Halymenia villosa Huisman & De Clerck

Scientific Description

Habit and structure. Thallus erect, light red to dark red-brown, to 7 cm tall, with a woody stipe to 12 mm long and 2.0–2.5 mm diam., abruptly transitioning to a firm blade to 6 cm tall and 9 cm wide. Blade mostly entire or shallowly laciniate, with marginal spines 2–3 mm long. Medulla with traversing filaments 8–14 µm diam., mixed with numerous dark-staining ganglionic cells. Cortex with 6 or 7 cell layers, the inner 3 or 4 layers of stellate cells with interlinking arms; outer layers progressively smaller and more pigmented. Outermost layer of elongate anticlinal cells 15–35 µm long and 3–5 µm diam., often tapering distally, forming a palisade.

Reproduction. Tetrasporangia in the outer cortex, postero-laterally attached, subspherical, 17–30 µm long and 12–27 µm wide, cruciately or decussately divided. Other reproductive structures not observed.

Distribution. Known from scattered locations in the Kimberley region, north-western Australia.

Habitat. Epilithic in the intertidal to 16 m depth.

[After J.M. Huisman & O. De Clerck in Algae of Australia: Marine Benthic Algae of North-western Australia, 2. Red Algae: 291–292 (2018)]