to the odour as a threat. Fish from the high-risk background showed a much different response. These fish did not learn the odour as non-threatening, probably because the cost of falsely learning an odour as non-threatening is higher when the background level of risk is higher. Our work highlights that background level of risk appears to drive plasticity in cognition of prey animals learning to discriminate threats in their environment.
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The SAGA histone deubiquitinase module controls yeast replicative lifespan via Sir2 interaction.
Cell Rep
PUBLISHED: 05-20-2014
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We have analyzed the yeast replicative lifespan of a large number of open reading frame (ORF) deletions. Here, we report that strains lacking genes SGF73, SGF11, and UBP8 encoding SAGA/SLIK complex histone deubiquitinase module (DUBm) components are exceptionally long lived. Strains lacking other SAGA/SALSA components, including the acetyltransferase encoded by GCN5, are not long lived; however, these genes are required for the lifespan extension observed in DUBm deletions. Moreover, the SIR2-encoded histone deacetylase is required, and we document both a genetic and physical interaction between DUBm and Sir2. A series of studies assessing Sir2-dependent functions lead us to propose that DUBm strains are exceptionally long lived because they promote multiple prolongevity events, including reduced rDNA recombination and altered silencing of telomere-proximal genes. Given that ataxin-7, the human Sgf73 ortholog, causes the neurodegenerative disease spinocerebellar ataxia type 7, our findings indicate that the genetic and epigenetic interactions between DUBm and SIR2 will be relevant to neurodegeneration and aging.
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Protocol for a mixed-methods study of supplemental oxygen in pulmonary fibrosis.
BMC Pulm Med
PUBLISHED: 03-17-2014
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Little is known about whether or how supplemental oxygen affects patients with pulmonary fibrosis.
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Habitat degradation is threatening reef replenishment by making fish fearless.
J Anim Ecol
PUBLISHED: 01-24-2014
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Habitat degradation is one of the 'Big Five' drivers of biodiversity loss. However, the mechanisms responsible for this progressive loss of biodiversity are poorly understood. In marine ecosystems, corals play the role of ecosystem engineers, providing essential habitat for hundreds of thousands of species and hence their health is crucial to the stability of the whole ecosystem. Climate change is causing coral bleaching and degradation, and while this has been known for a while, little do we know about the cascading consequences of these events on the complex interrelationships between predators and their prey. The goal of our study was to investigate, under completely natural conditions, the effect of coral degradation on predator-prey interactions. Settlement stage ambon damselfish (Pomacentrus amboinensis), a common tropical fish, were released on patches of healthy or dead corals, and their behaviours in situ were measured, along with their response to injured conspecific cues, a common risk indicator. This study also explored the effect of habitat degradation on natural levels of mortality at a critical life-history transition. We found that juveniles in dead corals displayed risk-prone behaviours, sitting further away and higher up on the reef patch, and failed to respond to predation cues, compared to those on live coral patches. In addition, in situ survival experiments over 48 h indicated that juveniles on dead coral habitats had a 75% increase in predation-related mortality, compared to fish released on live, healthy coral habitats. Our results provide the first of many potential mechanisms through which habitat degradation can impact the relationship between prey and predators in the coral reef ecosystem. As the proportion of dead coral increases, the recruitment and replenishment of coral reef fishes will be threatened, and so will the level of diversity in these biodiversity hot spots.
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Temporal Links in Daily Activity Patterns between Coral Reef Predators and Their Prey.
PLoS ONE
PUBLISHED: 01-01-2014
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Few studies have documented the activity patterns of both predators and their common prey over 24 h diel cycles. This study documents the temporal periodicity of two common resident predators of juvenile reef fishes, Cephalopholis cyanostigma (rockcod) and Pseudochromis fuscus (dottyback) and compares these to the activity and foraging pattern of a common prey species, juvenile Pomacentrus moluccensis (lemon damselfish). Detailed observations of activity in the field and using 24 h infrared video in the laboratory revealed that the two predators had very different activity patterns. C. cyanostigma was active over the whole 24 h period, with a peak in feeding strikes at dusk and increased activity at both dawn and dusk, while P. fuscus was not active at night and had its highest strike rates at midday. The activity and foraging pattern of P. moluccensis directly opposes that of C. cyanostigma with individuals reducing strike rate and intraspecific aggression at both dawn and dusk, and reducing distance from shelter and boldness at dusk only. Juveniles examined were just outside the size-selection window of P. fuscus. We suggest that the relatively predictable diel behaviour of coral reef predators results from physiological factors such as visual sensory abilities, circadian rhythmicity, variation in hunting profitability, and predation risk at different times of the day. Our study suggests that the diel periodicity of P. moluccensis behaviour may represent a response to increased predation risk at times when both the ability to efficiently capture food and visually detect predators is reduced.
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Reproductive acclimation to increased water temperature in a tropical reef fish.
PLoS ONE
PUBLISHED: 01-01-2014
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Understanding the capacity of organisms to cope with projected global warming through acclimation and adaptation is critical to predicting their likely future persistence. While recent research has shown that developmental acclimation of metabolic attributes to ocean warming is possible, our understanding of the plasticity of key fitness-associated traits, such as reproductive performance, is lacking. We show that while the reproductive ability of a tropical reef fish is highly sensitive to increases in water temperature, reproductive capacity at +1.5°C above present-day was improved to match fish maintained at present-day temperatures when fish complete their development at the higher temperature. However, reproductive acclimation was not observed in fish reared at +3.0°C warmer than present-day, suggesting limitations to the acclimation possible within one generation. Surprisingly, the improvements seen in reproduction were not predicted by the oxygen- and capacity-limited thermal tolerance hypothesis. Specifically, pairs reared at +1.5°C, which showed the greatest capacity for reproductive acclimation, exhibited no acclimation of metabolic attributes. Conversely, pairs reared at +3.0°C, which exhibited acclimation in resting metabolic rate, demonstrated little capacity for reproductive acclimation. Our study suggests that understanding the acclimation capacity of reproductive performance will be critically important to predicting the impacts of climate change on biological systems.
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Shifting from right to left: the combined effect of elevated CO2 and temperature on behavioural lateralization in a coral reef fish.
PLoS ONE
PUBLISHED: 01-01-2014
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Recent studies have shown that elevated CO2 can affect the behaviour of larval and juvenile fishes. In particular, behavioural lateralization, an expression of brain functional asymmetries, is affected by elevated CO2 in both coral reef and temperate fishes. However, the potentially interacting effects of rising temperatures and CO2 on lateralization are unknown. Here, we tested the combined effect of near-future elevated-CO2 concentrations (930 µatm) and temperature variation on behavioural lateralization of a marine damselfish, Pomacentrus wardi. Individuals exposed to one of four treatments (two CO2 levels and two temperatures) were observed in a detour test where they made repeated decisions about turning left or right. Individuals exposed to current CO2 and ambient temperature levels showed a significant right-turning bias at the population level. This biased was reversed (i.e. to the left side) in fish exposed to the elevated-CO2 treatment. Increased temperature attenuated this effect, resulting in lower values of relative lateralization. Consequently, rising temperature and elevated CO2 may have different and interactive effects on behavioural lateralization and therefore future studies on the effect of climate change on brain functions need to consider both these critical variables in order to assess the potential consequences for the ecological interactions of marine fishes.
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Parental effects improve escape performance of juvenile reef fish in a high-CO2 world.
Proc. Biol. Sci.
PUBLISHED: 01-01-2014
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Rising CO2 levels in the oceans are predicted to have serious consequences for many marine taxa. Recent studies suggest that non-genetic parental effects may reduce the impact of high CO2 on the growth, survival and routine metabolic rate of marine fishes, but whether the parental environment mitigates behavioural and sensory impairment associated with high CO2 remains unknown. Here, we tested the acute effects of elevated CO2 on the escape responses of juvenile fish and whether such effects were altered by exposure of parents to increased CO2 (transgenerational acclimation). Elevated CO2 negatively affected the reactivity and locomotor performance of juvenile fish, but parental exposure to high CO2 reduced the effects in some traits, indicating the potential for acclimation of behavioural impairment across generations. However, acclimation was not complete in some traits, and absent in others, suggesting that transgenerational acclimation does not completely compensate the effects of high CO2 on escape responses.
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Suspended sediment prolongs larval development in a coral reef fish.
J. Exp. Biol.
PUBLISHED: 12-05-2013
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Increasing sediment input into coastal environments is having a profound influence on shallow marine habitats and associated species. Coral reef ecosystems appear to be particularly sensitive, with increased sediment deposition and re-suspension being associated with declines in the abundance and diversity of coral reef fishes. While recent research has demonstrated that suspended sediment can have negative impacts on post-settlement coral reef fishes, its effect on larval development has not been investigated. In this study, we tested the effects of different levels of suspended sediment on larval growth and development time in Amphiprion percula, a coral reef damselfish. Larvae were subjected to four experimental concentrations of suspended sediment spanning the range found around coastal coral reefs (0-45 mg L(-1)). Larval duration was significantly longer in all sediment treatments (~12.5d) compared to the average larval duration in the control treatment (11d). Approximately three quarters of the fish in the control had settled by day 11, compared to only 40-46% among the sediment treatments. In the highest sediment treatment, some individuals had a larval duration twice that of the mean median duration in the control treatment. Unexpectedly, in the low sediment treatment, fish at settlement were significantly were longer and heavier compared to the other treatments, suggesting delayed development was independent of individual condition. A sediment-induced extension of the pelagic larval stage could significantly reduce numbers of larvae competent to settle, and in turn, have major effects on adult population dynamics.
