Predaea laciniosa Kraft

Scientific Description

Habit and structure. Thallus erect, pale red, to 4 cm tall, mucilaginous, attached by a discoid holdfast. Branches terete to compressed, in part covered with short lobes giving the thallus a ruffled appearance. Cortex of loosely associated fascicles, pseudodichotomously to trichotomously branched every 1 or 2 cells, with ellipsoidal pyriform or subspherical cells 2.5–7.0 µm long and 2.5–3.0 µm diam. Spherical vesicular cells intercalary in cortical filaments below the surface, 15–25 µm diam.; adjacent cells often cutting off an adventitious filament.

Reproduction. Monoecious or dioecious. Spermatangia solitary or paired on outer cortical cells, pyriform to subspherical, c. 2 µm diam. Carpogonial branches lateral on lower cortical filaments, 3-celled, the hypogynous cell subspherical. Auxiliary cells transformed vegetative cells, clearly differentiated, subspherical to obovoid, initially 10–12 µm diam., enlarging to c. 20 µm diam., the adjacent distal and proximal cells with clustered densely branched filaments of spherical nutritive cells. Connecting filament fusing with lateral surface of auxiliary cell, then forming adjacent to the fusion site a lateral protuberance from which the gonimoblast initial arises. Carposporophyte subspherical, with 1–3 gonimolobes, composed of carposporangia 7–10 µm broad.

Distribution. Widely distributed in tropical seas.

Habitat. Epilithic in the subtidal zone.

[After J.M. Huisman in Algae of Australia: Marine Benthic Algae of North-western Australia, 2. Red Algae: 266–267 (2018)]