Shell-less Tylodina perversa

May 23, 2006
From: Hervé Limouzin

Dear Bill,

I'm French diver, interesting in submarine biology. On a recent dive in the Mediterranean Sea, at Cadaques, Spain,  I saw a Tylodina perversa on its Verongia sponge but this specimen did not have the characteristic limpet-shaped shell.

Two days after, when diving at the same place, I saw it again (same animal
on the same sponge) but there was is egg ribbon and I saw the shell, just
close to the Tylodina, on the sponge ! Can Tylodina change shell (annual change ?) or what else ?
Thank you for your answers.

Sincerly
Hervé Limouzin

limouzin.herve@wanadoo.fr

Limouzin, H., 2006 (May 23) Shell-less Tylodina perversa. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/16654

Dear Hervé,
Thanks for this interesting find. It is definitely not usual for these animals to lose their shells. I can only guess that some predator has ripped off the shell and then been deterred from eating the Tylodina by the poisonous chemicals it has in its body. Like many nudibranchs, Tylodina retains metabolites from the sponge it feeds on.

Seeing a shell-less 'limpet' reminds me of an article that was published in The Veliger in the late 1960s or early 70s about a 'clean' way for shell collectors to collect limpets without the bother of removing the animal. It involved walking around the rocks with a gas cigarette lighter. When you found the shell you wanted you gently played the flame over the shell until steam built up between the mantle and the shell and it popped off - leaving the now partly cooked, half alive and naked animal behind!  I hope attitudes to collecting have changed.
Best wishes,
Bill Rudman

Rudman, W.B., 2006 (May 23). Comment on Shell-less Tylodina perversa by Hervé Limouzin. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/16654

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