Nudibranch

ID points

• A tuft of naked feathery or finger-like gills on the back
• A pair of club-shaped rhinophores at the front of the head
• No shell, uses bright body colours to warn off predators

Basics

Family

Nudibranchia

Length

2–10 cm

Depth

0-100 m

Regions

Indo-Pacific reefs · Caribbean & W. Atlantic · Open ocean · Deep sea

Distribution

Reef areas of every ocean, from shallow water to the deep

Habitat

Reefs and rocky bottoms at all depths

Diet

Sponges, hydroids, sea squirts

Easily confused with

FlatwormBody as thin as a sheet of paper, with rippling edgesGobyThe two pelvic fins are fused into a single suckerHarlequin ShrimpLarge purple-red blotches edged in dark on a creamy white ground

Fun fact

Nudibranchs, one branch of the sea slugs, have no shell and wear their gills naked on their backs like an open flower. They can swallow the stinging cells of prey such as anemones and redeploy them as their own defence, a trick of borrowed weapons that is extremely rare in the animal kingdom. About 3000 species are known worldwide.