Sargassum herporhizum Setchell & Gardner (1924: 739

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 : 206-208

Sargassum herporhizum Setchell & Gardner (1924: 739 , pl. 20, figs. 69–71) ( Figs. 2A–B ).

Heterotypic synonym: Sargassum brandegeei Setchell & Gardner (1924: 736 , pl. 21, fig. 79), syn. nov.

Type:— MEXICO. Isla San Jorge, Gulf of California. Collected from rocks in the upper littoral zone, I.M. Johnston no. 72 ( CAS! 1342) .

Description: —Short stipes and a primary axis initially arising from a small discoid base that develops numerous, narrow-branching (<3 mm) repent cylindrical rhizomes attached at various points to small hapterae. Several erect secondary axes arise along horizontal rhizomes as they lengthened. Leaf-like blades linear, long and narrow (15–25 mm long and 2–5 mm wide), with a percurrent costa that vanishes in the apical region.A small number of inconspicuous cryptostomata are observed and margins are uneven or slightly to irregularly dentate. Vesicles spherical to ovoid, mostly smooth, up to 3 mm in diameter, on pedicels, receptacles not present. Thalli up to 30 cm, with several erect terete and smooth axes, with alternate to irregular branches, which are often whorled above entangled rhizomes

Habitat: —Thalli grew on rocks in the subtidal zone (3–5 m depth) together with S. johnstonii .

Current distribution: — Bahía de Los Angeles (Baja California) ; Bahía Concepción (Baja California Sur) ; La Cueva (Sonora) .

Remarks: —The original description of S. herporhizum considered all the structures observed on Sargassum thalli, and included the short stipe giving rise to erect primary and horizontal branches, which in turn developed branches and haptera above and below the erect branches. In the present study, the blade (upper blade linear-lanceolate and acute) ranged from 3–5 mm (lower area) to 1–2 mm (upper area), and the percurrent nerve character was evaluated. However, the measurements could not be used to distinguish between species because they were highly variable. Norris (2010) described the nerve as being less distinct or faint on the uppermost blades, although the shape of the blade was not described. The type material of S. herporhizum was complete; the characteristics described by Setchell & Gardner (1924) could be seen on this specimen and were useful for identifying S. herporhizum . However, these characteristics could not be used to differentiate this species from S. brandegeei because there were no discriminant characteristics for the blades or vesicles, nor did the branching pattern differ. Thus, we propose that S. brandegeei should be considered a synonym of S. herporhizum . We consider the holdfast to be the strongest characteristic for distinguishing this species from other Sargassum species. This structure (with rhizoid characteristics) was unique in the Gulf of California specimens and among herbarium material and type material.

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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.