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Marine mollusc predator-escape behaviour altered by near-future carbon dioxide levels.
Proc. Biol. Sci.
PUBLISHED: 11-15-2013
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Ocean acidification poses a range of threats to marine invertebrates; however, the potential effects of rising carbon dioxide (CO2) on marine invertebrate behaviour are largely unknown. Marine gastropod conch snails have a modified foot and operculum allowing them to leap backwards rapidly when faced with a predator, such as a venomous cone shell. Here, we show that projected near-future seawater CO2 levels (961 µatm) impair this escape behaviour during a predator-prey interaction. Elevated-CO2 halved the number of snails that jumped from the predator, increased their latency to jump and altered their escape trajectory. Physical ability to jump was not affected by elevated-CO2 indicating instead that decision-making was impaired. Antipredator behaviour was fully restored by treatment with gabazine, a GABA antagonist of some invertebrate nervous systems, indicating potential interference of neurotransmitter receptor function by elevated-CO2, as previously observed in marine fishes. Altered behaviour of marine invertebrates at projected future CO2 levels could have potentially far-reaching implications for marine ecosystems.
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Ocean acidification reverses competition for space as habitats degrade.
Sci Rep
PUBLISHED: 08-13-2013
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How marine communities are affected by CO2-induced climate change depends on the ability of species to tolerate or adapt to the new conditions, and how the altered characteristics of species influence the outcomes of key processes, such as competition and predation. Our study examines how near future CO2 levels may affect the interactions between two damselfish species known to compete for space, and the effects of declining habitat quality on these interactions. The two focal species differed in their tolerance to elevated CO2, with the species that is competitively dominant under present day conditions being most affected. Field experiments showed that elevated CO2 (945??atm) reversed the competitive outcome between the two species with mortal consequences, and this reversal was accentuated in degraded habitats. Understanding these complex interactions will be crucial to predicting the likely composition of future communities under ocean acidification and climate change.
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Integration of multiple nutrient cues and regulation of lifespan by ribosomal transcription factor Ifh1.
Cell Rep
PUBLISHED: 07-29-2013
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Ribosome biogenesis requires an enormous commitment of energy and resources in growing cells. In budding yeast, the transcriptional coactivator Ifh1p is an essential regulator of ribosomal protein (RP) gene transcription. Here, we report that Ifh1p is dynamically acetylated and phosphorylated as a function of the growth state of cells. Ifh1p is acetylated at numerous sites in its N-terminal region by Gcn5p and deacetylated by NAD(+)-dependent deacetylases of the sirtuin family. Acetylation of Ifh1p is responsive to intracellular acetyl-CoA levels and serves to regulate the stability of Ifh1p. The phosphorylation of Ifh1p is mediated by protein kinase A and is dependent on TORC1 signaling. Thus, multiple nutrient-sensing mechanisms converge on Ifh1p. However, instead of modulating overall rates of RP gene transcription or cell growth, the nutrient-responsive phosphorylation of Ifh1p plays a more prominent role in the regulation of cellular replicative lifespan.
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Ocean acidification and responses to predators: can sensory redundancy reduce the apparent impacts of elevated CO2 on fish?
Ecol Evol
PUBLISHED: 06-03-2013
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Carbon dioxide (CO2) levels in the atmosphere and surface ocean are rising at an unprecedented rate due to sustained and accelerating anthropogenic CO2 emissions. Previous studies have documented that exposure to elevated CO2 causes impaired antipredator behavior by coral reef fish in response to chemical cues associated with predation. However, whether ocean acidification will impair visual recognition of common predators is currently unknown. This study examined whether sensory compensation in the presence of multiple sensory cues could reduce the impacts of ocean acidification on antipredator responses. When exposed to seawater enriched with levels of CO2 predicted for the end of this century (880 ?atm CO2), prey fish completely lost their response to conspecific alarm cues. While the visual response to a predator was also affected by high CO2, it was not entirely lost. Fish exposed to elevated CO2, spent less time in shelter than current-day controls and did not exhibit antipredator signaling behavior (bobbing) when multiple predator cues were present. They did, however, reduce feeding rate and activity levels to the same level as controls. The results suggest that the response of fish to visual cues may partially compensate for the lack of response to chemical cues. Fish subjected to elevated CO2 levels, and exposed to chemical and visual predation cues simultaneously, responded with the same intensity as controls exposed to visual cues alone. However, these responses were still less than control fish simultaneously exposed to chemical and visual predation cues. Consequently, visual cues improve antipredator behavior of CO2 exposed fish, but do not fully compensate for the loss of response to chemical cues. The reduced ability to correctly respond to a predator will have ramifications for survival in encounters with predators in the field, which could have repercussions for population replenishment in acidified oceans.
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Predator-induced changes in the growth of eyes and false eyespots.
Sci Rep
PUBLISHED: 06-03-2013
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The animal world is full of brilliant colours and striking patterns that serve to hide individuals or attract the attention of others. False eyespots are pervasive across a variety of animal taxa and are among natures most conspicuous markings. Understanding the adaptive significance of eyespots has long fascinated evolutionary ecologists. Here we show for the first time that the size of eyespots is plastic and increases upon exposure to predators. Associated with the growth of eyespots there is a corresponding reduction in growth of eyes in juvenile Ambon damselfish, Pomacentrus amboinensis. These morphological changes likely direct attacks away from the head region. Exposure to predators also induced changes in prey behaviour and morphology. Such changes could prevent or deter attacks and increase burst speed, aiding in escape. Damselfish exposed to predators had drastically higher survival suffering only 10% mortality while controls suffered 60% mortality 72 h after release.
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Degrading habitats and the effect of topographic complexity on risk assessment.
Ecol Evol
PUBLISHED: 05-24-2013
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Topographic complexity is a key component of habitats that influences communities by modulating the interactions among individuals that drive population processes such as recruitment, competition, and predation. A broad range of disturbance agents affect biological communities indirectly through their modifications to habitat complexity. Individuals that best judge the threat of predation within their environment and can trade-off vigilance against behaviors that promote growth will be rewarded with the highest fitness. This study experimentally examined whether topographic habitat complexity affected the way a damselfish assessed predation risk using olfactory, visual, or combined cues. Fish had higher feeding rates in the low complexity environment. In a low complexity environment, damage-released olfactory cues and visual cues of predators complemented each other in the preys assessment of risk. However, where complexity was high and visual cues obscured, prey had lower feeding rates and relied more heavily on olfactory cues for risk assessment. Overall, fish appear to be more conservative in the high complexity treatment. Low complexity promoted extremes of behavior, with higher foraging activity but a greater response to predation threats compared with the high complexity treatment. The degree of flexibility that individuals and species have in their ability to adjust the balance of senses used in risk assessment will determine the extent to which organisms will tolerate modifications to their habitat through disturbance.
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Impaired learning of predators and lower prey survival under elevated CO2 : a consequence of neurotransmitter interference.
Glob Chang Biol
PUBLISHED: 05-15-2013
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Ocean acidification is one of the most pressing environmental concerns of our time, and not surprisingly, we have seen a recent explosion of research into the physiological impacts and ecological consequences of changes in ocean chemistry. We are gaining considerable insights from this work, but further advances require greater integration across disciplines. Here, we showed that projected near-future CO2 levels impaired the ability of damselfish to learn the identity of predators. These effects stem from impaired neurotransmitter function; impaired learning under elevated CO2 was reversed when fish were treated with gabazine, an antagonist of the GABA-A receptor - a major inhibitory neurotransmitter receptor in the brain of vertebrates. The effects of CO2 on learning and the link to neurotransmitter interference were manifested as major differences in survival for fish released into the wild. Lower survival under elevated CO2 , as a result of impaired learning, could have a major influence on population recruitment.
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Increased CO2 stimulates reproduction in a coral reef fish.
Glob Chang Biol
PUBLISHED: 05-13-2013
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Ocean acidification is predicted to negatively impact the reproduction of many marine species, either by reducing fertilization success or diverting energy from reproductive effort. While recent studies have demonstrated how ocean acidification will affect larval and juvenile fishes, little is known about how increasing partial pressure of carbon dioxide (pCO(2)) and decreasing pH might affect reproduction in adult fishes. We investigated the effects of near-future levels of pCO(2) on the reproductive performance of the cinnamon anemonefish, Amphiprion melanopus, from the Great Barrier Reef, Australia. Breeding pairs were held under three CO(2) treatments [Current-day Control (430 ?atm), Moderate (584 ?atm) and High (1032 ?atm)] for a 9-month period that included the summer breeding season. Unexpectedly, increased CO(2) dramatically stimulated breeding activity in this species of fish. Over twice as many pairs bred in the Moderate (67% of pairs) and High (55%) compared to the Control (27%) CO(2) treatment. Pairs in the High CO(2) group produced double the number of clutches per pair and 67% more eggs per clutch compared to the Moderate and Control groups. As a result, reproductive output in the High group was 82% higher than that in the Control group and 50% higher than that in the Moderate group. Despite the increase in reproductive activity, there was no difference in adult body condition among the three treatment groups. There was no significant difference in hatchling length between the treatment groups, but larvae from the High CO(2) group had smaller yolks than Controls. This study provides the first evidence of the potential effects of ocean acidification on key reproductive attributes of marine fishes and, contrary to expectations, demonstrates an initially stimulatory (hormetic) effect in response to increased pCO(2). However, any long-term consequences of increased reproductive effort on individuals or populations remain to be determined.
