Differentiation and Evolution of the W Chromosome in the Fish Species of <b><i>Megaleporinus </i></b>(Characiformes, Anostomidae)

Abstract

The W chromosome of Megaleporinus trifasciatus was isolated in order to analyze its behavior in the karyotype of this and other species of the family, including forms with differentiated and undifferentiated sex chromosomes. The chromosome was microdissected, and the WMt probe was prepared for the chromosome painting procedure. M. trifasciatus was also cross-hybridized (cross-FISH) using existing probes available for M. macrocephalus (WMm) and M. elongatus (WMe). Two Leporinus species and Semaprochilodus taeniurus, representing a clade close to the Anostomidae, were also cross-hybridized with the objective to better understand the evolution of the sex chromosomes. In the metaphase of female M. trifasciatus, the WMt probe highlighted the whole long arm of the W chromosome and a small, distal portion of the long arm of the Z chromosome. In males, the probe highlighted the distal portion of the long arm of the Z chromosomes. The hybridization of female M. trifasciatus with the WMe and WMm probes revealed a pattern similar to that encountered using the WMt probe. The WMt, WMm, and WMe probes revealed broad similarities among the species of the genus Megaleporinus, which has a ZZ/ZW system of sex chromosomes, with only minor alterations becoming apparent when analyzed separately.

Cytogenetic analysis of Hypomasticus copelandii and H. steindachneri: relevance of cytotaxonomic markers in the Anostomidae family (Characiformes)

“…Ramirez et al (2017) proposed the creation of Megaleporinus based on morphological, molecular and cytogenetic data, synonymizing some Leporinus and Hypomasticus species, and considering the ZZ/ZW sex system as a synapomorphic trait of this new genus. This hypothesis has been corroborated by other studies, which also included Megaleporinus elongatus (Valenciennes, 1850) with a Z 1 Z 2 /W 1 W 2 multiple sex chromosome system (Parise-Maltempi et al 2007Marreta et al 2012;Barros et al 2018;Crepaldi and Parise-Maltempi 2020). However, not all current Megaleporinus species have been karyotyped (Fig.…”

“…However, not all current Megaleporinus species have been karyotyped (Fig. 3), and a ZZ/ZW system has also been observed in Leporinus multimaculatus Birindelli, Teixeira et Britski, 2016, which may have arisen independently (Venere et al 2004;Barros et al 2018). The inclusion of this species in the phylogenetic analyzes will help to elucidate this question, as well as the cytogenetic characterization of the remaining Megaleporinus spp.…”

Comparative Cytogenetics and Neo-Y Formation in Small-Sized Fish Species of the Genus Pyrrhulina (Characiformes, Lebiasinidae)

“…Lastly, we employed WCP with the PSEMI-Y probe in order to evaluate our hypotheses about the origin of the sex chromosome system present in P. semifasciata and to map the orthologous regions in other Pyrrhulina species in an attempt to predict potential homomorphic sex chromosomes in these species. Indeed, this approach facilitated many times a finer-scale survey of fish sex chromosomes with a common (Machado et al, 2011; Parise-Maltempi et al, 2013; Pansonato-Alves et al, 2014; Scacchetti et al, 2015; Yano et al, 2017b; Barros et al, 2018) or independent (Reed et al, 1995; Phillips et al, 2001; Henning et al, 2008; Henning et al, 2011; Cioffi et al, 2011b; Cioffi et al, 2013; Oliveira et al, 2018) origin within the frame of certain family, genus, or species/species complex. Here, WCP with the PSEMI-Y probe applied back against its own chromosome complement painted not only the entire metacentric Y chromosome in males but also the entire acrocentric X 1 and X 2 chromosomes in both male and female karyotypes.…”

Genomic Differences Between the Sexes in a Fish Species Seen Through Satellite DNAs

“…Our second approach regarded a more evolutionary focus in the sex chromosome system and its satDNA content in Megaleporinus elongatus, as sex chromosome dynamics analysed through sex-linked repetitive DNA profiles has been shown to be effective ( Traut and Winking, 2001 ; Schemberger et al, 2011 ; Cioffi et al, 2012 ; Terencio et al, 2012 ; Yano et al, 2016 ; Yano et al, 2017 ; Sember et al, 2018 ; Deakin et al, 2019 ; Schemberger et al, 2019 ). The heteromorphic sex chromosomes (W and W 1 ) in Megaleporinus have already been deemed derived from a common ancestral chromosomic pair and differentiated from the Z chromosomes via massive heterochromatinization ( Galetti and Foresti, 1986 ; Marreta et al, 2012 ; Parise-Maltempi et al, 2013 ; de Barros et al, 2018 ). However, variation in repetitive content within the genus could be caused by the expansion and contraction of these sequences ( Utsunomia et al, 2019 ; Crepaldi and Parise-Maltempi, 2020 ).…”