Opisthobranch of the Week Data
Pteraeolidia ianthina is considered to be very common on Okinawa; I usually post in the above collection data area a range for all Okinawa-collected specimens of the species, but due to the extreme commonness of the species, I've quite remarkably, collected relatively few animals and therefore I haven't added data to the section.
Pteraeolidia ianthina is commonly found in shallow water, although I've collected and photographed two individuals from 60m and 64m. I typically find the animals amid dense patches of a common hydroid (Ralpharia sp.) upon which they are known to feed (Willan, 1989). These beautiful aeolids are one of several of the group which harvest energy from the sun. They capture and farm microscopic dinoflagellate algae (zooxanthellae) within their bodies for energy conversion and the literature suggests that the adult animals may receive most of their nutrition from the symbiotic algae. Bill Rudman has a great discussion on these "Solar-powered Sea Slugs".
Here are two additional close-up photos of different animals:
Literature & WWW Sites Cited: