Karyotypic diversity among three species of the genus Astyanax (Characiformes: Characidae)

Abstract

The group Incertae sedis within the Characidae family currently includes 88 genera, previously included in the subfamily Tetragonopterinae. Among them is the genus Astyanax comprising a group of species with similar morphology and widely distributed in the Neotropics. Thus, the present study aimed to analyze the karyotype diversity in Astyanax species from different watersheds by conventional Giemsa staining, C-banding and fluorescence in situ hybridization (FISH rDNA 18S) probe.specimens of Astyanax aff. paranae belonging to the "scabripinnis complex", Astyanax asunsionensis and Astyanax aff. bimaculatus were analyzed". Two sympatric karyomorphs were observed in Astyanax. aff paranae, one of them having2n=48andthe other one with 2n=50 chromosomes. Other population of this same species also presented 2n=50 chromosomes, but differing in the karyotype formula and with macro supernumerary chromosome found in 100% of the cells in about 80%of females analyzed. Two population of A. asuncionensis and one population of Astyanax. aff. bimaculatus, also showed a diploid number of 50 chromosomes, but also differing in their karyotype formulas. Therefore, A. asuncionensis was also characterized by intraspecific chromosome diversity. The C-banding analysis was able to demonstrate a distinctable to demonstrate a distinct pattern of heterochromatin differing A. asuncionensis from Astyanax aff. paranae and Astyanax aff. bimaculatus. The supernumerary chromosome of Astyanax aff. paranae proved completely heterochromatic. Only Astyanax.aff. bimaculatus multiple showed multiple sites of nucleolar organizing regions. The other species were characterized by having a simple system of NOR. These data contributes to the know ledge of the existing biodiversity in our fish fauna, here highlighted by the inter-and intraspecific chromosomal diversity in the genus Astyanax.Keywords: cytogenetics, biodiversity, B chromosomes, C-bands, NORs. Diversidade Cariotípica entre três espécies do gênero

Integrative approach detects natural hybridization of sympatric lambaris species and emergence of infertile hybrids

“…paranae 2n = 50 and A . fasciatus 2n = 46–48) 62 – 64 . Therefore, the interrupted meiosis and sterility of the hybrids found in the present study are probably related to the presence of extra chromosomes, which possibly do not have homologous pairs, preventing the progression of meiosis and, consequently, formation of gametes in these specimens 1 .…”

New parameters for the in vitro development of cell lines from fish species

“…The G. proximus and A. bimaculatus cells at the 6 and 4 th subculture, presented 2n=48 and 50, respectively, conserving the original karyotype of the species, both in diploid number and chromosomal morphology (Fig. 6) (Feldberg et al, 2003;Nishiyama et al, 2016). This confirms that these fish cell lines are reliable models for toxicology essays and studies of environmental biology (Sousa et al, 2022;Morcillo et al, 2016), important aspects for the reduction in the use of live animals in scientific investigations.…”

Characterization of a new cytotype and ocurrence of a B microchromosome in two spot astyanax, Astyanax bimaculatus Linnaeus, 1758 (Characiformes: Characidae)

“…aff. bimaculatus in the literature, none of the specimens analysed in these studies could in fact belong to the species A. bimaculatus because the collection sites are not compatible with the distribution of this species in Brazil, that is, in the Amazon region (Cunha et al ., 2019; Jorge & Moreira‐Filho, 2001; Kavalco et al ., 2011; Morelli et al ., 1983; Nishiyama et al ., 2016; Pamponet et al ., 2008; Peres et al ., 2012).…”