Chromosomal analysis of Astyanax fasciatus (PISCES, CHARACIDAE) from the Araguari river, Uberlândia, MG, Brazil

Abstract

ABSTRACTthe genus Astyanax is one of the most numerous of the family Characidae, comprising a large number of similar-shaped species, but displaying innumerable karyotypic variations in its chromosome number and/or structure. the literature describes A. fasciatus populations with diploid chromosome numbers varying from 2n = 45 to 2n = 48. in this study, A. fasciatus specimens captured in the Araguari river (Alto Paraná basin) were cytogenetically characterized, revealing a diploid chromosome number of 2n = 46. the nucleolar organizing regions (nors), detected with silver nitrate staining, showed a multiple system with two pairs of marked chromosomes. these findings are congruent with those of other studies involving populations of the same species.Keywords: cytogenetics, Astyanax, Astyanax fasciatus. ReSumoAnálise cromossômica em Astyanax fasciatus (Pisces, Characidae) da população do Rio Araguari, uberlândia, mG, Brasil o gênero Astyanax é um dos mais numerosos da família Characidae, englobando um grande número de espécies muito semelhantes na forma, mas que apresentam inúmeras variações cariotípicas no número e/ou estrutura cromossômica. Encontram-se descritas na literatura populações de A. fasciatus com o número diplóide variando de 2n = 45 a 2n = 48 cromossomos. no presente trabalho, espécimes de Astyanax fasciatus da população da calha do rio Araguari (bacia do Alto Paraná), foram caracterizados citogeneticamente. o número diplóide observado foi 2n = 46 cromossomos. As regiões organizadoras de nucléolo (nors), detectadas com nitrato de prata, apresentaram um sistema múltiplo, com dois pares de cromossomos marcados. Esses dados estão de acordo com os descritos para outras populações da mesma espécie.Palavras-chave: citogenética, Astyanax, Astyanax fasciatus.

Cytogenetic analysis in three species from genusAstyanax(Pisces; Characiformes) with a new occurrence of B chromosome inAstyanax paranae

“…Among the populations with the same diploid number, similar markings were observed in the population from Rosas Stream (Fernandes et al 2009) and a multiple-NOR system with up to four chromosomes marked were observed in the Araguari River population (Torres-Mariano and Morelli 2004). Although featuring only one silver-marked pair, the Rosas Stream population evidenced four pairs of markings with 18S probe through FISH analysis, indicating that only one submetacentric pair was expressed in that population, similar to the same active pair in the population of the present study.…”

Highly Similar Morphologies Between Chromosomes Bearing U2 snRNA Gene Clusters in the Group Astyanax Baird and Girard, 1854 (Characiformes, Characidae): An Evolutionary Approach in Species with 2n = 36, 46, 48, and 50

“…Diploid number ranges from 2n = 36 chromosomes (e.g., A. schubarti) 2 to 2n = 50 chromosomes (most species) as in A. altiparanae 3 and A. bockmanni. 4 Intermediate diploid numbers are also observed in species such as A. fasciatus (2n = 46) 5 and Astyanax scabripinnis Jenyns, 1842 (2n = 48). 6 However, the latter two species are considered to be species complexes that present variable diploid numbers (karyomorphs).…”

B chromosomes in a population of Astyanax eigenmanniorum (Characiformes, Characidae) from the Araguari River Basin (Uberlândia, MG, Brazil)

“…Further studies confirmed that the chromosomal number in this fish group ranges from 2n = 36 in A. schubarti (Morelli et al, 1983) to 2n = 50 in A. altiparanae (Pacheco et al, 2001;Fernandes and Martins-Santos, 2004) and A. eigenmanniorum (Stripecke et al, 1985;Fauaz et al, 1994;Pfister and Moreira-Filho, 1997). A. scabripinnis (Morelli et al, 1983;Araujo and Morelli, 2006), A. fasciatus (Morelli et al, 1983;Torres-Mariano and Morelli, 2006), and A. altiparanae correspond to the species with the highest number of cytogenetic studies.…”