Gibsmithia larkumii Kraft

Scientific Description

Habit and structure. Thallus to 3 cm tall, red, growing from a basal pad, lacking a cartilaginous stalk, with lobed smooth mucilaginous branches. Medullary filaments with cylindrical cells 5–8 µm diam. [L:B 5–20]. Cortical fascicles dichotomously branched every 1 or 2 cells, but with ultimate branches 2–4 cells long. Cells of cortical filaments 3–5 µm diam. [L:B 2–4]. Slender rhizoidal filaments common, 3–6 µm diam.

Reproduction. Carpogonial branches 6–8-celled, straight, with the distal cells enlarged; subhypogynous cell smaller than adjacent cells and the carpogonum slightly lateral on the hypogynous cell, which often has a lateral bulge. Lower cells of carpogonial branches with unbranched sterile laterals. Auxiliary cell branches 8–14 cells long, the lower 4 cells spherical and inflated, the distal cells similar to vegetative cells, basal and suprabasal cells bearing several simple to once-branched filaments, the third cell the auxiliary cell and naked. Immediate post-fertilisation not observed. Connecting filaments prominent, mostly hyaline and thicker than medullary filaments, fusing laterally with the auxiliary cell and then continuing to additional auxiliary cells. Gonimoblasts produced from connecting filament adjacent to fusion with auxiliary cell. Mature cystocarps with a spherical mass, 150–250 µm diam., of angular to spherical similarly sized carpospores 12–20 µm diam. Other reproductive structures not observed.

Distribution. Possibly widespread in the tropical Indo-Pacific.

Habitat. Epilithic in the subtidal.

[After J.M. Huisman in Algae of Australia: Marine Benthic Algae of North-western Australia, 2. Red Algae: 179–181 (2018)]