Tylodina fungina from California

July 29, 2005
From: Chris Grossman

I took these pictures of Tylodina fungina on a two day trip. The first are from about 10 meters deep at Ship Rock, Catalina Island, California on July 15, 2005. I observed about 20 individuals in the area. However only two pictures came out well because of the surge and the fact that most were too deep in the rock crevices. They were about 2 cm in length [middle photo ].

The following day (July 16, 2005) at the East End reserve of Anacapa Island I found another lone example on a large rock at about 12 meters of depth. It was about 1.5 cm in length. However it was in a position to be easily photographed and there was almost no surge [upper and lower photos ].

Locality: Catalina & Anacapa Islands, California, USA. Depth: 10-12 m. Length: 1.5 to 2 cm. July 15-16, 2005. rocks with kelp. Photographer: Chris Grossman

Chris Grossman


Grossman, P. C., 2005 (Jul 29) Tylodina fungina from California. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/14432

Dear Chris,
Thanks for these photos. They give us quite an interesting look at some of the external features of this primitive opisthobranch. Firstly it has a large, conical, limpet-shaped shell, and you can see the slightly recurved larval shell [protoconch] right at the tip. The shell is covered by a horny layer [periostracum] - all very snail-like for a slug! Tylodina has a pair of large enrolled head tentacles [rhinophores] like those found in the related pleurobranchs. It differs from its shelled relative, Umbraculum, in having a much more elongate body, and in having a 'snout' extending out from the front of the body. In Umbraculum, the mouth is at the bottom of a groove down the front of the circular body.

One interesting feature we can see in your upper photo, is a light yellow crescent shaped gland, at the front of the mantle, under the shell. This is almost certainly the same organ as the 'pre-mantle gland' reported by Burn (1960) from the Australian Tylodina corticalis. I can't find any reference to it being present in T. fungina.

  • Burn, R.F. (1960) On Tylodina corticalis, a rare opisthobranch from south-eastern Australia. Journal of the malacological Society of Australia, 1(4): 64-69.
Best wishes,
Bill Rudman
Rudman, W.B., 2005 (Jul 29). Comment on Tylodina fungina from California by Chris Grossman. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/14432


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