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Degradation of chemical alarm cues and assessment of risk throughout the day.
Ecol Evol
PUBLISHED: 05-02-2013
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The use of chemical information in assessment of predation risk is pervasive across animal taxa. However, by its very nature, chemical information can be temporally unreliable. Chemical cues persist for some period of time after they are released into the environment. Yet, we know surprisingly little about the rate of degradation of chemical cues under natural conditions and hence little about how they function in temporal risk assessment under natural conditions. Here, we conducted an experiment to identify a concentration of fresh alarm cues that evoke a strong antipredator response in coral reef damselfish, Pomacentrus ambonensis. We then tested the rate at which these alarm cues degraded under natural conditions in ocean water, paying attention to whether the rate of degradation varied throughout the day and whether the temporal pattern correlated with physicochemical factors that could influence the rate of degradation. Fresh alarm cues released into ocean water evoke strong avoidance responses in juvenile fish, while those aged for 30 min no longer evoke antipredator responses. Fish exposed to cues aged for 10 or 20 min show intermediate avoidance responses. We found a marked temporal pattern of response throughout the day, with much faster degradation in early to mid-afternoon, the time of day when solar radiation, temperature, dissolved oxygen, and pH are nearing their peak. Ecologists have spent considerable effort elucidating the role of chemical information in mediating predator-prey interactions, yet we know almost nothing about the temporal dynamics of risk assessment using chemical information. We are in dire need of additional comparative field experiments on the rate of breakdown of chemical cues, particularly given that global change in UV radiation, temperature, and water chemistry could be altering the rates of degradation and the potential use of this information in risk assessment.
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Screening for suicidal ideation and attempts among emergency department medical patients: instrument and results from the Psychiatric Emergency Research Collaboration.
Suicide Life Threat Behav
PUBLISHED: 02-16-2013
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Joint Commission National Patient Safety Goal 15 calls for organizations "to identify patients at risk for suicide." Overt suicidal behavior accounts for 0.6% of emergency department (ED) visits, but incidental suicidal ideation is found in 3%-11.6%. This is the first multicenter study of suicide screening in EDs. Of 2,243 patients in six diverse emergency settings, 1,068 (47.7%) were screened with a brief instrument. Depression was endorsed by 369 (34.5%); passive suicidal ideation by 79 (7.3%); and active suicidal ideation by 24 (2.3%). One hundred thirty-seven (12.8%) reported prior attempts, including 35 (3.3%) with current suicidal ideation. Almost half of those with current ideation had a prior attempt (43.8%) versus those without current ideation, 10.3%, ?2 (1) = 75.59, p < .001. Twenty cases (25%) were admitted to medical services, but only 10 (12.5%) received mental health assessment; none were admitted directly to a psychiatry service. The prevalence of suicidal ideation here is similar to previous studies but the frequency of prior attempts has not been reported. The 35 cases with current ideation and prior attempt are at risk. As they did not present psychiatrically, they would likely have gone undetected. Despite reporting these cases to clinical staff, few received risk assessment.
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Determining trigger values of suspended sediment for behavioral changes in a coral reef fish.
Mar. Pollut. Bull.
PUBLISHED: 02-09-2013
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Sediment from land use increases water turbidity and threatens the health of inshore coral reefs. This study performed experiments with a damselfish, Pomacentrus moluccensis, in four sediment treatments, control (0 mg l?¹), 10 mg l?¹ (?1.7 NTU), 20 mg l?¹ (?3.3 NTU) and 30 mg l?¹ (?5 NTU), to determine when sediment triggers a change in habitat use and movement. We reviewed the literature to assess how frequently P. moluccensis would experience sub-optimal sediment conditions on the reef. Preference for live coral declined from 49.4% to 23.3% and movement between habitats declined from 2.1 to 0.4 times between 20 mg l?¹ and 30 mg l?¹, suggesting a sediment threshold for behavioral changes. Inshore areas of the Great Barrier Reef, P. moluccensis may encounter sub-optimal conditions between 8% and 53% of the time. Changes in these vital processes may have long-term effects on the persistence of populations, particularly as habitat loss on coral reefs increases.
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Elevated CO2 affects predator-prey interactions through altered performance.
PLoS ONE
PUBLISHED: 02-07-2013
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Recent research has shown that exposure to elevated carbon dioxide (CO2) affects how fishes perceive their environment, affecting behavioral and cognitive processes leading to increased prey mortality. However, it is unclear if increased mortality results from changes in the dynamics of predator-prey interactions or due to prey increasing activity levels. Here we demonstrate that ocean pCO2 projected to occur by 2100 significantly effects the interactions of a predator-prey pair of common reef fish: the planktivorous damselfish Pomacentrus amboinensis and the piscivorous dottyback Pseudochromis fuscus. Prey exposed to elevated CO2 (880 µatm) or a present-day control (440 µatm) interacted with similarly exposed predators in a cross-factored design. Predators had the lowest capture success when exposed to elevated CO2 and interacting with prey exposed to present-day CO2. Prey exposed to elevated CO2 had reduced escape distances and longer reaction distances compared to prey exposed to present-day CO2 conditions, but this was dependent on whether the prey was paired with a CO2 exposed predator or not. This suggests that the dynamics of predator-prey interactions under future CO2 environments will depend on the extent to which the interacting species are affected and can adapt to the adverse effects of elevated CO2.
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Syndromes or Flexibility: Behavior during a Life History Transition of a Coral Reef Fish.
PLoS ONE
PUBLISHED: 01-01-2013
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The theory of behavioral syndromes focuses on quantifying variation in behavior within and among individual organisms and attempts to account for the maintenance of differences in behavior that occur in a consistent manner among individuals. Behavioral syndromes have potentially important ecological consequences (e.g. survivorship tradeoffs) and can be shaped by population dynamics through selective mortality. Here, we search for any evidence for consistency of behavior across situations in juveniles of a common damselfish, Pomacentrus amboinensis (Pomacentridae) at the transition between larval habitats in the plankton and juvenile habitats on the reef. Naïve fish leaving the pelagic phase to settle on reefs were caught by light traps and their behaviors observed using similar methods across three different situations (small aquaria, large aquaria, field setting); all of which represent low risk and well-sheltered environments. Seven behavioral traits were compared within and among individuals across situations to determine if consistent behavioral syndromes existed. No consistency was found in any single or combination of behavioral traits for individuals across all situations. We suggest that high behavioral flexibility is likely beneficial for newly-settled fish at this ontogenetic transition and it is possible that consistent behavioral syndromes are unlikely to emerge in juveniles until environmental experience is gained or certain combinations of behaviors are favored by selective mortality.
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Ultimate predators: lionfish have evolved to circumvent prey risk assessment abilities.
PLoS ONE
PUBLISHED: 01-01-2013
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Invasive species cause catastrophic alterations to communities worldwide by changing the trophic balance within ecosystems. Ever since their introduction in the mid 1980s common red lionfish, Pterois volitans, are having dramatic impacts on the Caribbean ecosystem by displacing native species and disrupting food webs. Introduced lionfish capture prey at extraordinary rates, altering the composition of benthic communities. Here we demonstrate that the extraordinary success of the introduced lionfish lies in its capacity to circumvent prey risk assessment abilities as it is virtually undetectable by prey species in its native range. While experienced prey damselfish, Chromis viridis, respond with typical antipredator behaviours when exposed to a common predatory rock cod (Cephalopholis microprion) they fail to visibly react to either the scent or visual presentation of the red lionfish, and responded only to the scent (not the visual cue) of a lionfish of a different genus, Dendrochirus zebra. Experienced prey also had much higher survival when exposed to the two non-invasive predators compared to P. volitans. The cryptic nature of the red lionfish has enabled it to be destructive as a predator and a highly successful invasive species.
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A comparison of measures of boldness and their relationships to survival in young fish.
