Polycera quadrilineata is a medium sized polycerid
nudibranch. It is white in colour, occasionally with
diffused black pigmentation and feeds on the bryozoan
Membranipora sp., which grows on Posidonia oceanica
and other macroalgae. It is found in different habitats
and colour varieties may prefer different habitats.
Propodial tentacles: Foot expanded with yellow
colouration at the edge. Oral processes: 4 in number (occasionally 6, but never
more), very long, white in colour with yellow tips. Rhinophores: Long and rather wide, lamellate,
non-retractile, white with yellow tips. Gills: Simple pinnate, white with yellowish tips. Body: Polycerid like, base colour is white with dotted or
continuous longitudinal lines on the back, but diffused
black pigmentation may or may not be present; two large
finger-like appendages present dorso-laterally alongside
gills, white with yellow tips. Foot: Transparent white in colour, expanded at the
anterior end with yellow pigment deposit.
Size range: 4-15mm. Common in some areas.
Specific characteristics: This species is easily identified
in the field, the 4 oral processes, its shape and the
yellow/white colour are typical characters for this