Udotea argentea Zanardini

Scientific Description

Habit and structure. Thallus grey-green, occasionally slightly bluish or with new growth dark green, to 12 cm tall, with a small fibrous holdfast when growing on consolidated substrata, or a massive particle-binding holdfast (to 10 cm long and 1.5 cm diam.) when growing in sand, and a simple stipe to 4 mm long and 2.5 mm diam., grading into cuneate or flabellate blades 3–4 cm wide, these generally with visible concentric markings. Blades often in clusters and proliferating from the margins. Structure of stipe and blade multistratose; blade composed of sparsely dichotomously divided terete primary siphons 30–50 μm diam., with numerous distichous to radial lateral appendages 100–200 μm long, these unbranched, slightly constricted 25–35 μm from the base, and with expanded irregularly shaped apices 50–150 μm wide forming a pseudocortex, obscuring the primary siphons. Primary siphons comparatively uniform in width, but lateral appendages slightly larger and with more digitate apices near the base of the thallus.

Distribution. Widespread in the tropical Indo-Pacific, including Qld. In W.A. south to Shark Bay.

Habitat. Typically in sand, rarely on consolidated substrata.

[After Huisman, Algae of Australia: Mar. Benthic Algae of North-western Australia, 1. Green and Brown Algae 148 (2015)]