Rhizolamellia colli Shevejko

Scientific Description

Habit and structure. Thallus consisting of many overlapping but non-adherent layers, 70–160 μm thick, monomerous in construction. Medulla multilayered, coaxial, often comprising more than 60% of the thallus thickness; cells 31–50 μm long, 12–36 μm diam., lateral fusions common. Trichocytes common in the outer medullary layer. Secondary outgrowths from the medulla common, giving the appearance of struts between the thallus layers. Cortex multilayered; cells 7–11 μm long, 4.5–7.5 μm diam., with lateral fusions between several adjacent filaments. Cortical filaments each ending in an intercalary initial cell that subtends a rounded epithallial cell, 3–6 μm long, 4.5–6.0 μm diam. Intercalary initials generally longer than the cortical cells that they generate, 5–12 μm long, 4–8 μm diam. Trichocytes common in the cortex.

Reproduction. Carposporangial conceptacles uniporate, conical, 1100–1350 μm outside diam., 400–600 μm height (not including the tubular extension) with a pronounced elongate pore (tubular extension) that is extremely fragile and up to 700 μm long. Tetrasporangial conceptacles circular to elongate, 425–1500 μm outside diam., 270–1000 μm inside diam., 115–128 μm internal height. Tetrasporangia 95–145 μm long, 38–70 μm diam. Apical sporangium with a wedge-shaped beak that subtends the pore plug; pore lined with 4 or 5 cells, with an elongate cell at the base of the pore adjacent to the wedge-shaped area of the apical spore. Pore cells not noticeably different in anatomy from the surrounding roof cells.

Distribution. Occurs in warmer waters of the Western Australian coast.

Habitat. Epilithic in the subtidal.

[After R.A. Townsend, W.J. Woelkerling, G.W. Saunders & J.M. Huisman in Algae of Australia: Marine Benthic Algae of North-western Australia, 2. Red Algae: 141 –142 (2018)]