Re: Costasiella ocellifera development types

March 4, 2004
From: Skip Pierce

Hi Bill
-This seems to be sacoglossan week. the situation you've described for Costasiella ocellifera in the Keys [#12361] reminded me of a paper I published 100 years or so ago (with Hillary West and June Harrigan -Veliger 26: 199-206) on Elysia chlorotica - same reproductive issue north and south of Cape Cod. Northern slugs are basically direct developers - veligers passed entirely in the egg - maybe a short (24hr or less) free swimming period. Southern slugs have a lengthy (couple of weeks) planktonic veliger. Clearly the 2 populations are the same species - we crossed them several times. As I recall the F1's had a sort of intermediate result - ie, shorter planktonic stage than the southern slugs, but longer than the northern. The environments north and south of the Cape are quite different with regard to things like summer water temps - but we never fooled around with that. Geographically the 2 populations are maybe only 50 miles apart - separated by the Cape, of course, but conjoined by the Cape Cod Canal which the southern veligers could easily traverse in a tidal cycle. So I agree that differences such as those you've pointed to in C. ocellifera in the Keys probably shouldn't be used at the species level without something else.

• West, H.H., Harrigan, J.F. & Pierce, S.K. (1984) Hybridization of two populations of a marine opisthobranch with different developmental patterns. The Veliger, 26(3) 199-206.


Pierce, S.K., 2004 (Mar 4) Re: Costasiella ocellifera development types. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

Thanks Skip,
Yes the sacoglossans are certainly getting a good run this week
Bill Rudman

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