Neoralfsia expansa (J.Agardh) Cormaci & G.Furnari

Scientific Description

Habit and structure. Thallus light to dark brown, occasionally reddish yellow, rounded to irregularly spreading, to 30 mm diam. and 350–500 μm thick, with a smooth surface but following the contours of the substratum, attached by direct adherence of the lower surface and by rhizoidal filaments. Structure with a spreading layer of horizontal filaments, these forming a basal layer with downwardly directed filaments 20–25 µm diam. [cells L:B 1–4], also giving rise upwardly to assurgent tightly adherent medullary filaments 10–25 µm diam. [cells L:B 1–4], and these capped with a morphologically distinct cortical layer 3–6 cells thick, the cells 5–10 µm diam. [L:B c. 1]. Layers often of different colours, the basal layer reddish brown and contrasting with the tan medullary layer. Clusters of hairs arising from pits. Reproductive structures not observed.

Distribution. Widespread in tropical seas.

Habitat. Epilithic in the lower intertidal and shallow subtidal.

[After Huisman, Algae of Australia: Mar. Benthic Algae of North-western Australia, 1. Green and Brown Algae 182 (2015)]