Thecacera pennigera from South Australia

June 20, 2005
From: Dennis Hutson

Can you please confirm this is Thecacera pennigera.

Locality: Outer Harbour, Adelaide, South Australia. Depth: 3 metres. Length: 12 mm. 18 June 2005. silty. Photographer: Dennis Hutson

Is it native to Adelaide, South Australia?
Cheers.
Dennis Hutson

dghutson@ozemail.com.au

Hutson D.G., 2005 (Jun 20) Thecacera pennigera from South Australia. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/14077

Dear Dennis,
Yes this is Thecacera pennigera. Your question about where it comes from is quite interesting. It was originally described from England so we have assumed that it is a North Atlantic species. However it has since been found in many parts of the world as you will see from the Fact Sheet and accompanying messages. It feeds on bryozoans which are part of the 'fouling community' a name for plants and animals which grow on hard surfaces, and in particular, the bottom of boats.  We have assumed that this species has spread from the Nth Atlantic on the bottom of boats. However most species of Thecacera are found in the Indo-West Pacific region, and as you will see from looking at the photos on the Forum, there is much more colour variation in animals from the Pacific than from the Nth Atlantic. This could suggest that the Pacific is the original home of this species and what we now find in the Nth Atlantic is a population based on a few Pacific animals with small spots that were transported there on the bottom of sailing ships two centuries ago.

I guess this could be tested by DNA analysis.
Best wishes,
Bill Rudman

Rudman, W.B., 2005 (Jun 20). Comment on Thecacera pennigera from South Australia by Dennis Hutson. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/14077

Factsheet

Thecacera pennigera

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