Lithophyllum socotraense, Basso & Caragnano & Gall & Rodondi, 2015

Basso, Daniela, Caragnano, Annalisa, Gall, Line Le & Rodondi, Graziella, 2015, The genus Lithophyllum in the north-western Indian Ocean, with description of L. yemenense sp. nov., L. socotraense sp. nov., L. subplicatum comb. et stat. nov., and the resumed L. affine, L. kaiseri, and L. subreduncum (Rhodophyta, Corallinales), Phytotaxa 208 (3), pp. 183-200 : 193-195

Lithophyllum socotraense sp. nov.

Figure 10 ; Table 3

HOLOTYPE: sample DB635 (leg. Caragnano: Socotra, 15.iii.2010) including stub 09062010b6 and histological slide DB635- SO20 b, conserved in TRH ( TRH-A3881 ).

ETYMOLOGY: the specific epithet refers to the type locality, the island of Socotra, Yemen.

TYPE LOCALITY: Yemen, Indian Ocean, Ras Adho on the NE coast of Socotra Island, 22 m depth.

MATERIAL EXAMINED: Indian Ocean , NE Socotra Island: Rosh, 16 m, samples DB615-616 (leg. Caragnano: 12.iii.2010) ; Ras Adho , 22 m (the holotype) and 13 m (sample DB636 ) (leg. Caragnano: 16.iii.2010) .

HABITAT AND PHENOLOGY: plants unattached as rhodoliths, enveloping coral fragments at nucleus, at depth> 12 m.

GEOGRAPHIC DISTRIBUTION: L. socotraense nov. sp. is known only from the NW Indian Ocean, Socotra Island.

HABIT AND VEGETATIVE STRUCTURE: Plants non-endophytic, with warty to lumpy growth form. The protuberances have a smooth surface, up to about 5 mm long and about 3–6 mm wide ( Fig. 10A ).

Plant structure pseudoparenchymatous ( Fig. 10B–C ). Basal or ventral layer (= hypothallium) dimerous ( Fig. 10D ). Hypothallial cells 15–18 μm long and 11–18 μm in diameter ( Tab. 3). Peripheral region (= perithallium) composed of filaments of cells curving outwards toward the thallus surface, 12–23 μm long and 10–13 μm in diameter ( Fig. 10C– D ). Cells of adjacent filaments joined by secondary pit-connections, cell fusions not observed ( Fig. 10D–F ). Palisade cells not observed. Single trichocytes 22–58 μm long and about 12–13 μm in diameter, abundantly distributed in the perithallium and at the thallus surface ( Fig. 10C, E ). Single epithallial cells flattened, about 7–15 μm in diameter and 2–5 μm long ( Fig. 10F ).

REPRODUCTION: Uniporate tetrasporangial conceptacle chambers protruding over the surrounding thallus surface, becoming buried in the thallus, 180–250 μm in diameter and 60–90 μm high, with pore-canal 45–60 μm long ( Fig. 10G–H ; Tab. 3). Floor of the conceptacle chamber convex upward below a central columella. The conceptacle chamber floor is 9–11 cells below the thallus surface. Roof filaments 4–5 cells long, including the terminal epithallial cell ( Fig. 10H ; Tab. 3). Gametangial and carposporangial conceptacles not found.

REPRESENTATIVE SEQUENCES: KP696790 (LSU), KP976402 (CO1) & KP976409 (psb A).

Figures

FIGURE 10. Lithophyllum socotraense sp. nov.A) The holotype, sample DB635, a rhodolith, conserved in TRH. Note the lumpy growthform. The sample has been cut for histological analyses. B) Microscopical anatomy of a fertile thallus, slide DB635-SO20b_9. C) Sparse trichocytes (arrow) in the perithallus (p) of sample DB636, slide DB636-SO25b_7; e = epithallial cells. D) Same as in C, detail of ventral hypothallial cells (h) and the dimerous organization of the thallus. E) Same as in C, magnification of trichocytes (t). F) Flattened epithallial cells (e) in slide DB635-SO20b_10. G) Tetrasporangial conceptacle with central columella in the holotype, SEM stub 09062010b6. H) Holotype sample DB635. Tetrasporangial conceptacle in slide DB635-SO20b_10; inset: a tetraspore, slide DB635-SO20b_7.