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

Los alveolados incluyen ciliados, dinoflagelados y apicomplejos. Se caracterizan por la presencia de alvéolos, sacos citoplasmáticos ubicados debajo de la membrana celular. Los ciliados como el Paramecium se reconocen por la presencia de cilios que ayudan en el movimiento. Los ciliados poseen dos tipos de núcleos, macronúcleos y micronúcleos, que participan en la regulación de las funciones celulares básicas y la reproducción sexual, respectivamente. Los dinoflagelados son protistas fotosintéticos. Se mueven con un movimiento giratorio utilizando dos flagelos de diferentes longitudes colocados en diferentes ángulos. Las especies de Gonyaulax producen bioluminiscencia, emitiendo luz cuando se les molesta, creando un efecto centelleante en las aguas costeras. Los apicomplejos son protistas inmóviles, no fotosintéticos y parásitos. Estos organismos suelen producir esporozoítos, estructuras especializadas que ayudan en la infección del huésped. Los apicomplejos también contienen apicoplastos, que son cloroplastos degenerados que contribuyen a la biosíntesis de ácidos grasos, isoprenoides y hemo. Los apicomplejos más conocidos son el Plasmodium, que causa la malaria, y el Toxoplasma, que causa la toxoplasmosis.

diversidad de protozoos

Diversity of Protists II

Los alveolados constituyen un grupo de organismos caracterizados por la presencia de alveolos, que son sacos citoplasm&#225;ticos situados debajo de la membrana celular. Aunque su funci&#243;n sigue siendo incierta, los alveolos podr&#237;an contribuir a la regulaci&#243;n del equilibrio h&#237;drico controlando la cantidad de agua que entra y sale de la c&#233;lula. En los dinoflagelados, estas estructuras podr&#237;an actuar como placas de armadura. Existen tres tipos principales de alveolados: los ciliados, que se desplazan mediante cilios; los dinoflagelados, que utilizan flagelos para moverse; y los apicomplejos, que son par&#225;sitos e infectan a seres humanos y otros animales.
Los ciliados poseen cilios en alguna fase de su ciclo vital. Estas peque&#241;as estructuras similares a pelos facilitan el movimiento y pueden cubrir toda la c&#233;lula o disponerse en mechones o hileras, dependiendo de la especie. Uno de los ciliados m&#225;s conocidos es Paramecium, que utiliza los cilios tanto para la locomoci&#243;n como para la alimentaci&#243;n. Paramecium consume bacterias y otras part&#237;culas arrastr&#225;ndolas hacia un surco oral en forma de embudo. El material es transportado hasta la boca celular, o citostoma, donde queda encerrado en una vacuola mediante fagocitosis. Las enzimas digestivas descomponen el contenido para obtener nutrientes.
Los ciliados son &#250;nicos entre los protistas porque presentan dos tipos de n&#250;cleos: micron&#250;cleos y macron&#250;cleos. El macron&#250;cleo controla funciones celulares esenciales como el crecimiento y la alimentaci&#243;n, mientras que el micron&#250;cleo participa en la reproducci&#243;n sexual. En Paramecium, la reproducci&#243;n sexual se produce cuando dos c&#233;lulas se fusionan parcialmente e intercambian micron&#250;cleos. El genoma macronuclear de Paramecium contiene aproximadamente 40.000 genes, casi el doble que el genoma humano.
Muchas especies de Paramecium y otros protistas sirven de hospedadores a bacterias, arqueas o eucariotas endosimbi&#243;ticos, como las algas verdes. Estos organismos simbi&#243;ticos suelen proporcionar a su hospedador nutrientes esenciales, incluidos vitaminas o factores de crecimiento. Algunos ciliados, en particular aquellos presentes en el aparato digestivo de las termitas, albergan arqueas endosimbi&#243;ticas que convierten hidr&#243;geno y di&#243;xido de carbono en metano. Adem&#225;s, algunos ciliados anaerobios se encuentran en el rumen de los animales rumiantes, donde contribuyen a la digesti&#243;n y fermentaci&#243;n.
Aunque la simbiosis es com&#250;n, algunos ciliados son par&#225;sitos. Un ejemplo es Balantidium coli, un par&#225;sito intestinal que se encuentra principalmente en animales dom&#233;sticos, pero que ocasionalmente infecta a humanos, causando s&#237;ntomas similares a la disenter&#237;a. Este par&#225;sito forma quistes que permiten la transmisi&#243;n de la enfermedad a trav&#233;s de alimentos o agua contaminados.
