Cytogenetics of two sympatric Corydoras species (pisces, siluriformes, challichtyidae) of Southern Brazil

R F Artoni,L A C Bertollo,M R Vicari,M C A Matiello,M M Cestari,M L Terêncio

doi:10.1590/s1519-69842006000200002

Abstract

Karyotypic data are presented for two sympatric Corydoras species of the Lagoa Dourada, namely, C. ehrhadti and C. paleatus, which are found in the upper Tibagi river basin (Ponta Grossa, State of Paraná, Brazil). The same diploid number and karyotypic formula were observed in both species/populations. A great similarity in the constitutive heterochromatin distribution and in the activity of nucleolar organizer regions was also found. The use of in situ hybridization with a fluorescent 18S rDNA probe allowed for the identification of the species/populations through the location of ribosomal sites.

Highlights

The genus Corydoras (Callichthyidae) is widespread throughout South America, comprising approximately 142 recognized species (Reis, 1998).According to Oliveira et al (1992), this genus encompasses five natural groups of species that present karyotypic and DNA content similarities.Vicariance events such as those that occurred in the costal basin are mechanisms that help explain the high interspecific diversity in this group (Weitzman et al, 1988).Karyotypic data and DNA content suggest an intense polyploidization process in the diversification and evolutionary history of this group (Oliveira et al, 1993a, b)
We investigated the karyotypic structure of C. ehrhardti and C. paleatus in a sympatric zone, especially in relation to the presence and location of the 18 S rDNA
The Corydoras species analyzed here (C. ehrhardti and C. paleatus) presented 2n = 4 chromosomes with a fundamental number (FN) of 88 and a karyotypic formula composed of 9 metacentric chromosome pairs and submetacentric chromosome pairs (Table 1)

Summary

Introduction

The genus Corydoras (Callichthyidae) is widespread throughout South America, comprising approximately 142 recognized species (Reis, 1998).According to Oliveira et al (1992), this genus encompasses five natural groups of species that present karyotypic and DNA content similarities.Vicariance events such as those that occurred in the costal basin are mechanisms that help explain the high interspecific diversity in this group (Weitzman et al, 1988).Karyotypic data and DNA content suggest an intense polyploidization process in the diversification and evolutionary history of this group (Oliveira et al, 1993a, b). According to Oliveira et al (1992), this genus encompasses five natural groups of species that present karyotypic and DNA content similarities. Vicariance events such as those that occurred in the costal basin are mechanisms that help explain the high interspecific diversity in this group (Weitzman et al, 1988). Karyotypic data and DNA content suggest an intense polyploidization process in the diversification and evolutionary history of this group (Oliveira et al, 1993a, b). The diploid chromosome number varies from 2n = 40 in C. natterei (Oliveira et al, 1990) to 2n = 134 in C. aeneus (Turner et al., 1992), while the nuclear DNA content varies from.

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Conclusion