Thecacera pacifica - sensory organ

March 10, 2006
From: Roberto Sozzani

Dear Bill,
I notice you don't have many records of this species. Here is a photo which shows, in transparency, the circular mouth of this species. I hope this can be of interest for you.

This species was very common in Sangeang Island (Indonesia) on a black sandy slope starting at 22 meters, at the base of a very fragile sand and coral wall. But Sangeang has an active volcano, so the wall is almost all fallen down now and many species disappeared.

Location: Sangeang Island, Indonesia. Depth: 22 meters, Size: 3-4 cm. August 2001. Photos: Roberto Sozzani

Roberto Sozzani

roberto.sozzani@fastwebnet.it

Sozzani, R., 2006 (Mar 10) Thecacera pacifica - sensory organ. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/11724

Dear Roberto,
The structure which looks like a mouth is very interesting. It is in fact a sensory organ which this species has on either side of the head just below the rhinophores. Quite a few polycerids, but not all, have similar organs, but as the organ is a groove which is often closed, it is seldom noticed. If you look in other photos of the species in the Forum you will see this organ as a little whitish line just below the rhinophores. In preserved polycerids it is often invisible. Have a look at my message about similar organs in Tambja morosa [#10513].

Thank you very much for sending this photo. I made some pencil sketches of this organ in Thecacera some years ago, but this is the first time I have seen a photo of it.

Best wishes
Bill Rudman

Rudman, W.B., 2006 (Mar 10). Comment on Thecacera pacifica - sensory organ by Roberto Sozzani. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/11724

Factsheet

Thecacera pacifica

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