Black-margined Nudibranch
Doriprismatica atromarginata
Sky Blue Phyllidia
Phyllidia coelestis
About
A small, boldly patterned sea slug that grazes reef sponges in broad daylight, confident its colours warn predators off. It reaches about 6 cm in length.
- Length
- 6 cm
How to tell it apart
Several Phyllidiidae sea slugs share this grey-blue, tubercled look. The one detail that confirms this species is the median black line down the back: instead of running straight, it splits at the front end into a distinct 'Y' shape.
Appearance
The body is elongated and slug-shaped, with a grey-blue mantle whose margin is covered in many small tubercles (soft bumps). Larger, yellow-capped tubercles run along the midline of the back, alongside three thin black lines - one down each side of the mantle. The rhinophores (the paired sensory horns on its head) are yellow and ridged.
Habitat
Lives on coral reefs across the tropical Indo-West Pacific, from the outer reef slope and reef top into the lagoon, in shallow water within normal diving range.
Log it in Into the Blue
Describe what you saw and we name it, then keep every species you find in your Oceandex.
