Dawsoniolithon gabrielsonii R.A.Towns. & Huisman

Scientific Description

Habit and structure. Thallus encrusting to warty, 100–1000 μm thick, with branches 1–3 mm long, or lumpy with branches 6 mm wide, monomerous in construction. Medulla of branched filaments with cells 29–45 μm long, 20–45 μm diam. Cortical filaments each ending in an intercalary initial cell that subtends an epithallial cell, these either transversely elliptical to transversely rectangular, with the proximal half consisting of cytoplasm, 2.5–7.5 μm long, 4.5–17.5 μm diam. Intercalary initials generally similar in size to the cortical cells they generate, 4.5–15 μm long, 4.5–7.5 μm diam. Megacyte groups not pustular, scattered throughout the upper cortex, not evident deeper in cortex, formed from modified cortical cells 35–70 μm long, 25–35 μm diam.

Reproduction. Sexual thalli dioecious. Mature conceptacles shallowly convex mounds with obvious white pores when mature. Carpogonial branches central below the conceptacle pore, consisting of a supporting cell subtending a carpogonial branch and a ‘sterile cell’. Tetrasporangial conceptacles conical (observable with the naked eye), 200–500 μm outside diam. Tetrasporangia 77–135 μm long, 19–75 μm diam.

Distribution. Only known from the northern Kimberley and offshore shoals, Western Australia.

Habitat. epilithic in the subtidal.

[After R.A. Townsend & J.M. Huisman in Algae of Australia: Marine Benthic Algae of North-western Australia, 2. Red Algae: 119 (2018), as Oztralia gabrielsonii]