Despite being one of the most productive fisheries in the Northwest Atlantic, much remains unknown about the natural reproductive dynamics of American lobsters. Recent work in exploited crustacean populations (crabs and lobsters) suggests that there are circumstances where mature females are unable to achieve their full reproductive potential due to sperm limitation. To examine this possibility in different regions of the American lobster fishery, a reliable and noninvasive method was developed for sampling large numbers of female lobsters at sea. This method involves inserting a blunt-tipped needle into the female's seminal receptacle to determine the presence or absence of a sperm plug and to withdraw a sample that can be examined for the presence of sperm. A series of control studies were conducted at the dock and in the laboratory to test the reliability of this technique. These efforts entailed sampling 294 female lobsters to confirm that the presence of a sperm plug was a reliable indicator of sperm within the receptacle and thus, mating. This paper details the methodology and the results obtained from a subset of the total females sampled. Of the 230 female lobsters sampled from George's Bank and Cape Ann, MA (size range = 71-145 mm in carapace length), 90.3% were positive for sperm. Potential explanations for the absence of sperm in some females include: immaturity (lack of physiological maturity), breakdown of the sperm plug after being used to fertilize a clutch of eggs, and lack of mating activity. The surveys indicate that this technique for examining the mating success of female lobsters is a reliable proxy that can be used in the field to document reproductive activity in natural populations.
21 Related JoVE Articles!
Regular Care and Maintenance of a Zebrafish (Danio rerio) Laboratory: An Introduction
Institutions: Edith Cowan University, Graylands Hospital, University of Western Australia, McCusker Alzheimer's Research foundation, University of Western Australia , University of Adelaide, Curtin University of Technology, University of Western Australia .
This protocol describes regular care and maintenance of a zebrafish laboratory. Zebrafish are now gaining popularity in genetics, pharmacological and behavioural research. As a vertebrate, zebrafish share considerable genetic sequence similarity with humans and are being used as an animal model for various human disease conditions. The advantages of zebrafish in comparison to other common vertebrate models include high fecundity, low maintenance cost, transparent embryos, and rapid development. Due to the spur of interest in zebrafish research, the need to establish and maintain a productive zebrafish housing facility is also increasing. Although literature is available for the maintenance of a zebrafish laboratory, a concise video protocol is lacking. This video illustrates the protocol for regular housing, feeding, breeding and raising of zebrafish larvae. This process will help researchers to understand the natural behaviour and optimal conditions of zebrafish husbandry and hence troubleshoot experimental issues that originate from the fish husbandry conditions. This protocol will be of immense help to researchers planning to establish a zebrafish laboratory, and also to graduate students who are intending to use zebrafish as an animal model.
Basic Protocols, Issue 69, Biology, Marine Biology, Zebrafish, Danio rerio, maintenance, breeding, feeding, raising, larvae, animal model, aquarium
High Throughput Microinjections of Sea Urchin Zygotes
Institutions: University of Delaware .
Microinjection into cells and embryos is a common technique that is used to study a wide range of biological processes. In this method a small amount of treatment solution is loaded into a microinjection needle that is used to physically inject individual immobilized cells or embryos. Despite the need for initial training to perform this procedure for high-throughput delivery, microinjection offers maximum efficiency and reproducible delivery of a wide variety of treatment solutions (including complex mixtures of samples) into cells, eggs or embryos. Applications to microinjections include delivery of DNA constructs, mRNAs, recombinant proteins, gain of function, and loss of function reagents. Fluorescent or colorimetric dye is added to the injected solution to enable instant visualization of efficient delivery as well as a tool for reliable normalization of the amount of the delivered solution. The described method enables microinjection of 100-400 sea urchin zygotes within 10-15 min.
Developmental Biology, Issue 83, Sea Urchins, microinjection, sea urchin embryos, treatment delivery, high throughput, mouth pipette, DNA constructs, mRNAs, morpholino antisense oligonucleotides
Assessing Differences in Sperm Competitive Ability in Drosophila
Institutions: University of California, Irvine.
