Ercolania fuscovittata or Stiliger fuscovittatus ?
March 3, 2006
From: Cynthia Trowbridge
Concerning message #13436:
Dear Bill,
Throughout temperate and tropical areas of the world, there are numerous sacoglossan opisthobranchs that feed selectively on red algal species belonging to the order Ceramiales; these sacoglossans belong to at least three sacoglossan genera: Hermaea, Stiliger, and Elysia.
Contrary to recent discussion on the Sea Slug Forum, the Pacific specimens of Stiliger fuscovittatus Lance, 1962 clearly belong to the genus Stiliger, not to Ercolania: (1) the teeth are blade-shaped, not sabot-shaped and(2) the species eats red algae, not septate, green algae (characteristic of Ercolania spp.). To my knowledge, there are no Ercolania spp. (as currently recognized) that feed on red algae.
Please excuse me for suggesting that it may not be appropriate to switch a species to another genus in the absence of a published report, particularly if there is strong evidence that the original genus identification is deemed correct by local malacologists. Kerry's specimen may or may not have been Ercolania; with no published record of Florida tooth shape, it is hard to determine. However, there are published records of teeth, feeding, etc. of the NE Pacific species (Lance 1962, Case 1972, Trowbridge 2002, references therein).
In private communication, Jim Lance expressed his concern about your change; I expressed my concern in message #13436. I note that David W. Behrens & Alicia Hermosillo (2005) also consider the species Stiliger fuscovittatus in their recent identification book. With at least four malacologists supporting the Stiliger position based on radular and dietary evidence, I wish you would change the Ercolania fuscovittata (Lance, 1962) back to its original name for the Pacific populations.
Finally, Jim added a new algal genus to the repertoire of genera consumed by Stiliger fuscovittatus (excerpt from letter from Jim Lance to Cynthia, 31 March 2005):
"To the algal food substrates of S. fuscovittatus may be added Dasya (San Diego). Along with Callithamnion and Polysiphonia, I have personally observed rhodoplast ingestion into the alimentary tract (contrary to the opinion expressed in Morris, Abbott & Haderlie. My algal IDs were always verified by Joan Stewart at SIO."
Thank you for considering my comments. Hopefully, Kathe and Terry will respond to settle the issue.
Cordially,
Cynthia
trowbric@onid.orst.edu
Trowbridge, C.D., 2006 (Mar 3) Ercolania fuscovittata or Stiliger fuscovittatus ?. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/15996Dear Cynthia,
I think my calling it Ercolania would count as a sin of omission. I didn't realise I had changed the 'generic placement' of the species. The first query called it Ercolania, Kerry Clark called it Ercolania, and Kathe called it Ercolania. After I received your message I asked Kathe for advice and am still waiting. If you had sent me an email last year saying what your present one says I would have readily changed it to Stiliger. I'm afraid in some groups I need guidance - or 48 hrs in the day to check the literature! However I appreciate that as there are so few opisthobranch workers, sometimes none of us have time to respond immediately. Anyway - better late than never!
Dave Behrens has prepared a new Fact Sheet - as Stiliger fuscovittatus - and it includes a copy of Jim Lance's photo. Perhaps the Caribbean record is of a completely different species.
Best wishes,
Bill Rudman
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