Mystery from Hawaii

August 25, 2001
From: David Kearnes

I have observed many tiny (grain of rice sized, 1mm) sea slugs, don't know what family. They are lemon yellow, the lateral flaps that fold over their back are margined in white, and they have dark red rhinophores that appear to originate from a single stalk and then branch to two points. Where the gills should be is what looks like a single dark red point. They were observed from 90 ft of water to about 25 ft. We live in Hawaii, dive weekly for several years and this is the first time we've seen them and they are everywhere. Don't know if this event is related but it is that time of year that the lined sea hare, Stylocheilus longicauda is in great numbers. I've searched the site but have not had luck.

Dave Kearnes.

Kearnes, D., 2001 (Aug 25) Mystery from Hawaii. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

Dear Dave,
I am wondering whether your mystery beast is a species of Gastropteron or the related Siphopteron. If the 'rhinophore' you describe didn't branch, it woud be a reasonable description for the anterior siphon. Go to the Species List and have a look at photos of a few of the species. It will at least enable you to decide whether the shape is right or not. If not, perhaps a rough drawing would help me.

By the way, the lined sea hare you mention has had a name change. Stylocheilus longicauda is in fact a yellow unlined species, the lines species being Stylocheilus striatus. The reason are discussed on a separate page on the Forum
Best wishes,
Bill Rudman.

Rudman, W.B., 2001 (Aug 25). Comment on Mystery from Hawaii by David Kearnes. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

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