Halymenia lunata Huisman & De Clerck

Scientific Description

Habit and structure. Thallus erect, to 35 cm tall, pale pink or pale yellow to almost translucent, membranous, attached by a discoid holdfast, generally with a short terete stipe 3–10 mm long and 1–2 mm wide, bearing 1–several blades. Blades branched to 3 orders, with a percurrent primary axis 5–50 mm wide, tapering towards the apices, bearing numerous marginal branches 2–10 mm wide, slightly narrower at the branch base; these branches, in turn, subdivided. Medulla with dark-staining ganglionic cells (in aniline blue) and relatively broad traversing filaments 5–15 µm diam., these subtending hyaline stellate subcortical cells with elongate arms. Cortex with 3 (–4) layers of pigmented cells, the outermost borne 2–4 per subtending cell, divaricate, ellipsoidal, occasionally tapering, 5–7 µm diam.

Reproduction. Tetrasporangia scattered in the outer cortex, spherical to ellipsoidal, 12–20 µm diam., cruciately or decussately divided.

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

Habitat. Epilithic in the subtidal.

[After J.M. Huisman & O. De Clerck in Algae of Australia: Marine Benthic Algae of North-western Australia, 2. Red Algae: 285–288 (2018)]