Notodoris gardineri from Papua New Guinea

Dear Mary Jane,
The Notodoris species pages are certainly filling out! Let's look at some of your questions.

•The brittle star question. This certainly raises an interesting point. As your upper feeding photo shows there are species of little brittle stars which are often found on sponges. I don't know if anyone has shown they exclusively live on sponges or whether they are just more easily seen on sponges. If they do live exclusively on sponges then I suppose hitching a ride on a sponge feeder would be a good way to move from sponge to sponge.

•Mating size in nudibranchs. Opisthobranchs are all hermaphrodite which means they have both a male and female reproductive system. Often the male system develops early in the growth of the animal and some species, which we call protandrous, become functional males at a much smaller size than they become functional females. In others both systems are fully mature and working at half the species full adult size. So it is possible that the small Notodoris is a functional male. The only way to be sure would be to have given them a nudge and seen if they were attached to each other.

•Anatomical differences in Notodoris.
Certainly some colour forms of N. gardineri look like very black forms of while in other cases, as at the Top of the Page, the black patches are distinct 'islands' of black. However, I can't find anything obviously different in the size and the shape of the radular teeth of the two 'species' and don't know of any published discussion suggesting other anatomical differences. It is certainly something that field observers could help on. See if you can find and photograph interbreeding N. gardineri and N. minor.

Best wishes,
Bill Rudman.