Competition among conspecific males for fertilizing the ova is one of the mechanisms of sexual selection, i.e.
selection that operates on maximizing the number of successful mating events rather than on maximizing survival and viability 1
. Sperm competition represents the competition between males after copulating with the same female 2
, in which their sperm are coincidental in time and space. This phenomenon has been reported in multiple species of plants and animals 3
. For example, wild-caught D. melanogaster
females usually contain sperm from 2-3 males 4
. The sperm are stored in specialized organs with limited storage capacity, which might lead to the direct competition of the sperm from different males 2,5
Comparing sperm competitive ability of different males of interest (experimental male types) has been performed through controlled double-mating experiments in the laboratory 6,7
. Briefly, a single female is exposed to two different males consecutively, one experimental male and one cross-mating reference male. The same mating scheme is then followed using other experimental male types thus facilitating the indirect comparison of the competitive ability of their sperm through a common reference. The fraction of individuals fathered by the experimental and reference males is identified using markers, which allows one to estimate sperm competitive ability using simple mathematical expressions 7,8
. In addition, sperm competitive ability can be estimated in two different scenarios depending on whether the experimental male is second or first to mate (offense and defense assay, respectively) 9
, which is assumed to be reflective of different competence attributes.
Here, we describe an approach that helps to interrogate the role of different genetic factors that putatively underlie the phenomenon of sperm competitive ability in D. melanogaster
Developmental Biology, Issue 78, Molecular Biology, Cellular Biology, Genetics, Biochemistry, Spermatozoa, Drosophila melanogaster, Biological Evolution, Phenotype, genetics (animal and plant), animal biology, double-mating experiment, sperm competitive ability, male fertility, Drosophila, fruit fly, animal model
Ablation of a Single Cell From Eight-cell Embryos of the Amphipod Crustacean Parhyale hawaiensis
Institutions: Harvard University.
The amphipod Parhyale hawaiensis
is a small crustacean found in intertidal marine habitats worldwide. Over the past decade, Parhyale
has emerged as a promising model organism for laboratory studies of development, providing a useful outgroup comparison to the well studied arthropod model organism Drosophila melanogaster
. In contrast to the syncytial cleavages of Drosophila
, the early cleavages of Parhyale
are holoblastic. Fate mapping using tracer dyes injected into early blastomeres have shown that all three germ layers and the germ line are established by the eight-cell stage. At this stage, three blastomeres are fated to give rise to the ectoderm, three are fated to give rise to the mesoderm, and the remaining two blastomeres are the precursors of the endoderm and germ line respectively. However, blastomere ablation experiments have shown that Parhyale
embryos also possess significant regulatory capabilities, such that the fates of blastomeres ablated at the eight-cell stage can be taken over by the descendants of some of the remaining blastomeres. Blastomere ablation has previously been described by one of two methods: injection and subsequent activation of phototoxic dyes or manual ablation. However, photoablation kills blastomeres but does not remove the dead cell body from the embryo. Complete physical removal of specific blastomeres may therefore be a preferred method of ablation for some applications. Here we present a protocol for manual removal of single blastomeres from the eight-cell stage of Parhyale
embryos, illustrating the instruments and manual procedures necessary for complete removal of the cell body while keeping the remaining blastomeres alive and intact. This protocol can be applied to any Parhyale
cell at the eight-cell stage, or to blastomeres of other early cleavage stages. In addition, in principle this protocol could be applicable to early cleavage stage embryos of other holoblastically cleaving marine invertebrates.
