Gracilaria vieillardii P.C.Silva

Scientific Description

Habit and structure. Thallus to 10 cm tall, deep red, arising from a small holdfast, dichotomously to irregularly branched, mostly divaricate, with flattened branches 0.5–3.0 cm long and 350–450 μm thick; width variable, mostly 4–10 mm wide in mid-portions, slightly broader and 7–10 mm wide below obtuse apices. Blade margins with numerous short simple or compound spines. Surface bladelets present. Medulla of large subspherical hyaline cells, centrally 100–150 μm diam., grading abruptly to a cortex of 2 or 3 layers of smaller pigmented cells. Cortical cells in surface view in pairs or triplets, 4–6 μm diam.

Reproduction. Cystocarps protuberant, hemispherical, arising singly or in clusters of up to 3, to 1.2 mm diam. Tetrasporangia in nemathecia on one surface of frond only, ellipsoidal, cruciately divided, 17–25 μm long, 10–15 μm diam. Spermatangia not seen.

Distribution. Occurs in warmer waters of the Indian and western Pacific Oceans.

Habitat. Epilithic in the intertidal and shallow subtidal.

[After J.M. Huisman in Algae of Australia: Marine Benthic Algae of North-western Australia, 2. Red Algae: 353–354 (2018)]