PLoS ONE
PUBLISHED: 01-01-2013
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Boldness is the propensity of an animal to engage in risky behavior. Many variations of novel-object or novel-environment tests have been used to quantify the boldness of animals, although the relationship between test outcomes has rarely been investigated. Furthermore, the relationship of outcomes to any ecological aspect of fitness is generally assumed, rather than measured directly. Our study is the first to compare how the outcomes of the same test of boldness differ among observers and how different tests of boldness relate to the survival of individuals in the field. Newly-metamorphosed lemon damselfish, Pomacentrus moluccensis, were placed onto replicate patches of natural habitat. Individual behavior was quantified using four tests (composed of a total of 12 different measures of behavior): latency to enter a novel environment, activity in a novel environment, and reactions to threatening and benign novel objects. After behavior was quantified, survival was monitored for two days during which time fish were exposed to natural predators. Variation among observers was low for most of the 12 measures, except distance moved and the threat test (reaction to probe thrust), which displayed unacceptable amounts of inter-observer variation. Overall, the results of the behavioral tests suggested that novel environment and novel object tests quantified similar behaviors, yet these behavioral measures were not interchangeable. Multiple measures of behavior within the context of novel environment or object tests were the most robust way to assess boldness and these measures have a complex relationship with survivorship of young fish in the field. Body size and distance ventured from shelter were the only variables that had a direct and positive relationship with survival.
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New genes that extend Caenorhabditis elegans lifespan in response to reproductive signals.
Aging Cell
PUBLISHED: 12-28-2011
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In Caenorhabditis elegans and Drosophila, removing germline stem cells increases lifespan. In C. elegans, this lifespan extension requires DAF-16, a FOXO transcription factor, and DAF-12, a nuclear hormone receptor. To better understand the regulatory relationships between DAF-16 and DAF-12, we used microarray analysis to identify downstream genes. We found that these two transcription factors influence the expression of distinct but overlapping sets of genes in response to loss of the germline. In addition, we identified several new genes that are required for loss of the germline to increase lifespan. One, phi-62, encodes a conserved, predicted RNA-binding protein. PHI-62 influences DAF-16-dependent transcription, possibly by collaborating with TCER-1, a putative transcription elongation factor, and FTT-2, a 14-3-3 protein known to bind DAF-16. Three other genes encode proteins involved in lipid metabolism; one is a triacylglycerol lipase, and another is an acyl-CoA reductase. These genes do not noticeably affect bulk fat storage levels; therefore, we propose a model in which they may influence production of a lifespan-extending signal or metabolite.
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Putting prey and predator into the CO2 equation--qualitative and quantitative effects of ocean acidification on predator-prey interactions.
Ecol. Lett.
PUBLISHED: 09-21-2011
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Little is known about the impact of ocean acidification on predator-prey dynamics. Herein, we examined the effect of carbon dioxide (CO(2)) on both prey and predator by letting one predatory reef fish interact for 24 h with eight small or large juvenile damselfishes from four congeneric species. Both prey and predator were exposed to control or elevated levels of CO(2). Mortality rate and predator selectivity were compared across CO(2) treatments, prey size and species. Small juveniles of all species sustained greater mortality at high CO(2) levels, while large recruits were not affected. For large prey, the pattern of prey selectivity by predators was reversed under elevated CO(2). Our results demonstrate both quantitative and qualitative consumptive effects of CO(2) on small and larger damselfish recruits respectively, resulting from CO(2)-induced behavioural changes likely mediated by impaired neurological function. This study highlights the complexity of predicting the effects of climate change on coral reef ecosystems.
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Well-informed foraging: damage-released chemical cues of injured prey signal quality and size to predators.
Oecologia
PUBLISHED: 08-26-2011
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Predators use a variety of information sources to locate potential prey, and likewise prey animals use numerous sources of information to detect and avoid becoming the meal of a potential predator. In freshwater environments, chemosensory cues often play a crucial role in such predator/prey interactions. The importance of chemosensory information to teleost fish in marine environments is not well understood. Here, we tested whether coral reef fish predators are attracted to damage-released chemical cues from already wounded prey in order to find patches of prey and minimize their own costs of obtaining food. Furthermore, we tested if these chemical cues would convey information about status of the prey. Using y-maze experiments, we found that predatory dottybacks, Pseudochromis fuscus, were more attracted to skin extracts of damselfish, Pomacentrus amboinensis, prey that were in good condition compared to prey in poor body condition. Moreover, in both the laboratory and field, we found that predators could differentiate between skin extracts from prey based on prey size, showing a greater attraction to extracts made from prey that were the appropriate size to consume. This suggests that predators are not attracted to any general substance released from an injured prey fish instead being capable of detecting and distinguishing relatively small differences in the chemical composition of the skin of their prey. These results have implications for understanding predator foraging strategies and highlights that chemical cues play a complex role in predator-prey interactions in marine fish.
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To fear or to feed: the effects of turbidity on perception of risk by a marine fish.
Biol. Lett.
PUBLISHED: 08-17-2011
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Coral reefs are currently experiencing a number of worsening anthropogenic stressors, with nearshore reefs suffering from increasing sedimentation because of growing human populations and development in coastal regions. In habitats where vision and olfaction serve as the primary sources of information, reduced visual input from suspended sediment may lead to significant alterations in prey fish behaviour. Here, we test whether prey compensate for reduced visual information by increasing their antipredator responses to chemically mediated risk cues in turbid conditions. Experiments with the spiny damselfish, Acanthochromis polyacanthus, found that baseline activity levels were reduced by 23 per cent in high turbidity conditions relative to low turbidity conditions. Furthermore, risk cues elicited strong antipredator responses at all turbidity levels; the strongest antipredator responses were observed in high turbidity conditions, with fish reducing their foraging by almost 40 per cent, as compared with 17 per cent for fish in clear conditions. This provides unambiguous evidence of sensory compensation in a predation context for a tropical marine fish, and suggests that prey fish may be able to behaviourally offset some of the fitness reductions resulting from anthropogenic sedimentation of their habitats.
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Elevated carbon dioxide affects behavioural lateralization in a coral reef fish.
Biol. Lett.
PUBLISHED: 08-17-2011
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Elevated carbon dioxide (CO(2)) has recently been shown to affect chemosensory and auditory behaviour, and activity levels of larval reef fishes, increasing their risk of predation. However, the mechanisms underlying these changes are unknown. Behavioural lateralization is an expression of brain functional asymmetries, and thus provides a unique test of the hypothesis that elevated CO(2) affects brain function in larval fishes. We tested the effect of near-future CO(2) concentrations (880 µatm) on behavioural lateralization in the reef fish, Neopomacentrus azysron. Individuals exposed to current-day or elevated CO(2) were observed in a detour test where they made repeated decisions about turning left or right. No preference for right or left turns was observed at the population level. However, individual control fish turned either left or right with greater frequency than expected by chance. Exposure to elevated-CO(2) disrupted individual lateralization, with values that were not different from a random expectation. These results provide compelling evidence that elevated CO(2) directly affects brain function in larval fishes. Given that lateralization enhances performance in a number of cognitive tasks and anti-predator behaviours, it is possible that a loss of lateralization could increase the vulnerability of larval fishes to predation in a future high-CO(2) ocean.
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Long-term cleaner fish presence affects growth of a coral reef fish.
Biol. Lett.
PUBLISHED: 07-06-2011
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Cleaning behaviour is considered to be a classical example of mutualism. However, no studies, to our knowledge, have measured the benefits to clients in terms of growth. In the longest experimental study of its kind, over an 8 year period, cleaner fish Labroides dimidiatus were consistently removed from seven patch reefs (61-285 m(2)) and left undisturbed on nine control reefs, and the growth and parasite load of the damselfish Pomacentrus moluccensis determined. After 8 years, growth was reduced and parasitic copepod abundance was higher on fish from removal reefs compared with controls, but only in larger individuals. Behavioural observations revealed that P. moluccensis cleaned by L. dimidiatus were 27 per cent larger than nearby conspecifics. The selective cleaning by L. dimidiatus probably explains why only larger P. moluccensis individuals benefited from cleaning. This is the first demonstration, to our knowledge, that cleaners affect the growth rate of client individuals; a greater size for a given age should result in increased fecundity at a given time. The effect of the removal of so few small fish on the size of another fish species is unprecedented on coral reefs.
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Metamorphosing reef fishes avoid predator scent when choosing a home.
Biol. Lett.
PUBLISHED: 06-08-2011
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Most organisms possess anti-predator adaptations to reduce their risk of being consumed, but little is known of the adaptations prey employ during vulnerable life-history transitions when predation pressures can be extreme. We demonstrate the use of a transition-specific anti-predator adaptation by coral reef fishes as they metamorphose from pelagic larvae to benthic juveniles, when over half are consumed within 48 h. Our field experiment shows that naturally settling damselfish use olfactory, and most likely innate, predator recognition to avoid settling to habitat patches manipulated to emit predator odour. Settlement to patches emitting predator odour was on average 24-43% less than to control patches. Evidence strongly suggests that this avoidance of sedentary and patchily distributed predators by nocturnal settlers will gain them a survival advantage, but also lead to non-lethal predator effects: the costs of exhibiting anti-predator adaptations. Transition-specific anti-predator adaptations, such as demonstrated here, may be widespread among organisms with complex life cycles and play an important role in prey population dynamics.
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Friend or foe?: the role of latent inhibition in predator and non-predator labelling by coral reef fishes.
