Sargassum horridum Setchell & Gardner (1924: 734

Andrade-Sorcia, Gabriela, Riosmena-Rodríguez, Rafael, Muñiz-Salazar, Raquel, López-Vivas, Juan Manuel, Boo, Ga Hun, Lee, Kyung Min & Boo, Sung Min, 2014, Morphological reassessment and molecular assessment of Sargassum (Fucales: Phaeophyceae) species from the Gulf of California, Mexico, Phytotaxa 183 (4), pp. 201-223 : 209-210

Sargassum horridum Setchell & Gardner (1924: 734 , pl. 20, figs. 65, 66) ( Figs. 2C–F ).

Heterotypic synonyms: Sargassum marchantae Setchell & Gardner (1924: 735 , pl. 19, fig. 63), syn. nov.; S. camouii Dawson (1944: 248 , pl. 35, figs. 9, 11–13), syn. nov.

Type:— MEXICO. La Paz, Baja California. Collected after being cast ashore. Marchant no. 22 ( UC! 221179) .

Description: —Wood-like holdfasts initially discoid and becoming conical or hapteroid. The stipe and branches are cylindrical with spiny (muricate) margins. Leaf-like blades lanceolate, mostly 30–60 mm long, and 3–8 mm wide. Some blades are undulated, with a prominent nerve serrated margins, and numerous cryptostomata. Vesicles spherical, smooth, or spiny, 3.0– 4.5 mm in diameter. Cryptostomata could be observed on the vesiclesand the thallus. Receptacles cylindrical, with multiple branches, showing spiny or smooth margins, growing from the middle part of the thallus to the apical side. Thalli reached up to 60 cm in length, rigid and densely branched.

Habitat:— Growth was observed on rocks or calcareous substrates (as shells) in the intertidal or subtidal zone, some thalli were growing in intertidal pools. This species was growing together with S. lapazeanum , S. sinicola , or S. herporhizum at temperatures between 13 and 28 °C.

Current distribution:— Bahía Asunción (Baja California); Bahía Concepción, Balandra, Calerita, Bahía La Paz, El Coyote (Baja California Sur); San Luis Island, San Marcos Island, San Pedro Martir Island; Turner Island, Kino Nuevo (Sonora); Guaymas, Topolobampo, Navachiste (Sinaloa); Playa Agua Blanca, Santa Elena (Oaxaca). Pacific coast: Cerritos Baja California Sur, Conquista Agraria Baja California Sur.

Sargassum johnstonii Setchell & Gardner (1924: 737 , pl. 20, fig. 72; pl. 21, fig. 80) f. johnstonii ( Figs. 3A–E ). Heterotypic synonyms:— Sargassum johnstonii f. laxius Setchell & Gardner (1924: 21 , figs. 75, 81), Sargassum guardiense Setchell & Gardner (1924: 732 , pl. 19, fig. 64).

Type:— MEXICO. Sonora, Isla San Jorge. From rocks in the upper littoral zone. I.M. Johnston no. 71, 27 April 1912 ( CAS! 1341) .

Description: —Holdfast crustose or conical (with few haptera) and terete, with smooth primary axes, usually continuous from the base. Secondary branches bifarious in some thalli. Blades narrowly lanceolate and linear or aciculate. Some blades flat, 1.0– 2.5 cm in length and 1.0– 2.5 mm wide, expanded, ecostate or rarely faintly midirb, with denticulate to smooth margins. Cryptostomata present, vesicles elliptical with smooth margins. Pedicels shorter than the vesicle length, the apical part of the vesicle (with apiculae or crowns) is blade-shaped. Receptacles cylindrical and branched several times, with few denticulations (thorns). Thalli reach up to 1–2 m in length.

Habitat:— Growth was observed on rocks in the subtidal zone (2–5 m depth) in beds containing S. herporhizum or S. lapazeanum .

