Description: This striking paddle worm is 150-300 mm long and usually has a bright blue back, often with an iridescent sheen, but may sometimes be darker grey. The paddles are initially large, and heart-shaped, narrowing and lengthening towards the rear of the animal, and are green with yellow edges. It has four small, flat antennae and four pairs of yellow tentacles.

Habitat: From low water to offshore, usually under stones and boulders.

Distribution: Possibly a northern species – there are records from the Isle of Man, Northern Ireland and Scotland.

Similar Species: Unlikely to be confused with any other worm due to its striking appearance. Nereiphylla rubiginosa is also found in Britain and Ireland but differs in colour.

Key Identification Features:

• Striking worm that usually has bright blue back and an iridescent sheen.
• Large green paddles lined with yellow.
• Four pairs of yellow tentacles.

Distribution Map from NBN: Nereiphylla paretti at National Biodiversity Network mapping facility, data for UK.

iNaturalist: Nereiphylla paretti at iNaturalist World Species Observations database.

WoRMS: Nereiphylla paretti at World Register of Marine Species.