A red seaweed (Aglaothamnion diaphanum)

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

Summary

Description

Aglaothamnion diaphanum is a pale pink coloured red seaweed, 2-10 mm high, with a delicate texture. The fronds are branched in one plane, with a single principal axis and linear to fan-shaped (flabellate) outline. This species shows little variation except in the degree of development of branching. In some thalli, occasional branching become equal in length to the main axis, producing a fan-shape (flabellate) rather than linear frond outline.

Recorded distribution in Britain and Ireland

This rare species is known in the British Isles from only a few records from the Isles of Scilly.

Global distribution

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Habitat

Usually grows on large algae as an epiphyte but also on bedrock, and rarely found growing on pebbles. This subtidal species grows from 7-25 m depth and can tolerate moderately wave exposed sites.

Depth range

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Identifying features

  • Uninucleate vegetative cells.
  • Zig-zag or U-shaped short side branches (carpogonial branches).
  • Thalli consisting of one to a few erect axes attached by small discoid filamentous holdfast and secondary creeping axes.
  • Hairs are abundant on female plants but absent during the spore-producing phase in the life cycle (bisporophytes).

Additional information

Could be confused with very small non-reproductive thalli of some growth forms of Compsothamnion gracillimum but Compsothamnion species are multinucleate in contrast to Aglaothamnion, which is uninucleate. Thalli reproductive from a small size and are usually easily recognisable by the reproductive spores (bisporangia). Identification of single specimens can be difficult, so if possible a number of thalli should be collected.

Listed by

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Further information sources

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Bibliography

  1. Howson, C.M. & Picton, B.E., 1997. The species directory of the marine fauna and flora of the British Isles and surrounding seas. Belfast: Ulster Museum. [Ulster Museum publication, no. 276.]

  2. Maggs, C.A. & Hommersand, M.H., 1993. Seaweeds of the British Isles: Volume 1 Rhodophycota Part 3A Ceramiales. London: Natural History Museum, Her Majesty's Stationary Office.

Datasets

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

  2. OBIS (Ocean Biodiversity Information System),  2025. Global map of species distribution using gridded data. Available from: Ocean Biogeographic Information System. www.iobis.org. Accessed: 2025-05-21

Citation

This review can be cited as:

Edwards, R.V. 2003. Aglaothamnion diaphanum A red seaweed. In Tyler-Walters H. and Hiscock K. Marine Life Information Network: Biology and Sensitivity Key Information Reviews, [on-line]. Plymouth: Marine Biological Association of the United Kingdom. [cited 21-05-2025]. Available from: https://www.marlin.ac.uk/species/detail/1929

Last Updated: 11/07/2003