Polycera quadrilineata
Ventral view
Polycera quadrilineata
Lateral view
Polycera quadrilineata with black pigment
Lateral view
Polycera quadrilineata
Polycera quadrilineata
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 species.

Identified by Dr. A Perrone.
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15mm, Dwejra-Gozo 37m depth 20/03/94
Marine species
Polycera quadrilineata (O.F. Müller, 1776)
5mm, Ghar Lapsi 3-5m depth, on algae 30/05/93
Lateral view of 4-5mm specimen found with the 8-9mm specimen on Posidonia oceanica
Ventral view
8-9mm, White Tower 21m depth 17/3/94 Leg. J.Borg
Posidonia oceanica
Lateral view of 15mm
4mm, Ahrax point 10m depth, on algae 27/02/94
15mm, Dwejra-Gozo 37m depth 20/03/94