Nereia intricata Yamada

Scientific Description

Habit and structure. Thallus medium brown, erect, to 15 cm tall, attached by a narrow rhizoidal holdfast and by additional rhizoids descending from lower branches of the thallus. Axes subterete to compressed, cross-sections with L:B of 0.25–0.65:1. Branching irregularly alternate and radial, with long and short branches interspersed and mamillate spur branches common along all axes and giving a verrucose appearance to the thallus. Overlapping branches intricate, attached to one another by rhizoids. All branches terminated by a tuft of trichothallic assimilatory filaments up to 5 mm long, each filament with a meristem 3–6 cells above the base and distal cells 110–136 µm long and 26–32 µm diam. [L:B 3.4–5.5]. Medulla composed of thin-walled cylindrical cells with rounded ends, 100–265 μm long and 30–80 μm diam. [L:B 2–6]. Cortex differentiated into vegetative and fertile types. Vegetative cortex 34–48 μm thick, composed of 1 or 2 cell layers; terminal cell broadly rounded, 24–47 μm long, 11–35 μm diam. [L:B 1.2–2.9]. Fertile cortex 40–75 μm thick, composed of clavate filaments of 2 (–3) cell layers, with an inflated terminal cell 22–42 μm long and 12–32 μm diam. [L:B 1.0–2.5], subtended by 1 (–2) narrow elongate stalk cells. Unilocular sporangia ovoid to clavate, 22–38 µm long, 10–14 µm diam. [L:B 1.6–3.2], sessile on the basal cells of clavate filaments or terminating a short pedicel, aggregated into sori that surround the base of the trichothallic hair tufts and spread along the entire short axes of mamillate spur branches to cover small portions of the surfaces of primary axes.

Distribution. Known from northern W.A. south to the Houtman Abrolhos Island, and in Qld. Also in Japan and the Hawaiian Islands.

Habitat. On rock or coral rubble in the intertidal and subtidal.

[After Yee, Millar & Huisman, Algae of Australia: Mar. Benthic Algae of North-western Australia, 1. Green and Brown Algae 239 (2015)]