Lithophyllum yemenense, 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 : 195-196

Lithophyllum yemenense sp. nov.

Figures 11–12 ; Table 3

HOLOTYPE: sample DB567 (tetrasporangial plant, Fig. 11 ; legit Caragnano: Balhaf, Yemen, iii.2008), including histological slides DB567-13y2, DB567-13y4, conserved in TRH ( TRH-A3882 ).

ETYMOLOGY: the specific epithet is dedicated to the Arabian country where samples were collected.

TYPE LOCALITY: Balhaf, Yemen, on biogenic calcareous rock, 2 m depth.

MATERIAL EXAMINED: Red Sea : Yemen, Kamaran, 1.5 m (legit Caragnano: DB575-576, 28.ix.2009) ; Indian Ocean : Gulf of Aden, Yemen, Balhaf, 2–3 m (leg. Benzoni: DB559 , ix 2006; DB563, xi.2006; leg. Caragnano: DB568-570, iii.2008; DB657, DB659, DB660, DB692, xi.2008) ; Yemen, Socotra Is., 9 m (leg. Caragnano: DB612 , iii.2010) .

GEOGRAPHIC DISTRIBUTION: L. yemenense is distributed in the Red Sea, Gulf of Aden and Arabian Sea. The occurrence of L. yemenense outside this area is unknown.

HABIT AND VEGETATIVE STRUCTURE: The coralline may be attached on corals or other biogenic substrate or form unattached nodules (rhodoliths). Thallus non-endophytic, encrusting, lumpy to fruticose. The protuberances, up to about 10 mm long and about 2–5 mm wide, have a smooth surface, are cylindrical or compressed, branched, sometimes fused and apically enlarged and flattened ( Fig. 11A ).

Plant structure pseudoparenchymatous ( Fig. 11B–E ). Basal or ventral layer (= hypothallium) dimerous, hypothallial cells 7–20 μm long and 10–15 μm in diameter ( Fig. 11E ). Peripheral region (= perithallium) composed of cell filaments curving outwards towards the thallus surface, 5–30 μm long and 7–14 μm in diameter ( Fig. 11B–E ). Cells of adjacent filaments joined by secondary pit connections, cell fusions not observed ( Fig. 11C ). Palisade cells not observed. Single trichocytes 15–45 μm long and about 10–18 μm in diameter occurring in the perithallium and at the thallus surface ( Fig. 11C ). Single epithallial cells flattened, about 7–13 μm in diameter and 2–5 μm long ( Fig. 11D ; Tab. 3).

REPRODUCTION: Uniporate tetrasporangial conceptacles flush or weakly protruding above the surrounding thallus surface, conceptacle chamber 250–300 μm in diameter and 80–120 μm high, with a pore-canal 50–61 μm long ( Fig. 11B, F ; Tab. 3). Floor of the conceptacle chamber with a central columella, 11–14 cells below the thallus surface. Roof filaments 4–6 cells long, including the terminal epithallial cell ( Fig. 11F ).

Gametangial thalli dioecious; carpogonia and spermatangia produced in separate uniporate conceptacles ( Fig. 12 ). Spermatangial filaments unbranched, arising from the male conceptacle chamber floor ( Fig. 12A ). Mature male conceptacle roof weakly raised above the surrounding thallus surface or flush, composed of 5–7 layers of cells above the chamber. Male conceptacle chambers 250–315 μm in diameter and 40–45 μm high, plus a pore canal 38–55 μm long ( Fig. 12A , Tab. 3).

Female conceptacles chamber about 170 μm in diameter. Carposporangial conceptacle chamber 325 μm in diameter, 125 μm high, with a pore-canal about 75 μm long ( Fig. 12B , Tab. 3). Carposporophyte composed of a central fusion cell and short peripheral gonimoblast filaments bearing terminal carposporangia ( Fig. 12B ).

REPRESENTATIVE SEQUENCES: KP696789 (LSU), KP976401 (CO1) & KP976408 (psb A).

A ML phylogenetic analysis inferred from psb A ( Fig. 13 ) revealed that the two last species ( L. socotraense and L. yemenense ) were only distantly related to the specimens so far sequenced for this gene and available in GenBank.

Figures

FIGURE 11. Lithophyllum yemenense sp. nov. A) The holotype, sample DB567 conserved in TRH. B) Appearance of a fertile portion of the holotype; h=hypothallus; p=perithallus; e=epithallial cells, slide DB567-13y4. C) Same as in B, detail of secondary pit-connections (arrow) and trichocytes (t). D) Magnification of the flattened epithallial cells (e), slide DB567-13y2. E) Detail of B to show the dimerous organization with a ventral one-cell layer of hypothallial cells (h) each one giving rise to the perithallial filaments, slide DB567-13y5. F) Uniporate tetrasporangial conceptacle chamber with floor showing a central columella, slide DB567-13y2.

FIGURE 12. L. yemenense sp. nov., male and carposporangial plants. A) Male conceptacle with unbranched spermatangial filaments, slide DB563-4ya4. B) Carposporangial conceptacle with short peripheral gonimoblast filaments (arrow) bearing terminal carposporangia. Sample DB569, slide DB569-10y5.

FIGURE 13. Phylogenetic analysis inferred from psbA including sequences from GenBank (with either incomplete or doubtful identification) and the type specimens of L. socotraense and L. yemenense. Supports at nodes are bootstrap values (1000 replicates).