Siphopteron flavum feeding?

September 8, 2006
From: Ayumi Murakami

Dear Bill
I'm sending you several pictures that I took on the 26th of August 2006 of what I think is Siphopteron flavum feeding. I saw 7 individuals on this day and three of them appeared to be feeding on the white sponge attatched to the seaweed.

Locality: Futoh, Izu Peninsula, 5m, Japan, Pacific ocean, 26 August 2006, on lock wall in beach Water Temp: 25C. Length: 5 mm. Photographer: Ayumi murakami.

Unfortunately, I can't identify the white sponge. What do you think it may be?

I hope these pictures are useful for your research.

Ayumi murakami.

Ayumi Murakami, 2006 (Sep 8) Siphopteron flavum feeding?. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

Dear Ayumi,
Thanks for these photos. I am afraid I can't tell whether the pale whitish lumps are small sponge colonies or not. They could be, or they could be the tubes of small polychaete worms encrusted with sand grains, or even small bryozoan colonies. All these animals can form lumps like this on branching algae.

We don't know what any gastropterid [Gastropteron, Siphopteron and Sagaminopteron ] feed on, but I think they are closely related to the carnivorous aglajids, philinids and scaphandrids, which all feed on particular prey, including polychaete worms, flatworms, sea slugs, and small bivalves. The shape of the teeth in gastropterids is very similar to that of philinids and scaphandrids so I am pretty sure they feed on something similar and are not sponge feeders.

Perhaps they are feeding on polychaete worms living in burrows or tubes? There certainly seem to be a couple of holes visible in your close-up photo. These Siphopteron are quite small so it is difficult to see precisely what they are doing in the field. Unfortunately though, I think that is the only way we are going to discover what they eat. All I can say is good luck and please keep looking.

Best wishes,
Bill Rudman

Rudman, W.B., 2006 (Sep 8). Comment on Siphopteron flavum feeding? by Ayumi Murakami. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from


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