A burrowing sea cucumber known only the east or south-east coast in Northern Ireland, living buried in muddy sands. Its habitat has been heavily impacted by fishing.

In brief

• Found at scattered sites on the east and SE coast of Northern Ireland.
• Lives buried in muddy sands.
• Likely to be visible, through careful searching, throughout the year.
• Population is thought to be in decline.
• Main cause of decline is probably bottom trawling and dredging.

Species description: A rather worm-like sea cucumber (holothurian) ranging from 10 to 30 cm in length. It has a pinkish, transparent skin and body, and the five longitudinal muscles within show clearly. It has twelve pinnate (feather-like) tentacles, each of which has 8-11 pairs of digits, and these are somewhat longer towards the end of the tentacle. The animal lacks tube feet. The spicules (skeletal structures) are anchor in form, with pear-shaped plates.

Life cycle: Sexes are separate in this species, and spawning and fertilisation occurs externally. It has a planktonic life stage before metamorphosing into a juvenile of the adult form.

Similar species: All the British synaptids are similar, and need to be sorted by close examination of the tentacles and spicules (skeletal structures in the body wall).

How to see this species: It occurs buried in sublittoral muddy sands, and has been found at scattered locations around the east and SE coasts of Northern Ireland.

Current status: Rare. Previously there was believed to be only one known location in Northern Ireland, although it is now known to have a wider distribution. There are a few records from Ireland and it is recorded sparsely around a number of northern locations in Britain. The species has no legal protection. Northern Ireland appears to be a stronghold for this species.

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).

Threats: This species is highly sensitive to bottom fishing, through causing disruption and loss of habitat. The species is also recorded as being sensitive to industrial waste and dumping.

Objectives:

• Maintain the number of viable populations of the species.
• Maintain the range of the species.
• Establish appropriate management known sites, and of any others that are discovered.

Conservation:

• Strangford Lough is a Marine Protected Area with multiple designations.
• 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.
• The relevant Northern Ireland Habitat Action Plans are for Horse Mussel Beds and for Mud Habitats in Deep Water.

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

iNaturalist: Leptosynapta bergensis at iNaturalist World Species Observations database.

WoRMS: Leptosynapta bergensis at World Register of Marine Species. Accepted name: Leptosynapta bergensis (Östergren, 1905). AphiaID: 124462.

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