The twin-crowned nudibranch,

scientific name In taxonomy, binomial nomenclature ("two-term naming system"), also called nomenclature ("two-name naming system") or binary nomenclature, is a formal system of naming species of living things by giving each a name composed of two parts, bot ...

''Polycera'' sp., as designated by Gosliner, 1987, is a

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

dorid ''Doridacea'' is a taxonomic grouping of dorid nudibranchs, shell-less marine gastropod mollusks.Bouchet P. & Rocroi J.-P. (Ed.); Frýda J., Hausdorf B., Ponder W., Valdes A. & Warén A. 2005''Classification and nomenclator of gastropod families ...

nudibranch Nudibranchs () are a group of soft-bodied marine gastropod molluscs which shed their shells after their larval stage. They are noted for their often extraordinary colours and striking forms, and they have been given colourful nicknames to matc ...

. It is a

marine Marine is an adjective meaning of or pertaining to the sea or ocean. Marine or marines may refer to: Ocean * Maritime (disambiguation) * Marine art * Marine biology * Marine debris * Marine habitats * Marine life * Marine pollution Military * ...

gastropod The gastropods (), commonly known as snails and slugs, belong to a large taxonomic class of invertebrates within the phylum Mollusca called Gastropoda (). This class comprises snails and slugs from saltwater, from freshwater, and from land. T ...

mollusc Mollusca is the second-largest phylum of invertebrate animals after the Arthropoda, the members of which are known as molluscs or mollusks (). Around 85,000 extant species of molluscs are recognized. The number of fossil species is esti ...

in the

family Family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its ...

Polyceridae The Polyceridae are a taxonomic family of sea slugs, dorid nudibranchs, marine gastropod mollusks within the superfamily Polyceroidea. Taxonomy The family Polyceridae is classified within the clade Doridacea, itself belonging to the clade Euct ...

. As of November 2009, it was undescribed by science.

Distribution

This species has been found off the

southern African Southern Africa is the southernmost subregion of the African continent, south of the Congo and Tanzania. The physical location is the large part of Africa to the south of the extensive Congo River basin. Southern Africa is home to a number of ...

coast off the

Cape Peninsula The Cape Peninsula ( af, Kaapse Skiereiland) is a generally mountainous peninsula that juts out into the Atlantic Ocean at the south-western extremity of the African continent. At the southern end of the peninsula are Cape Point and the Cape of ...

False Bay False Bay (Afrikaans ''Valsbaai'') is a body of water in the Atlantic Ocean between the mountainous Cape Peninsula and the Hottentots Holland Mountains in the extreme south-west of South Africa. The mouth of the bay faces south and is demarcat ...

and off

Durban Durban ( ) ( zu, eThekwini, from meaning 'the port' also called zu, eZibubulungwini for the mountain range that terminates in the area), nicknamed ''Durbs'',Ishani ChettyCity nicknames in SA and across the worldArticle on ''news24.com'' from ...

in 2–30 m.

Description

The twin-crowned nudibranch is a smooth-bodied variably coloured nudibranch. The ground colour is white or grey and there are usually black, yellow or orange stripes longitudinally along the

notum The notum (plural nota) is the dorsal portion of an insect's thoracic segment, or the dorsal surface of the body of nudibranch gastropods. The word "notum" is always applied to dorsal structures; in other words structures that are part of the back ...

, though these can be absent. The head has six yellow projections. The

gill A gill () is a respiratory organ that many aquatic organisms use to extract dissolved oxygen from water and to excrete carbon dioxide. The gills of some species, such as hermit crabs, have adapted to allow respiration on land provided they are ...

s and

rhinophore A rhinophore is one of a pair of chemosensory club-shaped, rod-shaped or ear-like structures which are the most prominent part of the external head anatomy in sea slugs, marine gastropod opisthobranch mollusks such as the nudibranchs, sea har ...

s are black, and may be spotted with yellow. There are raised yellow spots on the mid-dorsal region. Alongside the gills are two or three pairs of yellow projections, which differentiate the animal from the

crowned nudibranch The crowned nudibranch (''Polycera capensis'') is a species of dorid nudibranch. It is a marine gastropod mollusc in the family Polyceridae. Distribution This species is found off the southern African coast from Luderitz in Namibia to Port Alfr ...

and the fourline nudibranch. The animal may reach 30 mm in total length. A study using DNA sequencing found that there were two species amongst specimens identified as ''P. capensis'' and this species was categorized as ''Polycera'' sp. A.Palomar, G.; Pola, M.; Garcia-Vazquez, E. (2013). First molecular phylogeny of the subfamily Polycerinae (Mollusca, Nudibranchia, Polyceridae). Helgoland Marine Research. 68(1): 143-153.

Ecology

The egg ribbon of this species is a wavy white spiral collar.

References

{{Taxonbar, from=Q7858055 Polyceridae Undescribed gastropod species