Phyllodesmium longicirrum on Sarcophyton

January 15, 2004
From: Mary Jane Adams


Hi Bill,
I photographed this Phyllodesmium longicirrum at Kapalai Island, east of Sabah, Malaysian Borneo, on Nov. 26, 2003. It was about 12 cm long and about 10 meters deep. It appeared to be grazing on a Sarcophyton sp leather coral. In the upper image I noticed that the brown patches of zooxanthellae occur not only at the terminal branches of the digestive gland in the cerata, but also on the
notum, oral tentacles and even on the rhinophores. How do you interpret this finding?

Best regards,
Mary Jane

divepng@yahoo.com

Adams, M.J., 2004 (Jan 15) Phyllodesmium longicirrum on Sarcophyton. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/11902

Thanks Mary Jane,
Many of the Solar powered sea slugs have branches of the gut forming a network of ducts throughout the body wall. In sacoglossans which store chloroplasts from their algal food branching digestive gland ducts are found in both the slugs which keep chloroplasts alive and slugs that don't. I suspect the branching developed initially as a way fro the animal to camouflage itself when in its food.

In the nudibranchs, such as Phyllodesmium, which keep zooxanthellae alive, branches of the gut in the body wall is a new development and only found in those with the zooxanthellae symbiosis. In these species all parts of the body which are not shaded from sunlight have branches of the digestive gland just beneath the skin. Clearly this is a way of maximising the use of available space for photosynthesis - just like plants arrange their leaves
Best wishes
Bill Rudman

Rudman, W.B., 2004 (Jan 15). Comment on Phyllodesmium longicirrum on Sarcophyton by Mary Jane Adams. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/11902

Factsheet

Phyllodesmium longicirrum

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