Name: alveolates: ciliates, dinoflagellates, apicomplexans
Uploaded: 2025-06-12T09:27:31.000Z
Duration: 1 min 27 s
Channel: JoVE

Gli alveolati includono ciliati, dinoflagellati e apicomplexani. Sono caratterizzati da alveoli, sacche citoplasmatiche situate sotto la membrana cellulare. I ciliati come il Paramecio si riconoscono per la presenza di ciglia che aiutano nel movimento. I ciliati possiedono due tipi di nuclei, macronuclei e micronuclei, che sono coinvolti rispettivamente nella regolazione delle funzioni cellulari di base e della riproduzione sessuale. I dinoflagellati sono protisti fotosintetici. Si muovono con un movimento rotatorio utilizzando due flagelli di diverse lunghezze posizionati ad angoli diversi. Le specie di Gonyaulax producono bioluminescenza, emettendo luce quando vengono disturbate, creando un effetto scintillante nelle acque costiere. Gli apicomplexani sono protisti non mobili, non fotosintetici e parassiti. Questi organismi producono tipicamente sporozoiti, strutture specializzate che aiutano nell'infezione dell'ospite. Gli apicomplexani contengono anche apicoplasti, che sono cloroplasti degenerati che contribuiscono alla biosintesi degli acidi grassi, degli isoprenoidi e dell'eme. Gli apicomplexani ben noti sono il Plasmodium, che causa la malaria, e il Toxoplasma, che causa la toxoplasmosi.

