Hydrolithon rupestre (Foslie) Penrose (1996: 265)

Villas-Bôas, Alexandre B., Riosmena-Rodriguez, Rafael, Tâmega, Frederico T. S., Amado-Filho, Gilberto M., Maneveldt, Gavin W. & Figueiredo, Marcia A. O., 2015, Rhodolith-forming species of the subfamilies Neogoniolithoideae and Hydrolithoideae (Rhodophyta, Corallinales) from Espírito Santo State, Brazil, Phytotaxa 222 (3), pp. 169-184 : 174-175

Hydrolithon rupestre (Foslie) Penrose (1996: 265)

Basionym: Lithophyllum rupestre Foslie (1906: 26) .

≡ Mesophyllum rupestre (Foslie) Adey (1970: 26) .

Plants non-geniculate warty bearing cylindrical protuberances 1.0– 2.5 mm long ( Fig. 9). The internal thallus construction is pseudoparenchymatous and monomerous ( Fig. 12 ). The basal region comprises rectangular cells that are 13–16 μm long and 6.5–9.0 μm in diameter ( Fig. 12 ). The core region is non-coaxial (plumose) and comprises rectangular cells that are 9–12 μm long and 4–5 μm in diameter. Peripheral filaments are comprised of elongate cells that measure 9.2–11.5 μm long by 4–7 μm in diameter. Peripheral filaments are terminated by a single layer of rounded to flattened epithelial cells ( Fig. 10 ). Sub-epithelial initials are square and measure 7.0–11.5 μm long by 7.0–9.2 μm in diameter. Cells of adjacent filaments are joined by cell fusions, secondary pit connections have not been observed. Solitary trichocytes are found only at the thallus surface. Gametangial plants were not observed. Tetra/bisporangial conceptacles are uniporate and flush with the surrounding thallus surface. The base of the pore canal is surrounded by a ring of enlarged cells ( Fig. 13 ), these cells do not project into the pore canal, but are orientated vertically. Mature tetra/ bisporangial conceptacles measure 110–120 μm in diameter and 70–100 μm in height. The conceptacle chamber lacks a central columella and zonately divided tetra/bisporangia are scattered across the chamber floor. Tetra/bisporangial conceptacle roofs are 5–6 cells thick and the floor of the conceptacle chamber is situated 14–15 cell layers below the surrounding thallus surface ( Fig. 11 ).

Type:— AUSTRALIA. Victoria: Phillip Island (lectotype TRH, Penrose 1996: 266)

Ecological observations:—Plants forming multispecific rhodoliths, 3–23 cm in diameter. Hydrolithon rupestre has no depth gradient at studied area, present only at 17 m depth.

Geographical distribution:— Australia (Penrose 1996, Harvey et al. 2006), New Zealand ( Nelson 2012), Pacific Islands ( Payri et al. 2000, N’Yeurt & Payri 2010, Tsuda & Walsh 2013) and Brazil (Pereira-Filho et al. 2012, Crespo et al. 2014) and this study.

Distribution in the study sites:— Hydrolithon rupestre was the species with the most restricted distribution in the study, found only at one site.

Examined material:— BRAZIL. Espírito Santo State (21° 02’ 27” S, 40° 41’ 33” W, 4 May 2004, G. M. Amado-Filho, RB 480488 ; RB 480489 ) .

Diagnostic features:— Hydrolithon rupestre differs from species of Hydrolithon in having the following combination of features: 1) tetrasporangial conceptacle chamber 110–120 μm in diameter and 70–100 μm in height, and 2) tetrasporangial conceptacle chambers lack a central columella and tetrasporangia are scattered across the floor of the conceptacle chamber.

Figures

FIGURES 10–13. Hydrolithon rupestre. 10. Longitudinal sections showing solitary trichocytes (white arrow), rounded to flattened epithelial cells (grey arrow), fusion cells (black arrow). Scale = 14 μm. 11. Tetrasporangial conceptacle. Scale = 15 μm. 12. Monomerous growth (white arrow). Scale = 17 μm. 13. Tetrasporangial roof detail with large cells characteristic of genus Hydrolithon. Scale = 19 μm.