Developmental Biology, Issue 85, Amphipod, experimental embryology, micromere, germ line, ablation, developmental potential, vasa
Reconstitution Of β-catenin Degradation In Xenopus Egg Extract
Institutions: Vanderbilt University Medical Center, Cincinnati Children's Hospital Medical Center, Vanderbilt University School of Medicine.
egg extract is a well-characterized, robust system for studying the biochemistry of diverse cellular processes. Xenopus
egg extract has been used to study protein turnover in many cellular contexts, including the cell cycle and signal transduction pathways1-3
. Herein, a method is described for isolating Xenopus
egg extract that has been optimized to promote the degradation of the critical Wnt pathway component, β-catenin. Two different methods are described to assess β-catenin protein degradation in Xenopus
egg extract. One method is visually informative ([35
S]-radiolabeled proteins), while the other is more readily scaled for high-throughput assays (firefly luciferase-tagged fusion proteins). The techniques described can be used to, but are not limited to, assess β-catenin protein turnover and identify molecular components contributing to its turnover. Additionally, the ability to purify large volumes of homogenous Xenopus
egg extract combined with the quantitative and facile readout of luciferase-tagged proteins allows this system to be easily adapted for high-throughput screening for modulators of β-catenin degradation.
Molecular Biology, Issue 88, Xenopus laevis, Xenopus egg extracts, protein degradation, radiolabel, luciferase, autoradiography, high-throughput screening
Flat Mount Preparation for Observation and Analysis of Zebrafish Embryo Specimens Stained by Whole Mount In situ Hybridization
Institutions: University of Notre Dame.
The zebrafish embryo is now commonly used for basic and biomedical research to investigate the genetic control of developmental processes and to model congenital abnormalities. During the first day of life, the zebrafish embryo progresses through many developmental stages including fertilization, cleavage, gastrulation, segmentation, and the organogenesis of structures such as the kidney, heart, and central nervous system. The anatomy of a young zebrafish embryo presents several challenges for the visualization and analysis of the tissues involved in many of these events because the embryo develops in association with a round yolk mass. Thus, for accurate analysis and imaging of experimental phenotypes in fixed embryonic specimens between the tailbud and 20 somite stage (10 and 19 hours post fertilization (hpf), respectively), such as those stained using whole mount in situ
hybridization (WISH), it is often desirable to remove the embryo from the yolk ball and to position it flat on a glass slide. However, performing a flat mount procedure can be tedious. Therefore, successful and efficient flat mount preparation is greatly facilitated through the visual demonstration of the dissection technique, and also helped by using reagents that assist in optimal tissue handling. Here, we provide our WISH protocol for one or two-color detection of gene expression in the zebrafish embryo, and demonstrate how the flat mounting procedure can be performed on this example of a stained fixed specimen. This flat mounting protocol is broadly applicable to the study of many embryonic structures that emerge during early zebrafish development, and can be implemented in conjunction with other staining methods performed on fixed embryo samples.
Developmental Biology, Issue 89, animals, vertebrates, fishes, zebrafish, growth and development, morphogenesis, embryonic and fetal development, organogenesis, natural science disciplines, embryo, whole mount in situ hybridization, flat mount, deyolking, imaging
Effect of Male Accessory Gland Products on Egg Laying in Gastropod Molluscs
Institutions: VU University.
In internally fertilizing animals, seminal fluid is usually added to the spermatozoa, together forming the semen or ejaculate. Besides nourishing and activating sperm, the components in the seminal fluid can also influence female physiology to augment fertilization success of the sperm donor. While many studies have reported such effects in species with separate sexes, few studies have addressed this in simultaneously hermaphroditic animals. This video protocol presents a method to study effects of seminal fluid in gastropods, using a simultaneously hermaphroditic freshwater snail, the great pond snail Lymnaea stagnalis
, as model organism. While the procedure is shown using complete prostate gland extracts, individual components (i.e.
, proteins, peptides, and other compounds) of the seminal fluid can be tested in the same way. Effects of the receipt of ejaculate components on egg laying can be quantified in terms of frequency of egg laying and more subtle estimates of female reproductive performance such as egg numbers within each egg masses. Results show that seminal fluid proteins affect female reproductive output in this simultaneous hermaphrodite, highlighting their importance for sexual selection.
