Re: Geitodoris portmanni (?) from Sorrento

October 12, 2009
From: Marina Poddubetskaia Ossokine

Concerning message #15692:

Dear Bill,

To continue my analysis of unidentified species, I agree with your ID of Fabio's dorid [message 15692] : it is probably a juvenile Geitodoris planata.

Several years ago, I discovered in Arcachon Bay small yellow dorids like this one, feeding on a yellow sponge. Initially, I was puzzled by their ID and supposed an unidentified species. But they were so numerous (each year I was seeing several dozens of it) and I concluded it could hardly be a rare or undescribed species. While observing them closely, with binocular, I noted a common characteristic with Geitodoris planata: small yellow spots ringed with brown, present in all the specimens ! That's how I arrived to the conclusion they were the juveniles of this very common species. Like adults, juveniles can have or not stellate pattern and acid glands. And their underside of the mantle can have dark spots or not.

Later, I saw subadults which seemed to confirm my ID.

The upper photo  shows the juvenile aggregation on the yellow sponge.
Locality: 'Le Mimbeau', Cap Ferret, Arcachon Bay, 9 m, France, Atlantic Ocean, 14 August 2005. Length: 7-10 mm. Photographer: Marina Poddubetskaia.

The middle photos show the details of a juvenile with mantle underside view and characteristic yellow spots.
Locality: 'Le Mimbeau', Cap Ferret, Arcachon Bay, 9m, France, Atlantic Ocean, 14 August 2005. Length: 9 mm. Photographer: Marina Poddubetskaia.

The lower photo  shows another juvenile, always with yellow spots.
Locality: 'Le Mimbeau', Cap Ferret, Arcachon Bay, 4m, France, Atlantic Ocean, 17 August 2005. Length: 10 mm. Photographer: Marina Poddubetskaia.

I will put other growing stages in a separate message.

Best wishes,
Marina.

nembro@yahoo.fr

Poddubetskaia Ossokine, M., 2009 (Oct 12) Re: Geitodoris portmanni (?) from Sorrento. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/22694

Dear Marina,

I was going to say when commenting on your other related messages, that these animals seem very well camouflaged on their sponge food. The brown rings which seem even more characteristic than the white stellate pattern around the acid glands, seem to mimic the large water current pores in the sponge colony. I know that saying such things is risky, as we don't really know what potential predators can see, but the size of the rings and their spacing is almost indentical to that of the sponge pores.

Best wishes,
Bill Rudman

Rudman, W.B., 2009 (Oct 12). Comment on Re: Geitodoris portmanni (?) from Sorrento by Marina Poddubetskaia Ossokine. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/22694

Factsheet

Geitodoris planata

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