Re: A very hairy Elysia

November 27, 2008
From: Cory Pittman

Concerning message #22036:

Dear Bill,
I've spent a lot of time in Hawaii and have kept Elysia tomentosa alive for several weeks on a number of occasions, feeding them on various Caulerpa spp.

On three occasions, I've held relatively "hairy" animals for several weeks with food but under fairly low light. In all three cases, they changed from having long, slender branching papillae with branches of the digestive gland in their centers to having low, conical unbranched papillae that lacked visible branches of the digestive gland. The attached photos illustrate this. The first is of a 14 mm animal taken shortly after capture on June 7, 2005. The second is of the same animal on July 18, 2005. It was fed intermittently with Caulerpa but didn't increase in length over that period. Since the initial and end states roughly cover the range of variation seen in the field in Hawaii, the ability of single individuals to switch between the two (in at least one direction) would probably argue against using the degree of "hairiness" to split the species. Of course, I'm by no means certain that it won't be found to be a complex based on other traits...

Locality: Hekili Point, Maui, 1 m, Hawaii, USA, Pacific, 7 June 2005, back reef. Length: 14 mm. Photographer: Cory Pittman.

By the way, Pauline and I have our site on-line now so, if I may be permitted a bit of "shameless promotion," you can see more photos of Hawaiian E. tomentosa at: http://seaslugsofhawaii.com/species/Elysia-tomentosa-a.html

Also, two other suggestions regarding photos of E. tomentosa on the forum:

To me, it seems likely that Elysia sp. #3 is a juvenile E. tomentosa.

Meanwhile, I think Jun Imamoto's photo (message #10564 ) probably falls outside the "E. tomentosa complex." That species has relatively thick parapodia that form long, narrow lobes with in-rolled margins. It also has relatively thick rhinophores, no marginal lines and evenly scattered, dark green flecks. She has photos of two more animals on her site (in addition to the ones she sent you)--shots 12, 13, 14, 31, 32, 33 & 36 (juv.) at: http://www.umiushi.info/kanri/photo_sql_eng.php?act=PSP&gakumei1=Elysia&gakumei2=cf.+tomentosa&location_code=0000

We also have it from Hawaii: http://seaslugsofhawaii.com/species/Elysia-sp5-a.html

I hope this will be of interest.
Best wishes,
Cory

cory@cet.com

Pittman, C. C., 2008 (Nov 27) Re: A very hairy Elysia. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/22052

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

Rudman, W.B., 2008 (Nov 27). Comment on Re: A very hairy Elysia by Cory Pittman. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/22052

Related messages

  1. Elysia expansa? from India
    From: Vishal Bhave, November 6, 2009
  2. Re: Elysia tomentosa from Ratnagiri, India
    From: Vishal bhave, May 15, 2009
  3. Re: Elysia tomentosa from Ratnagiri, India
    From: Cynthia D. Trowbridge, May 13, 2009
  4. Elysia tomentosa from Ratnagiri, India
    From: Vishal Jayant Bhave, May 12, 2009
  5. Elysia tomentosa from Moreton Bay, Queensland
    From: Stan O'Donnell, August 25, 2008
  6. Elysia tomentosa from Turkey
    From: Carol Cox, April 18, 2008
  7. Elysia tomentosa from Japan
    From: Hironori Ozaki, November 22, 2005
  8. Re: Elysia cf. tomentosa from Turkey
    From: M. Baki Yokes, October 15, 2005
  9. Re: Elysia cf. tomentosa from Turkey
    From: Ferda Buyukbaykal, October 14, 2005
  10. Elysia cf. tomentosa from Turkey
    From: Ferda Buyukbaykal, October 11, 2005
  11. Elysia tomentosa from Hawaii
    From: Keoki Stender, October 4, 2003
  12. Re: Elysia on Caulerpa taxifolia
    From: Tim Glasby, August 18, 2003
  13. Re: Elysia on Caulerpa taxifolia
    From: Kathe R. Jensen, August 7, 2003
  14. Elysia tomentosa from Abrolhos Islands
    From: Kathe R. Jensen, August 7, 2003
  15. Re: Elysia on Caulerpa taxifolia
    From: Baki Yokes, August 1, 2003
  16. Elysia on Caulerpa taxifolia
    From: Tim Glasby, July 25, 2003
  17. Elysia pilosa & E. tomentosa
    From: Bill Rudman, July 25, 2003
  18. Elysia tomentosa - colour variation
    From: Bil Rudman, July 25, 2003
  19. Re: Elysia tomentosa in the Mediterranean?
    From: Kathe R. Jensen, May 20, 2002
  20. Elysia tomentosa in the Mediterranean?
    From: Baki Yokes, May 16, 2002
  21. Elysia tomentosa in the Mediterranean?
    From: Rob Brown, May 7, 2002
  22. Re: An alien? from Turkey
    From: Kathe R. Jensen, January 17, 2002
  23. Re: An alien? from Turkey
    From: Baki Yokes, January 16, 2002
  24. Re: An alien? from Turkey
    From: Kathe R. Jensen, January 15, 2002
  25. An alien? from Turkey
    From: Baki Yokes, January 14, 2002
  26. Re: Elysia pilosa?
    From: Kathe R. Jensen, April 16, 1999
  27. Elysia pilosa from Sulawesi
    From: Lindsay Warren, March 24, 1999
  28. ?Elysia pilosa
    From: David & Leanne Atkinson, March 19, 1998

Show factsheet and all related messages