Muscle Protein Phenotypes and the Probable Evolutionary Origin of a Unisexual Fish, Poecilia Formosa, and Its Triploid Derivatives

Document Type

Article

Publication Date

1-1-1982

Description

Several species‐specific proteins have been identified by polyacrylamide gel electrophoresis (PAGE) of skeletal muscle extracts from the diploid gynogen, Poecilia formosa, its related triploid unisexuals, and their sympatric, bisexual species, P. mexicana and P. latipinna. These water‐soluble, low molecular weight proteins (7,000‐13,000) comigrate with a fraction of purified rabbit parvalbumin on nondenaturing gels and show staining properties similar to rabbit parvalbumins. The electrophoretic patterns of these muscle proteins provide a set of distinctive phenotypic markers for each of the host species involved in naturally occurring breeding complexes with P. mexicana × P. latipinna show no evidence of sexual dimorphisms. Furthermore, the hybrid phenotypes are those that would be predicted from appropriate combinations of parental alleles at three gene loci. The patterns found by PAGE for several generations of pedigreed stocks of P. formosa show strictly matroclinous inheritance of a characteristic muscle protein phenotype and coupled with the electrophoretic patterns of several enzymic proteins reflect the probable hybrid origin of this diploid unisexual. Finally, paternal contributions by P. mexicana to the hybrid genome of triploid unisexuals are clearly demonstrated by comparative analyses of muscle protein phenotypes for P. formosa and its contemporary host species. Our identification of distinctive phenotypic markers in the muscle proteins of several poeciliid species involved in unisexual‐bisexual breeding complexes provides an important new tool for further studies on the adaptive significance of unisexuality, hybridization, and fixed heterozygosity in the evolutionary biology of these fishes.

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