Siphopteron flavum from Kerama Island

July 30, 1999
From: Atsushi Ono

Dear Bill,
I have attached the photos you requested.

S. flavum is rare on Kerama Is, near Okinawa. I have seen a few individuals this 3 years. They are seen in winter season.
This animal is very small too, 3mm long.

The lower photo is in my book as a variation.
But I doubt it now. It has dull white patch on parapodia.

For a gastropterid feeding, I have never seen that. I will try to catch the scene in a photo when I find them. My acquaintance in Hatijyou Island (middle Japan) saw about 20 individuals of S. flavum together on a rock. There are short algae sparsely on that rock. I think their association is for breeding, not for feeding. And I asked him "Do you see a egg of S. flavum?"
He said "No, nothing."

Atushi Ono

Ono, A., 1999 (Jul 30) Siphopteron flavum from Kerama Island. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

Dear Atsushi,
Thank you for the photos and the information.

I asked Atsushi if he would mind sending photos of Siphopteron flavum and Siphopteron tigrinum as his photos show the typical siphonal crest of species of Siphopteron so well. It certainly suggests that Siphopteron sp.1. and Siphopteron sp.2., which seem to lack this crest, are most possibly not Siphopteron.

I also asked Atsushi whether he has ever seen any sign of a gastropterid feeding. To me this is another great unsolved mystery. Perhaps like Chelidonura they are flatworm feeders. If anyone sees a feeding incident, please let us know!

Has anyone got any views on Atsushi's colour variant? Apart from the obvious colour differences, I wonder if the apparently right lateral position of the posterior flagellum is significant? Terry Gosliner states that S. flavum is peculiar in having a centrally placed flagellum, as can be seen in the upper photo of a typically coloured animal.

Best wishes,
Bill Rudman.

Rudman, W.B., 1999 (Jul 30). Comment on Siphopteron flavum from Kerama Island by Atsushi Ono. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from


Siphopteron flavum

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