| Ciliates Fossil range: Ediacaran - Recent |
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 "Ciliata" from Ernst Haeckel's Kunstformen der Natur, 1904
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Karyorelictea |
The ciliates are one of the most important groups of protists, common almost everywhere there is water — lakes, ponds, oceans, rivers, and soils, with many ectosymbiotic and endosymbiotic members, as well as some obligate and opportunistic parasites included. Protists (ˈproʊtɨst are a diverse group of eukaryotic Microorganisms Historically protists were treated as the kingdom Protista but this Ectosymbiosis is Symbiosis in which the Symbiont lives on the body surface of the host, including internal surfaces such as the lining of the digestive An endosymbiont is any Organism that lives within the body or cells of another organism i Ciliates tend to be large protozoa, a few reaching 2 mm in length, and are some of the most complex in structure. Protozoa (in Greek πρῶτον proton "first" and ζῷα zoia "animals" are unicellular Eukaryotes (singular The name ciliate comes from the presence of hair-like organelles called cilia, which are identical in structure to flagella but typically shorter and present in much larger numbers with a different undulating pattern than flagella. A cilium (plural cilia) is an Organelle found in eukaryotic cells Cilia are tail-like projections extending approximately A flagellum ( plural flagella) is a tail-like structure that projects from the Cell body of certain Prokaryotic and Eukaryotic cells and it Cilia occur in all members of the group (although the peculiar suctoria only have them for part of the life-cycle) and are variously used in swimming, crawling, attachment, feeding, and sensation. Suctoria are peculiar Ciliates which are sessile feed by extracellular digestion and lack cilia in the adult phase
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Cell structure
Unlike other eukaryotes, ciliates have two different sorts of nuclei: a small, diploid micronucleus (reproduction), and a large, polyploid macronucleus (general cell regulation). Animals Plants fungi, and Protists are eukaryotes (juːˈkærɪɒt or -oʊt Organisms whose cells are organized into complex In Cell biology, the nucleus (pl nuclei; from Latin la ''nucleus'' or la ''nuculeus'' "little nut" or kernel is a membrane-enclosed "Haplo" redirects here For the fictional character see The Death Gate Cycle. A micronucleus is the smaller nucleus in Ciliate Protozoans such as the paramecium Polyploidy occurs in cells and Organisms when there are more than two homologous sets of Chromosomes. A macronucleus (formerly also meganucleus is the larger type of nucleus in Ciliates Macronuclei are Polyploid and undergo direct division without The latter is generated from the micronucleus by amplification of the genome and heavy editing. Division of the macronucleus occurs by amitosis, the segregation of the chromosomes is by a process, whose mechanism is unknown. This process is by no means perfect, and after about 200 generations the cell shows signs of aging. Periodically the macronuclei must be regenerated from the micronuclei. In most, this occurs during conjugation. Here two cells line up, the micronuclei undergo meiosis, some of the haploid daughters are exchanged and then fuse to form new micronuclei and macronuclei. In Biology or life science meiosis (pronounced my-oh-sis is a process of reductional division in which the number of chromosomes per cell is cut in half "Haplo" redirects here For the fictional character see The Death Gate Cycle.
Most ciliate cell membranes are surrounded by a pellicle - a clear, elastic layer of protein. With a few exceptions, there is a distinct cytostome or mouth where ingestion takes place. A cytostome or cell mouth is a part of a cell specialized for Phagocytosis, usually in the form of a Microtubule -supported funnel or groove Food vacuoles are formed through phagocytosis and typically follow a particular path through the cell as their contents are digested and broken down via lysosomes so the substances the vacuole contains are then small enough to diffuse through the membrane of the food vacuole into the cell. In general vacuole functions include Removing unwanted structural debris Isolating materials that might be harmful or a threat to the cell Containing Phagocytosis is the cellular process of engulfing solid particles by the Cell membrane to form an internal Phagosome, or "food vacuole Lysosomes are Organelles that contain Digestive enzymes (acid Hydrolases. Diffusion is the net movement of particles (typically molecules from an area of high concentration to an area of low concentration by uncoordinated random movement Anything left in the food vacuole by the time it reaches the cytoproct (anus) is discharged via exocytosis. Exocytosis (ek-soh-sy-TOH-sis Greek: Έξω - external and κύτος - cell is the durable process by which a cell directs secretory vesicles out of the Cell Most ciliates also have one or more prominent contractile vacuoles, which collect water and expel it from the cell to maintain osmotic pressure, or in some function to maintain ionic balance. These often have a distinctive star-shape, with each point being a collecting tube.
