I didn't even know there were any Pteraeolidia ianthina outside of Australia, so you can imagine how excited I was when Heather pointed out this beauty. Actually, this was the second we saw, but the first was during the first dive, when I didn't bring my camera so I could concentrate on remembering how to dive.
Amazingly, these are one of several nudibranch species that sequester photosynthetic dinoflagellates living in symbiosis with their hydroid prey, protecting them as they feed the slug sweet, sweet sun sugar. I mean, symbiosis is cool, but stealing symbionts? Unbeatable.
Totally, totally awesome slug.