Cottoniella spinosa Huisman

Scientific Description

Habit and structure. Thallus light pink to red, with prostrate axes to 18 mm long and erect axes to 15 mm tall. Prostrate axes 100–120 µm wide, attached by multicellular, mostly simple but occasionally branched rhizoids arising singly from the distal cell of each pair of flanking cells, the flanking cell protruding laterally before cutting off the rhizoid. Rhizoids to 1.4 mm long, with cells 20–25 µm diam. [L:B 4–7], tapering to cells 7–8 µm diam. Erect axes 60–150 µm wide, slightly narrowed at the base (where flanking cells are lacking) and tapering evenly to the apices. Unbranched monosiphonous filaments arising 1 per segment from the concave (dorsal) surface of branch apices, to 1.2 mm long, fusiform, with cells to 30–40 (–50) µm diam. [L:B 0.6–2.2]. Basal cells of monosiphonous filaments not conspicuously shorter than distal cells, forming secondary pit connections with the proximal pericentral cell. Cells of monosiphonous filaments narrow near the base, broadening markedly at mid-filament, then tapering to a distinct apical point. All axes with 4 pericentral cells; lateral cells each cutting off a pair of flanking cells. Polysiphonous lateral branches arising from concave surface, near thallus apices at regular 6-segment intervals. Lower axes lightly corticated by adventitious filaments arising from pericentral cells.

Reproduction. Reproduction not seen.

Distribution. This species is currently known only from Gidley Island, Dampier Archipelago, Western Australia.

[After J.M. Huisman in Algae of Australia: Marine Benthic Algae of North-western Australia, 2. Red Algae: 585–588 (2018)]