''Kentrophoros'' is a genus of

ciliates 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 ...

in the class

Karyorelictea Karyorelictea is a class of ciliates in the subphylum Postciliodesmatophora. Most species are members of the microbenthos community, that is, microscopic organisms found in the marine interstitial habitat, though one genus, ''Loxodes'', is foun ...

. Ciliates in this genus lack a distinct oral apparatus and depend primarily on

symbiotic bacteria Symbiotic bacteria are bacteria living in symbiosis with another organism or each other. For example, rhizobia living in root nodules of legumes provide nitrogen fixing activity for these plants. Symbiosis was first defined by Marko de Bary in 186 ...

for their nutrition.

Systematics

''Kentrophoros'' is the sole genus in the family Kentrophoridae Jankowski 1980. The type species of the genus is ''K. fasciolatus'' Sauerbrey 1928, first described from the

Bay of Kiel The Bay of Kiel or Kiel Bay (, ; ) is a bay in the southwestern Baltic Sea, off the shores of Schleswig-Holstein in Germany and the islands of Denmark. It is connected with the Bay of Mecklenburg in the east, the Little Belt in the northwest, ...

. Synonyms are ''Centrophorus'' Kahl 1931 (an illegitimate synonym because the name was already used for a genus of sharks) and ''Centrophorella'' Kahl 1935. Fifteen species of ''Kentrophoros'' have been formally described, although several of these names may be synonyms for the same species.

Description

The ciliates are long and ribbon-shaped, like other karyorelictean ciliates that live in the marine interstitial habitat. In some species, the cell body is folded or involuted into a tube or more elaborate shapes. The ventral side is

ciliated The cilium, plural cilia (), is a membrane-bound organelle found on most types of eukaryotic cell, and certain microorganisms known as ciliates. Cilia are absent in bacteria and archaea. The cilium has the shape of a slender threadlike projecti ...

, while the dorsal side is mostly unciliated except for a single "circle kinety" at the margin. The dorsal side is covered with a single layer of symbiotic bacteria. ''Kentrophoros'' lacks a distinct oral apparatus, although densely-spaced kinetids associated with fibers (nematodesmata) at the anterior part of the cell may be vestiges of the oral apparatus. The number and arrangement of nuclei within the cell are also variable between species. Some species have only one

micronucleus Micronucleus is the name given to the small nucleus that forms whenever a chromosome or a fragment of a chromosome is not incorporated into one of the daughter nuclei during cell division. It usually is a sign of genotoxic events and chromosomal i ...

and two

macronuclei A macronucleus (formerly also meganucleus) is the larger type of nucleus in ciliates. Macronuclei are polyploid and undergo direct division without mitosis. It controls the non-reproductive cell functions, such as metabolism. During conjugation, t ...

, but others can have multiple clusters of macro- and micronuclei, or so-called "composite nuclei" where each cluster of macro- and micronuclei is enclosed in another membrane. ''Kentrophoros'' live in coastal

marine sediments Marine sediment, or ocean sediment, or seafloor sediment, are deposits of insoluble particles that have accumulated on the seafloor. These particles have their origins in soil and rocks and have been transported from the land to the sea, mainly ...

, where they prefer the interface between

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