Re: Adalaria proxima? from British Columbia?

October 9, 2003
From: Jeff Goddard

Hi Bill,
I agree with your suggestion that the onchidoridid in Marli Wakeling's recent photo is probably not Onchidoris muricata, based on the shape of the tubercles and the arrangement of the spicules in the center of the notum [in O. muricata the latter are visibly transverse and parallel]. However, assuming that the specimen was found on the substrate pictured (the bryozoan Membranipora), it may well be Adalaria jannae Millen, 1987. I found this species in abundance feeding and laying eggs on Membranipora growing on kelps in south central Alaska a couple of years ago (Goddard & Foster, 2002). At first glance I thought they were Onchidoris muricata, but the radula turned out to lack medial teeth and also had 4 to 6 small marginal teeth per half row. These traits, especially in specimens more than a few millimeters long, separate A. jannae from both O. muricata and A. proxima.

Millen (1987) also reported Adalaria jannae from Membranipora. In hindsight, my own report of Onchidoris muricata on Membranipora in Coos Bay (Goddard, 1998) is probably incorrect and needs confirmation. I did not look at the radula of those specimens, and I would now bet they were actually A. jannae.

• Goddard, J. H. R. (1998) A summary of the prey of nudibranchs from Cape Arago, Oregon. Opisthobranch Newsletter, 24(2): 11-14.
• Goddard, J. H. R. & N. R. Foster (2002) Range extensions of sacoglossan and nudibranch mollusks (Gastropoda: Opisthobranchia) to Alaska. The Veliger 45(4): 331-336.
• Millen, S. V. The nudibranch genus Adalaria, with a description of a new species from the northeastern Pacific. Canadian Journal of Zoology 65(11): 2696-2702.

Best wishes,
Jeff Goddard

Goddard, J. H., 2003 (Oct 9) Re: Adalaria proxima? from British Columbia?. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

Thanks Jeff,
I had looked at Sandra Millen's paper, and she said that the spicule pattern on the notum of A. jannae was similar to that of Onchidoris muricata and specifically compares it to A. proxima which she says differs in having a 'star-like pattern of spicules' at the base of the tubercles. A. proxima grows to a much larger size, but that character is only good in identifying a large specimen - Marli's 8mm long animal could be either. I agree that its presence on Membranipora is a point in favour of identifying it as A. jannae, but my understanding is that although A. proxima prefers Electra pilosa it will eat other encrusting bryozoans.

I guess my problem is that without an anatomical examnination, we can't be sure of this animal's identification, so it could probably lead to confusion if I were to move it to a Adalaria jannae page at this stage. If you have photos of this species which have been confirmed anatomically it would be great to add them to the Forum
Best wishes
Bill Rudman

Rudman, W.B., 2003 (Oct 9). Comment on Re: Adalaria proxima? from British Columbia? by Jeff Goddard. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from


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