Costasiella nonatoi from Bahamas

March 3, 2004
From: Marina Poddubetskaia

Dear Bill,
During my diving cruise in the Northern Bahamas I found 3 tiny black guys in a sandy (beach) area while snorkelling. All of them were 2mm in length and they were crawling on the sand. At first sight, under the water, I mistook them for Ercolania viridis. But a look at photos revealed 2 close eyes, so I have no doubts they are a Costasiella species.

I've asked Kathe Jensen about a possible identification and she answered they could be Costasiella nonatoi. I'd like to have your opinion too, please. I'm sorry for so poor photos, but my camera couldn't do better with so small specimens.

Bimini Islands, Bahamas, Western Atlantic. Site: Bimini Road. Depth: 1m. Size: 2mm. February 12, 2004. Photos: Marina Poddubetskaia - Nembro website


Poddubetskaia, M., 2004 (Mar 3) Costasiella nonatoi from Bahamas. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

Dear Marina,
I am sure Kathe's suggestion is the most likely. Colin Redfern says that it doesn't grow much larger than 3mm long. Although it is normally associated with it algal food [Avrainvillea nigricans, and sometimes Cladophora] I guess at times they wash off their food, or the plant dies, or is eaten. Redfern's animals from the Bahamas show quite a bit of white spotting and mottling, but the Marcus's original description from Brazil describe a predominantly black animal with white along the anterior edge of the foot, and a large white patch around each eye, which matches your animals well

• Redfern. C., 2001. Bahamian Seashells: a Thousand Species from Abaco, Bahamas.

Best wishes
Bill Rudman

Rudman, W.B., 2004 (Mar 3). Comment on Costasiella nonatoi from Bahamas by Marina Poddubetskaia. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

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