Wrangelia elegantissima R.E.Norris

Scientific Description

Habit and structure. Thallus to 3 cm tall, with prostrate and assurgent axes, red to yellow-brown. All axial cells with 5 whorl branches, 1 or 2 long and the remainder short. Indeterminate branches arising from the basal or suprabasal cells of whorl branches, arranged alternately along the primary axis, eventually branching in a pattern similar to the primary axis. Apices curved, with long whorls arising from the convex surface. Primary axial cells 40–60 µm diam. near apex [L:B 3–3.5]; lower cells 290–350 µm diam. [L:B c. 2]. Long whorls unequally dichotomously divided, generally with 1–4-celled terminal branches, with basal cell 30–50 µm diam. [L:B c. 2]; median cells 30–35 µm diam. [L:B 5–7], abruptly tapering at apices with single or paired spinous cells, although these apparently dehiscent as many apices have only blunt cells. Primary axes initially becoming corticated by much-branched essentially transversely orientated rhizoidal filaments arising from basal cells of whorl branches, later by basipetal filaments also from basal cells of whorl branches.

Reproduction. Tetrasporangia borne on lower cells of modified whorl branches, spherical, 85–110 µm diam. when mature (including a wall to 25 µm thick in young tetrasporangia), tetrahedrally divided, with several branched involucral filaments, these dichotomous or with a 2–4-celled percurrent filament and opposite branches. Spermatangia formed in spherical to ellipsoidal heads on lower cells of whorl branches, 85–100 µm long and 75–85 µm diam., each with an involucre of 4 or 5 simple or once-divided filaments from the subtending cell. Spermatangial heads with a central axis 2 cells long, each bearing numerous whorled laterals, these 3 or 4 times branched and producing terminal elongate spermatangia. Cystocarps formed at apices of lateral branches.

Distribution. Ningaloo Reef north to Broom, Western Australia and the Hawaiian Islands.

Habitat. Epiphytic or epilithic in the intertidal and shallow subtidal.

[After J.M. Huisman in Algae of Australia: Marine Benthic Algae of North-western Australia, 2. Red Algae: 617–618 (2018); J.M. Huisman in Marine Plants of Australia: 187 (2019)]