Gracilaria silviae G.M. Lyra, C.F.D. Gurgel, M.C. Oliveira and J.M.C. Nunes, 2015

Lyra, Goia De Mattos, Gurgel, Carlos Frederico Deluqui, Costa, Emmanuelle Da Silva, Jesus, Priscila Barreto De, Caires, Taiara Aguiar, Matos, João Carlos Gama De, Oliveira, Mariana Cabral, Oliveira, Eurico Cabral & Nunes, José Marcos De Castro, 2015, A New Tropical Species of Gracilariaceae (Rhodophyta, Gracilariales): Gracilaria silviae sp. nov., Phytotaxa 222 (3), pp. 199-210 : 201-207

Gracilaria silviae G.M. Lyra, C.F.D. Gurgel, M.C. Oliveira and J.M.C. Nunes , sp. nov. ( Figs. 1−9 )

Type:— BRAZIL. Bahia: Santa Cruz de Cabrália , Coroa Vermelha ; 16°19’58,12” S, 39°00’19,50” W, 07 November 2010, G.M. Lyra and J. M. C. Nunes s.n. (holotype ALCB 99667!, male gametophyte, Fig. 1 ).

Isotype:— BRAZIL. Bahia: Santa Cruz de Cabrália, Coroa Vermelha ; 16°19’58,12” S, 39°00’19,50” W, 07 November 2010, G.M. Lyra and J. M. C. Nunes s.n. (isotype ALCB 99669!, infertile).

Paratypes:— BRAZIL. Bahia: Entre Rios, Subaúma , 12°14’10,10”S, 37°46’5,60”W, 25 October 2010, G.M. Lyra & J. M. C. Nunes, s.n. (ALCB99676!; ALCB99673!, tetrasporophytes) ; Santa Catarina: Florianópolis, Canal da Barra , 26°15’01.49”S, 48°45’01.26”W, 21 May 2011, E. C. Oliveira, s.n. (SPF57282!, female gametophyte) . USA. Florida: Harbour Branch , 13 July 1998, C. F. D. Gurgel, s.n. (female gametophyte) .

Diagnosis:— Thalli flattened throughout, delicate, sparsely branched, ultimate branching forming an antler-like branching pattern, with textorii-type spermatangia.

Etymology:— This species is named in honor of Dr. Silvia Maria Pita de Beauclair Guimarães (Instituto de Botânica de São Paulo) to celebrate her contributions for the consolidation of a group of algae taxonomy in Brazil.

Distribution:— western Atlantic Ocean from Florida, USA, to Santa Catarina, southern Brazil.

Description:— Thalli flattened throughout, ribbon-shaped except at certain portions of the base where it is sub-cylindrical ( Fig. 1 ), or sub-cylindrical throughout ( Fig. 2 ), 4−6 (−9) cm tall, 1−2 mm wide, 250−300 μm thick; yellowish to dark brown in colour.Thallus arising from small, rounded holdfasts.Main axes sparingly and dichotomously branched, up to 4 (−5) orders. Specimens with totally flattened thallus with ultimate branching forming an antler-like branching pattern; lateral branches, arising from thallus margin; apices mostly acute, dichotomously divided ( Figs. 3, 4 ). Gradual transition of cell size between cortical and medullary regions. Medullary region composed of 2−3 layers of large, thin-walled central cells, 60−80 μm by 105−120 μm and 1−2 outer layers of subcortical cells. Cortical region composed of 1−2 layers of small pigmented cells, 8−14 μm by 19−26 μm ( Fig. 5 ). Decussate cruciate tetrasporangia immersed in the cortical region of both sides, about two times the size of cortical cells ( Fig. 6 ). Spermatangia distributed in shallow crypts (textorii - type) on both sides of the blade ( Fig. 7 ). Cystocarps hemispherical ( Fig. 8 ), scattered on lower and upper surfaces of main axes, 0.8−1 mm diameter and slightly constricted at base where protruding from thallus. Carposporangia organized in irregularly packed branched files. Pericarp composed of 6−8 cell layers. Gonimoblasts at maturity completely filling cystocarp cavity and composed of regular, thin-walled, small cells, 14–18 μm diameter. Carpogonial fusion cell not pronounced. Nutritive tubular cells present in the upper portion of the cystocarp, connecting the gonimoblast to the outer pericarp, and also connecting the gonimoblasts to the cystocarp floor ( Fig. 9 ).

DNA barcoding analyzes:— Eleven new cox 1 sequences, three new UPA sequences and three new rbc L sequences were generated ( Table 1). In the cox 1 matrix (597 bp positions long), 195 were informative out of the 241 variable nucleotide positions within the ingroup, In the UPA matrix (300 bp positions long), 41 were informative out of the 67 variable positions within the ingroup, Trees generated from the individual data sets were highly congruent and similar topologies were obtained in each analysis (Figs. 10 and 11, respectively).

Intraspecific divergence was found only for cox 1 (0−0.5%) and the highest values were obtained between specimens from distant populations, i.e. between the northeast and southern regions of Brazil. For cox 1, the genetic distance between G. silviae from Brazil and other Gracilaria species varied from a minimum of 4.7% [ G. isabellana Gurgel, Fredericq & J.N. Norris (2004b: 384–387) from Brazil, with a barcoding gap of 9.4x] to 13.3% [ G. gracilis (Stackhouse) M. Steentoft, L.M. Irvine & W.F. Farnham (1995: 115) from Argentina, with a barcoding gap of 26.6x]. For UPA, the interspecific divergence was lower than that in cox 1, as expected, because it is a more conserved region. UPA sequences of G. silviae from Brazil diverged from those of G. parvispora I.A. Abbott (1985: 119) from Hawaii, USA by 1%.

Phylogenetic relationships of the new taxa:— In the rbc L matrix (1.071 bp positions), 393 were informative out of the 454 variable nucleotide positions within the ingroup, Gracilaria silviae was resolved as sister to G. parvispora in a well supported clade (100% BP; 0.1 PP, Fig. 12). Together, they formed a major clade containing G. silviae , G. parvispora , G. tikvahiae Mclachlan (1979: 19) , G. isabellana , and G. cuneifolia (Okamura) I.K. Lee & Kurogi (1977: 177) with maximum phylogenetic support (100% BP and 0.1% PP).

Figures

FIGURES 1−4. Habits of Gracilaria silviae Fig. 1. ALCB 99667, holotype, male gametophyte specimen, scale bar 1 cm. Fig. 2. LAF#13.07.98, cystocarpic specimen, scale bar 1 cm. Figs. 3−4. ALCB 99673, paratype, tetrasporophytic specimen, scale bars 1 cm and 0.5 cm, respectively. Fig 4. Apical portion of the branches.

FIGURES 5−9. Anatomical features of Gracilaria silviae Fig. 5. Traverse section of a female gametophyte thallus, showing medullar and cortical regions (SPF 57282), scale bar 20 μm. Fig. 6. Traverse section of tetrasporophyte cortical region showing decussate cruciate tetrasporangia (ALCB 99673), scale bar 40 μm. Fig. 7. Transverse section of male gametophyte cortical region, showing textorii type spermatangial crypts (ALCB 99667), scale bar 40 μm. Figs. 8–9. Longitudinal section of a cystocarp (LAF#13.07.98). Fig. 8. Scale bar 150 μm. Fig. 9. Black arrow shows a nutritive tubular cell connecting the gonimoblast to the cystocarp floor, scale bar 100 μm.