title: An uncommon condition for a sex chromosome system in Characidae fish. Distribution and differentiation of the ZZ/ZW system in Triportheus.
abstract: Triportheus is a neotropical freshwater Characidae fish that has a well-differentiated ZZ/ZW sex chromosome system. The W chromosome of this genus contains a large amount of heterochromatin and is smaller than the Z chromosome. This contrasts with other ZW fish systems where the W chromosome is larger in size due to increased heterochromatin. All species of Triportheus that have been studied cytologically (about 50% of the known species for this genus, from some of the major South American hydrographic basins) share this sex chromosome system, indicating a probable synapomorphic condition not present in other genera of the large Characidae family. However, while the Z chromosome appears to be largely conserved, the W chromosome shows a differential evolution with morphological differentiations not only among species, but also among populations from the same hydrographic basin, and with some species presenting a greater homology between the W and the Z chromosomes than others.
authors.affiliation: Universidade Estadual de Ponta Grossa, Departamento de Biologia Geral, PR, Brazil. rfartoni@convoy.com.br
authors.forename: R F
authors.initials: RF
authors.lastname: Artoni
authors.forename: J N
authors.initials: JN
authors.lastname: Falcão
authors.forename: O
authors.initials: O
authors.lastname: Moreira-Filho
authors.forename: L A
authors.initials: LA
authors.lastname: Bertollo
mesh_terms: D000818:Animals; D001938:Brazil; D005260:Female; D005399:Fishes / Q000235:genetics*; D006570:Heterochromatin / Q000235:genetics; D007621:Karyotyping; D008297:Male; D009697:Nucleolus Organizer Region; D012730:Sex Chromosomes / Q000235:genetics*; D012733:Sex Differentiation / Q000235:genetics*
chemical_list: D006570:Heterochromatin