Costasiella ocellifera: alga and egg-ribbons

March 3, 2004
From: Marina Poddubetskaia

Dear Bill,
To accompany my previous message on Costasiella ocellifera, [#12276] here is a photo of the alga on which I've found all the specimens seen in Southern Bahamas (Stocking Island).

Also, I have seen several translucent small egg-ribbons on this alga. But I didn't have any evidence that they belonged to this species. So, Anne and I, we decided to put 3 Costasiella specimens in the tank with their algae. Several hours later we noted these 2 egg-ribbons here, 3mm in diameter. They are very similar to the ones I saw 'in wild', but probably infertile. So, now I'm pretty sure they belong to this species.
Photos: Marina Poddubetskaia - Nembro website

Marina (and Anne).

Poddubetskaia, M., 2004 (Mar 3) Costasiella ocellifera: alga and egg-ribbons. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

Dear Marina,
Thanks for these photos. I assume this alga is Avrainvillea nigricans and hopefully a local expert can confirm that name. I read somewhere recently that some algologists consider there to be more than 20 species of the genus in the Caribbean, which doesn't augur well.

The egg ribbon is also interesting. Firstly could you check whether it is possible the photo was reversed in your scanning? I have a photo of this species egg ribbon which coils the opposite way. Either yours or theirs is reversed or the slug doesn't care which way it coils. Of special interest is that a paper has recently been published suggesting that there are two species of Costasiella which are impossible to distinguish externally - one with this type of egg ribbon and one with a different ribbon. See my separate message [#12361]
Best wishes
Bill Rudman

Rudman, W.B., 2004 (Mar 3). Comment on Costasiella ocellifera: alga and egg-ribbons by Marina Poddubetskaia. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

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