Anim Cogn
PUBLISHED: 04-11-2011
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In communities of high biodiversity, the ability to distinguish predators from non-predators is crucial for prey success. Learning often plays a vital role in the ability to distinguish species that are threatening from those that are not. Many prey animals learn to recognise predators based on a single conditioning event whereby they are exposed to the unknown predator at the same time as alarm cues released from injured conspecifics. The remarkable efficiency of such learning means that recognition mistakes may occur if prey inadvertently learn that a species is a predator when it is not. Latent inhibition is a means by which prey that are pre-exposed to an unknown species in the absence of negative reinforcement can learn that the unknown animal is likely not a threat. Learning through latent inhibition should be conservative because mistakenly identifying predators as non-predators can have fatal consequences. In this study, we demonstrated that a common coral reef fish, lemon damselfish, Pomacentrus moluccensis can learn to recognise a predator as non-threatening through latent inhibition. Furthermore, we showed that we could override the latent inhibition effect by conditioning the prey to recognise the predator numerous times. Our results highlight the ability of prey fish to continually update the information regarding the threat posed by other fishes in their vicinity.
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TOR and ageing: a complex pathway for a complex process.
Philos. Trans. R. Soc. Lond., B, Biol. Sci.
PUBLISHED: 03-11-2011
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Studies in invertebrate model organisms have led to a wealth of knowledge concerning the ageing process. But which of these discoveries will apply to ageing in humans? Recently, an assessment of the degree of conservation of ageing pathways between two of the leading invertebrate model organisms, Saccharomyces cerevisiae and Caenorhabditis elegans, was completed. The results (i) quantitatively indicated that pathways were conserved between evolutionarily disparate invertebrate species and (ii) emphasized the importance of the TOR kinase pathway in ageing. With recent findings that deletion of the mTOR substrate S6K1 or exposure of mice to the mTOR inhibitor rapamycin result in lifespan extension, mTOR signalling has become a major focus of ageing research. Here, we address downstream targets of mTOR signalling and their possible links to ageing. We also briefly cover other ageing genes identified by comparing worms and yeast, addressing the likelihood that their mammalian counterparts will affect longevity.
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Asymmetric segregation: the shape of things to come?
Curr. Biol.
PUBLISHED: 02-22-2011
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Yeast mother cells pay a sacrifice during budding: they keep the extrachromosomal rDNA circles (ERCs) so that their buds have a full lifespan ahead. Two new studies indicate that retention of ERCs in mother cells occurs not by tethering to the nuclear periphery but rather by the simple rules of diffusion in a time-limited and complex landscape.
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Ocean acidification affects prey detection by a predatory reef fish.
PLoS ONE
PUBLISHED: 02-05-2011
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Changes in olfactory-mediated behaviour caused by elevated CO(2) levels in the ocean could affect recruitment to reef fish populations because larval fish become more vulnerable to predation. However, it is currently unclear how elevated CO(2) will impact the other key part of the predator-prey interaction--the predators. We investigated the effects of elevated CO(2) and reduced pH on olfactory preferences, activity levels and feeding behaviour of a common coral reef meso-predator, the brown dottyback (Pseudochromis fuscus). Predators were exposed to either current-day CO(2) levels or one of two elevated CO(2) levels (?600 µatm or ?950 µatm) that may occur by 2100 according to climate change predictions. Exposure to elevated CO(2) and reduced pH caused a shift from preference to avoidance of the smell of injured prey, with CO(2) treated predators spending approximately 20% less time in a water stream containing prey odour compared with controls. Furthermore, activity levels of fish was higher in the high CO(2) treatment and feeding activity was lower for fish in the mid CO(2) treatment; indicating that future conditions may potentially reduce the ability of the fish to respond rapidly to fluctuations in food availability. Elevated activity levels of predators in the high CO(2) treatment, however, may compensate for reduced olfactory ability, as greater movement facilitated visual detection of food. Our findings show that, at least for the species tested to date, both parties in the predator-prey relationship may be affected by ocean acidification. Although impairment of olfactory-mediated behaviour of predators might reduce the risk of predation for larval fishes, the magnitude of the observed effects of elevated CO(2) acidification appear to be more dramatic for prey compared to predators. Thus, it is unlikely that the altered behaviour of predators is sufficient to fully compensate for the effects of ocean acidification on prey mortality.
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Coral reef fish rapidly learn to identify multiple unknown predators upon recruitment to the reef.
PLoS ONE
PUBLISHED: 01-10-2011
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Organisms often undergo shifts in habitats as their requirements change with ontogeny.Upon entering a new environment, it is vitally important to be able to rapidly assess predation risk. Predation pressure should selectively promote mechanisms that enable the rapid identification of novel predators. Here we tested the ability of a juvenile marine fish to simultaneously learn the identity of multiple previously unknown predators. Individuals were conditioned with a cocktail of novel odours (from two predators and two non-predators) paired with either a conspecific alarm cue or a saltwater control and then tested for recognition of the four odours individually and two novel odours (one predator and one non-predator) the following day. Individuals conditioned with the cocktail and alarm cue responded to the individual cocktail odours with an antipredator response compared to controls. These results demonstrate that individuals acquire recognition of novel odours and that the responses were not due to innate recognition of predators or due to a generalised response to novel odours. Upon entering an unfamiliar environment prey species are able to rapidly assess the risk of predation, enhancing their chances of survival, through the assessment of chemical stimuli.
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Old yeast cant handle the noise.
Mol. Cell
PUBLISHED: 09-14-2010
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In this issue of Molecular Cell, Feser et al. (2010) show that aging yeast lose chromatin-associated histones and, furthermore, that correcting this deficiency robustly enhances replicative life span, indicating that loss of normal chromatin packing contributes to the aging process.
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The somatic reproductive tissues of C. elegans promote longevity through steroid hormone signaling.
PLoS Biol.
PUBLISHED: 07-20-2010
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In Caenorhabditis elegans and Drosophila melanogaster, removing the germline precursor cells increases lifespan. In worms, and possibly also in flies, this lifespan extension requires the presence of somatic reproductive tissues. How the somatic gonad signals other tissues to increase lifespan is not known. The lifespan increase triggered by loss of the germ cells is known to require sterol hormone signaling, as reducing the activity of the nuclear hormone receptor DAF-12, or genes required for synthesis of the DAF-12 ligand dafachronic acid, prevents germline loss from extending lifespan. In addition to sterol signaling, the FOXO transcription factor DAF-16 is required to extend lifespan in animals that lack germ cells. DAF-12/NHR is known to assist with the nuclear accumulation of DAF-16/FOXO in these animals, yet we find that loss of DAF-12/NHR has little or no effect on the expression of at least some DAF-16/FOXO target genes. In this study, we show that the DAF-12-sterol signaling pathway has a second function to activate a distinct set of genes and extend lifespan in response to the somatic reproductive tissues. When germline-deficient animals lacking somatic reproductive tissues are given dafachronic acid, their expression of DAF-12/NHR-dependent target genes is restored and their lifespan is increased. Together, our findings indicate that in C. elegans lacking germ cells, the somatic reproductive tissues promote longevity via steroid hormone signaling to DAF-12.
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Density-dependent sex ratio adjustment and the allee effect: a model and a test using a sex-changing fish.
Am. Nat.
PUBLISHED: 07-14-2010
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Positive density dependence (i.e., the Allee effect; AE) often has important implications for the dynamics and conservation of populations. Here, we show that density-dependent sex ratio adjustment in response to sexual selection may be a common AE mechanism. Specifically, using an analytical model we show that an AE is expected whenever one sex is more fecund than the other and sex ratio bias toward the less fecund sex increases with density. We illustrate the robustness of this pattern, using Monte Carlo simulations, against a range of body size-fecundity relationships and sex-allocation strategies. Finally, we test the model using the sex-changing polygynous reef fish Parapercis cylindrica; positive density dependence in the strength of sexual selection for male size is evidenced as the causal mechanism driving local sex ratio adjustment, hence the AE. Model application may extend to invertebrates, reptiles, birds, and mammals, in addition to over 70 reef fishes. We suggest that protected areas may often outperform harvest quotas as a conservation tool since the latter promotes population fragmentation, reduced polygyny, a balancing of the sex ratio, and hence up to a 50% decline in per capita fecundity, while the former maximizes polygyny and source-sink potential.
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Replenishment of fish populations is threatened by ocean acidification.
Proc. Natl. Acad. Sci. U.S.A.
PUBLISHED: 07-06-2010
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There is increasing concern that ocean acidification, caused by the uptake of additional CO(2) at the ocean surface, could affect the functioning of marine ecosystems; however, the mechanisms by which population declines will occur have not been identified, especially for noncalcifying species such as fishes. Here, we use a combination of laboratory and field-based experiments to show that levels of dissolved CO(2) predicted to occur in the ocean this century alter the behavior of larval fish and dramatically decrease their survival during recruitment to adult populations. Altered behavior of larvae was detected at 700 ppm CO(2), with many individuals becoming attracted to the smell of predators. At 850 ppm CO(2), the ability to sense predators was completely impaired. Larvae exposed to elevated CO(2) were more active and exhibited riskier behavior in natural coral-reef habitat. As a result, they had 5-9 times higher mortality from predation than current-day controls, with mortality increasing with CO(2) concentration. Our results show that additional CO(2) absorbed into the ocean will reduce recruitment success and have far-reaching consequences for the sustainability of fish populations.
