August 8, 2008
From: David Mullins
Our recent shift from Brisbane to Woody Point on the Redcliffe Peninsula has resulted in my almost daily haunting of the gutters and reefs at low tide in our front yard.
Locality: Woody Point, Redcliffe Peninsula, Moreton Bay, intertidal, Queensland, Australia., Pacific Ocean, 08 July 2008, Intertidal weed, rocky substrate. Length: 3 mm to 6 mm. Photographer: David Mullins.
I thought that you and the readers of the Forum might find this particular species of Tergipedidae which we believe is a Cuthona/Trinchesia sp. to be of interest. I have to date been unable to find a match for this animal. They were chanced upon as a "colony" of approx. 6 specimens, ranging in size from 3 mm to 6 mm, grazing on hydroids growing on the thallus of "seaweed" attached to the rocky substrate.
I am intrigued by the manner in which they bear their cerata as being certainly quite distinctive if not perhaps characteristic. Additional photos showing a close up of the ceras shows the nematocysts acquired and accumulated from their hydroid prey, a ventral view of the head region, and a specimen upon the hydroids on which they were feeding.
Mullins, D.A., 2008 (Aug 8) Eubranchus echizenicus ? from sthn Queensland. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/21763
Thanks for this interesting record. I puzzled for a while over its identity, as I didn't think it was a cuthonid. The twisted cerata reminded me of some species of Phyllodesmium but your report of of it feeding on hydroids didn't fit, and neither did the rounded corners of the anterior foot.
I am pretty sure this is a species of Eubranchus, and most probably Eubranchus echizenicus, which up until now has only been reported from Japan. It has similarly twisted cerata, large spots, as in your animals, and rounded anterior foot corners. One other interesting feature is the accumulation of white spots at the tip of each ceras which you identified as the nematocysts. Nematocysts, when present, are stored in an internal sac [cnidosac] which opens terminally. These white spots are acid glands in the skin. They are present in some cuthonids but more importantly are particularly well-developed in many eubranchids, and when present often completely obscure the internal cnidosac as is the case in your animals.
Eubranchus echizenicus from Hachijo Islands, Japan
From: Nishina Masayoshi, July 11, 2002
Eubranchus? sp. from Hachijo Islands, Japan
From: Shouichi Kato, April 9, 2002