Porolithon maneveldtii R.A.Towns. & Huisman

Scientific Description

Habit and structure. Thallus encrusting to lumpy, 50–500 μm thick, pale pink, with a dull chalky surface giving it a powdery appearance, monomerous in construction. Medulla multilayered, of branched filaments produced from apical initials 9–47 μm long and 5–10 μm diam. (measured from underside). Medullary cells irregularly forming lateral fusions with adjacent cells; cells 7–32 μm long, 3–10 μm diam. Cortex multilayered; cells 4.5–15.0 μm long, 4.5–10.0 μm diam. Cortical filaments ending in intercalary initial cells that subtend 1 (rarely 2) rectangular epithallial cells 4.5–7.5 μm long, 7.0–12.5 μm diam., with rounded edges, their cytoplasm proximal; up to 80% of each epithallial cell is composed a thick distal wall. Intercalary initials generally of a similar size to the cortical cells that they generate. Megacyte fields throughout the upper cortex, obvious from the surface, becoming buried in the cortex, their appearance changing to resemble modified cortical cells. Megacytes formed from modified cortical cells, 27–32 μm long, 17–21 μm diam.; as fields mature, the megacytes appear to slough, leaving an open ‘honeycomb’.

Reproduction. Tetrasporangial conceptacles transversely ovate, slightly raised above the thallus surface, 165–350 μm outside diam.; pore lined with large cells 29–35 μm long, 7–10 μm diam., triangular in LS. Tetrasporangia 48–107 μm long, 19–58 μm diam. Mature conceptacles sloughed, leaving a scar that is filled with cortical ingrowth or becomes buried in cortex. Other reproductive structures not observed.

Distribution. Dampier Archipelago north to the Rowley Shoals, Western Australia.

[After R.A. Townsend & J.M. Huisman in Algae of Australia: Marine Benthic Algae of North-western Australia, 2. Red Algae: 124–125 (2018)]