Biodiversity & Conservation

A red seaweed - Ahnfeltia plicata

Ahnfeltia plicata

Image Francis Bunker - Bushy specimen of Ahnfeltia plicata in shallow sandy lower shore pool. Image width ca 15 cm.
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Distribution map

Ahnfeltia plicata recorded (dark blue bullet) and expected (light blue bullet) distribution in Britain and Ireland (see below)

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Ahnfeltia plicata is not listed under any importance categories.

Taxonomy icon Taxonomy Taxon English term
Phylum Rhodophyta Red seaweeds
Class Florideophyceae
Authority (Hudson) Fries
Recent synonyms None
Map icon Recorded Distribution in Britain and Ireland Occurs on all coasts of Britain and Ireland. There is a paucity of records from south east England, reflecting a lack of suitable substrata.
Habitat information icon Habitat information Ahnfeltia plicata forms turfs on shallow sublittoral bedrock and in rockpools on the lower shore, often partly buried by sand. It may form part of the turf on soft or friable rocks which are too unstable for large fucoids. The tetrasporophyte phase is common on pebbles, whereas the mature gametophytes only occur on more stable substrata.
Text page icon Description A perennial red seaweed which forms dense, tangled tufts. The fronds are very fine, tough and wiry with irregular or dichotomous branching and up to 21 cm in length. The holdfast is disc-like or encrusting, 0.5 to 2 cm in diameter. The fronds are dark brown when moist and appear almost black when dry. The uppermost branches are often green.
Identifying features
  • Gametangial thallus consists of discoid holdfast up to 10 mm in diameter, producing erect fronds.
  • Fronds are terete, of horn-like consistency, uniformly 0.5 mm in diameter.
  • Apices very blunt, axils usually rounded.
  • Branching highly variable, from dichotomous to completely irregular.
  • Male plants form spermatangial sori, visible as thickenings of mature axes, but absent from basal and apical regions of plant.
  • Female plants form gametangial sori, up to 5 mm long and 70 µm high, usually on one side of the mature axes. Individual mature carposporophytes are hemispherical and about 300 µm wide. They may be discrete but are usually coalesced into elongate clusters up to 5 mm long.
  • Tetrasporangial plants are crustose. Tetrasporangia occur in mucilaginous superficial sori with zonately arranged tetraspores.
Additional information icon Additional information

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This review can be cited as follows:

Will Rayment 2004. Ahnfeltia plicata. A red seaweed. Marine Life Information Network: Biology and Sensitivity Key Information Sub-programme [on-line]. Plymouth: Marine Biological Association of the United Kingdom. [cited 09/02/2010]. Available from: <http://www.marlin.ac.uk/speciesinformation.php?speciesID=2417>