Ercolania emarginata from Hong Kong

February 28, 2005
From: Kathe R. Jensen

Dear Bill,
Here is another sacoglossan from Hong Kong. This specimen was collected at Cape d'Aguilar at the Swire Marine Institute during the international workshop in April 1995. The picture was taken in the lab. on 12 April 1995. The species was collected - and feeding on Chaetomorpha antennina.

The species was originally described in 1985 based on specimens collected from the same locality in April 1983. Comparing it with pictures of Ercolania boodleae on the Sea Slug Forum in 2000 has made me almost certain that E. emarginata is identical to E. boodleae [see message #2441 ].

Locality:  Cape d'Aguilar, Hong Kong, South China Sea. Depth: less than 1 m during low tide. 12 April 1995. Very exposed rocky shore. Photographer: Kathe Jensen

All the best,

Jensen, K.R. , 2005 (Feb 28) Ercolania emarginata from Hong Kong. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

Dear Kathe,
Thanks for this photo. Even if I say so myself, the ability to compare photographs of living animals like this on the Forum, has become an indispensable tool in our taxonomic research.  It is unfortunate that some scientific administrators remain blind to its value.

To only difference in colour I can see is that in your photo the dorsum, between the cerata, is white or colourless, whereas in Japanese E. boodleae and Australian E. margaritae [as E. cf. boodleae] the back is black. I note in your description of E. emarginata, you describe 2 colour forms. A subtidal form which is identical in colour to E. boodleae, and an intertidal form in which the ceratal wall lacks black and orange pigmentation, and so the green of the digestive gland shows through the ceratal wall. In the intertidal form the black pigmentation on the back is not so intense. The animal in your photo seems to be intermediate between those two colour forms. What do you think?

Best wishes,
Bill Rudman

Rudman, W.B., 2005 (Feb 28). Comment on Ercolania emarginata from Hong Kong by Kathe R. Jensen. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

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  1. Re: Ercolania emarginata from Hong Kong
    From: Kathe R. Jensen, March 3, 2005

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