Description: This worm has a narrow body with elytra (scales) that overlap, covering the whole body and giving it a snake-like appearance. It is pale yellow to brown in colour, and sometimes has dark brown to bright orange bands. The body has 150-200 segments and usually ranges from 100-200 mm in length, although can occasionally be longer. There are four black eyes at the head, and it has two long, smooth palps. There is one long smooth antenna that has two finger-like projections that resemble shorter antennae. Hair-like gill is visible on all but the last few body segments.

Habitat: Muddy sand and seagrass, and under stones. Found around the low water mark.

Distribution: Recorded from all around Britain and Ireland, but less common on NE coast.

Similar Species: With experience this species could be reliably identified in the field, however specialist identification guides and microscopic examination may be required.

Key Identification Features:

• Long, narrow worm 100-200 mm in length.
• Overlapping elytra covering the whole body giving it a snake-like appearance.
• Four black eyes.
• Two long, smooth palps.
• One long median antennae with two antennae-like projections.

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

iNaturalist: Sthenelais boa at iNaturalist World Species Observations database.

GBIF data for Sthenelais boa

WoRMS: Sthenelais boa at World Register of Marine Species. Accepted name: Sthenelais boa (Johnston, 1833). AphiaID: 131074.

Classification: Biota; Animalia; Annelida; Polychaeta; Errantia; Phyllodocida; Aphroditiformia; Sigalionidae; Sigalioninae; Sthenelais