Philinopsis cyanea mating

May 4, 2001
From: Julie Marshall

Dear Bill,

These two Philinopsis cyanea were some of a number of this species I found at Heron Island [Great Barrier Reef, Queensland, Australia] in November 1999. All were between 20 and 25 mm in size and varied enormously in colour and patterns from black with only very faint markings, to pale animals like the ones in this picture. They began mating soon after I brought them into the laboratory and remained entwined for about 30 minutes.

Best wishes,
Julie Marshall

Marshall, J., 2001 (May 4) Philinopsis cyanea mating. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

Dear Julie,
Thanks for the great photo. P. cyanea is certainly very variable in colour. For those unfamiliar with aglajid mating behaviour, they are anatomically a bit different from nudibranchs. They have the penis at the front of the body, just to the right of the mouth, and the female genital opening is at the back of the body on the right hand side. In mating, if there are only two animals one usually acts as the male and the other as the female. In this photo, the one on the right is the acting male. However if there are three or more together they can form mating chains, a bit like sea hares, with one in the front acting only as the female and one at the bac of the chain acting only as a male, while the ones between these two act as male and female simultaneously.
Best wishes,
Bill Rudman

Rudman, W.B., 2001 (May 4). Comment on Philinopsis cyanea mating by Julie Marshall. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from


Philinopsis cyanea

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