Phyllodesmium hyalinum
Ehrenbergh, 1831

Family: Glaucidae


Originally described from the Red Sea, it has been reported from Tanzania, Japan and the Philippines. It also occurs on the Great Barrier Reef in eastern Australia.


Bongoyo Is, off Dar es Salaam, Tanzania, November 1976. 45mm long. PHOTO: Bill Rudman.


Phyllodesmium crypticum

Phyllodesmium hyalinum feeds on the soft coral Xenia. It is very difficult to find because it burrows into the fleshy 'trunk' of the colony only emerging to feed. 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.

Here are some distinguishing characters between the two species:
The cerata of P. crypticum are very nodulose, especially along the edges, whereas in P. hyalinum the cerata are basically smooth. In both species, the cerata are arranged in arches, but in P. hyalinum they are much more numerous and arranged in double rows. An important difference is the position of 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 which consists of a single row of cerata. The radular teeth are similarly shaped in both species but in P. hyalinum the denticles are approximately twice as numerous. The anterior foot corners in P. crypticum are developed into tentacular processes while in P. hyalinum they form only slightly rounded extensions.

Authorship details
Rudman, W.B., 1998 (October 15) Phyllodesmium hyalinum Ehrenbergh, 1831. [In] Sea Slug Forum. Australian Museum, Sydney. Available from

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