Lophosiphonia prostrata (Harv.) Falkenb.

Scientific Description

Habit and structure. Thallus prostrate on the host surface, 2–8(–20) cm long, with filaments extending and branching over the host length and their apices free and curled over the host growing margin; erect filaments few and short, associated with reproduction. Attached by rhizoids; epiphytic on Lobophora and Distromium. Structure. Apical cells hemispherical or shortly conical, 10–20 µm (including the thick sheath) in diameter, axial cells with 4 pericentral cells; filaments of uniform width, 55–90 µm in diameter, segments L/D 0.5–1(–1.5). Branching endogenous from the axial cells. Trichoblasts variable in abundance, on subapical segments of short free branches, 200–500 µm long, branched, basal cells 20–25 µm in diameter. Rhizoids unicellular, not cut off from pericentral cells. Cells uninucleate; rhodoplasts discoid.

Reproduction. Gametophytes dioecious. Procarps not observed. Carposporophytes with a small basal fusion cell and short branched gonimoblast with clavate terminal carposporangia 20–35 µm in diameter. Cystocarps on branches of short erect laterals, short-stalked, ovoid to slightly urceolate, 200–300 µm in diameter; pericarp 2 cells thick, ecorticate, outer cells angular, isodiametric. Spermatangial organs replacing trichoblasts, 35–55 in diameter and 90–180 µm long, with a sterile basal and 1(–2) sterile apical cell. Tetrasporangia in curved, sub-erect branches near recurved apices, the branches 300–500 µm long and 60–100 µm in diameter, tetrasporangia one per segment, 50–75 µm in diameter, with 3 cover cells.

Distribution.Rottnest I.,W. Aust., to Aldinga, S. Aust; N.S.W. New Zealand. Central Pacific. South Africa (?).

Habitat. L. prostrata has a remarkably wide distribution as an epiphyte on zonarioid algae.

[After Womersley, Mar. Benthic Fl. Southern Australia IIID: 333 (2003)]