Small, stalked jellyfish which may have a seasonal lifecycle.

In brief

• Small, stalked jellyfish up to 25 mm in size.
• Could be easily confused with some other species of stalked jellyfish, but in field identification is possible, as is identification with good quality photos.
• No specific threats, but at risk from habitat degradation, climate change and water quality issues.
• Scattered distribution but possibly under-recorded.

Species 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, coffee bean- or kidney-shaped primary tentacles/anchors. There are no nematocysts visible/present on the bell.

Life cycle: Unknown.

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 octoradiatus which has visible white nematocysts, H. auricula lacks these.

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

Current status: Declining. Records exist from all around Britain and Ireland but there is some confusion between this species and Haliclystus octoradiatus (which seems to be the more common species) so true distribution is currently unclear.

Why is this species a priority in Northern Ireland?

• Criterion 1: Internationally listed species.
• Criterion 2: Decline based on available data and expert judgement.

Threats: No threats specific to this species are known, however climate change, water quality issues and habitat degradation are likely to play a factor.

Action: Records of new sites for this species, with details of habitat and population are always valuable. Observations with a photograph can be recorded using iNaturalist, find the MBDP-NI iNaturalist project here.

Alternatively, records can be sent to CEDaR, National Museums Northern Ireland, 153 Bangor Road, Cultra, Holywood, County Down, BT18 0EU. Tel 028 9039 5257, e-mail cedar.records@nationalmuseumsni.org, or via the online portal.

Objectives:

• Maintain the number of viable populations of the species and safeguard their habitat.
• Establish range limits and maintain the range of the species.
• Establish appropriate management of known sites where possible.

Conservation:

• There is a Habitat Action Plan for Seagrass Beds with the relevant objective of maintaining the extent, quality and distribution of seagrass beds in Northern Ireland.

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

iNaturalist: Haliclystus auricula at iNaturalist World Species Observations database.

WoRMS: Haliclystus auricula at World Register of Marine Species. Accepted name: Haliclystus auricula James-Clark, 1863. AphiaID: 135322.

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