Chromosomal and sperm ultrastructure studies of brazilian species of Terrarana (Amphibia : Anura) / Analise de especies brasileiras de Terrarana (Amphibia : Anura) utilizando estudos cromossomicos e da ultra-estrutura do espermatozoide

AUTOR(ES)
DATA DE PUBLICAÇÃO

2008

RESUMO

The Terrarana is the largest taxon of the Anura order, comprising 900 species. Recently this anuran group has undergone a series of taxonomical rearrangements. At first, these species were removed from the Leptodactylidae family and transferred to the synonymy of Brachycephalidae, and lately they were placed into a new taxon named Terrarana. Currently, the Terrarana species are distributed in the families, Eleutherodactylidae, Craugastoridae, Strabomantidae and Brachycephalidae. Despite being intensively studied, many aspects of their inter- and intrageneric relationships remain unclear. The South American Strabomantidae and Brachycephalidae are the least known clades regarding molecular phylogeny. In the present work, Brazilian Terrarana species of Pristimantis, Ischnocnema, Barycholos, Haddadus and Brachycephalus were studied by means of cytogenetical and sperm ultrastructural characteristics. Metaphases obtained from suspensions of intestinal epithelium were stained with Giemsa or submitted to silver staining (Ag- NOR) and fluorescence in situ hybridization (FISH) techniques, in order to detect the nucleolus organizing region, and to C-banding for heterochromatin localization. Sperm ultrastructure was analyzed by transmission electron microscopy. The studied species were P. fenestratus (Borba and Manaus at Reserva Florestal Adolfo Ducke, Amazonas, and Rio Branco, Acre), P. dundeei (Chapada dos Guimarães, Rondonópolis, and Aripuanã, Mato Grosso), P. crepitans (Chapada dos Guimarães and São Vicente, Cuiabá, Mato Grosso), Ischnocnema paulodutrai (Ilhéus, Bahia), I. juipoca (Atibaia and Campos do Jordão, São Paulo), I. guentheri and I. parva (Mogi das Cruzes, São Paulo), B. ephippium (Mogi das Cruzes and Atibaia, São Paulo), Barycholos ternetzi (Uberlândia, Minas Gerais, and Porto Nacional, Tocantins), and Haddadus binotatus (Mogi das Cruzes and Ilhabela, São Paulo). The cytogenetical analyses allowed chromosomal characterization of the species P. fenestratus 2n=34 chromosomes, P. crepitans 2n=22, P. dundeei 2n=28 and I. paulodutrai 2n=30, which have not been previously analyzed in phylogenetical studies, in addition to B. ternetzi and I. juipoca 2n=22. The data revealed differences in C-banding and Ag-NOR, which indicated the existence of not yet described Pristimantis species in the Manaus, Rio Branco, and Aripuanã localities, and of Barycholos (from Tocantins) uncorrectly identified as P. fenestratus, P. dundeei and B. ternetzi. The cytogenetical analysis also indicates that the low chromosome number in P. crepitans is unique within this genus and suggests that this species is not closely related to its congeneric species. The karyotypical similarities between I. paulodutrai and P. dundeei indicate that these species could be close relatives. Moreover, an unusual case of intra-individual chromosomal variation in the fundamental number of several somatic cells was found in the P. fenestratus species, which may be a consequence of anomalous segregation of sister chromatids during mitosis. The sperm ultrastructure of the Brazilian species P. fenestratus, P. dundeei, P. crepitans, B. ternetzi, B. ephippiun, I. guentheri, I. parva, I. juipoca and H. binotatus revealed differences in the basic structures of the acrosome, midpiece and flagellum, showing distinct characteristics within the family Brachycephalidae and subfamily Strabomantinae, as well as within the genus Pristimantis. The most remarkable sperm characteristic was an axonemal fiber in H. binotatus, B. ephippium, B. ternetzi and P. crepitans, which has not been observed in P. fenestratus, P. dundeei and in all of the analyzed Ischnocnema specimens. The ultrastructural divergence in the axonemal fiber is in accordance with recent molecular data, which supported the transfer of H. binotatus from the Ischnocnema genus to a new taxon and also grouped the species I. guentheri, I. parva and I. juipoca in a same clade. In addition, the sperm ultrastructure showed that B. ephippium is not closely related to the Ischnocnema species, and that the taxonomy of the Brachycephalidae species should be reexamined. Furthermore, the sperm ultrastructure analysis corroborated chromosomal data indicating that P. crepitans is misallocated in the Pristimantis genus and that the I. paulodutrai and P. dundeei species are close relatives. Despite the small number of studied species, the cytogenetical and ultrastructural data on sperm ultrastructure of the three Brazilian Terrarana families revealed inter- and intrageneric non-conservative characteristics that generate new taxonomic questions within this anuran group and provide strong evidence of the existence of undescribed species in this taxon

ASSUNTO(S)

citogenetica anura spermatozoa anura espermatozoides - ultraestrutura cytogenetics

ACESSO AO ARTIGO

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