ドジョウの自然4倍体より生じる稚仔の染色体と発生能力〔英文〕

概要

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Experimental crossings were made between spontaneously occurring tetraploid (4n) and normal diploid (2n) loach, resulting in 4n×4n, 4n×2n, 2n×2n, and 2n×4n crosses. A part of 4n×2n and 2n×4n crosses were heat-shocked (HS) to inhibit second meiosis. Eggs from 4n and 2n loach were activated with ultraviolet (UV)-ray irradiated spermatozoa from 2n loach or minnow (G) to induce gynogenetic 4n×2n•UV and 2n×G•UV cross, respectively. Embryos from the 4n×4n, 4n×2n, 2n×4n, 4n×2n•HS, and 2n×4n•HS showed 4n=100, 3n=75, 3n=75, 5n=125, and 4n=100 chromosomes, respectively and a majority of these fry de-veloped normally. Gynogenetic haploid (n=25) from 2n×G•UV were inviable. Gynogenetic fry from 4n×2n UV with 2n=50 chromosomes represented normal to near-normal morphology and a part of them were viable beyond the feeding stage.