Predaea sophieae Huisman

Scientific Description

Habit and structure. Thallus erect, medium red, to 3 cm tall, mucilaginous, attached by a discoid holdfast. Branches terete to compressed, much-divided with numerous lobes, but lacking a ruffled appearance. Medulla filaments with elongate cylindrical cells, 3–5 µm diam. Cortex of loosely associated fascicles, pseudodichotomously branched every 2 or 3 cells, with ellipsoidal to subspherical cells 7–12 µm long and 3–5 µm diam.; outermost cells spherical to pyriform. Vesicular cells absent.

Reproduction. Monoecious or dioecious. Spermatangia solitary or paired on outer cortical cells. Carpogonial branches lateral on cortical filaments, rarely on medullary or adventitious filaments, often (but not excusively) in the same fascicle as auxiliary cells, (2–) 3-celled; hypogynous and basal cells expanded basally. Auxiliary cells transformed vegetative cells, clearly differentiated, subspherical to obovoid, the adjacent distal and proximal cells each with 4–6 simple or branched filaments of spherical nutritive cells, these also occasionally present on more distant cells. Connecting filaments branching near auxiliary cells, the branch fusing with the auxiliary cell, then forming adjacent to the fusion site a lateral protuberance from which the gonimoblast initial arises. Gonimoblast initial forming 2 gonimolobes (terminal and lateral) composed entirely of carposporangia 3–5 µm diam. Terminal gonimolobe conical, straight or sinuous, tapering to a single-celled tip, to 170 µm long and 100 µm diam. at the widest point; lateral gonimolobe smaller, subspherical; or both gonimolobes spherical, the largest to 140 µm diam.

Distribution. Known from southern Kimberley, Western Australia.

Habitat. Epilithic in the subtidal.

[After J.M. Huisman in Algae of Australia: Marine Benthic Algae of North-western Australia, 2. Red Algae: 267–269 (2018)]