Lithothamnion sonderi Hauck

Scientific Description

Habit and structure. Thallus encrusting, monomerous, glossy, 75–600 μm thick, overgrowing itself and other calcified organisms. Medullary filaments with cells rarely fusing laterally, 14.5–20.0 μm long, 4.5–7.5 μm diam., each cell with spherical inclusions. Cortex multilayered, lateral and diagonal fusions common between cells of up to 3 adjacent filaments; cells 4.5–10.0 μm long, 4.5–7.5 μm diam., each with a prominent plug staining parallel with the wall (not spherical). Cortical cell filaments ending in a cuboidal initial 4.5–7.5 μm long and wide. Initials subtending a single layer of flattened epithallial cells 1–2 μm long, 4.5–7.5 μm diam.

Reproduction. Sporangial conceptacles crowded, raised, 690–920 μm outside diam., 350–500 μm internal diam. Conceptacle roof sloughed when mature, not immersed in the thallus. Conceptacle roof up to 7 cell layers thick; pore and roof cells similar. Sporangia surrounded by filaments within the conceptacle lumen, each situated below an occluded pore with a pore plug to 50 μm long. Spermatangial conceptacles conical, some with an apical beak, 270–450 μm outside diam., 150–225 μm high; spermatangial branches dendroid across the floor.

Distribution. Known from temperate to cool-temperate Atlantic and Japanese waters.

[After R.A. Townsend & J.M. Huisman in Algae of Australia: Marine Benthic Algae of North-western Australia, 2. Red Algae: 134 (2018)]