diversità dei protozoi

Diversity of Protists II

Gli alveolati sono un gruppo di organismi riconoscibili per la presenza di alveoli, ovvero sacche citoplasmatiche situate sotto la membrana cellulare. Sebbene la loro funzione rimanga incerta, si ritiene che gli alveoli possano contribuire a regolare l&#8217;equilibrio idrico controllando la quantit&#224; di acqua che entra ed esce dalla cellula. Nei dinoflagellati, queste strutture possono fungere da piastre corazzate. Esistono tre principali tipi di alveolati: i ciliati, che si muovono mediante ciglia; i dinoflagellati, che utilizzano flagelli per il movimento; e gli apicomplessi, che sono parassiti e infettano l&#8217;uomo e altri animali.
I ciliati possiedono ciglia in qualche fase del loro ciclo vitale. Queste piccole strutture simili a peli facilitano il movimento e possono coprire l&#8217;intera cellula oppure apparire in ciuffi o file, a seconda della specie. Uno dei ciliati pi&#249; noti &#232; il Paramecium, che utilizza le ciglia sia per la locomozione sia per l&#8217;alimentazione. Il Paramecium consuma batteri e altre particelle convogliandole in un solco orale a forma di imbuto. Il materiale viene poi trasportato alla bocca cellulare, o citofaringe, dove viene inglobato in un vacuolo mediante fagocitosi. Gli enzimi digestivi decompongono il contenuto per l&#8217;assimilazione dei nutrienti.
I ciliati sono unici tra i protisti perch&#233; possiedono due tipi di nuclei: micronuclei e macronuclei. Il macronucleo regola le funzioni cellulari essenziali come la crescita e l&#8217;alimentazione, mentre il micronucleo &#232; coinvolto nella riproduzione sessuata. Nel Paramecium, la riproduzione sessuata avviene quando due cellule si fondono parzialmente e scambiano micronuclei. Il genoma macronucleare del Paramecium contiene circa 40.000 geni, quasi il doppio rispetto a quello umano.
Molte specie di Paramecium e altri protisti ospitano batteri, archei o eucarioti endosimbionti, come le alghe verdi. Questi organismi simbionti forniscono spesso nutrienti essenziali all&#8217;organismo ospite, tra cui vitamine o fattori di crescita. Alcuni ciliati, in particolare quelli presenti nei tratti digestivi delle termiti, contengono archei endosimbionti che convertono idrogeno e anidride carbonica in metano. Inoltre, alcuni ciliati anaerobici si trovano nel rumine degli animali ruminanti, dove contribuiscono alla digestione e alla fermentazione.
Sebbene la simbiosi sia comune, alcuni ciliati sono parassiti. Un esempio &#232; Balantidium coli, un parassita intestinale presente principalmente negli animali domestici, ma che occasionalmente pu&#242; infettare l&#8217;uomo causando sintomi simili alla dissenteria. Questo parassita forma cisti che permettono la trasmissione della malattia attraverso alimenti o acqua contaminati.
I dinoflagellati sono organismi eterogenei presenti sia in ambienti marini sia in ambienti d&#8217;acqua dolce. Hanno acquisito la capacit&#224; di fotosintetizzare tramite un endosimbiosi secondaria. Questi organismi si muovono grazie a due flagelli di lunghezza diversa, disposti ad angoli differenti. Il movimento dei flagelli provoca una rotazione dei dinoflagellati, riflessa nel loro nome, derivante dalla parola greca che significa &#8220;turbinare&#8221;. Alcuni dinoflagellati sono liberi, mentre altri vivono in simbiosi con animali delle barriere coralline, fornendo loro nutrimento in cambio di protezione.
Alcuni dinoflagellati producono bioluminescenza, emettendo luce quando vengono disturbati durante la notte, creando un effetto scintillante nelle acque costiere. Tuttavia, alcune specie sono dannose. Ad esempio, Gonyaulax forma fioriture dense note come &#8220;maree rosse&#8221;, che possono causare la morte dei pesci e intossicazioni negli esseri umani quando i molluschi accumulano le neurotossine dell&#8217;organismo. Questa condizione, chiamata intossicazione paralitica da molluschi, pu&#242; causare intorpidimento, vertigini e difficolt&#224; respiratorie, con casi gravi che portano all&#8217;insufficienza respiratoria. Un altro dinoflagellato dannoso, Pfiesteria piscicida, rilascia spore tossiche che infettano e uccidono i pesci. Queste tossine provocano lesioni che consentono l&#8217;invasione batterica del tessuto danneggiato. Gli esseri umani esposti a Pfiesteria possono sviluppare eruzioni cutanee e problemi respiratori.
Gli apicomplessi sono parassiti non fotosintetici che causano gravi malattie negli esseri umani e negli animali. Esempi includono Plasmodium, responsabile della malaria; Toxoplasma, che causa la toxoplasmosi; ed Eimeria, che provoca la coccidiosi. Gli apicomplessi adulti sono privi di mobilit&#224; e assorbono nutrienti direttamente attraverso la membrana cellulare.
Questi organismi producono sporozoiti, strutture specializzate che facilitano l&#8217;infezione dell&#8217;ospite. Il nome &#8220;apicomplessi&#8221; deriva dalla presenza di un complesso di organelli situato a un&#8217;estremit&#224; dello sporozoite, che aiuta il parassita a penetrare nelle cellule ospiti. Gli apicomplessi contengono anche apicoplasti, cloroplasti degenerati che non svolgono pi&#249; la fotosintesi ma che contribuiscono ancora alla biosintesi degli acidi grassi, degli isoprenoidi e dell&#8217;eme. Si ritiene che gli apicoplasti derivino da alghe rosse inglobate da un antenato degli apicomplessi in un evento di endosimbiosi secondaria. Col tempo, il cloroplasto ha perso la capacit&#224; fotosintetica, assumendo altre funzioni all&#8217;interno della cellula dell&#8217;apicomplesso.
Gli apicomplessi infettano sia vertebrati sia invertebrati, e alcune specie necessitano di due ospiti per completare il proprio ciclo vitale. Ad esempio, alcune specie di Plasmodium, responsabili della malaria, alternano tra zanzare e ospiti umani. I coccidi infettano principalmente gli uccelli, ma possono colpire anche altri animali. La malaria, che &#232; stata una delle malattie pi&#249; letali nella storia dell&#8217;umanit&#224;, continua a rappresentare una seria minaccia per la salute a livello globale.

Diversità dei Protozoi

Gli alveolati sono un gruppo di organismi riconoscibili per la presenza di alveoli, ovvero sacche citoplasmatiche situate sotto la membrana cellulare. ...

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alveolates: ciliates, dinoflagellates, apicomplexans

Alveolates are protists with tiny sacs called alveoli beneath the cell membrane. These sacs may help control water balance by limiting how much water moves in and out of the cell. In dinoflagellates, alveoli may also act like armor plates.

The three main alveolate groups are ciliates, dinoflagellates, and apicomplexans. Ciliates move with cilia, which are short hair-like structures that can cover the whole cell or appear in rows or tufts. One well-known ciliate is Paramecium, which uses cilia for movement and for feeding on bacteria and other small particles.

Paramecium sweeps food into a funnel-shaped oral groove. The food then moves to the gullet, or cell mouth, where it is enclosed in a vacuole by phagocytosis. Digestive enzymes break the food down so the cell can absorb nutrients. Ciliates are also unusual because they have two nuclei. The macronucleus controls everyday cell functions such as growth and feeding, while the micronucleus is involved in sexual reproduction.

