Re: Diaulula sandiegensis? from Puget Sound

March 31, 2006
From: Clinton Bauder

Concerning message #16150:

Hi Dave,
At some risk of opening a can of worms I wonder if I can revisit an earlier "Sea Lemon" post? Specifically I was thinking that the (one yellow and one white) animals shown mating in the lower image for the Geitodoris heathi Fact Sheet are actually D. montereyensis? Certainly they look very similar to my amateur eye and it isn't clear to me from the text of the various messages how to tell the difference.

What I usually ID as Geitodoris heathi is quite common at some of my favorite dive sites and I see a lot of them. Usually these animals have very fine black specks on the dorsum. Some have large black spots as well but nearly always the fine specks as well. Also the base color of the body is usually blotchy rather than solid. Somehow also the contrast between the spots and the base color seems less than in Doris montereyensis. Geitodoris usually looks like it has a fine layer of silt covering the mantle - ie it looks dirty or dull somehow.

On the other hand Doris montereyensis has large spots with none of the fine specks and the base color is very uniform rather than blotchy. White examples of this species are unusual but I have seen them. Usually this species looks bright to the eye rather than dull like Geitodoris.

I realize these differences are rather subjective and it may be that distinguishing these species without dissection is difficult but I'm hoping for a reliable method to choose between the two.


Bauder, C., 2006 (Mar 31) Re: Diaulula sandiegensis? from Puget Sound. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

Hi Clinton,
Well I can't disagree with you - this complex of yellowish dorids (I hate the name Sea Lemon) is difficult to identify.  Each of the species you mention is highly variable in color, creating the problem.  Let's discuss what is NOT varible.

So let me propose -- Sea Lemon 101:

Doris montereyensis - black spots on the dorsum cover the tubercles.  Tubercles are not uniform in size.  Gill yellow.

Peltodoris nobilis - dorsal tubercles nice and round and uniform.  Black spots are on the dorsum and do not extend up onto the tubercles.  Gill white.

Geitodoris heathi - Dorsal tubercles low and widely separated.  Has MINUTE brown-black flecks on the dorsum, especially in a patch in front of the gill.  None of the others have this.  These same flecks occur of the gill plumes and rhinophores.  Again not on the other species.

Peltodoris lentiginosa - a northern species north of Cape Arago, Oregon.  Should not be a problem in Monterey, California.  Color varies from pure white to white with large brown patched.  Tubercles are low, and are visible through even the darkest patches.  Gill is white.

Now with this said, PLEASE keep in mind that variabilty between specimens as seen in your message #3166 will continue to cause us confusion.  Visual ID's are always difficult, but I can tell you that internally these species are completely distinctive.

Thanks for keeping us on our toes,
Dave Behrens

Behrens, D.W., 2006 (Mar 31). Comment on Re: Diaulula sandiegensis? from Puget Sound by Clinton Bauder. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

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