Cytogenetic characterization of three allopatric species of Hypostomus Lacépède (1803) (Teleostei, Loricariidae)

Abstract

The genus Hypostomus is distributed throughout South America and is one of the most widely studied genera among Loricariidae, with approximately 130 species described. However, correct taxonomic identification is difficult due to subtle morphological differences between species. Thus, cytogenetic data on this genus are fundamental to clarifying the evolutional history of the group. Cytogenetic analyses were carried out on three species of Hypostomus in the state of Paraná, Brazil: one from the Tibagi river basin (Hypostomus aff. ancistroides) and two from the Iguaçu river basin (Hypostomus commersonii and Hypostomus derbyi). Hypostomus aff. ancistroides had 2n = 66 chromosomes (12m; 16sm; 10st; 28a) and number of arms (fundamental number, FN) = 104, with large heterochromatic blocks identified in two chromosome pairs and nucleolar organizing regions (NORs) detected in seven chromosomes of the complement. The H. commersonii population had 2n = 68 chromosomes (12m; 12sm; 8st; 36a) and FN = 100, with low heterochromatin located pericentromerically and NORs detected in only one chromosome pair. The H. derbyi population had 2n = 66 chromosomes (6m; 10sm; 20 st; 30a), with large heterochromatic blocks dispersed throughout the karyotype and multiple sites with NORs. The karyotype markers proved efficient in separating the species studied herein and corroborate the divergent karyotype evolution in the genus Hypostomus.

Comparative Cytogenetics Among Three Sympatric Hypostomus Species (Siluriformes: Loricariidae): An Evolutionary Analysis in a High Endemic Region

“…The chromosomal data in this study showed that 2n = 68 and different karyotype formulae between H. commersoni and H. derbyi could be explained by pericentric inversions. Cytogenetic analysis in H. derbyi from the Iguaçu river in Curitiba, Paraná state, showed a different karyotype formula 51 and can suggest chromosomal diversification and cryptic species for H. derbyi. In Hypostomus, the number of st/a chromosomes was postulated to be directly proportional to an increase in 2n 13 .…”

EVOLUTIONARY TRENDS IN SPECIES COMPLEX DIAGNOSED BY CYTOGENETIC POLYMORPHISM: THE CASE OFHypostomus ancistroides(SILURIFORMES, LORICARIIDAE)

“…The maintenance of the diploid number in the plecos in this study, for example, seems to be a group tendency, since the great majority of the studied populations present 2n = 68 chromosomes (Artoni and Bertollo 1996;Alves et al 2006;Bueno et al 2012;Rubert et al 2011;Endo et al 2012;Alves et al 2012;Fernandes et al 2012;Pansonato-Alves et al 2013;Traldi et al 2013;Lara-Kamei et al 2017) and this could represent an adaptive and ancestral state. The exception for this character is an isolated population in the Tibagi River (Maurutto et al 2012) and a case of a new species of the H. ancistroides complex carrying a differentiated sexual chromosomal system, which is very divergent from the others (Rocha-Reis et al 2018).…”

“…Although variable when observing the totality of the karyotype macrostructure, the presence of C-banding in some chromosomes of all karyomorphs may indicate the existence of some homology (Rubert et al 2011;Fernandes et al 2012;Maurutto et al 2012;Pansonato-Alves et al 2013;Traldi et al 2013;Lara-Kamei et al 2017;Rocha-Reis et al 2018), and may even be considered a phylogenetic sign. In this study, we observed the presence of conserved C+ blocks in pairs of chromosomes 4 (m), 7 (sm) and 26 (a), in a pericentromeric or subterminal region (Figures 2 and 4).…”

“…In the 15 natural populations of H. ancistroides already studied, there are 15 different karyomorphs, usually with 2n = 68 chromosomes (Artoni and Bertollo 1996;Alves et al 2006;Rubert et al 2011;Alves et al 2012;Bueno et al 2012;Endo et al 2012;Fernandes et al 2012;Pansonato-Alves et al 2013;Traldi et al 2013). However, different diploid numbers (Maurutto et al 2012) and even the presence of differentiated systems of sex chromosomes of the type XX/XY (Rocha-Reis et al 2018), and ZZ/ZW (Lara- Kamei et al 2017) have been observed. Markers, such as C-banding and the location of ribosomal cistrons, present significant variations, although for fish, especially Siluriformes, the available cytogenetic data is quite limited.…”

The Persevering Cytotaxonomy: Discovery of a Unique XX/XY Sex Chromosome System in Catfishes Suggests the Existence of a New, Endemic and Rare Species

“…All previously de- [Maurutto et al, 2012] and the one investigated here ( Fig. 1 A, B), which have 2n = 66.…”