Spontaneous hybridization in the laboratory and genetic markers for the identification of hybrids between two atherinid species, Odontesthes bonariensis (Valenciennes, 1835) and Patagonina hatcheri (Eigenmann, 1909)

This study reports the occurrence of spontaneous hybridization between Odontesthes bonariensis (Valenciennes, 1835) and Patagonina hatcheri (Eigenmann, 1909), two South American freshwater atherinids, while adults of both species were being held in a communal laboratory tank, and describes suitable genetic markers for distinction of both species and their hybrids. Combined allozyme and mitochondrial DNA restriction length polymorphism analyses of offspring from three spawnings in the communal tanks confirmed the presence of hybrids along with purebreds in each spawning. Hybrids of an O. bonariensis mother X a P. hatcheri father were produced along purebred O. bonariensis in one occasion, whereas hybrids of P. hatcheri mothers X O. bonariensis fathers were produced along purebred P. hatcheri in two occasions. Three enzyme systems (coded by loci LDH-B*, PGM*, and CK*) out of 15 (20 loci) screened allowed distinction of species and their hybrids, but the usefulness of LDH-B* for field work may be limited by intraspecific polymorphism. Eight restriction enzymes (Apa I, Bgl II, Eco RI, Eco RV, Eco T22I, Hinc II, Hind III, and Pvu II) among 11 produced diagnostic restriction fragments applicable for species (motherhood) distinction. The relevance of these findings for the management of natural genetic resources and the aquaculture of these two species is discussed.