A rare sponge that until recently was recorded only from one site on Rathlin island, but is now known from two other Northern Ireland locations, these being the only Irish records.

In brief

• Can be found off the White Cliffs on Rathlin Island, and off the Maidens.
• Its habitat is bedrock and boulders in areas of moderate currents, from about 20 m, but has been recorded elsewhere down to 400 m.
• It can probably be found throughout the year.
• Listed as a priority on account of its rarity and the importance of the Northern Ireland population.
• Not enough is known to positively identify specific threats to this species, but disturbance of seabed habitats would pose a major threat.

Species description: This is an extremely rare, thin and encrusting beige-coloured sponge. It has a slightly uneven surface, but is particularly unusual in that it has long spicules (skeletal structures) that project from the surface, and which are rooted in the basal layer of the 'skin' and underlaid by other spicules. This means that the otherwise somewhat loose consistency of the sponge is kept more intact and firm than would otherwise be the case.

Life cycle: Sponges have either separate sexes or are hermaphrodite. In the case of the latter, self-fertilisation is avoided by eggs and sperms maturing at different rates within the same individual, so when spawning takes place and sperms are released through exhalent openings, it is unlikely that the eggs will be fertilised. Alternatively, the eggs are retained within the sponge, and sperms drawn in from surrounding water. Fertilised eggs are released and develop into planktonic larvae. Asexual reproduction may also be achieved by budding, whereby a small unit of the sponge separates and develops as an independent entity.

Similar species: Alander (1942) who first described this species regarded it as fairly unmistakable, but advised caution in respect of Clathria cleistochela - however this species was thought to have a primarily Mediterranean distribution at the time, though improved survey methods might revise this. He also regarded Plociamiopsis signata as similar, with similar spicules which needed close examination for accurate determination.

How to see this species: In Northern Ireland it was formerly only known from Rathlin - found off the White Cliffs, in 1988. In the last two years however, more have been found there and on the Maidens and east coast (B. Picton, pers. comm.). It occurs on bedrock and stable boulders swept by moderate currents, from depths of about 20 m to depths of 400 m as reported by Alander from the Skaggerak. It is likely that it can be found throughout the year in Northern Ireland but there is insufficient information for certainty. It has not been found anywhere else in Ireland, but has been reported from Mingulay in the Hebrides and some other locations in the North-east Atlantic (see below), whilst it has also been reported from off Islay.

Current status: Rare. Known only from Rathlin Island, the Maidens, and a location on the north-east coast. The species has no legal protection. Northern Ireland is a stronghold for this species, it has the only Irish records and this species is also rare in Britain.

Why is this species a priority in Northern Ireland?

• Criterion 3: Rare or restricted range – rare breeding species confined to 5 hectads or less (based on expert judgement).
• Criterion 4: NI stronghold or endemic – both stronghold range/population and designation as ‘endemic’ subject to expert judgement.

Threats: No immediate threats have been documented for this little-known species, but where it is on the exposed surfaces of bedrock, or on boulders, it may be subject to damage from fishing pots, or in the case of boulders, by trawling or dredging operations.

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 existing populations and range.
• Manage known sites appropriately and monitor populations there.
• Protect any new sites, including the recently discovered location at the Maidens.

Conservation:

• Rathlin Island is a Marine Protected Area with multiple designations.
• There is Habitat Action Plan for Fragile Sponge and Anthozoan Communities on Rocky Habitats.
• The Maidens are a Marine Protected Area with multiple designations.

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

iNaturalist: Clathria elliptichela at iNaturalist World Species Observations database.

WoRMS: Clathria elliptichela at World Register of Marine Species. Accepted name: Clathria (Microciona) elliptichela (Alander, 1942). AphiaID: 167637.

Literature:

Alander, H. (1942). Sponges from the Swedish West Coast and adjacent waters. Unpublished PhD Thesis, University of Lund.

Picton, B.E. and Goodwin, C.E. (2007). Sponge biodiversity of Rathlin Island, Northern Ireland. Jour. Mar. biol. Ass. UK 87: 1441-1458.

Classification: Biota; Animalia; Porifera; Demospongiae; Heteroscleromorpha; Poecilosclerida; Microcionidae; Microcioninae; Clathria

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Adapted from text by Allen & Mellon Environmental Ltd. (2026). Clathria elliptichela. (Alander, 1942). [In] Priority species, Marine Biodiversity Portal NI. https://www2.habitas.org.uk/marbiop-ni/priorityaccounts.php?item=C8145. Accessed on 2026-09-13