Seisonidae is a family of

rotifer The rotifers (, from the Latin , "wheel", and , "bearing"), commonly called wheel animals or wheel animalcules, make up a phylum (Rotifera ) of microscopic and near-microscopic pseudocoelomate animals. They were first described by Rev. John H ...

s, found on the gills of ''

Nebalia ''Nebalia'' is a large genus of small crustaceans containing more than half of the species in the order Leptostraca, and was first described by William Elford Leach William Elford Leach FRS (2 February 1791 – 25 August 1836) was an Engl ...

'', a marine

crustacean Crustaceans (Crustacea, ) form a large, diverse arthropod taxon which includes such animals as decapoda, decapods, ostracoda, seed shrimp, branchiopoda, branchiopods, argulidae, fish lice, krill, remipedes, isopoda, isopods, barnacles, copepods, ...

. Peculiar among rotifers, males and females are both present and equal in size. Males and females are similar with paired

gonads A gonad, sex gland, or reproductive gland is a mixed gland that produces the gametes and sex hormones of an organism. Female reproductive cells are egg cells, and male reproductive cells are sperm. The male gonad, the testicle, produces sper ...

. It is considered to have diverged from the other rotifers early on, and in one treatment is placed in a separate

class Class or The Class may refer to: Common uses not otherwise categorized * Class (biology), a taxonomic rank * Class (knowledge representation), a collection of individuals or objects * Class (philosophy), an analytical concept used differently ...

Seisonoidea. They have a large and elongate body with reduced corona. Their muscular system is similar to that of other rotifers: they have longitudinal muscles as well as open annular muscles.

Species

Two genera with total three species belong to Seisonidae: * ''

Paraseison ''Paraseison'' is a monotypic genus of rotifers belonging to the family Seisonidae Seisonidae is a family of rotifers, found on the gills of ''Nebalia'', a marine crustacean. Peculiar among rotifers, males and females are both present and equa ...

'' Plate, 1887 ** ''

Paraseison annulatus ''Paraseison'' is a monotypic genus of rotifers belonging to the family Seisonidae Seisonidae is a family of rotifers, found on the gills of ''Nebalia'', a marine crustacean. Peculiar among rotifers, males and females are both present and equa ...

'' (Claus, 1876) —

ectoparasite 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 ...

of ''Nebalia'' * ''

Seison ''Seison'' is a genus of rotifers belonging to the family Seisonidae. Species: *'' Seison africanus'' *'' Seison nebaliae'' References {{Taxonbar, from=Q1042298 Rotifer genera Pararotatoria ...

'' Grube, 1861 ** ''

Seison nebaliae ''Seison'' is a genus of rotifers belonging to the family Seisonidae. Species: *'' Seison africanus'' *'' Seison nebaliae'' References {{Taxonbar, from=Q1042298 Rotifer genera Pararotatoria ...

'' Grube, 1861 –

commensal Commensalism is a long-term biological interaction (symbiosis) in which members of one species gain benefits while those of the other species neither benefit nor are harmed. This is in contrast with mutualism, in which both organisms benefit fro ...

of ''Nebalia'' ** ''

Seison africanus ''Seison'' is a genus of rotifers belonging to the family Seisonidae. Species: *'' Seison africanus'' *''Seison nebaliae ''Seison'' is a genus of rotifers belonging to the family Seisonidae. Species: *'' Seison africanus'' *'' Seis ...

'' Sorensen, Segers & Funch, 2005 — host is unknown.

References

Pararotatoria Rotifer families {{Rotifer-stub