Four-Lined Polycera

Polycera quadrilineata is a sea slug, a species of dorid nudibranch. It is a marine gastropod mollusc in the family Polyceridae. The specific epithet quadrilineata means four-lined and refers to the four longitudinal black lines present on the original specimen. This species is sometimes called the fourline nudibranch.

Description

The fourline 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, though these can be absent. The head has four or occasionally six yellow projections. The gills and rhinophores are translucent white, tipped with yellow. In the South African animals the gills and rhinophores are black, and may be spotted with yellow. Alongside the gills is a pair of yellow-tipped projections. The animal may reach 20 mm in total length. It is distinguished from the crowned nudibranch in having raised yellow spots on the mid-dorsal region.

Distribution

This nudibranch is described originally from Norway. In the NE Atlantic it is a common species in shallow water. It is distributed from Greenland to Norway and south along the European coasts into the Mediterranean Sea. It has also been reported off the South African coast from the Atlantic coast of the Cape Peninsula to Algoa Bay. The South African animals differ in having six instead of four papillae projecting from the frontal margin of the head, plus details of the coloration. It is found from the intertidal zone to 160 m.

Ecology

Polycera quadrilineata feeds mostly on the bryozoans Membranipora membranacea and Electra pilosa.