Aneuploid progenies of triploid hybrids between diploid and tetraploid loach Misgurnus anguillicaudatus in China

Triploid Chinese loach, Misgurnus anguillicaudatus, hybrids between tetraploids from Hubei Province and diploids from Liaoning Province were mated with either diploid wild-type or triploid hybrids to analyze viability and ploidy of the resultant progenies. Both triploid males and females generated fertile gametes, but progenies from the crosses using gametes of triploid hybrids did not survive beyond the larval stages. In crosses between wildtype diploid females and triploid hybrid males, embryos ranging from 2.2n to 2.6n were predominant with a mode of either 2.4n (chromosome numbers 59, 60, 61) or 2.5n (chromosome numbers 62, 63). Those from the crosses between triploid hybrid females and diploid males gave a modal ploidy level at approximately 2.5n in one case, but a shift to a higher ploidy level was observed in other embryos. In the progenies between triploid hybrid females and males, the ploidy level at approximately 3.0n (chromosome numbers 74, 75, 76) was most frequent. The cytogenetic results of the progenies suggest the production of aneuploid gametes with a modal ploidy level at approximately 1.5n in triploid hybrids. However, a shift to higher chromosome numbers in gametes was observed in certain cases, suggesting the involvement of mortality selection of gametes and/or zygotes with lower chromosome numbers.