Blue Dragon Nudibranch

Pteraeolidia semperi

Kingdom: Animalia
Phylum: Mollusca
Class: Gastropoda
Order: Nudibranchia
Family: Facelinidae
Genus: Pteraeolidia
Species: Pteraeolidia semperi

The blue dragon nudibranch (Pteraeolidia semperi) is a long, slender aeolid covered in bunches of blue-tipped to brown cerata. It was long known as Pteraeolidia ianthina, a name now treated as a separate species.

It grows to around 10 cm and feeds on hydroids. It farms symbiotic zooxanthellae in its cerata, which give it its brownish to bluish colour and help it survive on sugars from photosynthesis.

In the Philippines it is common on reefs and rubble slopes, often seen in the open during the day, and juveniles can be very small and translucent.