Polysiphonia atlantica is a small filamentous species of red marine algae Rhodophyta. The thalli form small tufts up to 3 cm long. The axes are ecorticate consisting of axial cells surrounded by four periaxial cells.Maggs, C.A. and Hommersand, M.H. 1993 Seaweeds of the British Isles. Volume 1 Rhodophyta Part 3A Ceramiales. The Natural History Museum, London.
Description Polysiphonia atlantica is a small alga 3 cm high and dark reddish-brown in colour. It grows in tufts from prostrate axes producing numerous erect branches all growing to the similar lengths. The axial cells are surrounded by 4 periaxial cells which are elongate to the same length as the axial cells which are ecorticate. Attached by rhizoids produced by the periaxial cells.
Reproduction The life history is a sequence of three phases: gametangial, carposporangial and tetrasporangial.Dixon, P.S. Biology of the Rhodophyta. p.187. Oliver & Boyd. The plants are dioecious with spermatangial branchlets at the apices of the branches, cystocarps are slightly urceolate. The tetrasporangia occur the branches in a straight series.
Habitat Growing on rock, mussels other invertebrates or epiphytic. Between high and low water levels.Hardy, F.G. and Guiry, M.D. 2003. A Check-list and Atlas of the Seaweeds of Britain and Ireland. The British Phycological Society.
Distribution Records have been made from the British Isles- England, Ireland, Wales and Scotland, to Morocco, east coast of America and the Indian Ocean. Most of the records from the British Isles are probably those of Polysiphonia stricta.
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