Feeding
Most ciliates feed on smaller organisms (heterotrophic), such as bacteria and algae, and detritus swept into the oral groove (mouth) by modified oral cilia. The Bacteria ( singular: bacterium) are a large group of unicellular Microorganisms Typically a few Micrometres in length bacteria have Algae ( sing. alga are a large and diverse group of simple typically Autotrophic organisms ranging from Unicellular to Multicellular forms This usually include a series of membranelles to the left of the mouth and a paroral membrane to its right, both of which arise from polykinetids, groups of many cilia together with associated structures. The food is moved by the cilia through the mouth pore into the gullet, which forms food vacuoles.
This varies considerably, however. Some ciliates are mouthless and feed by absorption, while others are predatory and feed on other protozoa and in particular on other ciliates. This includes the suctoria, which feed through several specialized tentacles
Reproduction
Ciliates can undergo both asexual and sexual reproduction. Asexual reproduction occurs by binary fission. The micronucleus undergoes by mitosis and the macronucleus elongates and splits in half. Both new cells each obtain a copy of the micronucleus and macronucleus. Sexual reproduction involves conjugation, which involve two cells. After conjugation, the two cells divide, forming four new cells.
Specialized structures
In some forms there are also body polykinetids, for instance, among the spirotrichs where they generally form bristles called cirri. The spirotrichs are a large and distinctive group of Ciliate protozoa More often body cilia are arranged in mono- and dikinetids, which respectively include one and two kinetosomes (basal bodies), each of which may support a cilium. These are arranged into rows called kineties, which run from the anterior to posterior of the cell. The body and oral kinetids make up the infraciliature, an organization unique to the ciliates and important in their classification, and include various fibrils and microtubules involved in coordinating the cilia. Microtubules are one of the components of the Cytoskeleton. They have a diameter of 25 nm and length varying from 200 nanometers to 25 micrometers
The infraciliature is one of the main component of the cell cortex. Another are the alveoli, small vesicles under the cell membrane that are packed against it to form a pellicle maintaining the cell's shape, which varies from flexible and contractile to rigid. Numerous mitochondria and extrusomes are also generally present. In Cell biology, a mitochondrion (plural mitochondria) is a membrane-enclosed Organelle found in most eukaryotic cells. Extrusomes are membrane-bound structures in some Eukaryotes which under certain conditions discharge their contents outside the cell The presence of alveoli, the structure of the cilia, the form of mitosis and various other details indicate a close relationship between the ciliates, Apicomplexa, and dinoflagellates. The dinoflagellates are a large group of Flagellate Protists Most are marine Plankton, but These superficially dissimilar groups make up the alveolates. The alveolates ("with cavities" are a major line of Protists There are three phyla, which are very divergent in form but are now known to be close relatives
Fossil record
Until recently, the oldest ciliate fossils known were tintinnids from the Ordovician Period. Tintinnids are Ciliates of the choreotrich Taxon Tintinnida, distinguished by vase-shaped shells called Loricae which are mostly protein but The Ordovician is a geologic period and system, the second of six of the Paleozoic era, and covers the time between 488 In 2007, Li et al. published a description of fossil ciliates from the Doushantuo Formation, about 580 million years ago, in the Ediacaran Period. The Doushantuo Formation is a lagerstätte in Guizhou Province China that is notable for being one of the oldest Fossil beds to contain highly The Ediacaran Period (ˌiːdiˈækərən named after the Ediacara Hills of South Australia) is the last geological period of the Neoproterozoic These included two types of tintinnids and a possible ancestral suctorian. Suctoria are peculiar Ciliates which are sessile feed by extracellular digestion and lack cilia in the adult phase [1]
Classification
Phylum Ciliophora
- Class Karyorelictea
