Padina okinawaensis Ni-Ni-Win, S.Arai & H.Kawai

Scientific Description

Habit and structure. Thallus erect, yellowish brown, to 7 cm wide and 5 cm tall, pale brown or whitish brown, circular or semicircular, with entire margins, attached by a stupose base with a short stipe, moderately to heavily calcified on the dorsal surface (except at the hairlines), and heavily calcified on the ventral surface, composed of 2 cell layers throughout (60–90 mm thick). Calcified glabrous zones and uncalcified hairlines formed in alternate sequence on the dorsal surface, forming brown stripes or furrows on the whitish brown calcified thallus surface. Ventral thallus surface exhibiting continuous calcification. Cells of the ventral surface layer slightly thicker than those of the dorsal surface layer. Concentric hairlines present on both surfaces, in alternate sequence at equal distance between the two surfaces. Hairlines on the dorsal surface broad and depressed, those on the ventral surface narrow, not depressed and sometimes inconspicuous or rudimentary.

Distribution. Known from southern Thailand, Indonesia, Japan, the Hawaiian Islands and tropical Australia.

Habitat. Grows in association with coral reefs in the subtidal.

[After Huisman & Phillips, Algae of Australia: Mar. Benthic Algae of North-western Australia, 1. Green and Brown Algae 212 (2015)]