Re: A very hairy Elysia

Dear Cory,

This is a very interesting observation. I suspected the branching gill-like papillae were retractile because they seem to be there sometimes and not at other times, but I must admit your onservation that they are apparently reabsorbed, makes using 'hairiness'  as a character  a rather risky businesss.  Obviously the presence of 'hairiness' could still be a useful identifier, but we couldn't use the absence of 'hairiness' to exclude an animal from being E. tomentosa. It would seem that the pink parapodial border may be a useful character. It is certainly present in your animals. One of the reasons I hesitated with Brian Mayes' animals [message #22036] was that they lacked any sign of pink along the parapodial edge.

Concerning Elysia sp. 3. That is another interesting suggestion. Although it a much deeper green than other photos we have, it has a pinkish edge to the parapodia, and the blue spot on its 'neck' links it to some other photos of animals with branched papillae and a pink border to the parapodia such as in Jun Imamoto's message #10567.

Concerning the animal in Jun Imamoto's message #10564, as I commented at the time, I also think it is not the same species as those in the other messages sent at that time.

If all these are indeed one species, it looks as though none of the characters mentioned  ['hairiness', blue spot on neck, pink parapodial border] are always present. Interestingly in Jun Imamoto's message #10567 I list these three characters - and a few more - and suggest they could define a species - but may not always be present. This is a bit awkward, but if it does turn out to be so, then this is a very good example of why looking at many specimens can be a very valuable activity. When I get a moment I will have to see just how many of the animals I presently have as Elysia cf tomentosa fit this broader concept of E. tomentosa.

Aside from the identification question, I was excited by your suggestion that the branching papillae contained digestive gland ducts. This suggests that as well as any camouflage function, the papillae are involved with the feeding physiology of the animal and perhaps even the 'farming' of chloroplasts. Your mention of keeping them in low light conditions reminds me of keeping the strange coral-feeding nudibranch Pinufius rebus in the dark [see Fact Sheet] to see what happened to it and its symbiotic zooxanthellae, only to find after a week that all its mantle papillae had been reabsorbed and the zooxanthellae ejected. Perhaps the loss of papillae in your animals was similarly related to unsatisfactory low light conditions for their captive chloroplasts. Certainly an interesting co-incidence which would be worth following up.

Best wishes,
Bill Rudman