Description: This distinctive worm is 15-30 mm in length with 66 body segments. It is white with large orange to yellow blotches running along the length of the body. The palps are fused and fold backwards over the head. Median and lateral antennae are both long, although lateral antennae are only half the length of median antennae. Dorsal cirri (tentacles) are distinctly flattened, and are quite long. Ventral tentacles are wedge-shaped.

Their form of reproduction is interesting. Adults reproduce by a process known as schizogamy in which the posterior end of the body splits into multiple segments called stolons that eventually bud off and develop into either male or female. These then spawn and die upon release of larva or eggs. The adult regenerates the lost section of their body and is ready to complete the process again. This process is unique in syllids.

Habitat: Amongst algae, sponges, hydroids etc. May be associated with Ascidiella aspersa.

Distribution: Scattered records from around Britain and Ireland. Seems to be largely absent from southern Ireland but may be under-recorded.

Similar Species: There are other species of Myrianida which may be encountered in some areas but this species is quite distinctive.

Key Identification Features:

• White worm with large orange to yellow blotches.
• Long, flattened palps folded backwards over the head.
• Dorsal cirri distinctively flattened, and long.
• Ventral tentacles wedge-shaped.

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

iNaturalist: Myrianida pinnigera at iNaturalist World Species Observations database.

GBIF data for Myrianida pinnigera

WoRMS: Myrianida pinnigera at World Register of Marine Species. Accepted name: Myrianida pinnigera (Montagu, 1808). AphiaID: 131324.

Classification: Biota; Animalia; Annelida; Polychaeta; Errantia; Phyllodocida; Nereidiformia; Syllidae; Autolytinae; Autolytini; Myrianida