Gelidium guimaraesiae Brunelli, Milstein, S.M. Boo & M.T. Fujii, 2019

Brunelli, Beatriz, Milstein, Daniela, Boo, Sung M. & Fujii, Mutue T., 2019, Gelidium guimaraesiae sp. nov. (Gelidiaceae, Rhodophyta) from the Western Atlantic segregated from G. floridanum by morphological and molecular evidence, Phytotaxa 388 (4), pp. 275-286 : 279-280

Gelidium guimaraesiae Brunelli, Milstein, S.M. Boo & M.T. Fujii sp. nov. ( Figs. 3–5 )

Misapplied name for Costa Rican Gelidium floridanum ( Thomas & Freshwater 2001, rbc L AF305797).

Diagnosis: —Plants tufted or isolated, vinaceous in color, up to 3 cm tall. Thalli flattened, with prominent apical cell. Thalli branched, with constricted branch bases. Erect axes with central medullary cells in a distinct central row. Rhizines abundant in medullary region of the erect thalli, and concentrated in the outer medullary region in the stoloniferous branches. Tetrasporangial sori ovoid and development on the distal portion of branchelets. Tetrasporangia decussately divided. Cystocarps bilocular and subterminally on the branchletes.

Holotype: — Castelhanos beach, Anchieta , Espírito Santo, Brazil (20° 50’ 04” S, 40° 37’ 21” W), 22 June 2013, C. H. Kano & L. P. Machado ( SP428772 ). Rbc L type sequence = GenBank accession number MF565764. Cox 1 type sequence = MF577009.

Isotypes: in SPF and CNU.

Paratypes: — BRAZIL. Espírito Santo: Serra, Capuba Beach (20° 06’ 29” S, 40° 10’ 19” W), 21 June 2013, col. C. H. Kano & L. P. Machado ( SP 469177). Anchieta, Castelhanos Beach (20° 50’ 04” S, 40° 37’ 21” W), 09 September 2014, col. M. T. Fujii, ( SP 469012).

Distribution: —Found so far only in Espírito Santo, Brazil, and in Cahuita, Costa Rica (as G. floridanum ).

Habitat: —Collected in the mid to low intertidal zones, growing on rocks or sandstone reefs.

Etymology: —Species epithet is named in honor to Brazilian phycologist, Prof. Silvia M.P.B. Guimarães, for her contribution to the knowledge of seaweed diversity from Espírito Santo, Brazil.

Extended description: —Thallus tufted or isolated, vinaceous in color, cartilaginous, up to 3 cm tall ( Figs. 3A, 3B ), arising from stoloniferous branches attached to the substratum by brush-like haptera ( Figs 3C, 3D ). Erect axes completely flattened with one to two orders of alternate to irregular, proximally constricted branches. Presence of a single prominent apical cell ( Fig. 3E ). Stolons terete, 150–250 μm diameter. In transverse section, stolon composed by four to five layers of medullary cells surrounded by two to three layers of cortical cells. Medullary cells rounded in transverse section, thick-walled, 7.5–10 μm in diameter and the outer cortical cells rounded, 2.5–5 μm in diameter. Large numbers of rhizines concentrated in the outer medullary region ( Fig. 3F ). In transverse sections of the middle part of erect axes, cortex composed of three to four cell layers. Outer cortical cells rounded, 7–13 μm in diameter. The medulla formed by three to four layers, with central medullary cells arranged in a distinct central row. Medullary cells thick-walled and rounded in transverse section, 7–13 μm in diameter. Rhizines abundantly spread in the medulla ( Fig. 4A ).

Tetrasporangial sori develop predominantly on the distal portion of branchelets, presenting a sterile margin, with rhizines ( Figs. 5A, 5B ). Tetrasporangia decussate, with 39 μm length and 25 μm wide ( Fig. 5C ). Cystocarps subterminal on lateral branchlets ( Figs. 5D, 5E ). Cystocarps spherical and bilocular with a pericarp of 3–5 cell layers and ostioles in both sides. Gonimoblast and nutritive filament cells develop in each side of the placenta ( Fig. 5F ). Male gametophytic thalli were not observed.

Figures

FIGURE 3. Vegetative aspects of Gelidium guimaraesiae sp. nov. Fig. 3A. Holotype (SP428772). Scale bar = 0.5 cm. Fig. 3B. Habit of paratypes (SP469012). Scale bar = 0.5 cm. Fig. 3C. Stoloniferous axes with haptera. Scale bar = 250 μm. Fig. 3D. Transverse section through stolon and longitudinal section of brush-like haptera. Scale bar = 25 μm. Fig. 3E. Apex. Scale bar = 25 μm. Fig. 3F. Transverse section of stolon. Scale bar = 25 μm.

FIGURE 4. Comparison between the cross section of the medial region of the thallus. Fig. 4A Gelidium guimaraesiae. Scale bar = 25 μm. Fig. 4B. Gelidium floridanum. Scale bar = 25 μm.

FIGURE 5. Reproductive aspects of Gelidium guimaraesiae sp. nov. Fig. 5A. Tetrasporophyte, arrows indicate tetrasporangial sorus. Scale bar = 0.5 cm. Fig. 5B. Tetrasporangial sori. Scale bar = 100 μm. Fig. 5C. Transverse section of a tetrasporangial with decussately divided tetrasporangia. Scale bar = 25 μm. Fig. 5D. Female gametophyte, arrows indicate cystocarps. Scale bar = 0.5 cm. Fig. 5E. Cystocarp. Scale bar = 100 μm. Fig. 5F. Transverse section of a bilocular cystocarp. Scale bar = 25 μm.