Ploidy of Backcross Hybrids of Largemouth Bass and Smallmouth Bass

Abstract

AbstractInterspecies hybridization in fish may trigger the transformation of oogenesis in hybrid females, resulting in formation of eggs with unreduced diploid chromosome number. This phenomenon is revealed by the triploidy of backcross offspring obtained from crossing F1 hybrid females with males of either parental species. To determine whether the F1 hybrids of largemouth bass Micropterus salmoides and smallmouth bass M. dolomieu produce diploid eggs, we designed a study for evaluating the ploidy of backcross offspring (F1 hybrid females × largemouth bass males). Fish ploidy was determined by flow cytometry measurement of DNA content. The results of flow cytometry analysis showed that backcross hybrids had the same amount of DNA as largemouth bass and F1 hybrids, which suggests diploidy (2n) of backcross hybrids. This indicates that the F1 hybrid females between largemouth bass and smallmouth bass generate haploid eggs and do not experience the transformation of oogenesis that has been described in several other distant fish hybrids. Results of this study will be used to evaluate hybrids of largemouth bass and smallmouth bass as potential candidates for aquaculture.