Re: Hermaea sp? from Okinawa

April 20, 2006
From: Cynthia Trowbridge

Concerning message #12489:

Dear Bill and colleagues,

It was of considerable excitement to read about the Hermaea cf. bifida from various Asian locations, including Okinawa, where I have been working since 2002 with Yoshi and Yakko Hirano (Chiba University). We are presently working on a manuscript on sacoglossan species that feed on red algae, hence my particular interest in the Hermaea reports. This message is intended as a focal point for discussion, not a viewpoint (as I have never collected the Asian Hermaea cf. bifida ).

First some background:
Of the Hermaea species that feed on red algae, perhaps the most abundant one is the NE Atlantic Hermaea bifida (Montagu, 1815). Uncommon to rare congeners include Hermaea variopicta (Costa, 1869), H. paucicirra Pruvot-Fol, 1953 and H. boucheti Cervera et al., 1991 on NE Atlantic shores; H. cruciata Gould, 1870 on NW Atlantic shores; H. coirala Marcus, 1955 on SW Atlantic shores; Hermaea oliviae (MacFarland, 1966) on NE Pacific shores; H. noto (Baba, 1959) on NW Pacific shores; and H. evelinemarcusae Jensen, 1993 on Australian shores. Numerous additional Hermaea sp. have been recorded, particularly in the Indo-Pacific region (e.g., Carlson & Hoff, 2003).

Bill, when you called the Asian specimens "cf. bifida", did you select that bifida as the morphologically most similar species or the most well known Hermaea species? I personally was not aware of half of the species just listed until I started to investigate these red algal feeders. With all these locally distributed species around the world, I think an overlooked endemic species may be as plausible as an introduced one.

Suggestion:

In 2001, Kathe transferred Aplysiopsis oliviae to Hermaea oliviae, based on shape of radular teeth (message #5616). Recently, when reading Ichikawa (1993), I thought of Kathe's genus change and wondered if it might apply to another species: Aplysiopsis wrangeliae Ichikawa, 1993. This species feeds on the genus Wrangelia, a filamentous red alga related to Griffithsia and other Ceramialean reds. Regretfully, Ichikawa did not illustrate the radula of her species so we cannot see if it could also be moved to Hermaea. A few weeks ago, I wrote to Ichikawa; all her specimens are at the Natural History Museum in Vienna [not at Seto Marine Biological Laboratory or in Ichikawa's own collection].

I bring this species to the attention of Forum folks because "Hermaea cf. bifida" specimens may belong to this species. The rhinophores should have 3 distinctive stripes. The photos submitted to date do not appear to have the stripes but additional close-up photos of the anterior region would be great (easier said than done for small animals); Ichikawa reports the holotype as 10 mm so it is an intermediate-sized sacoglossan. If someone in or near to Vienna could check the specimens (I have written but have received no response), we may be able to solve the mystery of whether this Okinawan species should be Aplysiopsis wrangeliae or Hermaea wrangeliae. If I learn additional information about the Okinawan species, I will let folks know. In the interim, please understand that this is merely a suggestion of possible identification. I look forward to hearing other people's thoughts.

ICHIKAWA, M. 1993. Saccoglossa (Opisthobranchia) from the Ryukyu Islands. Publications of the Seto Marine Biological Laboratory, 36: 119-139.

Cordially,
Cynthia

trowbric@yahoo.com

Trowbridge, C.D., 2006 (Apr 20) Re: Hermaea sp? from Okinawa. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/16344

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