Physiology, Issue 88, Allohormone, Fresh-water snail, Gastropod, Lymnaea stagnalis, Mollusc, Pond snail, Prostate, Semen, Seminal fluid Sexual selection, Sperm
Production of Haploid Zebrafish Embryos by In Vitro Fertilization
Institutions: University of Notre Dame.
The zebrafish has become a mainstream vertebrate model that is relevant for many disciplines of scientific study. Zebrafish are especially well suited for forward genetic analysis of developmental processes due to their external fertilization, embryonic size, rapid ontogeny, and optical clarity – a constellation of traits that enable the direct observation of events ranging from gastrulation to organogenesis with a basic stereomicroscope. Further, zebrafish embryos can survive for several days in the haploid state. The production of haploid embryos in vitro
is a powerful tool for mutational analysis, as it enables the identification of recessive mutant alleles present in first generation (F1) female carriers following mutagenesis in the parental (P) generation. This approach eliminates the necessity to raise multiple generations (F2, F3, etc.
) which involves breeding of mutant families, thus saving the researcher time along with reducing the needs for zebrafish colony space, labor, and the husbandry costs. Although zebrafish have been used to conduct forward screens for the past several decades, there has been a steady expansion of transgenic and genome editing tools. These tools now offer a plethora of ways to create nuanced assays for next generation screens that can be used to further dissect the gene regulatory networks that drive vertebrate ontogeny. Here, we describe how to prepare haploid zebrafish embryos. This protocol can be implemented for novel future haploid screens, such as in enhancer and suppressor screens, to address the mechanisms of development for a broad number of processes and tissues that form during early embryonic stages.
Developmental Biology, Issue 89, zebrafish, haploid, in vitro fertilization, forward genetic screen, saturation, recessive mutation, mutagenesis
A Manual Small Molecule Screen Approaching High-throughput Using Zebrafish Embryos
Institutions: University of Notre Dame.
Zebrafish have become a widely used model organism to investigate the mechanisms that underlie developmental biology and to study human disease pathology due to their considerable degree of genetic conservation with humans. Chemical genetics entails testing the effect that small molecules have on a biological process and is becoming a popular translational research method to identify therapeutic compounds. Zebrafish are specifically appealing to use for chemical genetics because of their ability to produce large clutches of transparent embryos, which are externally fertilized. Furthermore, zebrafish embryos can be easily drug treated by the simple addition of a compound to the embryo media. Using whole-mount in situ
hybridization (WISH), mRNA expression can be clearly visualized within zebrafish embryos. Together, using chemical genetics and WISH, the zebrafish becomes a potent whole organism context in which to determine the cellular and physiological effects of small molecules. Innovative advances have been made in technologies that utilize machine-based screening procedures, however for many labs such options are not accessible or remain cost-prohibitive. The protocol described here explains how to execute a manual high-throughput chemical genetic screen that requires basic resources and can be accomplished by a single individual or small team in an efficient period of time. Thus, this protocol provides a feasible strategy that can be implemented by research groups to perform chemical genetics in zebrafish, which can be useful for gaining fundamental insights into developmental processes, disease mechanisms, and to identify novel compounds and signaling pathways that have medically relevant applications.
Developmental Biology, Issue 93, zebrafish, chemical genetics, chemical screen, in vivo small molecule screen, drug discovery, whole mount in situ hybridization (WISH), high-throughput screening (HTS), high-content screening (HCS)
Unraveling the Unseen Players in the Ocean - A Field Guide to Water Chemistry and Marine Microbiology
Institutions: San Diego State University, University of California San Diego.
