Centroceras maccarthyi Huisman

Scientific Description

Habit and structure. Thallus with prostrate and assurgent axes, light red, to 3.5 mm tall, sparsely subdichomously branched every c. 8 cells, but often with long unbranched axes. Adventitious lateral branches commonly arising from nodes. Prostrate axes attached by multicellular rhizoids arising 1–3 per node from periaxial cells, basally as an extension of the periaxial cell and the first cross wall external to the node. Upright axes with forcipate apices. Segments 70–90 µm diam. [L:B < 1 near apices, to 5 in mature segments]. Periaxial cells 8–11 per node, each bearing 2 acropetal and 1 basipetal initials. First acropetal initial bearing either a spine or a vesicular cell, and 1 or 2 conical to elongate cells, these often forming elongate hairs. Second acropetal initial bearing 1 acropetal conical to elongate cell and a basipetal cortical filament. Basipetal initial bearing 1 basipetal cortical filament. Spines 2-celled (not including acropetal initial), in whorls of 4–6 per node. Vesicular cells ellipsoidal, 10–12 µm long, 7–10 µm diam. Basipetal cortical filaments 10–12 cells long, completely covering the axial cells, with cells of varying lengths, these often becoming transversely aligned towards the proximal portion of each segment.

Reproduction. Spermatangia in dense tufts arising from acropetal cells. Tetrasporangia solitary or in whorls at nodes, borne on periaxial cells, pyriform to clavate, 40–50 µm diam., tetrahedrally divided, with an involucre of 2- or 3-celled hyaline filaments, although these sometimes absent (possibly shed).

Distribution. Endemic to north-western Australia (Barrow Island, the Rowley Shoals and Scott Reef).

Habitat. Epiphytic in the shallow subtidal.

[After J.M. Huisman in Algae of Australia: Marine Benthic Algae of North-western Australia, 2. Red Algae: 382–384 (2018)]