Ercolania boodleae? on Valonia

March 4, 2000
From: Yasuhiro Shirai

Dear Bill,
Thank you for your earlier replies.
This time, I attach 2 image files. I think these animals are similar to Ercolania boodleae.

Usually I find Ercolania boodleae, on rocks with algae or moss. But these animals are usually on seaweed (Valonia macrophysa). I think these animals eat Valonia macrophysa. When they are attacked, they cut off their cerata themselves.

Are they Ercolania boodleae?

Location: Shima Pref. Mie, Japan (Kii Peninsula, east coast)
Length: 5-15mm
Water temperature: 14C
Date Jan.2000 - Feb.2000
Depth: 2-5m
Crawling on seaweed (Valonia macrophysa).

Best regards,
Yasuhiro Shirai

Shirai, Y., 2000 (Mar 4) Ercolania boodleae? on Valonia. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

Dear Yasuhiro,
I am pretty sure these are Ercolania boodleae. They look very similar to the paintings in Baba's Opisthobranchs of Sagami Bay. Baba & Hamatani (1970) state that this species is associated with green algae such as Chaetomorpha, Ulva, Enteromorpha, and Boodlea. I suspect your animals are not eating Valonia but feeding on tiny epiphytic filamentous green algae which grow on Valonia.

There is a very interesting sacoglossan that feeds on Valonia. Each 'bubble' of the algae is a giant cell and this sacoglossan is found inside the cell feeding on the cell contents. It has recently been named Ercolania endophytophaga by Kathe Jensen but is very difficult to find without collecting lots of Valonia and taking it back to the lab for examination.
Best wishes,
Bill Rudman.

Rudman, W.B., 2000 (Mar 4). Comment on Ercolania boodleae? on Valonia by Yasuhiro Shirai. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from


Ercolania boodleae

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