Dudresnaya barrowensis Huisman

Scientific Description

Habit and structure. Thallus to 6 cm tall, light pink, irregularly and profusely branched. Holdfast not observed. Primary axes terete to compressed, to 2 mm wide, bearing numerous slender lateral branches, these basally c. 500 µm diam., tapering to pointed apices. Lateral and minor branches terete, distinctly annulate, the annulations corresponding to the verticillate tufts of fascicles. Primary axial filaments obvious thoughout most of the thallus, with cylindrical cells 190–500 µm long and 50–100 µm diam. when mature, each bearing 4 or 5 lateral fascicles, these branched di- to tetrachotomously at most cells, but ultimate branches often consisting of 2 or 3 ellipsoidal cells. Hexagonal crystals absent. Periaxial cells also bearing descending rhizoids.

Reproduction. Carpogonial branches 8 cells long, mostly arising from periaxial cells; upper cells reflexed. After fertilisation the carpogonium fusing with 1 or 2 cells of the carpogonial branch, these then issuing connecting filaments. Auxiliary cell branches in similar positions to carpogonial branches, 11–13 cells long, the auxiliary cell intercalary, 4–6 cells from the base, the adjacent cells larger and darkly staining. Following diploidisation, a gonimoblast developing from the auxiliary cell and forming a spherical gonimolobe 110–170 µm diam., composed entirely of carposporangia, these angular to spherical and 7–13 µm diam. Other reproductive structures not observed.

Distribution. Known only from Barrow Island, north-western Australia.

Habitat. Habitat not recorded, but probably epilithic. The type specimens (possibly all fragments of a single plant) were collected during monitoring of subtidal habitats.

[After J.M. Huisman in Algae of Australia: Marine Benthic Algae of North-western Australia, 2. Red Algae: 175–176 (2018)]