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

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.Keywords: karyotype, sympatry, heterochromatin, NORs, rDNA. RESUMO Citogenética de espécies simpátricas de Corydoras (pisces, siluriformes, challichtyidae) do Sul do BrasilDados cariotípicos são apresentados para duas espécies simpátricas de Corydoras da Lagoa Dourada, C. ehrhadti e C. paleatus, pertencentes à bacia do alto Rio Tibagi (Ponta Grossa, Paraná, Brasil). O mesmo número diplóide e fórmula cariotípica foram observados em ambas espécies/populações. Grande similaridade foi verificada também para a distribuição da heterocromatina constitutiva e atividade das regiões organizadoras de nucléolos. O emprego da hibridação in situ com sonda fluorescente de DNAr 18S possibilitou identificar as espécies/populações por meio da localização dos sítios ribossomais. simpatria, heterocromatina, RONs, DNAr. 192 ARTONI, R. F. et al. Palavras

Karyotype analysis of three species of Corydoras (Siluriformes: Callichthyidae) from southern Brazil: rearranged karyotypes and cytotaxonomy

“…4). In the Tibagi population of C. ehrhardti, the constitutive heterochromatin blocks show a similar distribution to that found in a previous study of the Upper Tibagi (Artoni et al, 2006). Likewise, a similar pattern of heterochromatin has also been reported from an allopatric Atlantic drainage population from the coastal region of the Santa Catarina State, Brazil (Oliveira et al, 1993).…”

“…Corydoras aff. paleatus populations of the Ribeira and Iguaçu river basins (this study) and populations from the Atlantic drainage of southern Brazil (Oliveira et al, 1993) and the Tibagi River basin (Artoni et al, 2006) present consistent differences in the number and localization of the heterochromatin blocks in their karyotypes.…”

“…To date, only six species of Corydoras, from disparate river basins of southern Brazil, have been investigated cytogenetically. Like the genus as a whole, these species show considerable variation in diploid number (2n = 44, 2n = 46, 2n = 58, and 2n = 66), chromosome structure, and karyotype formula (Oliveira et al, 1993;Artoni et al, 2006;Rocha et al, 2016). Although these chromosome variations make Corydoras a promising model for the study of karyotype evolution, molecular analyses of the genus are relatively lacking.…”

“…Although these chromosome variations make Corydoras a promising model for the study of karyotype evolution, molecular analyses of the genus are relatively lacking. Nucleolar organizer regions (NORs) sites have been mapped in all six southern Brazilian species for which karyotypes are available (Oliveira et al, 1993;Artoni et al, 2006). In situ localization of both 5S and 18S rDNA sequences has been performed in a single species, Corydoras carlae Nijssen & Isbrücker, 1983(Rocha et al, 2016.…”

“…Corydoras aff. paleatus is also found in the Tibagi River, presumably as a result of former headwater river capture events (Artoni et al, 2006(Artoni et al, , 2009. Comparison of karyotypes associated with chromosomal markers has become the method of choice for the analysis of structural chromosome reorganization (Oliveira et al, 2016).…”