Formation And Biological Characterization Of An Improved Triploid Crucian Crap

The bisexual fertile allotetraploid(AT) population was obtained by crossing red crucian carp((?)) with common carp((?)).On the base of obtaining of AT,many types of improved polyploidy fishes and diploidy fishes were formed with some improved features in appearance,flesh quality,and growth rate,according to the biological methods including distant crossing,gynogenesis,androgenesis,sex reversal,transgenic technique,backcrossing and genetic selection.An improved triploid crucian carp(ITCC) was produced by crossing improved tetraploids (G₁×AT,(?)) with improved red crucian carp(IRCC,(?)),which were obtained by distant crossing and gynogenesis.In this paper,the biological characteristics of IRCC including the number and karyotype of chromosome,DNA content,gonadal and pituitary structures,phenotypes and growth rate were observed.The results are as follows:ITCC possessed 150 chromosomes with the karyotype 33m+51sm+33st+33t. The DNA content of ITCC was 1.48 times than that of red crucian carp. In the breeding season,both ovary-like and testis-like gonads of ITCC were proved not able to produce the normal mature gametes.The ultra-structure of the pituitary of ITCC showed that most of the endocrine particles in GTH cells were not released,providing endocrinology evidences for sterility of ITCC.Following one-year culture,ITCC averagely reached 400-500 gram that was similar with triploid crucian carp(TCC) produced by mating Japannese crucian carp with allotetraploid hybrids,whose growth rate was 1.43 times than that of red crucian carp and 4.21 times that of nature crucian carp.Compared with TCC,ITCC not only kept the excellent traits such as the fast growth rate and sterility,but also got some improved characteristics in morphology such as higher body,shorter tail and smaller head.