Pleonosporium boergesenii (A.B. Joly) R.E. Norris, 1985: 61

Mateo-Cid, Luz Elena, Mendoza-González, A. Catalina, Norris, James N. & García-López, Deisy Y., 2018, A taxonomic account of species in the tribe Spongoclonieae (Ceramiaceae, Ceramiales, Rhodophyta) reported from Atlantic and Pacific Mexico, Phytotaxa 340 (3), pp. 229-245 : 230

Pleonosporium boergesenii (A.B. Joly) R.E. Norris, 1985: 61 ( Figs. 1–4 )

Basionym : Mesothamnion boergesenii A.B. Joly, 1957: 142 .

Type locality: Paranapoan Beach, São Vicente, São Paulo State, Brazil.

Distribution. WESTERN ATLANTIC: North Carolina, Georgia and Florida, USA; Veracruz, México; and São Paulo State, Brazil ( Joly, 1957; Schneider and Searles, 1991; herein).

Specimens studied. WESTERN ATLANTIC. Veracruz ( Gulf of Mexico), México: Playa El Pulpo, Barra de Cazones (97°11´90.72´´W, 20°43´33.98’’N), coll. Mateo-Cid, Mendoza-González & Hernández Ortiz, 16-04-2016 ( ENCB 21801 ; polysporangia) .

Habitat. On rocks; shallow subtidal, 1–2 m deep.

Morphology, Anatomy and Reproductive structures. Thalli erect, bushy, up to 3 cm tall, rosy red, axes ecorticate; branching alternately radial and pseudodichotomous, becoming alternate in a 1/3 spiral in upper portions; branchlets incurved, with obtuse tips; attached by multicellular, uniseriate branched rhizoids arising from bases. Main axes cells in lower segments of proximal portions, cylindrical, 200–220 μm in diameter, 200–300 μm long; lateral axes gradually tapering, with middle cells 100-120 μm in diameter, 150–200 μm long; and, cells of ultimate segments, 12–15 μm in diameter, 30–50 μm long;

Polysporangia sessile, single, subglobose to slightly ellipsoid, 50–60 μm in diameter (including thick hyaline cell wall), divided into sixteen spores; borne distally and adaxially on branch cells. Gametangial thalli not observed.

Remarks. The Veracruz P. boergesenii is in general agreement with of Schneider and Searles (1991), and represent the first records for Atlantic México.

Figures

FIGURES 1–8. Species of Pleonosporium. 1–4: Pleonosporium boergesenii, Playa El Pulpo, Barra de Cazones, Veracruz (ENCB 21801). 1) An entire, mature sporophyte. Scale bar: 7 mm. 2) Ecorticate branching axis and determinate lateral branch. Scale bar: 250 μm. 3) Branch tip of sporophyte showing incurving branchlets. Scale bar: 20 μm. 4) Branch of sporophyte showing sessile polysporangia (arrow). Scale bar: 60 μm. 5–8: Pleonosporium borreri, Playa El Pulpo, Barra de Cazones, Veracruz (ENCB 21896). 5) Habit of mature sporophyte. Scale bar: 8 mm. 6) Basal portion of thallus showing rhizoidal attachment. Scale bar: 150 μm. 7) Branch tip of sporophyte showing incurving and curved branchlets. Scale bar: 125 μm. 8) Branch of sporophyte with sessile polysporangia (arrows). Scale bar: 50 μm.