Triploid hybridization of fast-growing transgenic mud loach Misgurnus mizolepis male to cyprinid loach Misgurnus anguillicaudatus female: the first performance study on growth and reproduction of transgenic polyploid hybrid fish

Abstract

Transgenic triploid hybrids between fast-growing transgenic mud loach ( Misgurnus mizolepis) males and cyprinid loach ( Misgurnus anguillicaudatus) females were generated, and their performance on growth, feed conversion ability and reproduction was evaluated. Although the growth acceleration of diploid and triploid transgenic hybrids was not as much as that of the original transgenic mud loaches, they still represented significant growth stimulation ranging between 11- and 28-fold when compared to their non-transgenic counterparts, with significantly improved feed conversion efficiency (FCE) up to maxima of 2-fold (compared to non-transgenic hybrid) and 1.5-fold (compared to non-transgenic mud loach). The gonad development of diploid hybrids was histologically normal regardless of transgenic genotype but the extent of gonad development in hybrid fish was less than that in mud loach diploids at the same age. On the other hand, sterility was observed in both sexes of the triploid hybrid transgenics: Ovarian and testicular development in transgenic triploid hybrids were significantly depressed, and no sign of maturation to ovum or spermatids was detected. No viable embryos were obtained in a fertilization trial using a suspension prepared from the minced testes of transgenic triploid hybrids. This study may indicate the potential usefulness of triploid hybridization as a mean for reproductive containment of transgenic mud loach.