Cannibalism? with Janolus cristatus

March 27, 2007
From: Mat Vestjens


Hello Bill,

Two weeks ago I observed something very interesting. I found a strangely curled specimen of Janolus cristatus. At first I could not tell head from tail and tried to make some shots to sort it out later (picture 1). Then the larger part of the entanglement moved on and a smaller part stayed in position (picture 2). My first thought was that a small and a big specimen had been mating, but after looking closely, the smaller part did not have a head (picture 3). Is cannibalism known from J. cristatus? As far as I know, they feed on bryozoans.

Locality: Selce, 12 metres, Croatia, Adriatic, 15 March 2007, Subtidal, rocky. Length: 30 mm. Photographer: Mat Vestjens.

Best regards,

Mat Vestjens

 

annenmat@natuurlijkmooi.net

Vestjens, M.G., 2007 (Mar 27) Cannibalism? with Janolus cristatus. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/19767

Dear Mat,
Most nudibranchs have teeth and mouth parts specialised for feeding on their normal food so I don't know if the teeth of a bryozoan feeder would be very good at eating a nudibranch body. Also, looking at the damaged animal, there seems to be a series of small bud-like cerata around the edge of the damaged region which would suggest regrowth is beginning to take place. If so, it would mean the damage was not caused while you were watching.  My guess would be that the healthy animal was passing by and was attracted to the other animal by normal chemical communication - and then moved on. I very much doubt it was having a bite of the damaged animal - but I could be wrong.

Best wishes,
Bill Rudman

Rudman, W.B., 2007 (Mar 27). Comment on Cannibalism? with Janolus cristatus by Mat Vestjens. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/19767

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