''Polyascus'' is a genus of

barnacles Barnacles are arthropods of the subclass Cirripedia in the subphylum Crustacea. They are related to crabs and lobsters, with similar nauplius larvae. Barnacles are exclusively marine invertebrates; many species live in shallow and tidal water ...

in infraclass

Rhizocephala Rhizocephala are derived barnacles that are parasitic castrators. Their hosts are mostly decapod crustaceans, but include Peracarida, mantis shrimps and thoracican barnacles. Their habitats range from the deep ocean to freshwater. Together w ...

. It was

circumscribed In geometry, a circumscribed circle for a set of points is a circle passing through each of them. Such a circle is said to ''circumscribe'' the points or a polygon formed from them; such a polygon is said to be ''inscribed'' in the circle. * Circum ...

in 2003 by Henrik Glenner, Jørgen Lützen, and Tohru Takahashi. They included three species, all transferred from ''

Sacculina ''Sacculina'' is a genus of barnacles that is a parasitic castrator of crabs. They belong to a group called Rhizocephala. The adults bear no resemblance to the barnacles that cover ships, whales, and piers; they are recognised as barnacles beca ...

''. The generic name ''polyascus'' (''poly'' "many" + ''ascus'' "bag") refers to the typical presence of multiple external sac-like female bodies, known as ''externae''. In ''Polyascus'' species, these originate from asexual reproduction.

Species

WoRMS The World Register of Marine Species (WoRMS) is a taxonomic database that aims to provide an authoritative and comprehensive catalogue and list of names of marine organisms. Content The content of the registry is edited and maintained by scien ...

recognizes the following three species, all included in the genus's circumscription.

References

Barnacles Parasites of crustaceans Parasitic crustaceans Crustacean genera {{maxillopoda-stub