刀额新对虾染色体核型及细胞核DNA含量

THE CHROMOSOME KARYOTYPE AND CELLULAR DNA CONTENTS OF METAPENAEUS ENSIS

以刀额新对虾胚胎、无节幼体、卵巢、精巢等为材料 ,空气干燥法制备染色体 ,并初步进行核型分析。结果表明 ,刀额新对虾的染色体数目为 2n=78,n =39,核型为 2n=78=40M +1 0SM +1 4ST+1 4T。以刀额新对虾血淋巴、卵巢、肌肉、鳃为材料 ,以鸡血细胞为DNA标准 (2 50pg/ 2c) ,使用PartecCCAⅡ型流式细胞仪测定了刀额新对虾细胞的基因组DNA含量 ,其值为鸡血细胞的 1 75倍 ,绝对含量为 4 375pg/ 2c。

There has been relatively little research undertaken on the chromosome number,structure and composition in the Penaeidae.One reason for this is the relatively small size and large number of chromosomes.This paper reports techniques for obtaining high qualitative somatic and meiotic chromosome from embryo,larvae and adult of sand shrimp Metapenaeus ensis. The somatic chromosomes were obtained from embryos, nauplius larvae and adult tissues including ovaries and testis.The embryos and larvae were treated in 0 04% colchicine for 1-2 hours and then placed in 0 075 mol/L KCl 40-60min and fixed with fresh Carnoy′s solution (methanol:acetic acid=3∶1)for 2 hour, fixative was change twice in the course.Air drying preparation stained with 10% Giemsa solution with a phosphate buffer (pH=7 0)were microscopically observed.The living adult shrimps were injected with colchicine solution (1 5μg per body weight g),the ovaries and testis dissected out after 5-6 hours, dip in 0 075mol/L KCl for 40-60min then fixed, prepared and observed as embryo chromosome above.The testis lobes contained both meiotic and mitotic cell,so diploid and haploid chromosome can be obtained.Diploid chromosome can be observed in ovaries,the majority of the chromosomes in testis and ovaries were the 'dot' shapes. The chromosome number of M.ensis is 2n=78,n=39.Preliminary results of karyotype is 40M+10SM+14ST+14T. Using DNA of chicken erythrocyte (2 50pg/2c)as a standard,diploid nucleus DNA contents of M.ensis were measured from the blood,ovaries,muscle,gill by flow cytometer (Partec CCAⅡ).DNA content of the shrimp is 4.375 pg/2c and the ratio to that of chicken is 1.75.