STUDIES ON ANEUPLOID BREEDING IN FISHES

1.超二倍体泥鳅：用受精后第二极体释放抑制法诱导三倍体泥鳅精子与正常二倍体泥鳅卵受精。二倍体×三倍体杂交后代为染色体数在51 ~ 59之间的非整倍体，孵化率（30%）较低，畸形率（76%）高于二倍体对照（80%孵化，4%畸形）。DNA流式细胞仪检测结果显示，2月龄存活的鱼为超二倍体（2.2 × 2.5n）.超三倍体泥鳅：自然四倍体雌性与诱导的三倍体雄性杂交的一年生后代出现外部异常，如尾巴发育不良、身体弯曲或两者兼而有之。DNA流式细胞仪检测结果表明，它们是超三倍体。在一个3.2n的非整倍体中，睾丸细胞DNA含量表明有1.7n的精子形成.天然非整倍体泥鳅：在一个实验室饲养的家系中，除正常二倍体核型（2n=50，10 m +4sm+36 t）外，还发现了两种类型的额外染色体。正常大小的额外染色体的大小与正常成员相似，而微染色体也被观察到。鳃组织中含有0.33个正常大小的染色体和0.44个微小的额外染色体。性腺组织中正常染色体0. 88条，微小额外染色体0. 55条。减数分裂像含有25 × 27个二价体，另外还有1 × 2个单价体和0 × 4个微染色体。单倍体-二倍体嵌合体：偶然发现一株活的单倍体-二倍体嵌合体。这个个体长到成年大小，但是不育的雌性。血液、肝脏和脾脏中的细胞大多数是单倍体，而脑中的细胞大多数是二倍体，这些结果表明，利用诱导的三倍体和自然的非整倍体个体作为非整倍体配子来源进行鱼类非整倍体育种是可能的。

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.