Lithophyllum artabricum V.Peña, 2021

Peña, Viviana, R, Tamara, G, uiz de & Torres, auna, 2021, Lithophyllum artabricum V. Peña, sp. nov. (Corallinales, Rhodophyta): a cryptic species in the Atlantic Iberian Peninsula hitherto assigned to Lithophyllum stictiforme (Areschoug) Hauck, Cryptogamie, Algologie 20 (11), pp. 153-172 : 157-158

Lithophyllum artabricum V.Peña , sp. nov.

( Figs 1 , 4 , 5 )

HOLOTYPE. — Spain. Galicia, Cabo Prior, Praia das Fontes, Covas ; 43°33’29.56”N, 8°16’52.69”W; 10 m depth; SANT-Algae 33667, 19.V.2012, leg. V. Peña & J. Souto ( Fig. 1A, F )

HOLOTYPE DNA SEQUENCES. — COI-5 P and psb A, GenBank accession numbers MZ129194 and MZ129197 .

COMPLEMENTARY COLLECTIONS. — Spain. Galicia, San Ciprián, Lugo, Punta Gallino; 21.VII.2015; 6 m depth, collectors I. Bárbara, A. García-Fernández & V.García-Redondo SANT-Algae 33616 (psb A: MZ 129195 ), SANT-Algae 33619 (psb A: MZ 129196 ). — Portugal. Douro Litoral, Apulia; 26.IX.2018; 9 m depth, collector J. Franco; SANT-Algae 26900 (COI-5 P: MZ 129193 ). — Spain. Cantabria, Bahía de Santander, Isla de Mouro; 16.VIII.2009; 15 m depth; collectors C. Peteiro & N. Sánchez. Additional collections in Table 1.

ETYMOLOGY. — The specific epithet refers to the geographic location of the type locality, the Artabrian Gulf (historically known as Portus Magnus Artabrorum).

DESCRIPTION

Non-geniculate, foliose lamellae or fan-like thallus, single or superimposed, up to 10 cm diameter and 2 mm thick ( Figs 1 A-F, 4A). Colour pink to violet, texture smooth and matt when dried ( Fig. 1 E-F). Concentric lines along the lower surface, particularly visible at the margins as the remaining surface is covered by sessile invertebrates ( Fig. 1G ). Thallus pseudoparenchymatous,monomerous with medulla non-coaxial to occasionally coaxial, composed of cells 6-47 µm long by 4-27 µm diameter ( Fig. 4 A-B, D). Cortical cells (3) 4-19 µm × 3-21 µm, arranged in filaments laterally aligned ( Fig. 4C ) and subepithallial cells 7-15 µm × 5-12 µm ( Fig. 4E ). Epithallial cells arranged in 1 (2) layers, flattened in transverse section, 1-3 µm long and 6-13 µm wide ( Fig. 4 E-F); in surface view, epithallial cells were polygonal ( Fig. 4G ). Secondary pit-connections present between cells of contiguous filaments ( Fig. 4C, E ). Trichocytes not observed. Gametangial plants were not observed. Tetra/bisporangial conceptacles were uniporate, flush with surface ( Fig. 4 H-I). Conceptacle chambers were dumbbell-shaped, 70-133 µm high and 236-448 µm wide, with canal pore conical tapering from bottom to top of the thallus surface ( Fig. 5 A-C). Conceptacle roofs were 8-14 cells thick, the depth of the floor between 14-25 cells. Central columella present ( Fig. 5D ). Tetra/bisporangia not observed. Buried conceptacles present, occasionally with inorganic infillings ( Figs 4D , 5E, F ).

HABITAT. — Lithophyllum artabricum V.Peña , sp. nov. is at presently known only from subtidal bedrock, sometimes in sciophilous habitats.

DISTRIBUTION. — Atlantic Iberian Peninsula, recorded from Cantabria to North Portugal (Douro Litoral province).

COMMENTS

The morpho-anatomical characters of Lithophyllum artabricum V.Peña , sp. nov. showed an overlap with vegetative and reproductive characters provided for many of the 13 clades recovered in the L. stictiforme complex, which also includes the Macaronesian L. lobatum and the NW Atlantic L. searlesii ( Pezzolesi et al. 2019) . However, the specimens of L. artabricum V.Peña , sp. nov. have a conspicuous monomerous thallus construction composed of a non-coaxial medulla to occasionally coaxial, whereas the clades comprising the L. stictiforme complex are described with mainly dimerous construction ( Table 2 ). Moreover, the combination of characters such as concentric lines in the margins of the lower surface, the absence of trichocytes, the conical shape of the canal pore and the presence of buried conceptacles are considered useful to differentiate L. artabricum V.Peña , sp. nov. from some of the Mediterranean clades reported as well as L. lobatum ( Table 2 ). In addition, L. artabricum V.Peña , sp. nov. differs from other species of Lithophyllum reported from the Atlantic European coasts by a combination of characters related to the external morphology consisting of single or superimposed lamellae or fan-like, the monomerous thallus construction with medulla non-coaxial to occasionally coaxial, the conical shape of the canal pore of sporangial conceptacles, and its occurrence seemingly limited to subtidal bedrocks ( Table 3 ).

Figures

FIG. 1. — Habitat and habit of Lithophyllum artabricum V.Peña, sp. nov.: A-D, characteristic habitat of this species growing in subtidal bedrock, sometimes sciophilous, in the type locality (A), and other Galician localities (B-D, Cedeira, Cambre and Sisargas, respectively); E, F,gross morphology consisted on foliose lamellae or fan-like thallus,single or superimposed (arrow) observed in the specimen SANT-Algae 15006 (E) and in the holotype (F, SANT-33667); G, lower surface of the specimen showing concentric lines, particularly visible at the margins as the remaining surface is covered by sessile invertebrates (SANT-Algae 11666). Scale bars: E, 2 cm; F, G, 1 cm.

FIG. 4. — Morpho-anatomy of Lithophyllum artabricum V.Peña, sp. nov.: A, B, vertical section of the thallus showing a monomerous thallus construction with non-coaxial medulla; C, vertical section of the thallus showing cortical cells disposed in filaments laterally aligned; D, vertical section of the thallus showing a monomerous thallus construction with coaxial medulla, and a tetra/bisporangial uniporate conceptacle empty and buried; E, F, Vertical section of the thallus showing secondary pit-connections between contiguous filaments of cortical cells (arrows) and epithallial cells flattened disposed in 1-2 layers (arrowheads), G, surface view of the thallus showing polygonal epithallial cells; H, I, surface view of two different development stages of tetra/bisporangial uniporate conceptacles showing the pore flush with thallus surface (arrows). A, H, SANT-Algae 11671; B, C, holotype SANT-Algae 33667; D, E, SANT-Algae 26900; F, SANT-Algae 7046; G, SANT-Algae 11683; I, SANT-Algae 15006. Scale bars: A, B, D, 200 µm; C, G-I, 50 µm; E, F, 20 µm.

FIG. 5. — Tetra/bisporangial conceptacles of Lithophyllum artabricum V.Peña, sp. nov.: A, B, chambers dumbbell-shaped, empty; C, canal pore conical, tapering from the bottom to the roof surface; D, central calcified columella; E, buried conceptacles within the thallus; F, buried conceptacle with inorganic infilling. A, SANT-Algae 7046; B-D, E, holotype SANT-Algae 33667; F, SANT-Algae 15005. Scale bars: A, B, D, 100 µm; C, 50 µm; E, 500 µm; F, 200 µm.