PRODUCTION OF HIGHER POLYPLOID STRAINS FOR AQUACULTURE OF CYPRINIFORMES

(1)六倍体泥鳅的诱导与表现：用天然四倍体(4N)系的2n精子与二倍体(2n)卵子受精后，通过抑制第二极体的释放而产生六倍体泥鳅(6n)。六倍体泥鳅产生了3n个配子。6n组的卵大小大于4n组和2n组。用6n、4n和2n的精子分别与6n、4n和2n的精子受精，分别获得六倍体、五倍体和四倍体品系。(2)四倍体表现。三倍体和二倍体：在集体饲养条件下，2年生三倍体(3n=2nx4n)的生长情况好于4n和2n。三龄鱼的四倍体(4n=4nx4n)小于3n(=4nx2n)和2n(2nx2n)。3n的性腺发育受到抑制。(3)六倍体、五倍体和四倍体的生长性能：在1龄鱼中，五倍体(5n=6nx4n)的生长效果好于6n(6nx6n)和4n(6nx2n)。在集体饲养条件下，3岁的六倍体生长不佳，体重约为5N和4N的一半。六倍体和五倍体的性别比为1：1，而四倍体为全雌性。6n组的头长与体长的比例大于5n组和4n组。(4)未减卵数：三倍体(2n×4n)的粘虫产下未减数的3n卵。由这类卵子诱导的第一代三倍体雌核也产生3n个卵子，但观察到少量非整倍体(1.5n)卵子。DNA指纹图谱显示，从这些未减数的卵子诱导出的第二代雌孕激素是无性系的，但在遗传上非常相似。(5)四倍体鲫鱼的生产：通过受精卵的冷、热和压力休克，将精子基因组整合到卵子中，诱导雌核发育三倍体鲫鱼发生四倍体。

(1)Induction and performance of hexaploid loaches : Hexaploid (6n) loaches were produced by inhibiting the second polar body release after fertilization of diploid (2n) eggs with 2n sperm of a natural tetraploid (4n) line. Hexaploid loaches generated 3n gametes. Egg sizes of 6n were larger than those of 4n and 2n loaches. Hexaploid, pentaploid (5n), and tetraploid lines were produced by fertilization of eggs of 6n loaches with sperm of 6n, 4n, and 2n loaches, respectively.(2)Performance of tetraploid. triploid, and diploid loaches : In communal rearing condition, 2-year-old triploids (3n=2nx4n) showed better growth than 4n and 2n. However, in three-year-old fishes, tetraploids (4n=4nx4n) were smaller than 3n (=4nx2n) and 2n (2nx2n). Gonadal development of 3n was suppressed. Proportion of head length to body length in 4n was larger than those in 2n and 3n.(3)Performance of hexaploid, pentaploid, and tetraploid loaches : In 1-year-old fish, pentaploids (5n=6nx4n) gave better growth than 6n (6nx6n) and 4n (6nx2n). In communal rearing condition, growth of 3-year-old hexaploid was poor ; about half body weight of 5n and 4n loashes. Hexaploids and pentaploids gave 1 : 1 sex ratio, but tetraploids were all-female. Proportion of head length to body length in 6n was larger than those in 5n and 4n.(4)Unreduced eggs in loaches : Triploid (2nx4n) loaches gave unreduced 3n eggs. First generation of triploid gynogens induced from such eggs also produced 3n eggs, but a small number of aneuploid (1.5n) eggs were observed. DNA fingerprinting revealed that second generation gynogens induced from these unreduced eggs were aclonal, but genetically very similar. Diploid loach which generated unreduced 2n eggs was also found in the wild population(5)Production of tetraploid crucian carp : Tetraploidy was induced in gynogenetic triploid crucian carp by incorporating sperm genome into eggs by means of cold, heat and pressure shock of fertilized eggs.