Herposiphonia secunda (C.Agardh) Ambronn

Scientific Description

Habit and structure. Thallus red, attached by unbranched unicellular rhizoids with digitate tips, arising from the distal end of ventral pericentral cells. Indeterminate prostrate axes with circinate apices, with indeterminate axes arising laterally on alternate sides every 3 or 4 segments. Determinate lateral branches arising dorsally every 3 or 4 segments, 1 segment proximal to the indeterminate lateral branch. Prostrate axes 70–100 µm diam. [segment L:B 0.8–1.2], with 8 pericentral cells in indeterminate and determinate axes. Determinate branches simple, 1.2–1.7 mm and 14 or 15 segments long, 70–100 µm diam. [L:B 1–1.5 (less in developing segments)]. Trichoblasts borne 1–5 in a spiral pattern on successive segments at apices of determinate branches, to 950 µm long, initially secund but appearing dichotomously branched when mature; proximal cells 40–50 µm diam. [L:B 1–4], tapering to slender elongate distal cells 7–10 µm diam. [L:B 10–20].

Reproduction. Reproductive structures not observed.

Distribution. Widespread in warmer seas.

Habitat. epilithic or epiphytic in the subtidal.

[After J.M. Huisman in Algae of Australia: Marine Benthic Algae of North-western Australia, 2. Red Algae: 518–519 (2018)]