Tall sea pen (Funiculina quadrangularis)

Close up of tall sea pen polyps and eggs
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Tall sea pen fact file

Tall sea pen description

GenusFuniculina (1)

Sea pens are colonial organisms that belong to the same group as corals and sea anemones (3). Each animal comprises of a colony of soft-bodied polyps, which occur along a stiffened (3) calcareous middle section, called an 'axis' or 'rachis' (3). The tall sea pen is the largest of the three sea pens that occur around the British Isles (2). It is very narrow, with a white axis that is square in cross-section (1). The polyps have eight tentacles (3), are pale pink or white in colour and occur irregularly along the axis or in rows in places (1).

Height: up to 2.1 m (2)

Tall sea pen biology

The tall sea pen is colonial (1), often occurring in dense 'forests' (3). This species is a passive suspension feeder, taking in plankton and organic particles from the water column with the tentacles (3). The sexes are separate, with male and female polyps occurring in separate colonies on different sea pens (1).

The tall sea pen can play host to a brittlestar (Asteronyx loveni), which encircles it with its arms in order to cling on, and an isopod (Astacilla lonicornis) (1).


Tall sea pen range

In Great Britain, this species is found off the west and north coasts of Scotland (1). It also occurs off the west and north of Ireland, in the North Atlantic and the Mediterranean, with further records from Japan and New Zealand (1).

You can view distribution information for this species at the National Biodiversity Network Atlas.

Tall sea pen habitat

Lives attached to soft mud plains that are permanently covered by seawater (2), with a preference for sheltered coasts, especially sea lochs, in depths of between 20 and 2000 metres (1).


Tall sea pen status

Not protected under the Wildlife and Countryside Act 1981. A UK Biodiversity Action Plan priority species (2).


Tall sea pen threats

This sea pen has fairly precise habitat requirements; the need for soft, undisturbed mud may be responsible for limiting the distribution of the species. In some otherwise suitable habitats the tall sea pen is absent, and it is thought that trawling may have removed colonies. Furthermore, where the species occurs in isolated sea lochs, water exchange with the open sea may be restricted; any pollutants are particularly damaging as their effects are concentrated within the loch (2).


Tall sea pen conservation

The tall sea pen is a UK Biodiversity Action Plan priority species, as such a Species Action Plan has been produced to guide its conservation (2). This plan aims to maintain the current distribution of the species (2). No conservation action has so far been directed at this species, but it does occur in a candidate marine Special Conservation Area and marine consultation areas, which should aid its protection, at least in a few sites (2).

The UK Biodiversity Action Plan for this species is available at UK BAP.
There may be further information about this species available via the National Biodiversity Network Atlas.


This information is awaiting authentication by a species expert, and will be updated as soon as possible. If you are able to help please contact: arkive@wildscreen.org.uk


Containing free calcium carbonate, chalky.
Relating to or belonging to a colony (a group of organisms living together in a group).
Aquatic organisms that drift with water movements; may be either phytoplankton (plants), or zooplankton (animals).
Typically sedentary soft-bodied component of cnidaria (corals, sea pens etc), which comprise of a trunk that is fixed at the base; the mouth is placed at the opposite end of the trunk, and is surrounded by tentacles.


  1. Ager, O. 2001. Tall sea pen, Funiculina quadrangularis. Marine Life Information Network: Biology and Sensitivity Key Information Sub-programme [On-line]. Plymouth: Marine Biological Association of the United Kingdom. (August, 2002)
  2. UK BAP (August, 2002)
  3. UK Marine SACS Project. (August, 2002)

Image credit

Close up of tall sea pen polyps and eggs  
Close up of tall sea pen polyps and eggs

© Sue Scott

Sue Scott
Strome House
North Strome
Loch Carron
IV54 8YJ
United Kingdom
Tel: +44 (0) 1520 722588


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