Ahnfeltia plicata

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Ahnfeltia plicata, commonly known as the landlady's wig, is a red seaweed found in the northern Atlantic. It grows on hard rock from the middle shore down to about 12 meters deep, often on rock that has sand or in rock pools.

It forms tufted, perennial plants with wiry, cylindrical fronds that branch irregularly in a dichotomous, or splitting, pattern. A typical plant is about 15 cm tall and 10 cm wide, with a discoid holdfast up to 2.5 cm wide that anchors it to the rock. Its reddish-black color comes from red pigments called phycoerythrin and phycocyanin, which mask chlorophyll and beta-carotene. Some unique xanthophylls are also present.

The landlady's wig can be confused with Cordylecladia erecta, but that species is less common and has thicker, more rigid, regularly branched fronds.

Habitat and growth: it grows on hard surfaces and is common on rock covered with sand, and in rock pools. Strong storms can tear it from the rock, creating floating mats. The base of the fronds can keep growing even after detachment. It grows slowly and may live for five to ten years.

Life cycle: on male plants, the middle parts of the frond have spermatangial sori; on female plants, there are gametangial sori up to 5 mm long. After fertilization, carpospores form on the female frond. These give rise to a second diploid generation, the tetrasporophyte, which often encrusts pebbles and produces tetraspores that grow into new gametophyte plants. The encrusting tetrasporophyte form is known as Porphyrodiscus simulans.

Edible and versatile: Ahnfeltia plicata is edible and was used in the Soviet Union to produce agar. It can be eaten raw or cooked and is said to have a crunchy texture and pleasant taste.