A small and almost transparent burrowing sea cucumber in Northern Ireland known only from three sites in Strangford Lough, all of which have been badly affected by fishing activities.

In brief

• Found in three sites in the central regions of Strangford Lough
• Lives on the surface or slightly below, fine muds and silts
• Can be found throughout the year
• Thought to have declined, and there are no other sites recorded in Ireland
• Main threats likely to come from fishing and use of mobile bottom gear.

Species description: First reported in British and Irish waters in 1972, this is a very small, almost obscure sea cucumber (or holothurian) that lives on, or slightly below, the surface of very soft muds and silts. It is about 2-4cm in length, and is almost transparent, such that the five longitudinal muscle bands can be seen through the skin. However, it also has brown glandular papillae appearing as dots on the surface. It is equipped with twelve tentacles, each ending with four digits. The spicules (small skeletal structures within the body wall) are anchor-shaped, narrowing into distinct ‘handles’. The species lacks tube feet or respiratory trees (branched structures).

Life cycle: It has been suggested that this species starts life as a male, and then with increasing size is able to switch to being a female. They may also brood the fertilised eggs internally, giving rise to a type of live birth situation.

Similar species: Labidoplax buski is very similar, but has eleven tentacles, each with a central long terminal digit and a part of lateral digits. However, it has been suggested that the two species are synonymous.

How to see this species: Labidoplax media can only be found in Northern Ireland at three sites in Strangford Lough; Bird Island Passage, Town Rock, and the Quoile estuary, on the surface or just below, very soft, watery or glutinous muds and silts in very sheltered locations. It has been found within the Modiolus modiolus community in the lough. For some time Strangford was regarded as the only location for this species in the British Isles, but it has since been found in sheltered lochs of the outer Hebrides and similar sites on the west coast of the Scottish mainland. It was originally discovered in Scandinavia.

Current status: In Northern Ireland it is only known from three sites in Strangford Lough, and it has not been found in any other part of Ireland. The species has no legal protection.

Why is this species a priority in Northern Ireland? The species is rare in Northern Ireland, and the population represents 100 per cent of the total Irish population. It has been reported as declining in Northern Ireland.

Threats: The three known sites in Strangford Lough have all been badly affected by fishing activities, particularly bottom trawling and dredging.

Action:

• Maintain the number of viable populations of the species
• Maintain the range of the species
• Establish appropriate management of known sites
• Proactively search for new sites containing appropriate habitats.

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.

Strangford Lough has been designated a Special Area for Conservation under the EU Habitats Directive, and is a Marine Nature Reserve. Following concerns about the impact of fishing on key features of the lough, a study on ecological change was conducted in 2004, and following this a project to restore the Modiolus modiolus community has commenced. Use of mobile fishing gear in the lough has been banned.

There is no Species Action Plan for this species, but the relevant UK Habitat Action Plans include:

• Modiolus modiolus beds
• mud habitats in deep water
• inshore sublittoral sediments.

The relevant Northern Ireland Habitat Action Plan is for Mud Habitats in Deep Water. It contains the following actions:

• where appropriate, maintain the extent of mud habitats in deep water and associated animal communities
• maintain representative examples of mud habitats in deep water and their associated animal communities which exhibit minimal anthropogenic influences
• where appropriate, enhance the extent and condition of nationally important mud habitats in deep water in Northern Ireland.

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

iNaturalist: Labidoplax media at iNaturalist World Species Observations database.

WoRMS: Labidoplax media at World Register of Marine Species. Accepted name: Labidoplax media Östergren, 1905. AphiaID: 124457.

Literature:

Gotto, D.M. and Gotto, R.V. (1972). Labidoplax media Oestergren: a sea-cucumber new to British and Irish waters, with observational notes. Ir. Nat. J. 17(8): 250-252.

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=ZB5340.

Tyler-Walters, H., 2005. Labidoplax media. A sea cucumber. Marine Life Information Network: Biology and Sensitivity Key Information Sub-programme [on-line]. Plymouth: Marine Biological Association of the United Kingdom. [cited 26/03/2008]. http://www.marlin.ac.uk/species/Labidoplaxmedia.htm.

Classification: Biota; Animalia; Echinodermata; Echinozoa; Holothuroidea; Paractinopoda; Apodida; Synaptidae; Labidoplax

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Allen & Mellon Environmental Ltd. (2026). Labidoplax media. (Ostergren, 1905). [In] Priority species, Marine Biodiversity Portal NI. https://www2.habitas.org.uk/marbiop-ni/priorityaccounts.php?item=ZB5340. Accessed on 2026-07-28