Sargassum aquifolium (Turner) C.Agardh

Scientific Description

Habit and structure. Thallus medium brown, 10–45 cm tall, with a discoid-crustose holdfast 7–11 mm wide. Primary axes terete, smooth, 3–4 mm long, 1.25–2.00 mm diam. Primary branches smooth to wrinkled, compressed, with sharp edges, 2–4 mm wide. Primary laterals alternate, linear-lanceolate to ovate-elongate, 13–30 mm long, 5–11 mm wide; margins undulate to deeply dentate; apices obtuse; base subsymmetrical, cuneate, arising directly from the stem and lacking a distinct stalk; margins vanishing 80% of the way to the apex. Secondary branches smooth, compressed 1–3 mm diam. Secondary laterals alternate, oblanceolate to ovate, 15–37 mm long, 8–15 mm wide; margins serrate to dentate; apices obtuse or acute; base cuneate, subsymmetrical; cryptostomata prominent. Vesicles subspherical to elongate, smooth, 3–6 mm diam., often with a small apical mucro. Receptacles monoecious, subterete to moderately compressed in dense cymose glomerules, 2–5 mm long, 0.75–2.00 mm wide, spinous, often divided. Conceptacles bisexual; oogonia oval, 105–160 µm long, 60–200 µm wide; antheridia trapezoid, oval or elongate, 14–24 µm long, 8–20 µm wide.

Distribution. Widespread in the tropical Indo-Pacific. In Australia known from Coral Bay northwards, presumably around northern Australia to Qld and Norfolk Island.

Habitat. Epilithic in the subtidal.

[After Dixon & Huisman, Algae of Australia: Mar. Benthic Algae of North-western Australia, 1. Green and Brown Algae 254-256 (2015)]