Adalaria proxima

(Alder & Hancock, 1854)

Body length up to 25 mm, yellow-orange in colour, sometimes very pale. The ample mantle bears abundant spiculose tubercles which are taller and more slender towards the periphery. The rhinophores are often darker than the rest of the body and each bears up to nineteen lamellae. Up to twelve gills are present, surrounding the anal papilla. The head is dilated to form a semi-circular oral veil, lacking tentacular processes.
This species is easily confused with Onchidoris muricata. A. proxima has a generally deeper colour (but not in the extreme north), the rhinophores are more bluntly tipped and the digestive gland (visible through the translucent pedal sole) extends further forwards. But it must be admitted that yellowish specimens of 0nchidoris muricata can only be distinguished from pale A. proxima by examination of the radula.

A. proxima feeds preferentially upon the common intertidal polyzoan Electra pilosa, which usually thrives attached to alga Other polyzoans are also eaten.

The nudibranch appears to be a boreo-arctic species, common in the North Sea (Distr. A. proxima). Further distribution from East Greenland and the White Sea to the Baltic and Massachusetts, to 60 m.