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Insulin/IGF-1 signaling mutants reprogram ER stress response regulators to promote longevity.
Proc. Natl. Acad. Sci. U.S.A.
PUBLISHED: 05-11-2010
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When unfolded proteins accumulate in the endoplasmic reticulum (ER), the unfolded protein response is activated. This ER stress response restores ER homeostasis by coordinating processes that decrease translation, degrade misfolded proteins, and increase the levels of ER-resident chaperones. Ribonuclease inositol-requiring protein-1 (IRE-1), an endoribonuclease that mediates unconventional splicing, and its target, the XBP-1 transcription factor, are key mediators of the unfolded protein response. In this study, we show that in Caenorhabditis elegans insulin/IGF-1 pathway mutants, IRE-1 and XBP-1 promote lifespan extension and enhance resistance to ER stress. We show that these effects are not achieved simply by increasing the level of spliced xbp-1 mRNA and expression of XBP-1s normal target genes. Instead, in insulin/IGF-1 pathway mutants, XBP-1 collaborates with DAF-16, a FOXO-transcription factor that is activated in these mutants, to enhance ER stress resistance and to activate new genes that promote longevity.
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Differing mechanisms underlie sexual size-dimorphism in two populations of a sex-changing fish.
PLoS ONE
PUBLISHED: 04-12-2010
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Variability in the density of groups within a patchy environment lead to differences in interaction rates, growth dynamics and social organization. In protogynous hermaphrodites there are hypothesised trade-offs among sex-specific growth, reproductive output and mortality. When differences in density lead to changes to social organization the link between growth and the timing of sex-change is predicted to change. The present study explores this prediction by comparing the social organisation and sex-specific growth of two populations of a protogynous tropical wrasse, Halichoeres miniatus, which differ in density. At a low density population a strict harem structure was found, where males maintained a tight monopoly of access and spawning rights to females. In contrast, at a high density population a loosely organised system prevailed, where females could move throughout multiple male territories. Otolith microstructure revealed the species to be annual and deposit an otolith check associated with sex-change. Growth trajectories suggested that individuals that later became males in both populations underwent a growth acceleration at sex-change. Moreover, in the high density population, individuals that later became males were those individuals that had the largest otolith size at hatching and consistently deposited larger increments throughout early larval, juvenile and female life. This study demonstrates that previous growth history and growth rate changes associated with sex change can be responsible for the sexual dimorphism typically found in sex-changing species, and that the relative importance of these may be socially constrained.
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Maladaptive behavior reinforces a recruitment bottleneck in newly settled fishes.
Oecologia
PUBLISHED: 01-22-2010
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Settlement from the plankton ends the major dispersive stage of life for many marine organisms and exposes them to intense predation pressure in juvenile habitats. This predation mortality represents a life-history bottleneck that can determine recruitment success. At the level of individual predator-prey interactions, prey survival depends upon behavior, specifically how behavior affects prey conspicuousness and evasive ability. We conducted an experiment to identify behavioral traits and performance levels that are important determinants of which individuals survive or die soon after settlement. We measured a suite of behavioral traits on late stage, pre-settlement Wards damsel (Pomacentrus wardi) collected using light traps. These behavioral traits included two measures of routine swimming (indicators of conspicuousness) and eight measures of escape performance to a visual startle stimulus. Fish were then released onto individual patch reefs, where divers measured an additional behavioral trait (boldness). We censused each patch reef until approximately 50% of the fish were missing (~24 h), which we assumed to be a result of predation. We used classification tree analysis to discriminate survivors from fish presumed dead based on poor behavioral performance. The classification tree revealed that individuals displaying the maladaptive combination of low escape response speed, low boldness on the reef, and high routine swimming speed were highly susceptible to predation (92.4% with this combination died within 24 h). This accounted for 55.2% of all fish that died. Several combinations of behavioral traits predicted likely survival over 24 h, but there was greater uncertainty about that prediction than there was for fish that were predicted to die. Thus maladaptive behavioral traits were easier to identify than adaptive traits.
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Smell, learn and live: the role of chemical alarm cues in predator learning during early life history in a marine fish.
Behav. Processes
PUBLISHED: 01-01-2010
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The speed with which individuals can learn to identify and react appropriately to predation threats when transitioning to new life history stages and habitats will influence their survival. This study investigated the role of chemical alarm cues in both anti-predator responses and predator identification during a transitional period in a newly settled coral reef damselfish, Pomacentrus amboinensis. Individuals were tested for changes in seven behavioural traits in response to conspecific and heterospecific skin extracts. Additionally, we tested whether fish could learn to associate a previously novel chemical cue (i.e. simulated predator scent) with danger, after previously being exposed to a paired cue combining the conspecific skin extract with the novel scent. Fish exposed to conspecific skin extracts were found to significantly decreased their feeding rate whilst those exposed to heterospecific and control cues showed no change. Individuals were also able to associate a previously novel scent with danger after only a single previous exposure to the paired conspecific skin extract/novel scent cue. Our results indicate that chemical alarm cues play a large role in both threat detection and learned predator recognition during the early post-settlement period in coral reef fishes.
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Influence of prey body characteristics and performance on predator selection.
Oecologia
PUBLISHED: 07-15-2009
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At the time of settlement to the reef environment, coral reef fishes differ in a number of characteristics that may influence their survival during a predatory encounter. This study investigated the selective nature of predation by both a multi-species predator pool, and a single common predator (Pseudochromis fuscus), on the reef fish, Pomacentrus amboinensis. The study focused on the early post-settlement period of P. amboinensis, when mortality, and hence selection, is known to be highest. Correlations between nine different measures of body condition/performance were examined at the time of settlement, in order to elucidate the relationships between different traits. Single-predator (P. fuscus) choice trials were conducted in 57.4-l aquaria with respect to three different prey characteristics [standard length (SL), body weight and burst swimming speed], whilst multi-species trials were conducted on open patch reefs, manipulating prey body weight only. Relationships between the nine measures of condition/performance were generally poor, with the strongest correlations occurring between the morphological measures and within the performance measures. During aquaria trials, P. fuscus was found to be selective with respect to prey SL only, with larger individuals being selected significantly more often. Multi-species predator communities, however, were selective with respect to prey body weight, with heavier individuals being selected significantly more often than their lighter counterparts. Our results suggest that under controlled conditions, body length may be the most important prey characteristic influencing prey survival during predatory encounters with P. fuscus. In such cases, larger prey size may actually be a distinct disadvantage to survival. However, these relationships appear to be more complex under natural conditions, where the expression of prey characteristics, the selectivity fields of a number of different predators, their relative abundance, and the action of external environmental characteristics, may all influence which individuals survive.
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Sexual selection explains sex-specific growth plasticity and positive allometry for sexual size dimorphism in a reef fish.
Proc. Biol. Sci.
PUBLISHED: 06-24-2009
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In 1950, Rensch noted that in clades where males are the larger sex, sexual size dimorphism (SSD) tends to be more pronounced in larger species. This fundamental allometric relationship is now known as Renschs rule. While most researchers attribute Renschs rule to sexual selection for male size, experimental evidence is lacking. Here, we suggest that ultimate hypotheses for Renschs rule should also apply to groups of individuals and that individual trait plasticity can be used to test those hypotheses experimentally. Specifically, we show that in the sex-changing fish Parapercis cylindrica, larger males have larger harems with larger females, and that SSD increases with harem size. Thus, sexual selection for male body size is the ultimate cause of sexual size allometry. In addition, we experimentally illustrate a positive relationship between polygyny potential and individual growth rate during sex change from female to male. Thus, sexual selection is the ultimate cause of variation in growth rate, and variation in growth rate is the proximate cause of sexual size allometry. Taken together, our results provide compelling evidence in support of the sexual selection hypothesis for Renschs rule and highlight the potential importance of individual growth modification in the shaping of morphological patterns in Nature.
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Replenishment success linked to fluctuating asymmetry in larval fish.
Oecologia
PUBLISHED: 05-29-2009
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Fluctuating asymmetry (FA), defined as random deviations from perfect symmetry, has become a popular tool with which to examine the effects of stress during the development of bilaterally symmetrical organisms. Recent studies have suggested that FA in otoliths may serve as an indicator of stress in fish larvae. We examined the relationship between otolith asymmetry and temporal patterns in the occurrence of late-stage larvae to a tropical reef (i.e. replenishment) for the Caribbean lizardfish, Saurida suspicio (family Synodontidae). Late-stage larvae were collected in light traps over a period of 18 consecutive lunar months in the San Blas Archipelago, Panama. Asymmetry within otolith pairs was calculated from 24 variables: area, perimeter, longest and shortest axis of the otolith and 20 shape descriptors (Fourier harmonics). Otolith asymmetry was correlated strongly with fluctuations in lunar light trap catches. Two measured variables, otolith area and one of the 20 shape descriptors, accounted for 60% of the variability in lunar replenishment of S. suspicio. Individuals from small replenishment pulses exhibited higher levels of asymmetry compared to larvae from large pulses. When dry and wet seasons were analysed separately, otolith asymmetry explained a surprising 70 and 97% of the variation, respectively. Although the generality of these results remain to be tested among other populations and species, otolith asymmetry may be an important indicator, and potentially a predictor, of larval quality and replenishment success.
