Karyotypic conservatism in samples of Characidium cf. zebra (Teleostei, Characiformes, Crenuchidae): physical mapping of ribosomal genes and natural triploidy

Abstract

Basic and molecular cytogenetic analyses were performed in specimens of Characidium cf. zebra from five collection sites located throughout the Tietê, Paranapanema and Paraguay river basins. The diploid number in specimens from all samples was 2n = 50 with a karyotype composed of 32 metacentric and 18 submetacentric chromosomes in both males and females. Constitutive heterochromatin was present at the centromeric regions of all chromosomes and pair 23, had additional interstitial heterochromatic blocks on its long arms. The nucleolar organizer regions (NORs) were located on the long arms of pair 23, while the 5S rDNA sites were detected in different chromosomes among the studied samples. One specimen from the Alambari river was a natural triploid and had two extra chromosomes, resulting in 2n = 77. The remarkable karyotypic similarity among the specimens of C. cf. zebra suggests a close evolutionary relationship. On the other hand, the distinct patterns of 5S rDNA distribution may be the result of gene flow constraints during their evolutionary history.

Species delimitation in Neotropical fishes of the genus Characidium (Teleostei, Characiformes)

“…Combined evidence including diploid chromosome numbers (2n = 50, 32 m + 18 sm), the presence of heteromorphic ZZ/ZW sex system, occurrence of B chromosomes sharing DNA sequences, location of constitutive heterochromatin, and location of ribosomal genes (Figure ) strongly suggest a conservative chromosome structure in the two mitochondrial lineages of C. alipioi . Indeed, previous cytogenetic studies have demonstrated interspecific conservativeness in the chromosome structure of various species of Characidium (e.g., Pansonato‐Alves, Oliveira, et al, ; Pansonato‐Alves et al, ) and in other characiforms (Feldberg, Porto, Nakayama, & Bertollo, ; Voltolin et al, ). There are no significant chromosomal or phenotypic differences among the sympatric C. alipioi lineages; however, there is evidence for independently evolving lineages based on COI genetic distances, phylogenetic and species delimitation analyses.…”

“…Several species of Characidium have been used as models for cytogenetic studies because they exhibit population variation with differential distribution of repetitive sequences (Machado et al, ; Pansonato‐Alves et al, ; Pansonato‐Alves, Oliveira, & Foresti, ; Scacchetti et al, ; Vicari, Artoni, Moreira‐Filho, & Bertollo, ), the ZZ/ZW sex chromosomes system with dimorphic morphologies and sizes (Centofante et al, ; Maistro, Jesus, Oliveira, Moreira‐Filho, & Foresti, ; Maistro, Mata, Oliveira, & Foresti, ; Noleto, Amorim, Vicari, Artoni, & Cestari, ; Pansonato‐Alves et al, ), and homoplastic occurrence of supernumerary chromosomes (Maistro et al, ; Pansonato‐Alves et al, ; Pansonato‐Alves, Oliveira, et al, ; Pansonato‐Alves, Paiva, Oliveira, & Foresti, ; Pansonato‐Alves, Vicari, Oliveira, & Foresti, ; Serrano, Utsunomia, Scudeller, Oliveira, & Foresti, ). Additionally, a recent biogeographic study suggested that the stem of Characidium was restricted to the Amazon basin during the Paleogene (~50 Myr), with subsequent dispersal throughout southern drainages, such as the São Francisco, Paraná and Atlantic coastal rivers (Poveda‐Martínez, Sosa, Chacón‐Vargas, & García‐Merchán, ).…”

Triploid Induction in the Yellowtail Tetra, Astyanax altiparanae, Using Temperature Shock: Tools for Conservation and Aquaculture

“…In Neotropical species, several natural triploids are found in the literature, including Curimata modesta (Venere and Galetti ); Leporinus elongatus (Molina et al ); Characidium sp. (Pansonato‐Alves et al ); Gymnotus carapo (Fernandes‐Matioli et al ); Eigenmannia sp. (Almeida Toledo et al ); Hoplias malabaricus (Utsunomia et al ); Hoplerythrinus unitaeniatus (Giulino‐Caetano and Bertollo ); Richomycterus davisi (Borin et al ); Rhamdia quelen (Tsuda et al ); Astyanax schubartii (Morelli et al ); Astyanax sp.…”

Single Origin of Sex Chromosomes and Multiple Origins of B Chromosomes in Fish Genus Characidium

“…Despite the conserved diploid number of 50 chromosomes in all species in this group [29], interspecific and interpopulational differences have been reported in relation to either sex chromosomes of the ZZ-ZW type [31], [32], the location and number of rDNA sites [27], the occurrence of natural triploidy [33], [34] and the presence of B chromosomes [28], [29], [30].…”