Re: Feeding habits of Roboastra

July 10, 2004
From: Bieke Daneels

Hi Bill,
I just saw some footage of Roboastra luteolineata engulfing Tambja morosa, there is smoke development. Can you or Lucas Cervera describe this chemical reaction; how do they digest species as big as themselves?

Thank you,
Bieke.

biekedaneels@yahoo.co.nz

Daneels, B., 2004 (Jul 10) Re: Feeding habits of Roboastra. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/12673

Dear Bieke,
I would be interested to know where the video you looked at was taken? Was it in New Zealand? We know so little about the feeding behaviour of these animals that every record is important. Concerning the 'smoke' you noticed. Species of Tambja, Nembrotha and Roboastra have special skin glands which at times exude coloured secretions. These are probably defensive and appear to contain antifeedant chemicals from their prey, which in the case of Tambja would be an arborescent bryozoan.

How do they digest such large prey? I'm afraid carnivorous molluscs are not very very well mannered when it comes to eating. An animal such as your Roboastra will just have to sit for many hours hugely distended until its digestive enzymes dissolve its prey. I have commonly seen the worm-eating slug Melanochlamys cylindrica feeding on worms it can only half swallow and then be trapped for hours with its head jammed in coralline algal turf waiting for the part of the worm it has swallowed to be digested. Another example is the large tun shells Tonna which feed on sea cucumbers, often larger than themselves. They somehow extend their head to envelope the whole sea cucumber and then have to sit for hours with their head swollen and unable to fit back into their shell.
Best wishes
Bill Rudman

Rudman, W.B., 2004 (Jul 10). Comment on Re: Feeding habits of Roboastra by Bieke Daneels. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/12673

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