[Triploid crucain carp-allotetraploid hybrids (male) x goldfish( hermaphrodite)].

A new type of triploid crucian carp was generated by mating the males of the allotetraploid hybrids of red crucian carp (Carassius auratus red var.) (female) x common carp (Cyprinus carpio L.) (male), with the females the goldfish( Carassius auratus red var.) which was red in color and possessed the biforked tails. The biological characteristics of one-year old triploid crucian carp including the number and karotype of chromosome, gonadosomatic indices and gonadal structures, appearance and growth rate were investigated. The results indicated that the triploid crucian carp possessed 150 chromosomes with the karyotype: 33m + 51sm + 33st + 33t. In the breeding season, the gonadosomatic indices (GSI) of the ovaries and testes in the triplpoid crcuian carp were, respectively, lower than those in the diploid red crucian carp, and the tissue sections showed that both the ovaries and the testes in the triploid cruican carp were not able to produce the mature ova and sperm, respectively, indicating that they were sterile during one year. The triploid crucian carp was gray in color and had a single fork tail. They had other morphological traits intermediate to the paternal allotetraploid hybrids and the maternal goldfish, for example, one pair of very short and not readily visible barbells, the formula of lateral line scales: 31-6/7, 18 dorsal fin spines, and 0.5 in ratio of the width to the length of the body which was evidently higher than that (0.41) in another kind of triploid crucian carp called Xiangyun crucian carp, generated by crossing the males of the allotetraploid hybrids with the females of the Japanese crucain carp (Carassius auratus cuvieri T. et S.). Following 8-month culture, the triploid crucian carp averagely reached 350 gram in which the maximum individual weighed 550 gram. Among one- year old triploid crucian carp, the females grew faster than the males. Compared with Xiangyun crucian carp, the new type of triploid crucian carp not only presented some advantages the Xiangyun crucian carp had, for example, fast growth rate and potential sterility, but also got some new good performances like the high ratio of the width to the length of the body and the sweet flesh, suggesting they will be very potential in the commercial interest.