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Behaviourally mediated phenotypic selection in a disturbed coral reef environment.
PLoS ONE
PUBLISHED: 04-23-2009
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Natural and anthropogenic disturbances are leading to changes in the nature of many habitats globally, and the magnitude and frequency of these perturbations are predicted to increase under climate change. Globally coral reefs are one of the most vulnerable ecosystems to climate change. Fishes often show relatively rapid declines in abundance when corals become stressed and die, but the processes responsible are largely unknown. This study explored the mechanism by which coral bleaching may influence the levels and selective nature of mortality on a juvenile damselfish, Pomacentrus amboinensis, which associates with hard coral. Recently settled fish had a low propensity to migrate small distances (40 cm) between habitat patches, even when densities were elevated to their natural maximum. Intraspecific interactions and space use differ among three habitats: live hard coral, bleached coral and dead algal-covered coral. Large fish pushed smaller fish further from the shelter of bleached and dead coral thereby exposing smaller fish to higher mortality than experienced on healthy coral. Small recruits suffered higher mortality than large recruits on bleached and dead coral. Mortality was not size selective on live coral. Survival was 3 times as high on live coral as on either bleached or dead coral. Subtle behavioural interactions between fish and their habitats influence the fundamental link between life history stages, the distribution of phenotypic traits in the local population and potentially the evolution of life history strategies.
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Fish ears are sensitive to sex change.
Biol. Lett.
PUBLISHED: 04-01-2009
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Many reef fishes change sex during their life. The testing of life-history theory and effective fisheries management therefore relies on our ability to detect when this fundamental transition occurs. This study experimentally illustrates the potential to glean such information from the otolithic bodies of the inner-ear apparatus in the sex-changing fish Parapercis cylindrica. It will now be possible to reconstruct the complete, often complex life history of hermaphroditic individuals from hatching through to terminal reproductive status. The validation of sex-change associated otolith growth also illustrates the potential for sex-specific sensory displacement. It is possible that sex-changing fishes alter otolith composition, and thus sensory-range specificity, to optimize life history in accordance with their new reproductive mode.
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Hormonally mediated maternal effects shape offspring survival potential in stressful environments.
Oecologia
PUBLISHED: 03-16-2009
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In most egg-laying vertebrates, maternal responses to stressful conditions are translated into the release of glucocorticoid hormones such as cortisol, which are then transmitted to their developing embryos. Although such maternally transmitted hormonal resources have been shown to influence or even interfere with the optimal developmental trajectories of offspring in many taxa, their influence on the dynamics of wild fish populations remains largely unexplored. Here, we examined the extent to which simulated hormonally mediated maternal effects influence the development and early survival of the coral reef damselfish, Pomacentrus amboinensis. Concentrations of cortisol in the eggs were manipulated within naturally occurring limits by immersion. We found that the proportion of embryos that delayed hatching when exposed to high levels of cortisol was considerably lower than in the other two treatments (low cortisol dose and control). High cortisol levels in P. amboinensis eggs resulted in increased egg mortality and greater asymmetry in hatchlings. For embryos that successfully hatched, individuals from the elevated cortisol treatments (especially low dose) survived longer after hatching. Although individuals that originated from eggs with elevated cortisol levels survived longer after hatching, they may not gain an overall survival advantage. Our results suggest that subtle increases in the allocation of maternally derived hormones, such as cortisol, to offspring are a direct way for stressed mothers to endow their young with an immediate survival advantage. We propose that this immediate benefit outweighs the developmental costs which may be expressed as reduced fitness at later life stages.
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Genome-scale studies of aging: challenges and opportunities.
Curr. Genomics
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Whole-genome studies involving a phenotype of interest are increasingly prevalent, in part due to a dramatic increase in speed at which many high throughput technologies can be performed coupled to simultaneous decreases in cost. This type of genome-scale methodology has been applied to the phenotype of lifespan, as well as to whole-transcriptome changes during the aging process or in mutants affecting aging. The value of high throughput discovery-based science in this field is clearly evident, but will it yield a true systems-level understanding of the aging process? Here we review some of this work to date, focusing on recent findings and the unanswered puzzles to which they point. In this context, we also discuss recent technological advances and some of the likely future directions that they portend.
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Degraded environments alter prey risk assessment.
Ecol Evol
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Elevated water temperatures, a decrease in ocean pH, and an increasing prevalence of severe storms have lead to bleaching and death of the hard corals that underpin coral reef ecosystems. As coral cover declines, fish diversity and abundance declines. How degradation of coral reefs affects behavior of reef inhabitants is unknown. Here, we demonstrate that risk assessment behaviors of prey are severely affected by coral degradation. Juvenile damselfish were exposed to visual and olfactory indicators of predation risk in healthy live, thermally bleached, and dead coral in a series of laboratory and field experiments. While fish still responded to visual cues in all habitats, they did not respond to olfactory indicators of risk in dead coral habitats, likely as a result of alteration or degradation of chemical cues. These cues are critical for learning and avoiding predators, and a failure to respond can have dramatic repercussions for survival and recruitment.
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Not all offspring are created equal: variation in larval characteristics in a serially spawning damselfish.
PLoS ONE
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The way organisms allocate their resources to growth and reproduction are key attributes differentiating life histories. Many organisms spawn multiple times in a breeding season, but few studies have investigated the impact of serial spawning on reproductive allocation. This study investigated whether resource allocation was influenced by parental characteristics and prior spawning history in a serial spawning tropical damselfish (Pomacentrus amboinensis). The offspring attributes of isolated parents of known characteristics were monitored over a 6-week breeding period in the field. Smaller females produced larvae of longer length and larger energy reserves at hatching. This finding is contrary to several other studies that found larger females produce offspring of greater quality. We found that resource allocation in the form of reproductive output was not influenced by the number of spawning events within the breeding season, with larger females producing the greatest number of offspring. Larval characteristics changed as spawning progressed. There was a general decline in length of larvae produced, with an increase in the size of the larval yolk-sac, for all females regardless of size as spawning progressed. This trend was accentuated by the smallest females. This change in larval characteristics may reflect a parental ability to forecast unfavourable conditions as the season progresses or a mechanism to ensure that some will survive no matter what conditions they encounter. This study highlights the importance of accounting for temporal changes in reproductive allocation in studies of reproductive trade-offs and investigations into the importance of parental effects.
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Impact of global warming and rising CO2 levels on coral reef fishes: what hope for the future?
J. Exp. Biol.
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Average sea-surface temperature and the amount of CO(2) dissolved in the ocean are rising as a result of increasing concentrations of atmospheric CO(2). Many coral reef fishes appear to be living close to their thermal optimum, and for some of them, even relatively moderate increases in temperature (2-4°C) lead to significant reductions in aerobic scope. Reduced aerobic capacity could affect population sustainability because less energy can be devoted to feeding and reproduction. Coral reef fishes seem to have limited capacity to acclimate to elevated temperature as adults, but recent research shows that developmental and transgenerational plasticity occur, which might enable some species to adjust to rising ocean temperatures. Predicted increases in P(CO(2)), and associated ocean acidification, can also influence the aerobic scope of coral reef fishes, although there is considerable interspecific variation, with some species exhibiting a decline and others an increase in aerobic scope at near-future CO(2) levels. As with thermal effects, there are transgenerational changes in response to elevated CO(2) that could mitigate impacts of high CO(2) on the growth and survival of reef fishes. An unexpected discovery is that elevated CO(2) has a dramatic effect on a wide range of behaviours and sensory responses of reef fishes, with consequences for the timing of settlement, habitat selection, predator avoidance and individual fitness. The underlying physiological mechanism appears to be the interference of acid-base regulatory processes with brain neurotransmitter function. Differences in the sensitivity of species and populations to global warming and rising CO(2) have been identified that will lead to changes in fish community structure as the oceans warm and becomes more acidic; however, the prospect for acclimation and adaptation of populations to these threats also needs to be considered. Ultimately, it will be the capacity for species to adjust to environmental change over coming decades that will determine the impact of climate change on marine ecosystems.
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Chemical alarm cues are conserved within the coral reef fish family Pomacentridae.
PLoS ONE
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Fishes are known to use chemical alarm cues from both conspecifics and heterospecifics to assess local predation risks and enhance predator detection. Yet it is unknown how recognition of heterospecific cues arises for coral reef fishes. Here, we test if naïve juvenile fish have an innate recognition of heterospecific alarm cues. We also examine if there is a relationship between the intensity of the antipredator response to these cues and the degree to which species are related to each other. Naïve juvenile anemone fish, Amphiprion percula, were tested to see if they displayed antipredator responses to chemical alarm cues from four closely related heterospecific species (family Pomacentridae), a distantly related sympatric species (Asterropteryx semipunctatus) and a saltwater (control). Juveniles displayed significant reductions in foraging rate when exposed to all four confamilial heterospecific species but they did not respond to the distantly related sympatric species or the saltwater control. There was also a strong relationship between the intensity of the antipredator response and the extent to which species were related, with responses weakening as species became more distantly related. These findings demonstrate that chemical alarm cues are conserved within the pomacentrid family, providing juveniles with an innate recognition of heterospecific alarm cues as predicted by the phylogenetic relatedness hypothesis.