Los dinoflagelados son organismos diversos que habitan tanto en ambientes marinos como de agua dulce. Adquirieron su capacidad fotosint&#233;tica mediante endosimbiosis secundaria. Estos organismos se mueven gracias a dos flagelos de diferentes longitudes, situados en &#225;ngulos distintos. El movimiento de estos flagelos hace que los dinoflagelados giren sobre s&#237; mismos, lo que se refleja en su nombre, derivado del t&#233;rmino griego que significa "girar". Algunos dinoflagelados son de vida libre, mientras que otros viven en simbiosis con animales de arrecifes de coral, proporcion&#225;ndoles alimento a cambio de refugio.
Algunos dinoflagelados producen bioluminiscencia, emitiendo luz cuando son perturbados por la noche, creando un efecto centelleante en las aguas costeras. Sin embargo, algunas especies son perjudiciales. Por ejemplo, Gonyaulax forma proliferaciones densas conocidas como &#8220;mareas rojas&#8221;, que pueden provocar la muerte de peces y el envenenamiento humano cuando los moluscos filtran y acumulan las neurotoxinas del organismo. Esta condici&#243;n, llamada intoxicaci&#243;n paralizante por mariscos, puede causar entumecimiento, mareos y dificultades respiratorias, y en casos graves, insuficiencia respiratoria. Otro dinoflagelado nocivo, Pfiesteria piscicida, libera esporas t&#243;xicas que infectan y matan a los peces. Estas toxinas tambi&#233;n provocan lesiones que permiten la invasi&#243;n bacteriana del tejido da&#241;ado del pez. Los humanos expuestos a Pfiesteria pueden desarrollar erupciones cut&#225;neas y problemas respiratorios.
Los apicomplejos son par&#225;sitos no fotosint&#233;ticos que causan enfermedades graves en humanos y animales. Ejemplos de ello son Plasmodium, responsable de la malaria; Toxoplasma, que provoca toxoplasmosis; y Eimeria, que produce coccidiosis. Los apicomplejos adultos carecen de movilidad y absorben los nutrientes directamente a trav&#233;s de su membrana celular.
Estos organismos producen esporozo&#237;tos, que son estructuras especializadas que facilitan la infecci&#243;n del hospedador. El nombre &#8220;apicomplejo&#8221; proviene de la presencia de un complejo de org&#225;nulos &#250;nico en un extremo del esporozo&#237;to, que ayuda al par&#225;sito a invadir las c&#233;lulas del hospedador. Los apicomplejos tambi&#233;n contienen apicoplastos, que son cloroplastos degenerados que ya no realizan la fotos&#237;ntesis, pero que siguen participando en la bios&#237;ntesis de &#225;cidos grasos, isoprenoides y hemo. Se cree que los apicoplastos se originaron a partir de algas rojas que fueron fagocitadas por un apicomplejo ancestral en un evento de endosimbiosis secundaria. Con el tiempo, el cloroplasto perdi&#243; su capacidad fotosint&#233;tica y asumi&#243; otras funciones dentro de la c&#233;lula apicompleja.
Los apicomplejos infectan tanto a vertebrados como a invertebrados, y algunas especies requieren dos hospedadores para completar su ciclo vital. Por ejemplo, ciertas especies de Plasmodium, que causan malaria, alternan entre el mosquito y el ser humano como hospedadores. Los coccidios infectan principalmente a las aves, aunque tambi&#233;n pueden afectar a otros animales. La malaria, que ha sido una de las enfermedades m&#225;s letales a lo largo de la historia de la humanidad, sigue representando una amenaza importante para la salud mundial.

Diversidad de protozoos

Los alveolados constituyen un grupo de organismos caracterizados por la presencia de alveolos, que son sacos citoplasm&#225;ticos situados debajo de la ...

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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 i

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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

Rhizaria: Pseudopods, Tests, and Skeletons

Rhizaria are unicellular protists with threadlike pseudopodia, which are thin cytoplasmic extensions used for movement and feeding. Their amoeboid shape once caused taxonomic confusion, but molecular phylogenetics has since shown where they fit on the evolutionary tree. This group includes Chlorarachniophyta, Radiolaria, and Foraminifera, and each lineage has adapted to a different ecological niche and metabolic strategy. Chlorarachniophyta are unicellular phototrophic protists found in marine...

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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