In Paramecium, sexual reproduction happens when two cells partially join and exchange micronuclei. The macronuclear genome of Paramecium has about 40,000 genes, which is nearly twice as many as humans. Many Paramecium species and other protists also host endosymbiotic bacteria, archaea, or eukaryotes such as green algae. These partners often supply vitamins or growth factors to the host.

Some ciliates have more specialized symbioses. Ciliates in termite digestive tracts can contain archaea that turn hydrogen and carbon dioxide into methane. Other anaerobic ciliates live in the rumen of ruminant animals and help with digestion and fermentation. Not all ciliates are helpful, though. Balantidium coli is an intestinal parasite that mainly infects domestic animals but can sometimes infect humans and cause dysentery-like symptoms. It spreads through cysts in contaminated food or water.

Dinoflagellates live in both marine and freshwater habitats. They gained photosynthesis through secondary endosymbiosis. They move with two flagella of different lengths that are set at different angles. This movement makes the cell spin, which fits the name dinoflagellate, from a Greek word meaning “whirling.”

Some dinoflagellates live freely, while others live with coral reef animals and provide food in exchange for shelter. Certain species also produce bioluminescence, so they glow when disturbed at night. Other dinoflagellates can be harmful. Gonyaulax can form red tides, which may kill fish and poison humans when shellfish collect its neurotoxins. This can cause paralytic shellfish poisoning, with numbness, dizziness, breathing trouble, and in severe cases respiratory failure. Pfiesteria piscicida is another harmful dinoflagellate. It releases toxic spores that infect and kill fish, and the toxins can also cause lesions that let bacteria enter damaged tissue. Humans exposed to Pfiesteria may develop skin rashes and breathing problems.

Apicomplexans are non-photosynthetic parasites that cause serious disease in humans and animals. Examples include Plasmodium, which causes malaria; Toxoplasma, which causes toxoplasmosis; and Eimeria, which causes coccidiosis. Adult apicomplexans do not move and absorb nutrients through their cell membrane. They form sporozoites, which help start infection in a host. Their name comes from a special organelle complex at one end of the sporozoite that helps the parasite enter host cells.

Apicomplexans also contain apicoplasts. These are degenerate chloroplasts that no longer do photosynthesis, but they still help with fatty acid, isoprenoid, and heme synthesis. Scientists think apicoplasts came from red algae in a secondary endosymbiotic event. Apicomplexans infect both vertebrates and invertebrates, and some need two hosts to finish their life cycle. In some Plasmodium species, the parasite alternates between mosquito and human hosts. Coccidia mainly infect birds, but they can also affect other animals. Malaria has been one of the deadliest diseases in human history and remains a major health threat worldwide.

Alveolates: Ciliates, Dinoflagellates, Apicomplexans

alveolates-ciliates-dinoflagellates-apicomplexans

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diversity of protists ii

Alveolates are protists with tiny sacs called alveoli beneath the cell membrane. These sacs may help control water balance by limiting how much water moves in and out of the cell. In dinoflagellates, alveoli may also act like armor plates. The three main alveolate groups are ciliates, dinoflagellates, and apicomplexans. Ciliates move with cilia, which are short hair-like structures that can cover the whole cell or appear in rows or tufts. One well-known ciliate is Paramecium, which uses cilia...

diversity of protists iii

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diversity of protists iv

Amoebozoa: Movement and Life Cycles

Amoebozoa are a diverse group of terrestrial and aquatic protists. They move and feed with lobe-shaped pseudopodia. This feature sets them apart from Rhizaria, which have threadlike pseudopodia. The group includes gymnamoebas, entamoebas, and the plasmodial and cellular slime molds. Phylogenetic evidence also shows that Amoebozoa split from a lineage that later gave rise to fungi and animals. Gymnamoebas are free-living protists that live in water and soil. They move by amoeboid movement,...

key terms and concepts

Learn how alveolates include ciliates, dinoflagellates, and apicomplexans, from Paramecium feeding to red tides, parasites, and malaria.

Alveolates: Ciliates, Dinoflagellates, Apicomplexans | JoVE K12

JoVE Core Microbiology provides an engaging introduction to the microbial world and its influence on health, industry, and the environment. This comprehensive collection covers key concepts such as microbial structure, metabolism, genetics, and ecology. It introduces essential laboratory techniques and microscopy methods through visually engaging animations. Corresponding scientist-in-action videos bridge classroom concepts with real-world research and applications.

microbiology

Alveolates: Ciliates, Dinoflagellates, Apicomplexans

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