Antithamnionella grallatoria Huisman

Scientific Description

Habit and structure. Thallus pale red, spreading laterally to 2.5 mm and up to 1.4 mm tall. Each cell of the prostrate axes bearing 3 or 4 lateral branches, one arising from the ventral surface and attaching the thallus to the substratum, multicellular but remaining unbranched with a digitate terminal pad. An indeterminate erect branch arising on every second cell of the prostrate axis, with the other 1 or 2 branches remaining reduced. Erect axes with a percurrent axis bearing 2 or 3 whorl branches at the distal end of each cell. Cells of erect axes 15–25 µm diam. [L:B 3–9], except the basal cell which is shorter [L:B c. 1]; distal axial cells c. 10 µm diam. [L:B 10–11]. Whorl branches markedly more slender than erect axes, simple or with 1–3 laterals, with cells 2–8 µm diam. [L:B 2–10]. Vesicular cells solitary or in series of 2–3 (–4) on whorl branch cells (not the basal cell), ellipsoidal, covering most of the distal adaxial surface of the bearing cell and causing a distortion. Distal ends of vesicular cells often slightly abutting the proximal end of the next cell.

Reproduction. Spermatangia arising on 2–4- celled branches borne adaxially in series on up 4 cells of whorl branches, with 1 or 2 spermatangial branches per cell. Cystocarps terminal on erect axes, with 3 or 4 sequentially maturing gonimolobes to 200 µm diam., composed entirely of carposporangia 20–25 µm diam. (when mature).

Distribution. Known only from the type locality and collection.

Habitat. Epilithic in the subtidal.

[After J.M. Huisman in Algae of Australia: Marine Benthic Algae of North-western Australia, 2. Red Algae: 375 (2018)]