Abstract

The F3-F11 hybrids of red crucian carp (Carassius auratus red var.) (+)common carp(Cyprinus carpio L.) (>) were proved to be allotetraploids with 200 chromosomes, showing that tetraploidy can be inherited from one generation to another. The tetraploid hybrids possessed the normal testes and ovary producing the normal diploid sperm and diploid eggs, respectively. The diploid sperm and diploid eggs were respectively larger than the haploid sperm and eggs in sizes. The diploid sperm and diploid eggs can normally fertilize to produce the next tetraploid generation.

During the breeding season?three types of gonadal structure of triploid crucian carp, produced by crossing allotetraploids (>) with Japanese crucian carp(Carassius auratus Cavieri T. et S) (+), were found. The first type was the testis that consisted of many lobules in which there were numerous spermatides. Some degenerated spermatides were found and no mature spermatozoon was observed. The second type was the ovary-like gonad consisting of many nests of small undeveloped cells and a few small growing oocytes as well as enlarged and degenerated oocytes. The third type was the fat tissue, in which case, only two strips of fat tissue were located on the gonadal positions, neither testis nor ovary being observed. For more than ten years, no fertile triploid was found. Combined with the structures of the tissues located in the gonad positions, the triploid crucian carp was proved to be sterile. The triploid caurian carp was produced on a larger scale in China.