Pleonosporium rhizoideum E.Y. Dawson 1962a: 42

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 : 236

Pleonosporium rhizoideum E.Y. Dawson 1962a: 42 ( Figs. 22–26 )

Type locality: Salina Cruz, Oaxaca, México.

Distribution. EASTERN PACIFIC. Gulf of California, México: Baja California Sur, Sonora, Sinaloa, Nayarit, and Jalisco. Pacific México: Colima, Michoacán, Guerrero and Oaxaca. ( Dawson, 1962a; Mendoza-González et al. 1994; Mateo-Cid et al. 2006; Mateo-Cid and Mendoza-González, 1992, 2001, 2012; Bucher and Norris, 2014; Norris et al., 2017; herein).

Specimens studied. Gulf of California, México: Sonora: Puerto Peñasco (113°34’48”W, 31°17’42”N), coll. Mendoza-González, Mateo-Cid, Aguilar Rosas L. E. & Aguilar Rosas R., 03-06-1997 ( ENCB 16338 ; polysporangia). Sinaloa: Mazatlán (Playa Norte) (106°26’23”W, 23°12’06”N), coll. Mendoza-González & Mateo-Cid, 27-07-1987 ( ENCB 8114 ; polysporangia). Baja California Sur: Bahía Concepción (Santispack) (111°53’06” W, 26°45’32” N), coll. Mateo-Cid, 14-03-1990 ( ENCB 10880 ; polysporangia). Nayarit: Punta Mita (105°32’09”W, 20°46’12”N), coll. Mateo-Cid & López Sánchez, 23-06-1989 ( ENCB 8116 ; ♂, polysporangia). PACIFIC MÉXICO: Colima: Manzanillo (104°20’51”W, 19°06’18”N), coll. Mendoza-González & Mateo-Cid, 05-10-1987 ( ENCB 8268 ; polysporangia). Michoacán: Bahía de Maruata (103°20’29”W, 18°16’55”N), coll. López Sánchez, 17-05-1986 ( ENCB 15555 ; polysporangia). Guerrero: Playa Las Gatas, Zihuatanejo (101°33’05” W, 17°37’12” N), coll. Mateo-Cid & Mendoza-González, 03-09-1995 ( ENCB 16794 ; polysporangia) ; and, Las Peñitas (102°03’88”W, 17°98’91”N), coll. Chávez Barrera, 03-01-1971 ( ENCB 2727 ; ♀, polysporangia). Oaxaca: Santa Elena Cozoaltepec (96°44’38”W, 15°43’14”N), coll. Mateo-Cid & Mendoza-González, 08-05-1997 ( ENCB 97-56 /01; ♂, polysporangia) ; Playa Agua Blanca (96°48’50” W, 15°43’58” N), coll. Mendoza-González & Mateo-Cid, 08-05-1997 ( ENCB 21832 ; polysporangia) ; Puerto Ángel (96°29’42”W, 15°39’46”N), coll. Mendoza-González & Mateo-Cid, 08-12-1994 ( ENCB 14956 ; polysporangia) ; and, Tangolunda (96°05’58”W, 15°46’10”N), coll. Mendoza-González & Mateo-Cid, 08-08-1993 ( ENCB 14959 ; polysporangia) .

Habitat. On rocks, and epiphytic on Jania sp. ; intertidal.

Morphology, Anatomy and Reproductive structures. Thalli erect, bushy, up to 2.5 cm tall, reddish green; primary axes ecorticate; attached by numerous, descending, branched, multicellular rhizoids that become densely entangled to form a felt-like basal attachment. Erect axes more or less loosely clothed in lower portions by entangled rhizoids; branching principally distichous; branches mostly simple and very long, at first strongly incurved, then becoming irregularly curved or recurved, somewhat entangled; terminating in blunt apices (may sometimes form a terminal hook, or become prolonged to form a rhizoid). Cells of main filaments (125–)140–150 (–170) μm in diameter and (180–) 220–450 μm long; middle cells of filaments, 60–70 μm in diameter and 90–100 μm long; determinate lateral branchlets usually simple, 10–20 cells in length, strongly incurved, about 30–45 μm in diameter and 45–50 μm long, with blunt apices.

Polysporangia sessile, spherical, (60–) 90–110 μm in diameter (including thick, hyaline cell wall), divided into 32 spores; borne in densely branched portions of thallus, on short, irregular specialized branches bearing groups of alternate, polysporangia. Gametangial thalli dioecious. Spermatangial clusters about 110–130 μm long, 40–50 μm in diameter; briefly pedicellate, adaxial on lateral branchlets. Cystocarps subspherical, in terminal portions of thallus, 200–210 μm in diameter.

Remarks. Our specimens are similar to Pleonosporium rhizoideum E.Y. Dawson (1962a) , described from Salina Cruz, Oaxaca on the coast of Pacific México. However, the cell diameter of the main filaments and the sizes of polysporangia and cystocarps are larger than those described by Dawson (1962a; see also: Bucher and Norris, 2014). Specimens from Bahía de Maruata represent new distribution records from the coast of Michoacán.

Figures

FIGURES 17–24. Species of Pleonosporium: Pleonosporium mexicanum, 17) Apical portion of a sporophyte with incurved branchlets. Scale bar: 600 μm. 18) Sessile mature polysporangium (arrows), and an immature polysporangium (arrowhead). Scale bar: 65 μm. 19) Sessile spermatangial cluster (arrow). Scale bar: 40 μm. 20) Young procarp (arrow); note that the trichogyne has not developed. Scale bar: 50 μm. 21) Mature carposporophyte (key), note the carposporangia (arrow) and mature carposporophyte (arrowheads). Scale bar: 130 μm. Pleonosporium pygmaeum, Punta Morro, Baja California (ENCB 9570). 22) Habit of sporophyte. Scale bar: 8 mm. 23) Basal portion of thallus showing strong rhizoidal cortication (arrow). Scale bar: 160 μm. 24) Branch tip of sporophyte with straight branchlets. Scale bar: 120 μm.

FIGURES 25–32. Species of Pleonosporium: Pleonosporium pygmaeum, 25) Branch of sporophyte showing sessile polysporangia (arrow). Scale bar: 90 μm. Pleonosporium rhizoideum, Puerto Peñasco, Sonora (ENCB 16338). 26) Habit of sporophyte. Scale bar: 5 mm. 27) Basal portion of the thallus; note the attachment structure (arrow). Scale bar: 280 μm. 28) Branch tip of a sporophyte with curved branchlets. Scale bar: 100 μm. 29) Group of spermatangial clusters (arrow) borne on a single branch. Scale bar: 80 μm. 30) Group of mature carposporophytes (key), with carposporangia (arrow). Scale bar: 200 μm. Species of Spongoclonium: Spongoclonium caribaeum, Escolleras Tuxpan, Veracruz (ENCB VER-2017/A). 31) Branch tips from sporophyte showing branching axis and determinate lateral branchlets. Scale bar: 600 μm. 32) Ecorticate axis and determinate lateral branches. Scale bar: 300 μm.