Hypselodoris acriba or H. edenticulata?

Thanks Anne,
For these wonderful photos. What a delight it must have been to go back to the same spot and find these animals again. Firstly about their biology. I am pretty sure they are mating - or at least seriously considering it! And I am also pretty sure they are feeding. To have their heads stuck like this for 80 minutes or so suggests they were doing something, and the chance of finding them with the same sponge as last time, just by coincidence, doesn't seem very high. One way to check if any of these dorids are feeding is the gently push their head aside. While you won't see them actually munching away you will almost certainly see the inflated sac-like oral tube which everts out of the mouth to bring the teeth in contact with the food. If that is visible its a good sign that feeding has been taking place.

Concerning its identity. I can really only repeat what I said in reply to your earlier message. It doesn't seem to be the H. edenticulata form of H. picta, or H. acriba or H. ruthae. Two characteristic features of your species seem to be the dark patch at the edge of the mantle about half way down each side, and the white spots on the gills. if you look at Dave Behren's photo of H. acriba you can see a similar dark patch at the mantle edge. This is not mentioned in the original description of the species but is clear in this photo. One of the major differences between the two is that in H. acriba the yellow lines on the mantle form a reticulate network while in your animal they form a series of longitudinal lines. However if you look closely at the head of the animal in your upper right photo you can see the lines form a reticulate pattern.

I guess we will have to wait until more is known about these animals, perhaps they are closely related but distinct species, perhaps they are extreme forms of one species. If it is a distinct species, it would appear to be unnamed.
Best wishes,
Bill Rudman.