Abstract
Karyotypic data on Iheringichthys labrosus from several populations of Paraná River/Argentina are presented. The diploid number was 2n=56 and the karyotype consisted of 42m/sm + 14st/a (NF= 98). The AgNORs were observed in telomeres of the long arm of a st/a chromosome pair. These sites were also positive after C-banding. Heterochromatin was observed in the telomeric position in some chromosomal pairs and can be found in one or both metacentric chromosome arms. The obtained results were compared with those reported for different populations from Brazilian rivers and the similarity among them was evident. However, discordant chromosome formulae and karyotype features between samples should be carefully taken because, in some cases, they seem to be more technical artifacts than real differences.
Highlights
The order Siluriformes (Fowler, 1951) comprises a large group of fish without scales, whose body is completely uncovered or covered totally or partially with lines of bony plates
Twenty five specimens of Iheringichthys labrosus, 19 females (f) and 6 males (m), caught in the Parana River (NE Argentina), lagoons alongside river, and small tributaries were cytogenetically analysed: the sample localities are shown in Figure 1: Posadas (Misiones Province: S 27° 21’ 06”; W 55° 53’ 54” -2f / 1m-), Reconquista (Santa Fé Province: S 29° 14’ 11”; W 59° 34’ 46” -2f / 1m), Ituzaingó (S 27° 29’ 57”; W 56° 42’ 42” -6 f-), Itá Ibaté (S 27° 25’ 46”; W 57° 21’ 40” -2f / 1m), Yahapé (S 27° 22’ 15”; W 57° 39’ 11” -1 m), Puerto Abra (S 27° 18’ 48”; W 57° 53’ 33” -3 f), and Corrientes (S 27° 27’ 23”; W 58° 49’ 06” -4f / 2m) (Corrientes Province)
The AgNORs were observed in a st/a pair staining telomeric regions on the long arms (Figure 3a), only cells with one or two active nucleoli were identified
Summary
The order Siluriformes (Fowler, 1951) comprises a large group of fish without scales, whose body is completely uncovered or covered totally or partially with lines of bony plates. This group comprises 30 families with a wide distribution around the world, predominates in freshwaters, and is very well represented in the Neotropical region (Reis et al, 2003). LeGrande (1981) proposed a hypothetical ancestral karyotype for Siluriformes with 2n= 56±2 and high Fundamental Number (NF), which was supported by other studies in different species of the order (Oliveira and Gosztonyi, 2000).
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