December 18, 2008
From: Brian Francisco
I've been meaning to send you these two photos for quite a while. I've hesitated because I'm not really sure if they are sea slugs, some other animal, or a figment of my imagination. What caught my eye was the resemblanse to the serata of a solar-powered Phyllodesmium.
My apologies for limited angles on the photos, but the animals (two?) were in a coral crevice. Although I can not discern any telltale features, I hope your expert eye can provide some help.
Locality: Dili Rock, 12 meters, East Timor, Banda Sea, 9 March 2008, coral reef. Length: 2cm. Photographer: Brian Francisco.
Thanks very much
firstname.lastname@example.orgFrancisco, B., 2008 (Dec 18) Coral-feeding Phestilla lugubris from East Timor. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/22105
These are the coral-feeding aeolid, Phestilla lugubris. This species feeds on species of Porites coral. Interestingly animals often pair up and form a 'home' spot on the underside of the coral colony they are feeding on, or in a dark crevice, as you describe. Small animals are very difficult to see because the colour of the digestive gland in the cerata is identical to the colour of the region of the coral they are feeding on. Have a look at the coral-feeding Fact Sheet for links to more information on this specialised life style. When I first studied them I wondered if they were solar-powered, like species of Phyllodesmium, but they do not retain the zooxanthellae in their tissues and have no anatomical adaptations to assist in 'farming' zooxanthellae.
The white 'caps' you can see covering the tips of the cerata are interesting because they cover a swollen layer of special sticky glands found in species of Phestilla [see coral-feeding defense]. As its coral food has feeble nematocyts, Phestilla replaces the cnidosac with this thick layer of gland cells.
Aloha from Hawaii
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