Lomathamnion epicodii Gordon-Mills

Scientific Description

Habit and structure. Thallus dark red-brown, tufted and spreading, 2–4 mm high, with prostrate filaments and erect, simple to sparingly branched, branches, 1–4 branches from each cell of prostrate filaments, tapering slightly above. Prostrate filaments attached by digitate haptera; epiphytic on Codium galeatum. Structure. Prostrate filaments 30–45 µm in diameter, cells L/D 1–4; erect filaments with median cells 30–40 µm in diameter, cells L/D 2–6, terminal cells often hair-like. Cells multinucleate; rhodoplasts discoid.

Reproduction. Gametophytes dioecious. Female axes (3–)4(–12) cells long, borne laterally on lower cells of erect filaments or occasionally on the prostrate axes, with the last 3 cells short and the subhypogenous cell 2–3 times as long. Subapical cell bearing 2 periaxial cells, one sterile and one (the supporting cell) with a sterile apical cell and a lateral carpogonial branch. Post-fertilization the supporting cell cuts off an auxiliary cell which produces 2–4 gonimoblast cells each dividing to form 3–4 cells which either directly or on subdivision become ovoid carposporangia 25–50 µm in diameter. Very little fusion occurs between cells of the procarp or gonimoblast, and a fusion cell is not produced. The apical cell, sterile periaxial cell, and sterile cell on the supporting cell all normally remain undivided. Spermatangial heads ovoid, 40–55 µm in diameter, borne on unicellular pedicels laterally on lower cells of erect filaments or directly on prostrate filaments. Tetrasporangia terminal on unicellular pedicels produced laterally on erect filaments, single or in opposite pairs, 40–50 µm in diameter, tetrahedrally divided but often almost cruciately arranged.

Distribution.Dongara, W. Aust., to Phillip I., Vic.

[After Womersley, Mar. Benthic Fl. Southern Australia IIIC: 216–217 (1998)]