Lophocladia robertae Huisman

Scientific Description

Habit and structure. Thallus tufted, delicate, pink to red, to 10 cm tall, arising from limited prostrate axes forming multiple attachments via multicellular rhizoids with digitate tips, or with several erect axes arising from a common holdfast. Erect axes irregularly branched, generally divaricate, 100–150 µm diam.; mid-thallus with segment L:B 1–2, broadening markedly towards base [L:B 0.5–0.7]. Lateral branches and pigmented trichoblasts arising exogenously at apices from each segment in a spiral sequence, the branches structurally indistinguishable from trichoblasts until the later development of pericentral cells. Lateral branches also rarely adventitious and endogenous, then in addition to the trichoblast on the bearing segment. Pigmented trichoblasts often forming a dense tuft at the branch apices. Structure uniaxial, with 4 pericentral cells, occasionally becoming lightly corticated in lower parts. Trichoblasts to 3 mm long, branching 2–7 times subalternately, with 1 cell between branches on the primary filament, with cells at mid-length 20–25 (–45) µm diam.; cells near trichoblast base to 50 µm diam. Trichoblast apices often with 1 or 2 shorter cells with a spinous tapering or rounded tip. Distal filaments and lateral branches of trichoblasts simple or sparingly branched.

Reproduction. Spermatangial branches on trichoblasts; fertile branch either the first or second lateral, with a 1–3-celled monosiphonous stalk and a sterile apical cell; spermatangial portion of branch up to 12 cells long, each cell bearing spermatangial mother cells and numerous spermatangia. Procarps developing on suprabasal cells of the trichoblasts. Cystocarps spherical, to 500 µm diam., with clavate carposporangia 100–130 µm long and 35–40 µm diam. Tetrasporangial stichidia arising on the suprabasal cell of trichoblasts, forming one branch of a dichotomy, with a 2–4-celled monosiphonous stalk, 1 or 2 stichidia per trichoblast. Tetrasporangia tetrahedrally divided, spherical, arising 1 per stichidial segment in a spiral pattern, to 50–70 µm diam.

Distribution. Known from the Montebello Islands and Long Island, north-western Australia, and eastern Queensland.

Habitat. Epilithic or epiphytic in the intertidal to shallow subtidal.

[After J.M. Huisman in Algae of Australia: Marine Benthic Algae of North-western Australia, 2. Red Algae: 534 (2018)]