Here we introduce a series of thoroughly tested and well standardized research protocols adapted for use in remote marine environments. The sampling protocols include the assessment of resources available to the microbial community (dissolved organic carbon, particulate organic matter, inorganic nutrients), and a comprehensive description of the viral and bacterial communities (via direct viral and microbial counts, enumeration of autofluorescent microbes, and construction of viral and microbial metagenomes). We use a combination of methods, which represent a dispersed field of scientific disciplines comprising already established protocols and some of the most recent techniques developed. Especially metagenomic sequencing techniques used for viral and bacterial community characterization, have been established only in recent years, and are thus still subjected to constant improvement. This has led to a variety of sampling and sample processing procedures currently in use. The set of methods presented here provides an up to date approach to collect and process environmental samples. Parameters addressed with these protocols yield the minimum on information essential to characterize and understand the underlying mechanisms of viral and microbial community dynamics. It gives easy to follow guidelines to conduct comprehensive surveys and discusses critical steps and potential caveats pertinent to each technique.
Environmental Sciences, Issue 93, dissolved organic carbon, particulate organic matter, nutrients, DAPI, SYBR, microbial metagenomics, viral metagenomics, marine environment
Production of Xenopus tropicalis Egg Extracts to Identify Microtubule-associated RNAs
Institutions: Massachusetts General Hospital, Harvard Medical School.
Many organisms localize mRNAs to specific subcellular destinations to spatially and temporally control gene expression. Recent studies have demonstrated that the majority of the transcriptome is localized to a nonrandom position in cells and embryos. One approach to identify localized mRNAs is to biochemically purify a cellular structure of interest and to identify all associated transcripts. Using recently developed high-throughput sequencing technologies it is now straightforward to identify all RNAs associated with a subcellular structure. To facilitate transcript identification it is necessary to work with an organism with a fully sequenced genome. One attractive system for the biochemical purification of subcellular structures are egg extracts produced from the frog Xenopus laevis.
However, X. laevis
currently does not have a fully sequenced genome, which hampers transcript identification. In this article we describe a method to produce egg extracts from a related frog, X. tropicalis,
that has a fully sequenced genome. We provide details for microtubule polymerization, purification and transcript isolation. While this article describes a specific method for identification of microtubule-associated transcripts, we believe that it will be easily applied to other subcellular structures and will provide a powerful method for identification of localized RNAs.
Molecular Biology, Issue 76, Genetics, Developmental Biology, Biochemistry, Bioengineering, Cellular Biology, RNA, Messenger, Stored, RNA Processing, Post-Transcriptional, Xenopus, microtubules, egg extract, purification, RNA localization, mRNA, Xenopus tropicalis, eggs, animal model
RNA In situ Hybridization in Whole Mount Embryos and Cell Histology Adapted for Marine Elasmobranchs
Institutions: Union College.
Marine elasmobranchs are valued animal models for biomedical and genomic studies as they are the most primitive vertebrates to have adaptive immunity and have unique mechanisms for osmoregulation 1-3
. As the most primitive living jawed-vertebrates with paired appendages, elasmobranchs are an evolutionarily important model, especially for studies in evolution and development. Marine elasmobranchs have also been used to study aquatic toxicology and stress physiology in relationship to climate change 4
. Thus, development and adaptation of methodologies is needed to facilitate and expand the use of these primitive vertebrates to multiple biological disciplines. Here I present the successful adaptation of RNA whole mount in situ
hybridization and histological techniques to study gene expression and cell histology in elasmobranchs.
Monitoring gene expression is a hallmark tool of developmental biologists, and is widely used to investigate developmental processes 5
. RNA whole mount in situ
hybridization allows for the visualization and localization of specific gene transcripts in tissues of the developing embryo. The expression pattern of a gene's message can provide insight into what developmental processes and cell fate decisions a gene may control. By comparing the expression pattern of a gene at different developmental stages, insight can be gained into how the role of a gene changes during development.
While whole mount in situ
's provides a means to localize gene expression to tissue, histological techniques allow for the identification of differentiated cell types and tissues. Histological stains have varied functions. General stains are used to highlight cell morphology, for example hematoxylin and eosin for general staining of nuclei and cytoplasm, respectively. Other stains can highlight specific cell types. For example, the alcian blue stain reported in this paper is a widely used cationic stain to identify mucosaccharides. Staining of the digestive tract with alcian blue can identify the distribution of goblet cells that produce mucosaccharides. Variations in mucosaccharide constituents on short peptides distinguish goblet cells by function within the digestive tract 6
. By using RNA whole mount in situ
's and histochemical methods concurrently, cell fate decisions can be linked to gene-specific expression.
