Dictyota crenulata

Dictyota crenulata J. Agardh

Dictyota crenulata J. Agardh, 1847:7; Setchell and Gardner, 1924a:730, pl. 18: figs. 50, 51; Setchell and Gardner, 1925:655; Taylor, 1939:8; Dawson, 1944:228; Taylor, 1945:90, pl. 10: fig. 1; Dawson, 1950a:88; Dawson, 1954a:3; Dawson, 1959a:5, 18; Dawson, 1961b:388; Brusca and Thomson, 1975:42; McEnroe et al., 1977:184; Huerta-Múzquiz and Mendoza-González, 1985:46; Salcedo-Martínez et al., 1988:82; Santelices, 1989:289, pl. GG: fig. 7; Rocha-Ramírez and Siqueiros-Beltrones, 1991:31; Lluch-Cota et al., 1993:366; León-Tejera and González-González, 1993:497; Servière-Zaragoza et al., 1993:482; Mateo-Cid and Mendoza-González, 1994b:43; González-González et al., 1996:294, fig. 16; Anaya-Reyna and Riosmena-Rodríguez, 1996:383; Mateo-Cid et al., 2000a:68; Mateo-Cid et al., 2000b:199, figs. 20, 21, 71, 96; Cruz-Ayala et al., 2001:190; De Clerck, 2003:145, 166; Riosmena-Rodríguez et al., 2005:101; Altamirano-Cerecedo and Riosmena-Rodríguez, 2007:575, figs. 1–6; Servière-Zaragoza et al., 2007:8; Pedroche et al., 2008:39.

Dilophus crenulatus (J. Agardh) Nizamuddin et Gerloff, 1979:867, pl. 1: figs. 1, 2, pl. 2: figs. 1, 2, pl. 7: figs. 1, 2 [note: lectotype (LD, Herb. Agardh-49042A) is illustrated in pls. 1, 2, 7].

Algae up to 15(–25) cm tall, of flat, dichotomously branched straplike fronds, (1–)2–4(–5.5) mm wide; margins with characteristic, conspicuous minute dentation; attached by multicellular rhizoids. Branching usually at wide angles; sometimes becoming subdichotomous;

branches narrower below and widening upward; surface sometimes with numerous proliferations. Transection of 3–6 cell layers (1–4 medulla: 2 cortical), 90–150 µm thick, up to 500 µm thick near base. Cortex a single layer; cortical cells rounded, 20–50 µm in diameter. Medulla single layer to multilayered (latter evident in basal portion); medullary cells 55–100 µm tall by 35–50 µm wide.

Reproductive structures mostly in sori, scattered over branch surface, mostly in upper portions. Sporangia may be singular or a few in sorus, rounded, 75–90 µm in diameter. Oogonia in groups of 30–45 (in surface view), 4–6 (in transection view) in sori; 75–80 µm tall by 66–70 µm in diameter.

HABITAT. On rocks; low intertidal to shallow subtidal.

DISTRIBUTION. Gulf of California: Bahía Concepción to Cabo San Lucas. Pacific coast: Bahía Vizcaíno to Todos Santos, Baja California Sur; Islas Revillagigedo; Jalisco to Oaxaca; Costa Rica; Chile.

TYPE LOCALITY. San Agustín, Oaxaca, Mexico (Agardh, 1847, “St. Augustin, Stilla Oceanen [Pacific Ocean]”).