Deep purple colored body with a wide speckled white margin, orange rhinophores and big yellow to orange gills.
Unassessed by the IUCN Red list.
This species is know from the West-Pacific, Malaysia, the Philippines and Indonesia, as well as Japan. Not much is known about the exact habitat, but it is likely to be found on or near sponges, which it feeds on. The depth range is at least 1-20 meters.
They are simultaneous hermaphrodites, being able to act as male or female. Upon encounter both individuals darts their penis toward each other to induce one to act as a male and the other as the female. The victorious one to penetrate the body wall is the dominant male. After fertilization eggs are deposited on a substratum where they develop into larvae and further grow as adults.
Up to 10cm.
It feeds on sponges only, mostly species from the Euryspongia genus.
The color schema is similar to that of Hypselodoris bullock, but that has a narrow, fully white lined margin and usually a less deeply purple color. There have been sightings of mating between both H. apolegma and H. bullocki, suggesting that they might be more closely related than we know think. Hypselodoris apolegma has also been described as Risbecia apolegma.