Although RNA in situ
's and histochemistry are widely used by researchers, their adaptation and use in marine elasmobranchs have met limited and varied success. Here I present protocols developed for elasmobranchs and used on a regular basis in my laboratory. Although further modification of the RNA in situ
's hybridization method may be needed to adapt to different species, the protocols described here provide a strong starting point for researchers wanting to adapt the use of marine elasmobranchs to their scientific inquiries.
Genetics, Issue 74, Developmental Biology, Molecular Biology, Cellular Biology, Anatomy, Physiology, Biochemistry, Marine Biology, Disciplines and Occupations, whole mount in situ hybridization, RNA in situs, RNA, acid mucins, alcian blue, nuclear fast red stain, elasmobranch, marine elasmobranchs, L. erinacea, Shh, Hoxa13, gene expression, hybridization, histology, skate, embryos, animal model
Microinjection of Zebrafish Embryos to Analyze Gene Function
Institutions: Harvard Medical School, Children’s Hospital Boston.
One of the advantages of studying zebrafish is the ease and speed of manipulating protein levels in the embryo. Morpholinos, which are synthetic oligonucleotides with antisense complementarity to target RNAs, can be added to the embryo to reduce the expression of a particular gene product. Conversely, processed mRNA can be added to the embryo to increase levels of a gene product. The vehicle for adding either mRNA or morpholino to an embryo is microinjection. Microinjection is efficient and rapid, allowing for the injection of hundreds of embryos per hour. This video shows all the steps involved in microinjection. Briefly, eggs are collected immediately after being laid and lined up against a microscope slide in a Petri dish. Next, a fine-tipped needle loaded with injection material is connected to a microinjector and an air source, and the microinjector controls are adjusted to produce a desirable injection volume. Finally, the needle is plunged into the embryo's yolk and the morpholino or mRNA is expelled.
Developmental Biology, Issue 25, zebrafish, morpholino, development, microinjection, heart of glass, heg
A High-Throughput Method For Zebrafish Sperm Cryopreservation and In Vitro Fertilization
Institutions: University of California, Davis, Fred Hutchinson Cancer Research Center - FHCRC.
This is a method for zebrafish sperm cryopreservation that is an adaptation of the Harvey method (Harvey et al., 1982). We have introduced two changes to the original protocol that both streamline the procedure and increase sample uniformity. First, we normalize all sperm volumes using freezing media that does not contain the cryoprotectant. Second, cryopreserved sperm are stored in cryovials instead of capillary tubes. The rates of sperm freezing and thawing (δ°C/time) are probably the two most critical variables to control in this procedure. For this reason, do not substitute different tubes for those specified. Working in teams of 2 it is possible to freeze the sperm of 100 males per team in ~2 hrs. Sperm cryopreserved using this protocol has an average of 25% fertility (measured as the number of viable embryos generated in an in vitro fertilization divided by the total number of eggs fertilized) and this percent fertility is stable over many years.
Developmental Biology, Issue 29, Zebrafish, sperm, cryopreservation, TILLING
Making Gynogenetic Diploid Zebrafish by Early Pressure
Institutions: University of Oregon, Fred Hutchinson Cancer Research Center - FHCRC.
Heterozygosity in diploid eukaryotes often makes genetic studies cumbersome. Methods that produce viable homozygous diploid offspring directly from heterozygous females allow F1 mutagenized females to be screened directly for deleterious mutations in an accelerated forward genetic screen. Streisinger et al.1,2
described methods for making gynogenetic (homozygous) diploid zebrafish by activating zebrafish eggs with ultraviolet light-inactivated sperm and preventing either the second meiotic or the first zygotic cell division using physical treatments (heat or pressure) that deploymerize microtubules. The "early pressure" (EP) method blocks the meiosis II, which occurs shortly after fertilization. The EP method produces a high percentage of viable embryos that can develop to fertile adults of either sex. The method generates embryos that are homozygous at all loci except those that were separated from their centromere by recombination during meiosis I. Homozygous mutations are detected in EP clutches at between 50% for centromeric loci and less than 1% for telomeric loci. This method is reproduced verbatim from the Zebrafish Book3
Developmental Biology, Issue 28, Zebrafish, Early Pressure, Homozygous Diploid, Haploid, Gynogenesis
Microinjection of Medaka Embryos for use as a Model Genetic Organism
Institutions: University of Bath.
In this video, we demonstrate the technique of microinjection into one-cell stage medaka embryos. Medaka is a small egg-laying freshwater fish that allows both genetic and embryological analyses and is one of the vertebrate model organisms in which genome-wide phenotype-driven mutant screens were carried out 1
, as in zebrafish and the mouse. Divergence of functional overlap of related genes between medaka and zebrafish allows identification of novel phenotypes that are unidentifiable in a single species 2
, thus medaka and zebrafish are complementary for genetic dissection of vertebrate genome functions.
To take advantage of medaka fish whose embryos are transparent and develop externally, microinjection is an essential technique to inject cell-tracers for labeling cells, mRNAs or anti-sense oligonucleotides for over-expressing and knocking-down genes of interest, and DNAs for making transgenic lines.
Developmental Biology, Issue 46, medaka , zebrafish, evolution, mutant, vertebrate, genome function
Mass Production of Genetically Modified Aedes aegypti for Field Releases in Brazil
Institutions: Oxitec Ltd, Universidade de São Paulo, Universidade de São Paulo, Moscamed Brasil, University of Oxford, Instituto Nacional de Ciência e Tecnologia em Entomologia Molecular (INCT-EM).
New techniques and methods are being sought to try to win the battle against mosquitoes. Recent advances in molecular techniques have led to the development of new and innovative methods of mosquito control based around the Sterile Insect Technique (SIT)1-3
. A control method known as RIDL (Release of Insects carrying a Dominant Lethal)4
, is based around SIT, but uses genetic methods to remove the need for radiation-sterilization5-8
. A RIDL strain of Ae. aegypti
was successfully tested in the field in Grand Cayman9,10
; further field use is planned or in progress in other countries around the world.
Mass rearing of insects has been established in several insect species and to levels of billions a week. However, in mosquitoes, rearing has generally been performed on a much smaller scale, with most large scale rearing being performed in the 1970s and 80s. For a RIDL program it is desirable to release as few females as possible as they bite and transmit disease. In a mass rearing program there are several stages to produce the males to be released: egg production, rearing eggs until pupation, and then sorting males from females before release. These males are then used for a RIDL control program, released as either pupae or adults11,12
To suppress a mosquito population using RIDL a large number of high quality male adults need to be reared13,14
. The following describes the methods for the mass rearing of OX513A, a RIDL strain of Ae. aegypti 8,
for release and covers the techniques required for the production of eggs and mass rearing RIDL males for a control program.
Basic Protocol, Issue 83, Aedes aegypti, mass rearing, population suppression, transgenic, insect, mosquito, dengue
Visualizing Bacteria in Nematodes using Fluorescent Microscopy
Institutions: University of Wisconsin-Madison.
Symbioses, the living together of two or more organisms, are widespread throughout all kingdoms of life. As two of the most ubiquitous organisms on earth, nematodes and bacteria form a wide array of symbiotic associations that range from beneficial to pathogenic 1-3
. One such association is the mutually beneficial relationship between Xenorhabdus
bacteria and Steinernema
nematodes, which has emerged as a model system of symbiosis 4
nematodes are entomopathogenic, using their bacterial symbiont to kill insects 5
. For transmission between insect hosts, the bacteria colonize the intestine of the nematode's infective juvenile stage 6-8
. Recently, several other nematode species have been shown to utilize bacteria to kill insects 9-13
, and investigations have begun examining the interactions between the nematodes and bacteria in these systems 9
We describe a method for visualization of a bacterial symbiont within or on a nematode host, taking advantage of the optical transparency of nematodes when viewed by microscopy. The bacteria are engineered to express a fluorescent protein, allowing their visualization by fluorescence microscopy. Many plasmids are available that carry genes encoding proteins that fluoresce at different wavelengths (i.e.
