Abstract
An alternative chromatic variation to the wild-type phenotype of the livebearing fish Phalloceros caudimaculatus (Phalloceros caudimaculatus var. reticulata) was detected in a single female from “Bañados del Este” Reserve of Biosphere Site, in Uruguay. The founder mutant female, which presented a melanic spotted pattern overlapping the wild-type pigmentation, produced laboratory breed strains. Four phenotypes showing different degrees of spotted patterns were obtained. In order to determine the inheritance of this chromatic mutation, experimental crosses and cytogenetic analyses of these laboratory strains were carried out. The breeding experiments among the spotted phenotypic classes and backcrosses suggest the dominant and non-sex linked inheritance of this mutation. Statistical tests demonstrated that the inheritance mechanism of this mutation does not correspond to a 2-gene independent segregation hypothesis as it was proposed in Poecilia sphenops, or to a single dominant gene hypothesis. Additionally, cytogenetic analyses detected a partially heterochromatic biarmed chromosome associated to the inheritance of the pigmentation pattern in laboratory breed strains.
