Phyllodesmium hyalinum from the Red Sea

March 3, 2005
From: Oren Lederman

Hi Bill,
We think this one is a mature Phyllodesmium sp.8. A few months ago I sent you a photo of a small one.

Locality: "Dekel" beach, Eilat Bay (Night dive). Israel, Red Sea. Depth: ~3 meters. Length: ~5 cm. 17 Feb 2005. Photographer: Oren Lederman

Oren Lederman

Lederman, O., 2005 (Mar 3) Phyllodesmium hyalinum from the Red Sea. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

Dear Oren,
I am pretty sure this Phyllodesmium hyalinum, which was described from the Red Sea in 1831. It feeds on the soft coral Xenia and is usually very difficult to find because it burrows into the fleshy 'trunk' of the colony only emerging to feed. In the photo on the left a bit of a Xenia colony can be seen at the top of the photo. It is very similar in appearance to Phyllodesmium crypticum which also feeds on Xenia. Both animals rapidly drop off many of their cerata when disturbed [see autotomy Fact Sheet], and I suspect your animal has lost quite a few of its cerata..

In the photo on the left above, I have ringed the anal papilla. In P. hyalinum it is situated above and slightly behind the second ceratal arch on the right side, while in P. crypticum it is inside the second arch. It is not clear in your photo because many of the cerata are missing, but it is certainly higher than I have seen in P. crypticum. Another difference is that the anterior foot corners in P. crypticum are developed into tentacular processes while in P. hyalinum they form only slightly rounded extensions. In the lower right photo above I have included an inset showing the front of the foot, which looks much more like P. hyalinum than P. crypticum, so my best guess is that this is P. hyalinum.

Best wishes,
Bill Rudman

Rudman, W.B., 2005 (Mar 3). Comment on Phyllodesmium hyalinum from the Red Sea by Oren Lederman. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

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