Abstract
Comparative cytogenetic analyses of hatchetfishes Carnegiella marthae and Carnegiella strigata (Gasteropelecidae) from the Rio Negro basin were performed using conventional Giemsa staining, silver (Ag) -staining and C-banding. The diploid chromosome numbers of both species equaled 2n = 50 but their karyotypes were distinct. We found evidence for sex chromosomes in C. marthae since karyotype of males presented 20 M + 12 SM + 4 ST + 14 A and ZZ ST chromosomes while the females presented 20 M + 12 SM + 4 ST + 14 A and ZW ST chromosomes of distinct size. Conversely, C. strigata presented 4 M + 4 SM + 2 ST + 40 A chromosomes without sex chromosome heteromorphism. Karyotypes of both species had two NOR-bearing SM chromosomes of distinct size indicating the presence of multiple NOR phenotypes. The sex chromosome pair had specific C-banding pattern allowing identification of both Z and W. This heteromorphic system has previously been described for the gasteropelecids.
Highlights
The family Gasteropelecidae (Characiformes) is a group of Neotropical fishes that includes three genera: Thoracocharax, Gasteropelecus, and Carnegiella
Taking into account that understanding the genetic features of gasteropelecids might be of fundamental importance either for future plans related to conservation genetics or even to reveal aspects related to their evolution, this paper describes and compares the karyotypes of two Carnegiella species with other gasteropelecids and reports the occurrence of a ZZ/ZW sex chromosome system
Cytogenetic analyses were performed on 22 specimens of blackwinged hatchetfish C. marthae (10 males and 12 females) and on 25 specimens of marbled hatchetfish C. strigata (10 males and 15 females) sampled in the middle Rio Negro basin, Amazonas, Brazil
Summary
The family Gasteropelecidae (Characiformes) is a group of Neotropical fishes that includes three genera: Thoracocharax (two species), Gasteropelecus (three species), and Carnegiella (four species). Taking into account that understanding the genetic features of gasteropelecids might be of fundamental importance either for future plans related to conservation genetics or even to reveal aspects related to their evolution, this paper describes and compares the karyotypes of two Carnegiella species with other gasteropelecids and reports the occurrence of a ZZ/ZW sex chromosome system.
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