An unusual ZZ/ZW sex chromosome system in<i>Characidium</i>fishes (Crenuchidae, Characiformes) with the presence of rDNA sites

Abstract

Characidium fishes with a sex chromosome system form a monophyletic group. This work presents data of Characidium lanei from the South Atlantic basin (Brazil), including an unknown type of ZW sex chromosome system for the groups including the presence of rDNA sites on sex chromosomes.