Madrella ferruginosa from South Africa

September 18, 2007
From: Riaan Marx

Hi Bill,
I made a preliminary ID on this critter of Madrella ferruginosa, but if it was not for the distribution and size I would have guessed it was M. sanguinea.

I see that since Valda's photo you have not yet posted another sighting of this species from South Africa, so I thought I'd send them on .... Also, in the second photo (it is the same individual) you can see the bryozoa I assume it is trying to get to.

Locality: Sodwana Bay, 18 metres, South Africa, Indian Ocean, 10 August 2007, Anton's Reef. Length: 20 mm. Photographer: Riaan Marx.

Kind regards

Marx, R., 2007 (Sep 18) Madrella ferruginosa from South Africa. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

Dear Riaan,

Apart from smaller size and bright red colour pattern there is little in shape or anatomy to separate M. sanguinea from the larger and usually browner M. ferruginosa. However M. sanguinea, apparently restricted to south eastern Australia, is reported to have much larger eggs and directly developing larvae, while M. ferruginosa, with a wide Indo-West Pacific distribution has small planktonic larvae. These species seem to take up the pigment from their prey bryozoan which could explain why your animal is brighter red than usual for M. ferruginosa.

Best wishes,
Bill Rudman

Rudman, W.B., 2007 (Sep 18). Comment on Madrella ferruginosa from South Africa by Riaan Marx. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

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