Adalaria proxima
(Alder & Hancock, 1854)

Suborder: DORIDINA
Family: Onchidorididae


Boreo-Arctic. Nth Atlantic: Known from east Greenland and southwards along the Nth American coast to southern Massachusetts, USA. Common around Iceland, Norway, the Baltic and south to the British Isles. Intertidal to 60m. Nth Pacific: From southern British Columbia, Canada to Sth Korea.


Strangford Lough, Co. Down, Northern Ireland, 28 April 2001. On bryozoan Electra pilosa. Photo: Bernard Picton.

Very similar in shape, colour variation, food and habitat to Onchidoris muricata. It grows to a larger size (17-25mm - compared to 12mm for O. muricata), and the mantle papillae taper to a slender rounded tip while in O. muricata they are flattened with projecting spicules.

It feeds preferentially on Electra pilosa which grows on brown algae, but will eat other encrusting bryozoans if necessary. Both species spawn from February to May (late winter, Spring) so only juveniles are present during Summer months. Differs from O. muricata in having larger eggs which hatch after approx 40 days into lecithotrophic non-feeding planktonic larvae.

Authorship details
Rudman, W.B., 2001 (July 5) Adalaria proxima (Alder & Hancock, 1854). [In] Sea Slug Forum. Australian Museum, Sydney. Available from

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