Gracilariopsis E.Y. Dawson 1949

Lyra, Goia De Mattos, Nunes, José Marcos De Castro, Pestana, Edilene Maria Dos Santos, Matos, João Carlos Gama De, Caires, Taiara Aguiar, Jesus, Priscila Barreto De, Costa, Emmanuelle Da Silva & Oliveira, Mariana Cabral, 2021, Diversity Of Gracilariaceae (Rhodophyta) In Brazil: Integrating Morphological And Molecular Data, Phytotaxa 496 (1), pp. 1-53 : 24-26

Gracilariopsis E.Y. Dawson 1949

Type species: Gracilariopsis sjoestedii (Kylin) Dawson. Currently accepted name for the type species: Gracilariopsis andersonii (Grunow) Dawson.

Gracilariopsis silvana C.F.D. Gurgel, Fredericq & J.N. Norris

Type locality: Playa Barranquilla , Estado Falcón, Venezuela ( Gurgel et al. 2003: 61). Holotype: C. F. D. Gurgel, J. E. Conde & C. Carmona FG-37; 14.vii.1999; US Alg. Coll. 204316.

Figs. 16, a–e

Thallus completely flattened,up to 12cm tall and 3mm wide,with several branching;dichotomously or subdichotomoulsy branched (Figs. 16, a–b), or slightly wavy, presenting a pinnate aspect with curved branchlets. Medullary region with sharp transition towards cortical region, with 5–6 layers of large hyaline medullary cells, measuring 250 μm in height and 120 μm in width; cortical region with 2 layers of cells (Fig. 16c). Tetrasporangia cruciate (Fig. 16c) embedded in the cortical region on both sides of the blade. Male gametophytes not observed. Cystocarps at different stages scattered throughout the female gametophyte main axes, with a slight constriction at the base; inner pericarp absent (Fig. 16d); gonimoblast and carposporangial chains radially organized; nutritive tubular cells not observed (Fig. 16e).

FIGURE. (a–e) Gracilariopsis silvana : (a, b) habit; (c) transverse section of the thallus showing tetrasporangia (arrow); (d) superficial view of the thallus showing distribution of cystocarps; (e) longitudinal section of a cystocarp. (f–h) Gracilariopsis tenuifrons : (f) habit; (g) transverse section of the thallus showing tetrasporangia (arrow); (h) longitudinal section of a cystocarp.

World distribution: Brazil and Venezuela.

Comments: Gracilariopsis silvana is the only one, among the 25 species described Gracilariopsis species , to present a flattened ribbon shaped thallus ( Gurgel et al. 2003). The apical regions are wider and present more branching than other parts of the thallus, and the presence of curved branchlets easily distinguishes this species from Gracilaria species with flattened thallus.

Gracilariopsis tenuifrons (C.J. Bird & E.C. Oliveira) Fredericq & Hommersand

Type locality: Praia Avenida , near Maceió, Alagoas, Brazil (Bird & Oliveira Filho 1986: 317). Holotype: E. C. de Oliveira F.; 18 July 1981; Approximately 1.0 m below mean sea level. SPF 23687 (male) (Bird & Oliveira Filho 1986: 317). Isotypes: SPF-23687, female; SPF-23680, tetrasporic; SPF-23682, female; SPF-23683, female, tetrasporic; NRCC-9173, female, tetrasporic ( Guiry and Guiry 2020).

Figs. 16, f–h

Thallus extremely delicate and slender cylindrical with a diameter of 0.4–0.5 mm, reaching up to 35 cm tall; numerous branches issued starting from the base, becoming sparse to absent distally (Fig. 16f). Medullary region with sharp transition to cortical region, with large hyaline cells, with up to 100 μm in diameter; cortical region with two layers of small, pigmented cells (Fig. 16g). Tetrasporangia decussate cruciate embedded in the cortical region of both sides of the blade, up to five times the size of the cortical cells (Fig. 16g). Male gametophytes not observed. Numerous and prominent cystocarps distributed throughout the thallus of female gametophytes, inner pericarp with 4–6 layers of cells; outer pericarp with 5–6 layers of cells; gonimoblast and carposporangial chains radially organized (Fig. 16h); tubular nutritive cells not observed.

World distribution: Antigua and Barbuda, Brazil, Cuba, Guadeloupe, Mexico, Panama, Saint Lucia, Saint Vincent and the Grenadines, Trinidad and Tobago and Venezuela.

Comments: Detailed morphological and anatomical descriptions of this species are found in Bird and Oliveira Filho (1986). The anatomical features, with emphasis on the ontogeny of cystocarp, are described in detail in Bellorin (2002).