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It pays to be pushy: intracohort interference competition between two reef fishes.
PLoS ONE
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Competition is often most intense between similar sized organisms that have similar ecological requirements. Many coral reef fish species settle preferentially to live coral at the end of their larval phase where they interact with other species that recruited to the same habitat patch at a similar time. Mortality is high and usually selective and individuals must compete for low risk space. This study examined the competitive interactions between two species of juvenile damselfish and the extent to which interactions that occurred within a recruitment cohort established the disjunct distribution patterns that were displayed in later life stages. Censuses and field experiments with juveniles found that one species, the ambon damsel, was dominant immediately after settlement and pushed the subordinate species higher up the reef and further from shelter. Presence of a competitor resulted in reduced growth for both species. Juvenile size was the best predictor of competitive success and outweighed the effects of short term prior residency. Size at settlement also dramatically influenced survival, with slightly larger individuals displaying higher aggression, pushing the subordinate species into higher risk habitats. While subordinates had higher feeding rates, they also sustained higher mortality. The study highlights the importance of interaction dynamics between species within a recruitment cohort to patterns of growth and distribution of species within communities.
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Lethal effects of habitat degradation on fishes through changing competitive advantage.
Proc. Biol. Sci.
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Coral bleaching has caused catastrophic changes to coral reef ecosystems around the world with profound ecological, social and economic repercussions. While its occurrence is predicted to increase in the future, we have little understanding of mechanisms that underlie changes in the fish community associated with coral degradation. The present study uses a field-based experiment to examine how the intensity of interference competition between juveniles of two species of damselfish changes as healthy corals degrade through thermal bleaching. The mortality of a damselfish that is a live coral specialist (Pomacentrus moluccensis) increased on bleached and dead coral in the presence of the habitat generalist (Pomacentrus amboinensis). Increased mortality of the specialist was indirectly owing to enhanced aggression by the generalist forcing the specialist higher up and further away from shelter on bleached and dead coral. Evidence from this study stresses the importance of changing interspecific interactions to community dynamics as habitats change.
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Midlife vs late-life depressive symptoms and risk of dementia: differential effects for Alzheimer disease and vascular dementia.
Arch. Gen. Psychiatry
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Depression and dementia are common in older adults and often co-occur, but it is unclear whether depression is an etiologic risk factor for dementia.
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Learning temporal patterns of risk in a predator-diverse environment.
PLoS ONE
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Predation plays a major role in shaping prey behaviour. Temporal patterns of predation risk have been shown to drive daily activity and foraging patterns in prey. Yet the ability to respond to temporal patterns of predation risk in environments inhabited by highly diverse predator communities, such as rainforests and coral reefs, has received surprisingly little attention. In this study, we investigated whether juvenile marine fish, Pomacentrus moluccensis (lemon damselfish), have the ability to learn to adjust the intensity of their antipredator response to match the daily temporal patterns of predation risk they experience. Groups of lemon damselfish were exposed to one of two predictable temporal risk patterns for six days. "Morning risk" treatment prey were exposed to the odour of Cephalopholis cyanostigma (rockcod) paired with conspecific chemical alarm cues (simulating a rockcod present and feeding) during the morning, and rockcod odour only in the evening (simulating a rockcod present but not feeding). "Evening risk" treatment prey had the two stimuli presented to them in the opposite order. When tested individually for their response to rockcod odour alone, lemon damselfish from the morning risk treatment responded with a greater antipredator response intensity in the morning than in the evening. In contrast, those lemon damselfish previously exposed to the evening risk treatment subsequently responded with a greater antipredator response when tested in the evening. The results of this experiment demonstrate that P. moluccensis have the ability to learn temporal patterns of predation risk and can adjust their foraging patterns to match the threat posed by predators at a given time of day. Our results provide the first experimental demonstration of a mechanism by which prey in a complex, multi-predator environment can learn and respond to daily patterns of predation risk.
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Ribosome deficiency protects against ER stress in Saccharomyces cerevisiae.
Genetics
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In Saccharomyces cerevisiae, 59 of the 78 ribosomal proteins are encoded by duplicated genes that, in most cases, encode identical or very similar protein products. However, different sets of ribosomal protein genes have been identified in screens for various phenotypes, including life span, budding pattern, and drug sensitivities. Due to potential suppressors of growth rate defects among this set of strains in the ORF deletion collection, we regenerated the entire set of haploid ribosomal protein gene deletion strains in a clean genetic background. The new strains were used to create double deletions lacking both paralogs, allowing us to define a set of 14 nonessential ribosomal proteins. Replicative life-span analysis of new strains corresponding to ORF deletion collection strains that likely carried suppressors of growth defects identified 11 new yeast replicative aging genes. Treatment of the collection of ribosomal protein gene deletion strains with tunicamycin revealed a significant correlation between slow growth and resistance to ER stress that was recapitulated by reducing translation of wild-type yeast with cycloheximide. Interestingly, enhanced tunicamycin resistance in ribosomal protein gene deletion mutants was independent of the unfolded protein response transcription factor Hac1. These data support a model in which reduced translation is protective against ER stress by a mechanism distinct from the canonical ER stress response pathway and further add to the diverse yet specific phenotypes associated with ribosomal protein gene deletions.
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Effects of ocean acidification on learning in coral reef fishes.
PLoS ONE
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Ocean acidification has the potential to cause dramatic changes in marine ecosystems. Larval damselfish exposed to concentrations of CO(2) predicted to occur in the mid- to late-century show maladaptive responses to predator cues. However, there is considerable variation both within and between species in CO(2) effects, whereby some individuals are unaffected at particular CO(2) concentrations while others show maladaptive responses to predator odour. Our goal was to test whether learning via chemical or visual information would be impaired by ocean acidification and ultimately, whether learning can mitigate the effects of ocean acidification by restoring the appropriate responses of prey to predators. Using two highly efficient and widespread mechanisms for predator learning, we compared the behaviour of pre-settlement damselfish Pomacentrus amboinensis that were exposed to 440 µatm CO(2) (current day levels) or 850 µatm CO(2), a concentration predicted to occur in the ocean before the end of this century. We found that, regardless of the method of learning, damselfish exposed to elevated CO(2) failed to learn to respond appropriately to a common predator, the dottyback, Pseudochromis fuscus. To determine whether the lack of response was due to a failure in learning or rather a short-term shift in trade-offs preventing the fish from displaying overt antipredator responses, we conditioned 440 or 700 µatm-CO(2) fish to learn to recognize a dottyback as a predator using injured conspecific cues, as in Experiment 1. When tested one day post-conditioning, CO(2) exposed fish failed to respond to predator odour. When tested 5 days post-conditioning, CO(2) exposed fish still failed to show an antipredator response to the dottyback odour, despite the fact that both control and CO(2)-treated fish responded to a general risk cue (injured conspecific cues). These results indicate that exposure to CO(2) may alter the cognitive ability of juvenile fish and render learning ineffective.
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Learn and live: predator experience and feeding history determines prey behaviour and survival.
Proc. Biol. Sci.
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Determining how prey learn the identity of predators and match their vigilance with current levels of threat is central to understanding the dynamics of predator-prey systems and the determinants of fitness. Our study explores how feeding history influences the relative importance of olfactory and visual sensory modes of learning, and how the experience gained through these sensory modes influences behaviour and survival in the field for a juvenile coral reef damselfish. We collected young fish immediately prior to their settlement to benthic habitats. In the laboratory, these predator-naïve fish were exposed to a high- or low-food ration and then conditioned to recognize the olfactory cues (odours) and/or visual cues from two common benthic predators. Fish were then allowed to settle on reefs in the field, and their behaviour and survival over 70 h were recorded. Feeding history strongly influenced their willingness to take risks in the natural environment. Conditioning in the laboratory with visual, olfactory or both cues from predators led fish in the field to display risk-averse behaviour compared with fish conditioned with sea water alone. Well-fed fish that were conditioned with visual, chemical or a combination of predator cues survived eight times better over the first 48 h on reefs than those with no experience of benthic predator cues. This experiment highlights the importance of a flexible and rapid mechanism of learning the identity of predators for survival of young fish during the critical life-history transition between pelagic and benthic habitats.
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JoVE Visualize is a tool created to match the last 5 years of PubMed publications to methods in JoVE's video library.

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In developing our video relationships, we compare around 5 million PubMed articles to our library of over 4,500 methods videos. In some cases the language used in the PubMed abstracts makes matching that content to a JoVE video difficult. In other cases, there happens not to be any content in our video library that is relevant to the topic of a given abstract. In these cases, our algorithms are trying their best to display videos with relevant content, which can sometimes result in matched videos with only a slight relation.