Aglaothamnion endostolon Huisman

Scientific Description

Habit and structure. Thallus with prostrate and erect axes, the former endophytic within the medulla of Halymenia maculata, irregularly branched, with cells of various widths and shapes, some slender and 4–5 µm diam., others irregularly shaped and reaching 17–25 µm diam. Erect axes emergent, to 900 µm tall, with cells to 25 diam. [L:B c. 1.5]. Lateral branches 1 (–2) per axial cell, often in unilateral alternating series of 1–3 branches, resulting in the primary axis forming a sinuous curve. Lateral branches 1–3 times dichotomously branched, the ultimate branches up to 16 cells long, with slender cells 5–7 µm diam. Procarps on unmodified intercalary cells of indeterminate axes, in series of up to 11 successive cells, with a supporting cell bearing a 4-celled (including carpogonium) zig-zag carpogonial branch, with a trichogyne to 100 µm long.

Reproduction. Fertile pericentral cell arising opposite the supporting cell. Auxiliary cells arising from the supporting cell and fertile pericentral cell. Immediate post-fertilisation development not observed, but immature carposporophytes with several gonimolobe initials arising from auxiliary cells. Mature carposporophytes and other reproductive structures not observed.

Distribution. Known only from the type locality and collection (Hermite Is., Montebello Is., Western Australia).

Habitat. Endophytic within the medulla of Halymenia maculata.

[After J.M. Huisman in Algae of Australia: Marine Benthic Algae of North-western Australia, 2. Red Algae: 359–361 (2018)]