The formation of tetraploid stocks of red crucian carp×common carp hybrids as an effect of interspecific hybridization

Abstract

F 3–F 8 hybrids of red crucian carp ( Carassius auratus red var.) (♀)×common carp ( Cyprinus carpio L.) (♂) were found to be allotetraploids by examining the numbers and karyotypes of chromosomes, the DNA content of red blood cells, and the mean nuclear erythrocyte volumes. The chromosome numbers of F 3–F 8 were 4 n=200. The chromosome numbers of two types of triploids produced by mating F 3–F 8 (♂), respectively, with diploid Japanese crucian carp ( C. auratus cuvieri T. et S.) (♀) and Xingguo red carp (♀) were 3 n=150. The mean DNA content of F 3 and the triploid are, respectively, two times and 1.5 times of that of diploid Japanese crucian carp. F 3 hybrids had mean erythrocyte nuclear volumes about two times larger than diploid Japanese crucian carp. The hybrids F 3–F 8 were fertile. It is easy for F 3–F 8 to produce their tetraploid offspring. The triploids were sterile. Based on the analysis of karyotype and the intermediate appearance with two pairs of small bases of barbels, F 3–F 8 hybrids were proved to be allotetraploids with two chromosome sets of red crucian carp and two chromosome sets of common carp. It is concluded that the females and males of F 2 hybrids were able to produce, respectively, diploid eggs and diploid spermatozoa and they fertilized to form tetraploid fish.