Current distribution:— Tiburon Island, Patos Island, Jorge Island, San Pedro Martir Island, Kino Bay, Canal de Ballenas, Raza Island, Turner Island, La Cueva (Sonora); Angel de la Guarda Island, La Gringa, De Los Angeles Bay (Baja California); Balandra, La Concha, Punta Perico, San Juan de la Costa, San Miguel (Baja California Sur).

Remarks:— Sargassum johnstonii f. johnstonii , S. johnstonii f. gracile , S. johnstonii f. laxius , and S. guardiense were described by Setchell & Gardner (1924) based on incomplete specimens (branches), and the descriptions overlapped. Dawson (1944) proposed a Johnstonii group for this species, but used S. guardiense as a synonym for S. johnstonii f. johnstonii , and S. johnstonii f. laxius as a synonym for S. johnstonii f. gracile . Norris (2010) reported one species ( S. johnstonii ) and one form ( S. johnstonii f. gracile ) from the northern part of the Gulf of California that belongs to this group. Several thalli were observed with all of the characteristics proposed by Setchell & Gardner (1924) in their description of S. johnstonii . Type specimen was similar, consisting on sections of branches; only the type specimen of S. johnstonii had reproductive structures, although it was difficult to identify the characteristics proposed by Setchell & Gardner (1924). To separate each form from the nominal form, they commented for S. johnstonii f. laxius that “the secondary branches and fructiferous ramuli are very much more widely scattered and several times longer, the blades are narrower, in fact they are filiform, the vesicles are very much shorter, about one and a half times as long as broad, and the receptacles are less branched and rarely if ever denticulate at the apices” ( Setchell & Gardner 1924). Regarding S. johnstonii f. gracile , they described this form as “being decidedly more slender throughout, much less frequently branched, and in having the branches much longer and more delicate, and in having filiform blades. In these respects they more nearly coincide with S. johnstonii f. laxius but are much more delicate though than that form. The receptacles are young in the specimens at hand; the vesicles are practically the same in form as those of the species” ( Setchell & Gardner 1924). However, type material is only a section of the branch from some thalli, this fact reduces the validity for any characteristics of these species. Although S. johnstonii was identified based on scattered fragments of some thalli, it was distinguished from other Sargassum species based on vesicle characteristics. Vesicles were elliptical and apiculate on the upper part, similar to Setchell & Gardner’s (1924) first description, our study included complete thalli and showed that the morphology differed slightly when the thalli were located at depths greater than 3 m. Thalli were longer and contained multiple branches; the constant characteristic state being the presence of a vesicle with a mucron at the apical side. The present study confirms the proposed characteristics for each specimen described as S. johnstonii , but we were unable to separate S. johnstonii f. gracile from S. johnstonii f. johnstonii because structures are incomplete or few samples were reproductive mature ( Fig. 5D ) lacked some of these characteristics over the type material.

Figures

FIGURE 2. Morphology of Sargassum herporhizum and S. horridum. A. Habit of S. herporhizum. B. Bladders (arrow) at the base of a blade. C Habit of S. horridum. D. Bladders (arrow) at the base of a blade. E. Holdfast and thorns on basal branches. F. Receptacles. Scale bars = 1 cm.

FIGURE 3. Morphology of Sargassum johnstonii, S. lapazeanum and S. sinicola. A. Habit of S. johnstonii. B, E. Blades (arrow) and vesicles (arrow heads) above the branch. D. Discoid holdfast and smooth branches. F.Habit of S. lapazeanum. G. Bladders (arrow) and blades growing in clusters. H. Discoid holdfast. I. Habit of S. sinicola. J. Leaves and vesicles (arrow) growing in clusters. Scale bars = 1 cm.

FIGURE 5. Conceptacles from Sargassum: A, B. Male S. horridum, scale bar = 400 µm. C. Female S. lapazeanum, scale bar = 200 µm. D. female S. johnstonii, scale bar = 200 µm. E. female and male S. lapazeanum, scale bar = 200 µm. F. Male S. sinicola, scale bar = 300 µm.