日本沼虾染色体及其核型的研究

CHROMOSOMAL AND KARYOLOGICAL STUDIES ON THE FRESHWATER PRAWN MACROBRACHIUM NIPPONENSE (CRUSTACEA, DECAPODA)

于1992年3月在上海青浦县采集日本沼虾，似改进的空气干燥法研究精巢细胞染色体及核型，特别较详细地研究了减数分裂前期Ⅰ染色体的行为。结果表明，日本沼虾染色体数n=52，2n=104，共分为A，B，C，D单个染色体组；核型组成是N=37M＋4ST＋11T；初级精母细胞减数分裂前期Ⅰ可分为细线期隔线期、粗线期、双线期和终变期5个时期，双线期的二价体存在弥散阶段；减数分裂的同步率高，大多处于双线期，且双线期二价作着丝点清晰，给核型分析带来了方便。

The chromosomes and karyotype of the freshwater prawn Macrobrachium nipponense were studied by the modified air-dry metkod applied to the testis, focussing on the chromosome behaviour at the first meiotic prophase. The specimens used in this experiment were collected from Qingpu County, Shanghai, in March 1993, and reared in aerated well water in the laboratory. 131 dividing cells were observed in 28 prawns. The results indicated that diploid and the haploid chromosome number of the prawn were 104 and 52, respectively. Most of the dividing cells were found to be of meiosis I and few mitotic divisions were observed. The haploid set of chromosomes, which had a chromosome formula of N = 37M + 4ST + 11T, was divided into 4 genomes (A,B,C,D) according to the relative size, arm ratio and shape of the bivalents at meiotic diplotene.The first meiosis prophase consisted of letotene/zygotema, pachytene, diplotene and diakinesis. The diplotene contained a diffuse stage, and was. most frequently observed in a large number of spermatocytes due to the high sychrony in thcir meioticdivision. Centromeres could be identified easily on tbe bivalents at diplotene, so it was convenient ta analyse the karyotype.