Description: This small flatworm reaches up to 16 x 9 mm in size. It is usually a yellow-white in colour and covered in small brown to red spots. The length of the tentacles is less than or equal to their basal width. There is a ring of pores around the outer edge of the body. The male genital pore is distinct from the mouth. Cerebral eyes are separate from the eyes on the marginal tentacles.

Habitat: Often found on Botrylloides or Botryllus ascidians, on which they feed.

Distribution: Scattered records from around Britain, but so far only recorded from east coast of Northern Ireland, with no other records from the island of Ireland.

Similar Species: Could be confused with Stylostomum ellipse which does not have a ring of pores around the body or a distinct male genital pore, or Cycloporus maculatus which is similar but covered in white spots, and cerebral and tentacular eyes are merged.

Key Identification Features:

• Yellow-white with brown/red spots.
• Ring of pores around outer edge of body.
• Male genital pore distinct from mouth.
• Cerebral eyes separate to eyes on tentacles.

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

iNaturalist: Cycloporus papillosus at iNaturalist World Species Observations database.

GBIF data for Cycloporus papillosus

WoRMS: Cycloporus papillosus at World Register of Marine Species. Accepted name: Cycloporus papillosus (Sars, 1878). AphiaID: 142815.

Classification: Biota; Animalia; Platyhelminthes; Rhabditophora; Polycladida; Cotylea; Euryleptidae; Cycloporus