Melyvonnea madagascariensis (Foslie) Athanas. & D.L.Ballant.

Scientific Description

Habit and structure. Thallus encrusting at first, but soon becoming lumpy (may form rhodoliths), monomerous in construction. Medulla multilayered, coaxial, often comprising more than 50% of the thallus thickness, with cells 10–20 μm long, 4–7 μm diam. Cortex multilayered, with cells 5–9 μm long, 4–6 μm diam. Cortical filaments each ending in an intercalary initial cell that subtends a flattened saucer- to crucible-shaped epithallial cell, 1.5–3.0 μm long, 6–10 μm diam. Intercalary initials generally longer than the cortical cells that they produce, 5–11 μm long, 4–6 μm diam. Trichocytes common in the cortex, especially the upper cortex.

Reproduction. Gametangial conceptacles not observed. Carposporangial conceptacles uniporate, conical, 400–550 μm outside diam., with a slightly projecting white pore. Sporangial conceptacles pale pink when immature, white when mature, 600–800 μm outside diam., 250–300 μm internal diam., leaving a rim as scars when old and dehiscent. Only bisporangia observed, with the upper spore partially occluding the pore; conceptacle pore lined with 4 pore cells, with an elongate cell at the base of the pore.

Distribution. Widespread in the tropical Indo-Pacific.

Habitat. Epilithic or as rhodoliths in the subtidal.

[After R.A. Townsend & J.M. Huisman in Algae of Australia: Marine Benthic Algae of North-western Australia, 2. Red Algae: 137 (2018)]