Halimeda gigas W.R.Taylor

Scientific Description

Habit and structure. Thallus erect, to 15 cm tall, grass-green, with a glossy surface when fresh, drying pale green to white, generally epilithic, arising from a small fibrous holdfast, sparingly dichotomously branched, mostly in one plane. Basal segment terete to subcompressed, often stalk-like, generally with 1 (–2) suprabasal segments becoming broad and flat. Segments mostly discoid, ovate or subcuneate, 12–29 mm wide, 12–23 mm long; distal margin often furrowed. Medullary filaments 60–120 µm diam.; secondary utricles 50–75 µm diam.; peripheral utricles 30–50 µm diam. in surface view, occasionally to commonly fusing laterally, pyriform to mallet-shaped in lateral view, with the lateral walls remaining joined after decalcification, to a length of 20–25 µm. Inner utricles large and bearing peripheral utricles directly (i.e. secondary utricles), or with smaller utricles intercalated (tertiary utricles). Nodal filaments fusing laterally in groups of 2 or 3 for short distances, not forming a distinct plate.

Distribution. Tropical regions of the Indian and West Pacific Oceans.

Habitat. Epilithic in the intertidal and shallow subtidal, but the species is known from considerable depths elsewhere.

[After Huisman & Verbruggen, Algae of Australia: Mar. Benthic Algae of North-western Australia, 1. Green and Brown Algae 128 (2015)]