Description: This scale worm reaches around 70 mm and can vary a lot in colour from grey right through to red, with or without patterning on the scales. The scales overlap, but some segments are exposed towards the rear of the animal. The first set of scales are round, with the rest being oval to kidney-shaped. There are some short papillae around part of the outer edge of the scales, and some small tubercles on the surface ringed by a row of larger tubercles towards the outer edge.

Habitat: Rocky shores, and in tubes of other polychaetes down to depths of over 1200 m.

Distribution: Recorded from most coasts around Britain and Ireland but seems less common on east coast of Britain.

Similar Species: There are many other species of scale worm present in Britain and Ireland which may need microscopic examination for a species level identification. Some species can be identified in the field with appropriate expertise and experience.

Key Identification Features:

• Reaches around 70 mm.
• First set of scales are round, with the rest kidney-shaped to oval.
• Very short papillae that are only around part of the scale edge.
• Small tubercles on scale surface surrounded by row of larger tubercles towards outer edge.

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

iNaturalist: Harmothoe extenuata at iNaturalist World Species Observations database.

GBIF data for Harmothoe extenuata

WoRMS: Harmothoe extenuata at World Register of Marine Species. Accepted name: Harmothoe extenuata (Grube, 1840). AphiaID: 130762.

Classification: Biota; Animalia; Annelida; Polychaeta; Errantia; Phyllodocida; Aphroditiformia; Polynoidae; Polynoinae; Harmothoe