Fucus vesiculosus Linnaeus

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Common names: Bladder wrack. Feamainn bhoilgíneach (Irish).
Description: Olive-green to yellow-brown, mid-shore wrack easily recognised by its paired bladders occurring on either side of a prominent midrib. The frond is generally not strongly spiralled and the receptacles do not have a sterile rim (see Fucus spiralis and F. macroguiryi), and the frond does not have a serrated margin (Fucus serratus). Fucus vesiculosus is attached by a small, strongly attached disc which gives rise to a short stipe. The reproductive receptacles are swollen area at the tips of fronds that have many flask-shaped cavities called conceptacle, which house the male and female reproductive structures known as antheridia (borne on antheridiophores) and stalked oogonia (containing 8 eggs), respectively. The eggs and sperm are liberated onto the surface of the receptacles and a pheromone (sex-attracting substance) is released by the eggs that attracts the sperm. Fertilization results in a zygote that forms a new Fucus adult. Should not be confused with Ascophyllum nodosum, which has bladders singly on the frond. This is the most morphologically diverse of the fucoid species, with individualvarying greatly in size and shape. For example, plants can reach up to 1 m on sheltered shores with many pairs of bladders while at the other extreme on exposed shores, plants rarely exceed 20 cm and may have no bladders.
Distribution: This species is very common in the North Atlantic south to the Canary Islands and North Carolina. Records from other areas require confirmation. A bladderless form occurs on more wave-exposed shores in the NE Atlantic (last picture below).
Usage: Fucus vesiculosus is widely used in cosmetic preparations and in thalassotherapy.

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