Flatworm

ID points

• Body as thin as a sheet of paper, with rippling edges
• Swims with the whole body rippling like a flowing skirt
• Unlike a sea slug, it has no gill tuft on its back

Basics

Family

Polycladida

Length

2–8 cm

Depth

1-40 m

Regions

Indo-Pacific reefs

Distribution

Tropical coral reefs

Diet

Sea squirts and bryozoans

Easily confused with

NudibranchA tuft of naked feathery or finger-like gills on the backGobyThe two pelvic fins are fused into a single suckerHarlequin ShrimpLarge purple-red blotches edged in dark on a creamy white ground

Fun fact

Its extravagant colours warn predators that it carries toxins, and some species go further and mimic nudibranchs. It is the gaudiest flat creature on the reef.