Thordisa bimaculata
Lance, 1966

Order: NUDIBRANCHIA
Suborder: DORIDINA
Superfamily: ELYSIOIDEA
Family: Dorididae

DISTRIBUTION

California, USA to Baja California, Mexico.

PHOTO

Mono Lobo wall, Carmel, California, approx 20M. Length 20mm, February 2001. Photo: Clinton Bauder.

Translucent white or yellowish with aggregations of dark brown spots in the dorsal midline, one just in front of the gills and one just behind the rhinophores. mantle covered in long tapering papillae. Grows to about 3cm.

Lance, J.R. (1966). New distributional records of some northeastern Pacific Opisthobranchiata with descriptions of two new species. The Veliger, 9(1): 69-81, text figs. 1-12

Authorship details
Rudman, W.B., 2001 (March 5) Thordisa bimaculata Lance, 1966. [In] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/thorbima

Related messages


Re: Thordisa bimaculata from Carmel, California

June 23, 2006
From: Phil Garner

Concerning message #3881:

I found one this morning at Marineland in Rancho Palos Verdes, California. I thought it was a color variation of Archidoris montereyensis until I got home and looked it up. It was crawling along some Kellet's Whelk eggs at 60 feet. It is the first one I've found in 214 dives at that site.

Locality: Marineland, Rancho Palos Verdes, 60 feet, California, USA, Eastern Pacific, 19 June 2006, Rocky reef. Length: 2 inches. Photographer: Phil Garner.

Phil Garner

PacificCoast101@cox.net

Garner, Philip, 2006 (Jun 23) Re: Thordisa bimaculata from Carmel, California. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/16924

Hi Phil,
Pretty nice find.  Thordisa bimaculata is not a common species at all.  Described by the late James Lance in 1966, it has been observed from Carmel, California south to Isla Navidad, Baja California.

Your specimen clearly shows the two large concentration of brownish black spots on the midlines.  Two inches in length makes this specimen a giant.

Thanks for sharing your find with us,
Dave Behrens

Behrens, D.W., 2006 (Jun 23). Comment on Re: Thordisa bimaculata from Carmel, California by Phil Garner. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/16924

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.

Clinton

gecko1@apple.com

Bauder, C., 2001 (Mar 7) Thordisa bimaculata from Carmel, California. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/3881

Thanks Clinton,
Bill Rudman