Thordisa bimaculata from Carmel, California

March 7, 2001
From: Clinton Bauder

Hi Bill,
Another week, another nudibranch I've never seen before! This is yet another of the "confusing yellow dorid" variety from the eastern Pacific. The characteristic that differentiates this one from the others is that its black spots are arranged into two large groups on the back. One group is just behind the rhinophores and the other just forward of the gills.

Like the Dentronotus I saw last week this branch was found at Mono Lobo wall in Carmel at a depth of around 20M. The animal was about 20mm long.

Behrens says Carmel is the northernmost extension of its range which may explain why I'd never seen it before. Or it could be that I just didn't realize it was a separate species. Sometimes it pays to look at the ID books even if you don't have a specific animal to look up. Had I not done this the day prior to diving I might not have remembered that dorids with this pattern were a distinct species and might have ignored it altogether.


Bauder, C., 2001 (Mar 7) Thordisa bimaculata from Carmel, California. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

Thanks Clinton,
Bill Rudman