Gastroclonium reflexum is a small red alga (Rhodophyta) reported from Ireland and Britain.
This small alga grows to about 6 cm long: the fronds grow from a branched holdfast are reflexed and form haptera where they meet the rock. The branches are hollow, terete to 6 cm long and constricted by septa giving a beaded appearance. The secondary branching is dichotomous, distichous. In colour they are dark purplish red. [1] The species is very similar to Chylocladia verticillata with which it may be confused. [2] Spermatangia, cystocarps and polysporangia have been recorded. [1]
Gastroclonium is widely distributed in the north Atlantic Ocean and Mediterranean Sea, where it grows epilithically or epiphytically in the littoral or sublittoral zones. [1] [3]
In Great Britain, it has been recorded from Cornwall, Devon, Sussex, Norfolk, Pembrokeshire and Glamorgan. [1] It was first recorded from Ireland by W.H.Harvey as Chylocladia reflexa Leorm. and published in 1846. [1] [4] [5] Outside the British Isles, Gastroclonium has been recorded from the Channel Islands, Spain, Portugal, the Canary Islands, the Mediterranean Sea, Namibia, Morocco and South Africa. [3]
Specimens collected from Lough Swilly by W. Sawers in 1854 are now preserved in the Ulster Museum (BEL) (F7058; F7059 and F7060) were redetermined as Chylocladia verticillata by Guiry as Chylocladia verticillata. [5]