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

F-3-F-8 hybrids of red crucian carp (Carassius auratus red var.) (female) x common carp (Cyprinus carpio L.) (male) 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 4n = 200. The chromosome numbers of two types of triploids produced by mating F-3-F-8 (male), respectively, with diploid Japanese crucian carp (C. auratus cuvieri T. et S.) (female) and Xingguo red carp (female) were 3n = 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. (C) 2001 Elsevier Science B.V. All rights reserved.