Amphiroa crassa J.V.Lamour.

Scientific Description

Habit and structure. Thallus to 10 cm tall, calcified, variable in habit; branching dichotomous and multiplanar (projecting in different planes). Intergenicula terete to compressed, to 32 mm long and 1–3 mm diam. Genicula composed of core region cells only; core region containing 10–16 arching tiers of cells with 1–8 tiers of longer cells followed by a tier of shorter cells; genicula occasionally associated with branching points, but generally independent of them. Calcified collars present.

Reproduction. Tetrasporangial conceptacles uniporate, scattered over intergenicula and protruding above the surrounding surface. Conceptacle pore canals flanked by filaments projecting laterally towards the pore canal; rings of large block-shaped cells absent. Mature conceptacle chambers 210–300 μm diam. and 90–110 μm tall; tetrasporangia 15–25 μm diam. and 40–75 μm long. Male conceptacles uniporate with unbranched spermatangial filaments on the conceptacle chamber floor. Female and carposporangial thalli not recorded from Australia.

Distribution. Worldwide distribution.

Habitat. on coral reef flats down to 26 m.

[After A.S. Harvey, W.J. Woelkerling & J.M. Huisman in Algae of Australia: Marine Benthic Algae of North-western Australia, 2. Red Algae: 100 (2018)]