Trichogloea requienii (Mont.) Kütz.

Scientific Description

Habit and structure. Thallus to 25 cm high, dark red-purple to greenish, paniculate, extremely mucilaginous, lightly calcified, generally with several axes arising from an ill-defined holdfast. Primary axes terete, to 7 mm in diameter, tapering to the apices; lateral branches 1–2 mm in diameter. Medullary cells elongate, 15–45 µm in diameter. Assimilatory filaments sparsely dichotomously (rarely trichotomously) branched, near periphery unbranched for 10–12 cells; lower cells elongate, 5–12 µm in diameter; distal cells becoming broader and shorter, 15–25 µm in diameter (L:B c. 1). Adventitious rhizoids common, arising from lower cells of assimilatory filaments.

Reproduction. Spermatangia subspherical, 3–5 µm in diameter. Carposporophyte 130–150 µm in diameter. Carposporangia terminal, obovoid to clavate, 11–18 × 5–7 µm, in clusters on bearing cells.

Distribution. Known from the Houtman Abrolhos, Dampier Archipelago and Montebello Is., north-western  Australia; probably growing around northern Australia to the Great Barrier Reef, Qld., Lord Howe I., and Norfolk I. Widespread in warm-temperate to tropical seas.

Habitat. T. requienii is usually associated with coral reefs in areas of high water movement.