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 20m, but has been recorded elsewhere down to 400m
• It probably can be found throughout the year
• Listed as a priority on account of its rarity and importance of the Northern Ireland population
• Not enough is known to positively identify threats, 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 20m to depths of 400m 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: Known only from Rathlin Island, the Maidens, and a location on the north-east coast. The species has no legal protection.

Why is this species a priority in Northern Ireland? Northern Ireland has the only Irish locations for this species and it is regarded as being extremely rare in a UK context. There is no evidence of any trends in conservation status at present, due to a lack of information.

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:

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

Objectives: Records of new sites for this species, with details of habitat and population are always valuable. Send these to CEDaR, National Museums Northern Ireland, 153 Bangor Road, Cultra, Holywood, County Down, BT18 0EU. Tel 028 9039 5257 or e-mail cedar.info [at] nmni.com. If you are a diver, and interested in becoming involved in recording marine life in Northern Ireland through the Seasearch project, contact Claire Goodwin at claire.goodwin [at] gmail.com or look at the web site www.seasearch.org.uk (Northern Ireland web pages).

Conservation: Survey work is being conducted throughout Northern Ireland waters (including the north coast) by Northern Ireland Environment Agency for this and other species and habitats generally.

Rathlin Island and its waters have been designated a Special Area for Conservation under the EU Habitats Directive.

There is no Species Action Plan for Microciona elliptichela, but the UK Habitat Action Plan for Inshore Sublittoral Rock has the following objectives:

• maintain the extent and quality of inshore sublittoral rock habitats in the UK, including the full diversity of communities.

Measures to be considered further include:

• protecting sites of conservation importance from damage through contamination and physical disturbance (for example, turbidity and towed fishing gear)
• requiring EIAs for coastal developments to examine potential effects on intertidal and nearshore areas
• monitoring any impact of dump sites on inshore sublittoral rock habitats, communities and wildlife, and taking action as appropriate
• implementing strategies for managing the coastal zone at local, regional and national levels.

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.

Maier, C. (2006). Biology and ecosystem functions of cold water bioherms at Mingulay (Hebrides) and the North-east Atlantic. ‘Pelagia’ Cruise Report, July 2006.

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

Picton, B.E. and Morrow, C.C. (2007). [In] Encyclopedia of Marine Life of Britain and Ireland.

http://www.habitas.org.uk/marinelife/species.asp?item=C8145.

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

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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 2026-07-28