Colaconema caespitosum (J. Agardh) Jackelman, Stegenga & Bolton
Description: Forming dense, brownish-red tassel-like tufts of sparingly branched erect, uniseriate hair-like filaments. Cells oblong, 3-4 times as long as broad. Several plastids, each with a pyrenoid, against cell wall. Reproducing by monosporangia, all year around. Tetrasporangia occasionally formed in winter.
Habitat: On limpets (Patella , mainly P. vulgata) on exposed shores and epiphytic on Codium fragile in the lower intertidal of exposed and semi-exposed coasts. Commoner on western and south-western coasts of Britain and Ireland than records indicate; south to Morocco. Adriatic. South Africa. Australia and New Zealand.
Similar species: Rhodochorton purpureum and Rhodothamniella floridula which are do not occur on limpets, are generally turf-forming and do not form monosporangia.
Key characteristics: Association with limpets; tasellated growth form of tufts. Abundant and large monosporangia.