Re: Development in Elysia obtusa

September 16, 2002
From: Kathe Jensen

Dear Bill,
I think that the animal in the pictures is a damaged specimen in which the left parapodium has started to regenerate (no white pigment along the border), and the remains of the right parapodium is sort of hanging loose because most of the foot has been lost as well. There also seems to have been damage to the head. The rhinophores are missing, which could indicate a recently metamorphosed animal. However, the anteriormost part of the head also looks strange. It seems that the pedal lobes extend far beyond the head (and there seem to be 3?). Most Elysias are less than 1 mm when they metamorphose, and at that stage there is no trace of parapodia. The visceral mass uncoils when the shell is lost, but trails after the foot for maybe 2-3 days. Most Elysias have dark pigment on the "face" just after metamorphosis and very little of the adult
pigmentation. In this animal the yellow adult colour is prominent, and the white pigment on the border of the right parapodium and pericardium also points against this being a recently metamorphosed animal. Probably this animal has only survived because it has been in a protected tide-pool. Otherwise sacoglossans that have lost most of their foot cannot attach to the substrate very well and they are dislodged from their food algae very easily.

You can find drawings of postmetamorphic development in E. subornata [as Elysia "cauze"] and E. timida in the papers listed below.

References:
• Clark, K.B., Busacca, M. & Stirts, H. 1979. Nutritional aspects of development of the ascoglossan, Elysia cauze. In: Reproductive Ecology of Marine Invertebrates (S.E. Stancyk, ed.), pp. 11-24. Univ. S. Carol. Press, Columbia, SC.
• Marin, A. & Ros, J. 1993. Ultrastructural and ecological aspects of the development of chloroplast retention in the sacoglossan gastropod Elysia timida. Journal of Molluscan Studies, 59: 95-104.

Best wishes,
Kathe

jensen@ait.ac.th

Jensen, K., 2002 (Sep 16) Re: Development in Elysia obtusa. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/7961

Thanks Kathe,
Bill Rudman

Factsheet

Elysia obtusa

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