SPONTANEOUS HYBRIDIZATION IN THE LABORATORY AND GENETIC-MARKERS FOR THE IDENTIFICATION OF HYBRIDS BETWEEN 2 ATHERINID SPECIES, ODONTESTHES-BONARIENSIS (VALENCIENNES, 1835) AND PATAGONINA-HATCHERI (EIGENMANN, 1909)

This study reports the occurrence of spontaneous between Odontesthes b onariensis 1835) and Patagonina hatcheri (Eigenmann, 1909), two South American freshwater atherinidsl while adults of both species were bein g held in a communal laboratory tank, and describes suitable genetic m arkers for distinction of both species and their hybrids, Combined all ozyme and mitochondrial DNA restriction length polymorphism analyses o f offspring from three spawnings in the communal tanks confirmed the p resence of hybrids along with purebreds in each spawning, Hybrids of a n O. bonariensis mother x a P, hatcheri father were produced along pur ebred O, bonariensis in one occasion, whereas hybrids of P, hatcheri m others x O. bonariensis fathers were produced along purebred P. hatche ri 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 Pvn II) amo ng 11 produced diagnostic restriction fragments applicable for species (motherhood) distinction, The relevance of these findings for the man agement of natural genetic resources and the aquaculture of these two species is discussed.