''Climacostomum virens'' is a species of

unicellular A unicellular organism, also known as a single-celled organism, is an organism that consists of a single cell, unlike a multicellular organism that consists of multiple cells. Organisms fall into two general categories: prokaryotic organisms and ...

ciliate The ciliates are a group of alveolates characterized by the presence of hair-like organelles called cilia, which are identical in structure to flagellum, eukaryotic flagella, but are in general shorter and present in much larger numbers, with a ...

protist A protist ( ) or protoctist is any eukaryotic organism that is not an animal, land plant, or fungus. Protists do not form a natural group, or clade, but are a paraphyletic grouping of all descendants of the last eukaryotic common ancest ...

s. It is one of just two formally described species in the genus

Climacostomum ''Climacostomum'' is a genus of unicellular ciliates, belonging to the class Heterotrichea. The genus has one well-described species, ''Climacostomum virens'', which usually carries a symbiotic alga, a variety of ''Chlorella'' that can be culti ...

Description

''Climacostomum virens'' has a flexible but non-contractile body, long, roughly ovoid or harp-shaped, and flattened from back to front. It has a large posterior

contractile vacuole A contractile vacuole (CV) is a sub-cellular structure (organelle) involved in osmoregulation. It is found predominantly in protists, including unicellular algae. It was previously known as pulsatile or pulsating vacuole. Overview The contrac ...

, and a characteristic posterior indentation, or dimple, that is more pronounced in underfed individuals. The posterior vacuole surrounds the cytoproct (anus), through which

food waste The causes of food going uneaten are numerous and occur throughout the food system, during food production, production, food processing, processing, Food distribution, distribution, Grocery store, retail and food service sales, and Social clas ...

is eliminated. The macronucleus of ''Climacostomum virens'' is normally long and wormlike (vermiform). The cell's most prominent feature is its large oral apparatus, which occupies most of the anterior region. This structure features an adoral zone of

membranelle Membranelles (also membranellae) are structures found around the mouth, or cytostome, in ciliates. They are typically arranged in series, to form an "adoral zone of membranelles", or AZM, on the left side of the buccal cavity (peristome). The membra ...

s (AZM) partly encircling a wide buccal cavity (mouth), which opens into the cytopharyngeal pouch where digestive vacuoles are formed before they travel down a distinctive long, bent tube into the body of the cell. Members of the species are normally green, because of symbiotic algae (

zoochlorella Zoochlorella (: zoochlorellae) is a colloquial term for any green algae that lives symbiotically within the body of an aquatic invertebrate animal or a protozoan. Classification Zoochlorellae are various genera belonging to the classes Chlo ...

e) that live in the

cytoplasm The cytoplasm describes all the material within a eukaryotic or prokaryotic cell, enclosed by the cell membrane, including the organelles and excluding the nucleus in eukaryotic cells. The material inside the nucleus of a eukaryotic cell a ...

. When individuals are grown in the dark, these algal

endosymbionts An endosymbiont or endobiont is an organism that lives within the body or cells of another organism. Typically the two organisms are in a mutualistic relationship. Examples are nitrogen-fixing bacteria (called rhizobia), which live in the root ...

are reduced in number and the cytoplasm may appear colorless. Climacostomum from Friedrich Stein

Classification

The species ''Climacostomum virens'' was first described in 1833 by

Christian Gottfried Ehrenberg Christian Gottfried Ehrenberg (19 April 1795 – 27 June 1876) was a German Natural history, naturalist, zoologist, Botany, botanist, comparative anatomist, geologist, and microscopy, microscopist. He is considered to be one of the most famous an ...

, under the name ''Spirostomum virens''. In 1859, Samuel Friedrich von Stein moved ''Spirostomum virens'' to a new genus, which he named ''Climacostomum''. In his ''Manual of Infusoria'' (1880),

William Saville-Kent William Saville-Kent (10 July 1845 – 11 October 1908) was an English marine biologist, naturalist, Commissioner and Inspector of Tasmanian Fisheries and author. He is perhaps best-known for his work in the development of the artificial pearl ...

rejected Stein's genus, assigning the species instead to ''Leucophrys patula'', which he described as synonymous with Ehrenberg's ''Spirostomum virens'' and ''Leucophrys patula'', as well as the ''Trichoda patula'' of O.F. Muller. However, the genus was retained by later researchers, including Alfred Kahl.Kahl, Alfred. Urtiere oder Protozoa. I: Wimpertiere oder Ciliata (Infusoria), eine Bearbeitung der freilebenden und ectocommensalen Infusorien der Erde, unter Ausschluss der marinen Tintinnidae, 3. Spirotricha. In F. Dahl (Ed.), Die Tierwelt Deutschlands. p. 459

References

{{Taxonbar, from=Q5133379 Heterotrichea Ciliate species