MarLIN

information on the biology of species and the ecology of habitats found around the coasts and seas of the British Isles

A red seaweed (Polyides rotunda)

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

Summary

Description

A dark red or blackish seaweed with smooth, cartilaginous, cylindrical fronds, branching dichotomously in roughly the same plane. The fronds rise from a fleshy, discoid holdfast up to 2 cm in diameter. The reproductive bodies occur as oval shaped swellings along the sides of the branches or occasionally encircling them. The seaweed grows up to 20 cm in length.

Recorded distribution in Britain and Ireland

Occurs around all coasts of Britain and Ireland. There is a paucity of records from south east England which may reflect a lack of suitable substrata.

Global distribution

In Europe, occurs from the Arctic Ocean to northern Spain and in the Baltic Sea. In North America, occurs from the Hudson Straits to New York.

Habitat

Grows attached to rock and stones in pools in the lower intertidal and subtidally to 20 m. The holdfast is often buried by coarse, sandy deposits.

Depth range

-

Identifying features

  • erect, cylindrical, dichotomously branching fronds.
  • fleshy, discoid holdfast.
  • dull red in colour, blackish when dry.
  • tetrasporangia cruciate or irregular, borne on uppermost branches which become slightly thickened.
  • cystocarps produced in oval, spongy, wart-like growths on one side of, or encircling, branch.
  • spermatangia thin, plate-like and colourless.

Additional information

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Listed by

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Further information sources

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Bibliography

  1. Dickinson, C.I., 1963. British seaweeds. London & Frome: Butler & Tanner Ltd.

  2. Dixon, P.S. & Irvine, L.M., 1977. Seaweeds of the British Isles. Volume 1 Rhodophyta. Part 1 Introduction, Nemaliales, Gigartinales. London: British Museum (Natural History) London.

  3. Fish, J.D. & Fish, S., 1996. A student's guide to the seashore. Cambridge: Cambridge University Press.

  4. Hardy, F.G. & Guiry, M.D., 2003. A check-list and atlas of the seaweeds of Britain and Ireland. London: British Phycological Society

  5. JNCC (Joint Nature Conservation Committee), 1999. Marine Environment Resource Mapping And Information Database (MERMAID): Marine Nature Conservation Review Survey Database. [on-line] http://www.jncc.gov.uk/mermaid

  6. Picton, B.E. & Costello, M.J., 1998. BioMar biotope viewer: a guide to marine habitats, fauna and flora of Britain and Ireland. [CD-ROM] Environmental Sciences Unit, Trinity College, Dublin., http://www.itsligo.ie/biomar/

Citation

This review can be cited as:

Rayment, W.J. 2003. Polyides rotunda A red seaweed. In Tyler-Walters H. and Hiscock K. (eds) Marine Life Information Network: Biology and Sensitivity Key Information Reviews, [on-line]. Plymouth: Marine Biological Association of the United Kingdom. Available from: http://www.marlin.ac.uk/species/detail/1615

Last Updated: 01/07/2003