On Elysia japonica, E. abei & E. amakusana

September 13, 2002
From: Skip Pierce

Hi Bill
I don't know the species that are being discussed here, but having looked at several Atlantic (and from Hawaii) species of Elysia in aquaria for many months as we continue to study the cell biology of the captured chloroplasts, I'm of the opinion that color is not a useful tool to distinguish species amongst Elysia species with otherwise similar morphology. As you allude, color may depend a lot on what they've eaten lately. Contrary to the literature, we've found that some (but not all) species will eat all kinds of algae (and possibly bacterial films)which could effect their color - although the plastids are captured from a single algal species (although, again, some Elysia species may be able to capture plastids from more than one algal species - on which I'll publish a paper if we get enough data). Also, generally, brown colored Elysia are those who are nearing the end of their life cycle and have lost their plastids - sort of like a leaf on a tree (homage to Trench) in the fall [autumn] - some will "re-green" if provided the correct algal species. Many species of Elysia have tiny red (and also blue) pigment clusters when you look closely. I don't know what the clusters are - nice master's thesis project there, but maybe someone else has looked at it already. Other species of Elysia turn yellow when they lose their chloroplasts and many years ago, Bleakney reported E. chlorotica "ghosts" which were white when not fed, but which we cross-bred with green E. chlorotica - thus likely the same species, just can't take up the chloroplasts. So, color may not be a reliable characteristic in Elysia spp. The answer to all these relationships will eventually be found from molecular evidence, of course, but the pictures are great in the meantime.

Hope you enjoyed your break.

Skip Pierce
Professor and Chair
Department of Biology
University of South Florida
Tampa, FL

pierce@chuma1.cas.usf.edu

Pierce, S., 2002 (Sep 13) On Elysia japonica, E. abei & E. amakusana. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/7932

Thanks Skip,
These sacoglossans are fascinating beasts. I have previously referred to Brian Brandley's 1984 study on an Elysia species here is Sydney which he showed changed food and plastids and hence colour during it life cycle, so its great to hear that you are making similar observations. I agree that colour in Elysia is a difficult character to use but I suspect many of these species can be identified as 'species' at the local level even if names are difficult to apply. People working with local populations soon get a 'feel' for similarities and differences. They are not always right, but with a little confirmation from the anatomy, it is not that difficult to get to know the range of colour and shape variation that exists in local populations. Until we have a better idea on variability within local populations I think it is very difficult to say anything sensible about variability on a wider geographic scale. That is why I welcome photos on the Forum showing colour variation in even the most common animals.

I hope your present research yields results, and look forward to reading about them in the future
Best wishes,
Bill Rudman

Rudman, W.B., 2002 (Sep 13). Comment on On Elysia japonica, E. abei & E. amakusana by Skip Pierce. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/7932

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