green or red), and conjugation of plasmids from a donor Escherichia coli
strain into a recipient bacterial symbiont is successful for a broad range of bacteria. The methods described were developed to investigate the association between Steinernema carpocapsae
and Xenorhabdus nematophila 14
. Similar methods have been used to investigate other nematode-bacterium associations 9,15-18
and the approach therefore is generally applicable.
The method allows characterization of bacterial presence and localization within nematodes at different stages of development, providing insights into the nature of the association and the process of colonization 14,16,19
. Microscopic analysis reveals both colonization frequency within a population and localization of bacteria to host tissues 14,16,19-21
. This is an advantage over other methods of monitoring bacteria within nematode populations, such as sonication 22
or grinding 23
, which can provide average levels of colonization, but may not, for example, discriminate populations with a high frequency of low symbiont loads from populations with a low frequency of high symbiont loads. Discriminating the frequency and load of colonizing bacteria can be especially important when screening or characterizing bacterial mutants for colonization phenotypes 21,24
. Indeed, fluorescence microscopy has been used in high throughput screening of bacterial mutants for defects in colonization 17,18
, and is less laborious than other methods, including sonication 22,25-27
and individual nematode dissection 28,29
Microbiology, Issue 68, Molecular Biology, Bacteriology, Developmental Biology, Colonization, Xenorhabdus, Steinernema, symbiosis, nematode, bacteria, fluorescence microscopy
Preparation and Fractionation of Xenopus laevis Egg Extracts
Institutions: Emory University.
Crude and fractionated Xenopus egg extracts can be used to provide ingredients for reconstituting cellular processes for morphological and biochemical analysis. Egg lysis and differential centrifugation are used to prepare the crude extract which in turn in used to prepare fractionated extracts and light membrane preparations.
Cellular Biology, Issue 18, Current Protocols Wiley, Xenopus laevis, Egg Extracts, Density Gradient Centrifugation, Light Membrane Fraction, Nuclear Fraction
Obtaining Eggs from Xenopus laevis Females
Institutions: Emory University.
The eggs of Xenopus laevis intact, lysed, and/or fractionated are useful for a wide variety of experiments. This protocol shows how to induce egg laying, collect and dejelly the eggs, and sort the eggs to remove any damaged eggs.
Basic Protocols, Issue 18, Current Protocols Wiley, Eggs, Xenopus laevis
Windowing Chicken Eggs for Developmental Studies
Institutions: University of California, Irvine (UCI).
The study of development has been greatly aided by the use of the chick embryo as an experimental model. The ease of accessibility of the embryo has allowed for experiments to map cell fates using several approaches, including chick quail chimeras and focal dye labeling. In addition, it allows for molecular perturbations of several types, including placement of protein-coated beads and introduction of plasmid DNA using in ovo electroporation. These experiments have yielded important data on the development of the central and peripheral nervous systems. For many of these studies, it is necessary to open the eggshell and reclose it without perturbing the embryo's growth. The embryo can be examined at successive developmental stages by re-opening the eggshell. While there are several excellent methods for opening chicken eggs, in this article we demonstrate one method that has been optimized for long survival times. In this method, the egg rests on its side and a small window is cut in the shell. After the experimental procedure, the shell is used to cover the egg for the duration of its development. Clear plastic tape overlying the eggshell protects the embryo and helps retain hydration during the remainder of the incubation period. This method has been used beginning at two days of incubation and has allowed survival through mature embryonic ages.
Developmental Biology, Issue 8, Neuroscience, Chicken, Embryos, Electroporation, In ovo