Cytogenetics of populations and species of Physalaemus cuvieri group (Anura, Leiuperidae) / Citogenetica de populações e especies de Physalaemus do grupo "cuvieri" (Anura, Leiuperidae)

AUTOR(ES)
DATA DE PUBLICAÇÃO

2007

RESUMO

The genus Physalaemus is composed by 41 species distributed in seven groups: “albifrons”, “cuvieri”, “deimaticus”, “gracilis”, “henselii”, “olfersii” and “signifer”. Nine species compose the group “cuvieri” but just P. cuvieri had already been karyotyped in details. Expressive intra and interpopulational variation related to the localization of the nucleolus organizer regions (NOR) was described for this species. Physalaemus cuvieri is widely geographically distributed and NOR variation was described based on populations from Southern and Southeastern Brazil. In the present work we analyzed the cytogenetic of four populations from Northeastern, one from Northern and one from Southeastern Brazil. Additionally, three Argentinian populations were also included. To cytogenetically compare P. cuvieri with other species of Physalaemus, species belonging to P. cuvieri group (i.e. P. albonotatus, P. centralis, P. cuqui and P. ephippifer), P. albifrons, recently removed from this group, and P. santafecinus, currently alocated in P. albifrons group, were also analyzed. All populations of P. cuvieri studied here showed diploid number of 22 chromosomes and high intraspecific variation was observed related to the NORs. Two populations of P. cuvieri (Urbano Santos, state of Maranhão (MA) and Crateús, state of Ceará (CE)) had pairs 8 and 9 as NOR-bearing chromosomes. In pair 8 the interstitial NOR was adjacent to C-bands whereas the NOR at the nineth pair was coincident with a heterochromatic block. In the population from São Pedro da Água Branca, state of Maranhão (MA), besides pairs 8 and 9, the seventh pair was also a NOR-bearing one. The specimens from Palmeiras, state of Bahia (BA) and Uberlândia, state of Minas Gerais (MG) showed only one NOR, which was located at pair 8. In the population from Uberlândia (MG) intraindividual differences was found related to the NOR size. In the populations from Argentina, the interstitial NOR in chromosome pair 8 was not found. In all the specimens of these Argentinean populations, pair 11 was the NOR-bearing chromosome pair and additional NORs were also found in chromosomes 1, 7 or 8 (in a pericentromeric position) in some of the individuals. The morph 11 of specimens from Argentina was very similar to the NOR-bearing eleventh pair described for specimens from Santa Maria (RS) previously analyzed. In contrast, in the population from Porto Nacional, state of Tocantins (TO), multiple NORs were visualized at least at five chromosomes (belonging to pair 1, 3, 4 and 10), a pattern that greatly differed from those found in the others populations of P. cuvieri. Also concerning the C-band distribution, the karyotype found in the population of Tocantins differed from the others. These findings are very interesting and can be useful for future taxonomic studies of this taxon. Regarding to chromosome morphology, P. albifrons, P. albonotatus, P. centralis, P. cuqui, P. ephippifer and P. santafecinus were very similar, specially for the seven first chromosome pairs, although in P. albonotatus and P. cuqui the position of some chromosome pairs was different. All the species could be differentiated by NOR localization and in P. ephippifer an interesting heteromorphism was detected in NOR bearing pair 8 of all the females. We do not discard the hypothesis that such heteromorphism could be related to sex determination in this species, but future studies are necessary to test it. Except for the karyotype of P. cuvieri from Tocantins, the karyotypes described here the principal (or only) NOR was found among the last chromosome pairs, resulting in different chromosome morphologies, what impaired interespecific inferences of homeologies and the recognition of possible rearrengements involving the NOR during the differentiation of the species analyzed. On the other hand, C-banding tecnique permitted to notice some interspecific homeologies. A band at an interstitial region in the short arm of pair 5, and pericentromeric C-bands in the short arm of pairs 3 and 7 were detected in P. cuvieri, P. centralis and P. ephippifer which seemed to be homeologous to C-bands found in pair 3, 5 and 7 of P. albonotatus.

ASSUNTO(S)

physalaemus citogenetica cromossomos anura physalaemus chromosomes anura nucleolus organizer region região organizadora do nucleolo cytogenetics

ACESSO AO ARTIGO

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