Mating? Phyllidia Sulawesi

Dear Mike,
I thinnk it would cause a few problems if the two large animals in your photo were mating. The blue one on the left is Phyllidia varicosa, while the large, predominantly black one is Phyllidia madangensis, although it is hard to distinguish it from P. carlsonhoffi  from this photo. Over on the right of the photo is a smaller phyllidiid which looks like a species of Phyllidiella or perhaps Phyllidiopsis. I don't recall a species like this which seems to have black pigment right to the mantle edge.

To answer your question. I don't think the two large animals are mating. If you look carefully you can see the anal papilla on P. madangensis which means the head of P. varicosa and the 'tail' of P. madangensis are together, which is not a mating position.

Best wishes,
Bill Rudman