Biological characteristics of an improved triploid crucian carp.

An improved triploid crucian carp (ITCC) was produced by crossing improved tetraploids (G1xAT, male symbol) with improved red crucian carp (IRCC, female symbol), which were obtained by distant crossing and gynogenesis. The biological characteristics of ITCC, including the number and karyotype of chromosomes, gonadad and pituitary structures, phenotype, and growth rate are reported. ITCC possessed 150 chromosomes with the karyotype 33m+51sm+33st+33t. In the breeding season, both ovary-like and testis-like gonads of ITCC were unable to produce normal mature gametes. The ultrastructure of the pituitary of ITCC showed that most of the endocrine granules in gonadotrophic hormone (GTH) cells had not been released, providing endocrinological evidence for the sterility of ITCC. Compared with triploid crucian carp (TCC) produced by mating Japanese crucian carp with allotetraploid hybrids, ITCC not only retained the excellent traits of fast growth rate and sterility, but also acquired improved morphological characteristics, including higher body, shorter tail and smaller head.