Erythroclonium elongatum Huisman

Scientific Description

Habit and structure. Thallus to 18 cm tall, dark red, epilithic, attached by a discoid holdfast. Axes segmented, dichotomously to trichotomously branched; segments elongate, terete, 8–30 mm long and 0.5–1.5 mm diam. Lower axes becoming cartilaginous, but essentially similar to upper axes. Cells of central axis thick-walled, 180–220 µm long and 50–70 µm diam. when mature, each with 2 periaxial filaments, these at slightly different heights on the bearing cell, curving distally and branching dichotomously, alternately or unilaterally (the lateral branches directed towards the cortex), with elongate cells 10–20 µm diam. Cortex 2 or 3 cells thick; inner layer of larger subspherical to slightly ellipsoidal cells 20–30 µm diam., grading abruptly to isodiametric outer cortical cells 8–15 µm diam. When mature the outer cortical layer incomplete, occasionally appearing as rosettes in surface view, although this not always present. Rhizoidal filaments forming a loose jacket around the central axis and a layer below the cortex, of elongate cells 7–10 µm diam.

Reproduction. Spermatangia not observed. Cystocarps embedded in the thallus, causing a slight swelling, with a central fusion cell and radiating gonimoblast filaments with chains of carposporangia. Tetrasporangia scattered in the cortex, terminal on inner cortical cells, ellipsoidal, 45–55 µm long, 25–30 µm diam., zonate. Other reproductive structures not observed.

Distribution. Western Australia.

Habitat. Epilithic in the shallow subtidal, occasionally exposed during extreme low tides.

[After J.M. Huisman in Algae of Australia: Marine Benthic Algae of North-western Australia, 2. Red Algae: 157 (2018)]