Abstract
In the present study, five callichthyid species belonging to the subfamily Corydoradinae were karyotyped: three species of Aspidoras and two of Corydoras. The three species of Aspidoras had the same diploid number, 2n = 46 chromosomes, similar karyotypic formulae, with most chromosomes metacentric or submetacentric, single interstitial Ag-NORs and C-band positive segments mainly found in the centromeric position. The comparative analysis of cytogenetic data available for the genus Aspidoras and other species of Corydoradinae suggest that several events of centric fusion occurred in the origin of the species of Aspidoras. The two analyzed species of Corydoras showed high diploid numbers, 2n = 74 in C. sodalis and 2n = 90 in C. britskii. While C. sodalis exhibited single Ag-NORs and terminal, interstitial and centromeric C-band positive segments in almost all chromosomes, C. britskii showed multiple Ag-NORs and a small number of C-band positive segments found in the terminal position in one acrocentric (A) pair and in the interstitial position in one subtelocentric (ST) pair. The occurrence of high diploid numbers and many ST and A chromosomes are uncommon among the Corydoradinae, suggesting the occurrence of a high number of chromosome rearrangements, mainly centric fissions, in the origin of the Corydoras species studied.
Highlights
The family Callichthyidae consists of two subfamilies: Corydoradinae and Callichthyinae (Reis, 2003)
Cytogenetic studies were conducted with the following species: Aspidoras taurus, three males and one female from the Itiquira River, 17°02’36.3” S 53°28’43.3” W, Alto Garça, Mato Grosso, Brazil; Aspidoras cf. fuscoguttatus, two males and two females from aquarium; Aspidoras poecilus, four females from the Araguaia River, 17°33’42.4” S 53°18’29.7” W, Alto Araguaia, Mato Grosso, Brazil; Corydoras sodalis, two males and one female from aquarium; and Corydoras britskii, one male and one female from a tributary of the Piraí River, 16°25.280’ S 56°25.143’ W, Poconé, Mato Grosso, Brazil
The species A. taurus (Figure 1a) and A. poecilus (Figure 1c) exhibited karyotypic formulae composed of 15 pairs of M chromosomes, 5 pairs of SM and 3 pairs of ST
Summary
The family Callichthyidae consists of two subfamilies: Corydoradinae and Callichthyinae (Reis, 2003). The subfamily Corydoradinae, with more than 90% of the species of the family Callichthyidae, presents 164 valid species divided in three genera: Aspidoras, Brochis and Corydoras (Reis, 1998; Reis, 2003). Phylogenetic studies, based on morphological data, showed that the subfamily Corydoradinae and the genera Aspidoras and Brochis were monophyletic groups while the genus Corydoras was paraphyletic or polyphyletic (Reis, 1998; Britto, 2003, respectively). With the main objective of identifying the monophyletic groups that compose the subfamily Corydoradinae, Britto (2003) proposed a new classification for the group, according to the tribe Aspidoradini, previously constituted only by the genus Aspidoras, is composed of Aspidoras and Scleromystax. The tribe Corydoradini, which included the genera Brochis and Corydoras, is composed only of the genus Corydoras, and the genus Brochis was considered a junior synonymous with Corydoras (Britto, 2003)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
