Multiple Sex Chromosomes in a Mexican Cyprinodontid Fish

Evidence of an XX/XY sex chromosome system in the fish Dormitator maculatus (Teleostei, Eleotrididae)

“…The ZZ/ZW system is the most common sex chromosome system and the XX/X0 (ten species) and ZZ/Z0 (three species) systems, are the most rare (Devlin and Nagahama, 2002). Cytogenetic differences detected between sex chromosomes include: additions or deletions of C-band positive segments (Phillips and Ihssen, 1985;Andreata et al, 1992Andreata et al, , 1993Cano et al, 1996;Stein et al, 2001), reductions in chromosome size (Park and Kang, 1979), increases in chromosome size (Galetti et al, 1981) and chromosome rearrangements (Uyeno and Miller, 1971;Thorgaard, 1978;Bertollo et al, 1983;Almeida Toledo et al, 1984;Pezold, 1984;Vitturi et al, 1991).…”

Cytogenetical studies on fishes. III. Multiple sex chromosome mechanism in the filefish, Stephanolepis cirrhifer.

“…The first observation was described by Chen and Ebeling (1968) for one mosquitofish species. Later on, twenty-three species were reported by Chen (1969), Chen and Reisman (1970), Ebeling and Chen (1970), Yosida and Hayashi (1971), Uyeno andMiller (1971), Thorgaard (1977) and Park (1978). The sex chromosome mechanism in these cases was mainly XX-XY, but XX-X0, X1X1X2X2-X1X2Y as the male heterozygote and also ZW-ZZ as the female heterozygote were rarely reported.…”

Bulked segregant analysis of the pirarucu (Arapaima gigas) genome for identification of sex-specific molecular markers

“…Even though genetic factors probably regulate sex determination in most fish species, only a small proportion of teleosts studied actually show distinct sex chromosomes that can be morphologically identified by standard cytogenetic analysis (Arkhipchuk, 1995). Nevertheless, heteromorphic sex chromosomes have been observed in more than 176 species of fish from different groups (Devlin and Nagahama, 2002); this includes species belonging to the family comprising A. gigas, such as Osteoglossum bicirrhosum (Uyeno and Miller, 1971). However, A. gigas has been shown to lack differentiated sex chromosomes (Marques et al, 2006) indicating that, if the species presents a chromosomal sex determination system, the differentiated genomic region associated with the sex determining locus (SDL) is not large enough to be morphologically identified through standard karyotype analysis.…”