Polysiphonia opaca explained

Polysiphonia opaca (C.Agardh) Moris et De Notaris is a small marine alga in the division Rhodophyta.

Description

This small seaweed consists of tufts of branches no more than 6 cm long.^[1] The tufts are of erect branches each consisting a series of axial cells surrounded by about 20 periaxial cells all of the same forming a "collar" around the axis. There is no cortication and the plant is attached by rhizoids which attach the plant to a surface.^[1] This alga may be confused with Lophosiphonia reptabunda, this alga has however a turf-like habit and is less than 3 cm high unlike P. opaca which grows to over 5 cm high.^[1]

Distribution

Very rare, recorded from the south of Wales.^[2] Europe: British Isles to Spain, West Indies and E.Australia.^[1]

Notes and References

1. Maggs, C.A. and Hommersand, M.H. 1993. Seaweeds of the British Isles Volume 1 Rhodophyta Part 3A Ceramiales. The Natural History Museum, London.
2. Hardy, F.G. and Guiry, M.D. 2003 A Check-list and Atlas of the Seaweeds of Britain and Ireland. British Phycological Society