''Meroselenidium'' is a

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial n ...

parasitic Parasitism is a close relationship between species, where one organism, the parasite, lives on or inside another organism, the host, causing it some harm, and is adapted structurally to this way of life. The entomologist E. O. Wilson ha ...

alveolates in the

phylum In biology, a phylum (; plural: phyla) is a level of classification or taxonomic rank below kingdom and above class. Traditionally, in botany the term division has been used instead of phylum, although the International Code of Nomenclatu ...

Apicomplexa The Apicomplexa (also called Apicomplexia) are a large phylum of parasitic alveolates. Most of them possess a unique form of organelle that comprises a type of non-photosynthetic plastid called an apicoplast, and an apical complex structure. The ...

. Species in this genus infect marine invertebrates.

Taxonomy

This genus was described by Mackinnon and Ray in 1933. There is one species in this genus – ''Meroselenidium keilini''.

Description

The trophozoites live within the gut lumen. They measure 200–300

μm The micrometre ( international spelling as used by the International Bureau of Weights and Measures; SI symbol: μm) or micrometer (American spelling), also commonly known as a micron, is a unit of length in the International System of Uni ...

× 40–70 μm. There are 30–40 grooves along the body. Four refringent rods are present in the

mucron A ''mucron'' is an attachment organelle found in archigregarines - an order of epicellular parasitic Conoidasida.Simdyanov TG, Guillou L, Diakin AY, Mikhailov KV, Schrével J, Aleoshin VV. (2017) A new view on the morphology and phylogeny of eugre ...

. A

vacuole A vacuole () is a membrane-bound organelle which is present in plant and fungal cells and some protist, animal, and bacterial cells. Vacuoles are essentially enclosed compartments which are filled with water containing inorganic and organic ...

may also be present in the mucron.

Schizogony Fission, in biology, is the division of a single entity into two or more parts and the regeneration of those parts to separate entities resembling the original. The object experiencing fission is usually a cell, but the term may also refer to how ...

occurs in the

intestinal epithelium The intestinal epithelium is the single cell layer that form the luminal surface (lining) of both the small and large intestine (colon) of the gastrointestinal tract. Composed of simple columnar epithelial cells, it serves two main functio ...

and gives rise to multiple

merozoites Apicomplexans, a group of intracellular parasites, have life cycle stages that allow them to survive the wide variety of environments they are exposed to during their complex life cycle. Each stage in the life cycle of an apicomplexan organism is ...

. Synergy is caudo-caudal. The gametocysts are 70 μm × 55 μm and give rise to multiple gametes. After fertilization the

zygote A zygote (, ) is a eukaryotic cell formed by a fertilization event between two gametes. The zygote's genome is a combination of the DNA in each gamete, and contains all of the genetic information of a new individual organism. In multicell ...

gives rise to ~20 sporocysts. There is no residual body. The sporocysts are bivalved and give rise to multiple sporozoites. The species in this genus, ''Merselenidium keilini'', forms transversely striated folds.

Life cycle

This species infects the anterior intestine of the

polychaete Polychaeta () is a paraphyletic class of generally marine annelid worms, commonly called bristle worms or polychaetes (). Each body segment has a pair of fleshy protrusions called parapodia that bear many bristles, called chaetae, which are ...

'' Potamilla reniformis''. The parasite infects the gastrointestinal tract and is presumably transmitted by the orofaecal route but the details of this mechanism are presently unknown.

References

Apicomplexa genera {{Apicomplexa-stub