- Class Heterotrichea (e. The heterotrichs are a class of Ciliates They typically have a prominent adoral zone of membranelles circling the mouth used in locomotion and feeding and shorter Cilia g. Stentor)
Stentor roeseli - Class Spirotrichea
- Subclass Choreotrichia (e. Stentor are a group of filter feeders and diggers a Genius of Ciliate Protozoa, representative of the Heterotrichs The body is generally The spirotrichs are a large and distinctive group of Ciliate protozoa The choreotrichs are a group of small marine Ciliates Their name reflects the impression that they appear to dance ('choreo' as in choreography g. Tintinnidium)
- Subclass Oligotrichia (e. The oligotrichs are a group of Ciliate Protozoa, included among the Spirotrichs They have prominent oral Cilia, which are arranged as a collar g. Halteria)
- Subclass Stichotrichia (e. The stichotrichs are a group of Ciliate Protozoa, included among the Spirotrichs Like the Hypotrichs with which they were originally classified g. Stylonychia)
- Subclass Hypotrichia (e. Stylonychia is a genus of Ciliate, included among the Stichotrichs It is very common in fresh water and soil found on filamentous algae surface films The hypotrichs are a group of Ciliate protozoa included among the Spirotrichs Most are oval in shape with a rigid pellicle and have cirri distributed in isolated g. Euplotes)
- Class Litostomatea
- Subclass Haptoria (e. The Litostomatea are a class of Ciliate Protozoa, divided into two groups ranked as subclasses g. Didinium)
- Subclass Trichostomatia (e. Didinium is a Genus of Ciliate. They are free-living Carnivores, mostly found in fresh and Brackish Water environments g. Balantidium)
- Class Phyllopharyngea
- Subclass Phyllopharyngia
- Subclass Rhynchodia
- Subclass Chonotrichia
- Subclass Suctoria (e. Balantidium coli is a species of Ciliate Protozoan. This parasite is the only member of this family known to be Pathogenic to humans A trophozoite (G trope, nourishment + zoon, animal is the activated feeding stage in the life cycle of protozoan Parasites such as the malaria-causing Balantidium coli is a species of Ciliate Protozoan. This parasite is the only member of this family known to be Pathogenic to humans The Phyllopharyngea are a class of Ciliate protozoa including some which are extremely specialized Suctoria are peculiar Ciliates which are sessile feed by extracellular digestion and lack cilia in the adult phase g. Podophrya)
- Class Nassophorea
- Class Colpodea (e. The Nassophorea are a class of Ciliate protozoa Members are free-living usually in freshwater but also in marine and soil environments The Colpodea are a class of Ciliate protozoa common in freshwater and soil habitats g. Colpoda)
- Class Prostomatea (e. g. Coleps)
- Class Oligohymenophorea
- Subclass Peniculia (e. The Oligohymenophorea are a large class of Ciliate protozoa There is typically a ventral groove containing the mouth and distinct oral cilia separate from those of the body The peniculids are an order of Ciliate protozoa including the well-known Paramecium and its close relatives g. Paramecium)
- Subclass Hymenostomatia (e. Paramecia are a group of Unicellular Ciliate Protozoa formerly known as “slipper Animalcules from their Slipper shape are commonly The hymenostomes are an order of Ciliate protozoa Most are free-living in freshwater such as the commonly studied genus Tetrahymena, but some are parasitic g. Tetrahymena)
- Subclass Scuticociliatia
- Subclass Peritrichia (e. Tetrahymena are free-living Ciliate Protozoa that can also switch from commensalistic to Pathogenic modes of survival The peritrichs are a large and distinctive group of Ciliate Protozoa. g. Vorticella)
- Subclass Astromatia
- Subclass Apostomatia
- Class Plagiopylea
References
- ^ Li, C. Vorticella is a genus of Protozoa, with over 100 known species Astomes (order Astomatida) are a group of Ciliate protozoans commonly found in the guts of Annelid worms especially Oligochaetes and other The plagiopylids are a small order of Ciliate protozoa including a few forms common in anaerobic habitats -W. ; et al (2007). "Ciliated protozoans from the Precambrian Doushantuo Formation, Wengan, South China". Geological Society, London, Special Publications 286: 151–156. doi:. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document.
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