An erect bryozoan (Porella compressa)

Distribution data supplied by the Ocean Biodiversity Information System (OBIS). To interrogate UK data visit the NBN Atlas.Map Help

Summary

Description

Porella compressa is a stags horn bryozoan with bright to pale pinkish orange erect colonies that can be long-lived. The growth extends upwards and thickly calcified irregular branches form in all directions from 3 to 4 cm high, and in some cases exceeding 9 cm. The branches start flat, composed of two layers of zooids (bilaminar), but become more irregularly rounded as they develop. The colonies are attached to bedrock or boulders by an encrusting base and stand erect from the substratum.

The individual zooids are rectangular to hexagonal in shape, typically 0.4 to 0.6 by 0.2 to 0.3 mm, and separated by deep grooves. The orifice (opening in zooid wall) is semicircular in shape with no oral spines present. The avicularium (a specialized zooid) is large, oval in shape and located below the orifice of the zooid. The frontal wall of the zooid is coarsely granular where the areolae (small, circular areas of tissue) mark the boundary of the zooid and appear as round pores. The brood chamber (ovicell) is hemispherical, finely granular, without pores and is visible only in early development when the embryos are pink to pinkish orange in colour.

Recorded distribution in Britain and Ireland

Recorded along the southwest coast of England and Wales with further records off the coast of Northumberland and Norwich. In Ireland, it is recorded along the southwest and north coast, and in Scotland, it is recorded along the west coast and St. Kilda.  

Global distribution

It is a boreal, arctic circumpolar species. It is recorded from various sites along the west coasts of Britain and Ireland, the North Sea and the Barents Sea. Also recorded around the Aleutian Islands, Avak Inlet, Vaygach Island, White Sea, and the Kattegat.

Habitat

Found in the sublittoral, on coarse ground attached to bedrock, large shell debris and boulders. They grow in areas of high current flow and occur below the kelp belt.  

Depth range

0-130 m (occasional records down to 500 m)

Identifying features

  • Bright to pale pinkish orange in colour.
  • The colonies range from 5 to 10 cm in height.
  • Thickly calcified irregularly rounded branches.
  • Zooids are typically 0.4-0.6 by 0.2-0.3 mm in size.
  • No oral spines are present around the orifice.
  • The avicularium is a large oval shape below the orifice.
  • The frontal wall is coarsely granular.
  • The embryos are pink to pinkish orange in colour.

Additional information

-none-

Listed by

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Further information sources

Bryozoa of the British Isles (https://britishbryozoans.myspecies.info/)

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Bibliography

  1. Hayward, P.J. & Ryland, J.S. 1999. Cheilostomatous Bryozoa. Part II Hippothooidea - Celleporoidea. London: Academic Press. [Synopses of the British Fauna, no. 14. (2nd edition)]

  2. Porter, J., 2012. Seasearch Guide to Bryozoans and Hydroids of Britain and Ireland.   Ross-on-Wye: Marine Conservation Society.

Datasets

  1. NBN (National Biodiversity Network) Atlas. Available from: https://www.nbnatlas.org.

  2. OBIS (Ocean Biodiversity Information System),  2024. Global map of species distribution using gridded data. Available from: Ocean Biogeographic Information System. www.iobis.org. Accessed: 2024-12-27

Citation

This review can be cited as:

Burdett, E.G. 2023. Porella compressa An erect bryozoan. In Tyler-Walters H. Marine Life Information Network: Biology and Sensitivity Key Information Reviews, [on-line]. Plymouth: Marine Biological Association of the United Kingdom. [cited 27-12-2024]. Available from: https://marlin.ac.uk/species/detail/2356

Last Updated: 27/09/2023