Ceramium keulenii Huisman

Scientific Description

Habit and structure. Thallus pale red, with indeterminate creeping axes attached by unicellular rhizoids arising from periaxial cells. Erect axes mostly simple, to 1.5 mm tall, perpendicular to the prostrate axes, with cells 50–75 µm long and 25–30 µm diam.; nodes 30–38 µm diam. Nodal cortication discrete, with 4 periaxial cells, each cutting off 2 acropetal cells and rarely an oblique basipetal cell, this sometimes appearing as a pseudoperiaxial cell. Nodal cortication in prostrate axes occasionally better-developed acropetally and basipetally.

Reproduction. Spermatangia arising on nodal cells near apices of erect axes, extending over 3–5 nodes, forming a stichidium-like structure. Cystocarps terminal on erect axes, with 1 or 2 sequentially developing gonimolobes c. 100 µm diam., subtended by 3 involucral branches. Tetrasporangia in stichidium-like swellings to 4 nodes long at the apices of erect branches, 2 or 3 per node, subspherical, 30–40 µm long, 20–35 µm diam. (including the thick wall), cruciately divided.

Distribution. Known only from the Dampier Archipelago and Broome, Western Australia.

Habitat. An obligate epiphyte on Pterocladiella caerulescens in the subtidal.

[After J.M. Huisman in Algae of Australia: Marine Benthic Algae of North-western Australia, 2. Red Algae: 399–400 (2018)]