Description: This small, stalked jellyfish has a body shaped like a funnel or bell up to 25 mm in diameter which is attached with a stalk that ends in an adhesive disc. It is variable in colour, ranging from pale grey, green, yellow, brown to red in colour. It usually has 8 equally sized arms, connected by a thin membrane, ending in tufts of knobbed tentacles (secondary tentacles). This species has obvious, globular primary tentacles/anchors. Nematocysts are present on the bell, visible as white spots, although these may be very few on juveniles.

Habitat: Typically found attached to seaweed or the seagrass Zostera marina; rarely rocks. Found from lower shore to around 10 m depth.

Distribution: Records exist from all around Britain and Ireland but there is some confusion between this species and Haliclystus auricula (which seems to be a rarer species) so true distribution of both species is currently unclear.

Similar Species: There are several species of stalked jellyfish found in Britain and Ireland, but careful examination of key features often allows for in situ identification. If in doubt several good quality photographs showing the bell, stalk, arms and tentacles should be sufficient for ID. The presence of the primary tentacles indicates genus Haliclystus, and the shape of the primary tentacles can be used to further distinguish between species. The other common species of Haliclystus found here is Haliclystus auricula which lacks the visible white nematocysts of H. octoradiatus.

Key Identification Features:

• Presence of primary tentacles/anchors.
• Globular shape of primary tentacles.
• Usually has 8 arms of equal size.
• Nematocysts visible on bell as white spots.

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

iNaturalist: Haliclystus octoradiatus at iNaturalist World Species Observations database.

GBIF data for Haliclystus octoradiatus

WoRMS: Haliclystus octoradiatus at World Register of Marine Species. Accepted name: Haliclystus octoradiatus James-Clark, 1863. AphiaID: 135323.

Classification: Biota; Animalia; Cnidaria; Medusozoa; Staurozoa; Stauromedusae; Myostaurida; Haliclystidae; Haliclystus