Onchidoris muricata from New England

July 5, 2001
From: Paul Young

Hi, Bill,
These tiny animals are only about 5 mm in length. Locally they are called Little White Dorids. They are found on kelp. My wife (Charlotte Richardson) shot this one in Southern Maine. Since these animals are so small, these photos were taken with a 2x teleconverter on the RS 50mm macro lens, so you can see the structure of the rhinophores. The third photo is the egg mass.
We believe this is Lamellidoris muricata.
Paul Young.


Young, P., 2001 (Jul 5) Onchidoris muricata from New England. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/4712

Thanks Paul,
I am pretty sure this is Onchidoris muricata. The genus Lamellidoris is now considered to be the same as Onchidoris.

As you show in these beautiful photos, O. muricata is found associated with encrusting bryozoans, often found growing on kelp and other brown algae. In northern Europe it, and the very similar looking Adalaria proxima have been the subject of many ecological studies. Smith & Sebens, (1983), have published and account of their ecological work on the species on the Atlantic coast of North America (as Onchidoris aspera)

Their study site was at 6-10m in a sheltered bay at Nahant, Massachusetts. The bryozoan Electra pilosa was the main food source of Onchidoris which used its buccal pump to suck the bryozoan animals (zooids) from their individual cases. They showed that spawning occurred only between -1 to 4 degrees C demonstrating that O. muricata is a cold-adapted species, reproductively active during the coldest part of the year.

• Smith, D.A. & Sebens, K.P. (1983). The physiological ecology of growth and reproduction in Onchidoris aspera (Alder & Hancock) (Gastropoda: Nudibranchia). J. Exp. Mar. Biol. Ecol., 72: 287-304.

Best wishes,
Bill Rudman

Rudman, W.B., 2001 (Jul 5). Comment on Onchidoris muricata from New England by Paul Young. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/4712

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