STUDIES ON ANEUPLOID BREEDING IN FISHES

1. 超二倍体泥鳅：将正常二倍体泥鳅卵与受精后抑制第二极体释放产生的诱导三倍体泥鳅精子进行受精。得到的二倍体x三倍体后代为染色体数目在51 ~ 59之间的非整倍体，与对照二倍体杂交（80%孵化，4%异常）相比，其孵化率较低（30%），异常发生率较高（76%）。DNA流式细胞术显示存活的2月龄鱼为超二倍体（2.2 ~ 2.5n）。超三倍体泥鳅：由天然四倍体雌泥鳅与诱导的三倍体雄泥鳅杂交而成的一岁泥鳅，表现出尾巴发育不全、身体弯曲或两者兼而有之的外部异常。DNA流式细胞术显示为超三倍体。在一个3.2n的非整倍体中，睾丸细胞的DNA含量表明形成了1.7n的精子。天然非整倍体泥鳅：在实验室饲养的泥鳅家族中，除了二倍体核型（2n=50, 10m+4sm+36t）的正常成员外，还检测到两种多余染色体的外部正常非整倍体。正常大小的多余染色体与正常成员大小相似，而微染色体也被观察到。鳃组织显示0 ~ 3个正常大小和0 ~ 4个微多余染色体。性腺组织中有0 ~ 8条正常大小的染色体和0 ~ 5条微多余染色体。减数分裂图含有25 ~ 27个二价体，外加1 ~ 2个单价体和0 ~ 4个微染色体。单倍体-二倍体嵌合体：偶然发现活的单倍体-二倍体嵌合体。这只个体长到了成年的大小，但却是一只不育的雌性。血、肝、脾细胞多为单倍体，脑细胞多为二倍体。本研究结果表明，利用诱导的三倍体和天然的非整倍体个体作为非整倍体配子的来源，在鱼类中进行非整倍体繁殖的可能性。

1. Hyperdiploid loaches: Eggs of normal diploid loach were fertilized with spermatozoa of induced triploid loach, which had been generated by inhibition of the second polar body release after fertilization. The resultant diploid x triploid progeny were aneuploids with chromosome numbers between 51 and 59 and showed lower hatching rate (30%) and higher incidence of abnormality (76%), when compared to control diploid cross (80% hatch, 4% abnormal). DNA flow cytometry revealed that surviving two-month-old fish were hyperdiploid (2.2〜2.5n).2. Hypertriploid loaches: One-year-old progeny of the cross between natural tetraploid female and induced triploid male exhibted external abnormalities such as ill-developed tail, bent body or both. DNA flow cytometry revealed that they were hypertriploids. In one 3.2n aneuploid, the formation of 1.7n spermatozoa was suggested by DNA content of testicular cells.3. Natural aneuploid loaches: Externally normal aneuploids which had two types of supernumerary chromosomes in addition to normal members of the diploid karyotype (2n=50, 10m+4sm+36t) were detected in a laboratory-reared family. Normal-sized supernumerary chromosomes had similar size to the normal members, whereas microchromosomes were also observed. Gill tissues exhibted 0〜3 normal-sized and 0〜4 micro supernumerary chromosornes. Gonadal tissues showed 0〜8 normal-sized and 0〜5 micro supernumerary chromosomes. Meiotic figures contained 25〜27 bivalents with additional 1〜2 univalents and 0〜4 micro chromosomes.4. Haploid-diploid mosaic charr: A live haploid-diploid mosaic charr was found by chance. This individual grew to the adult size but was infertile female. Most cells in blood, liver and spleen were haploid, whereas those in brain were diploid.The results obtained here suggest possibilities of aneuploid breeding in fishes using induced triploid and natural aneuploid individuals as sources of aneuploid gametes.