Phyllodesmium longicirrum feeding

December 6, 2006
From: Michael Henke

Concerning message #11902:

Dear Bill,
What is the Phyllodesmium longicirrum doing here  and why are some parts of the ducts totally white? Hope you enjoy the pictures.

Locality: Batu Tiga, 15 m, Nord Sulawesi, Indo Pacific, 2 November 2006, soft coral. Length: 20 cm. Photographer: Michael Henke.

Thanks for your time,

Henke, M., 2006 (Dec 6) Phyllodesmium longicirrum feeding. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

Dear Mike,
I guess you have looked at the solar powered sea slug page, and the related topics listed there. Phyllodesmium longicirrum is one of the most spectacular of the solar-powered slugs because of its large flattened cerata, which remind me of the large solar paddles on earth-orbiting satellites. In this species the brown rings you can see on the skin of the body, the rhinophores and the cerata, are gardens of single-celled plants [zooxanthellae] which the animal obtains from the soft coral Sarcophyton, on which it is feeding in your photos. The pale whitish branching in the cerata are the ducts of the gut which take the zooxanthellae from the stomach out to these gardens. I am not sure why a few of the cerata are colourless but its seems they lack both the ducts of the gut and the zooxanthellae. P. longicirrum, like all species ofPhyllodesmium, is able to cast off its cerata [autotomy], much like some lizards drop off their tail, as a defensive strategy. They are able to regrow these cerata quite quickly. Perhaps these are some replacement cerata which for some reason were unable to regrow the branches of the gut?

Best wishes,
Bill Rudman

Rudman, W.B., 2006 (Dec 6). Comment on Phyllodesmium longicirrum feeding by Michael Henke. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

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