¹ Institute of Oceanology, Chinese Academy of Sciences, 7 Nanhai Road, Qingdao, 266071, China

Progress in penaeid genetics and biotechnology research has been slow because of a lack of knowledge on fundamental aspects of their biology. There has been relatively little research undertaken on the chromosome number, structure and composition in the penaeidae. One reason for this is due to the relatively small size and large number of chromosomes. This paper reports techniques for obtaining high qualitative somatic and meiotic chromosome from embryo to adult stages of marine shrimp. These techniques were successfully applied to study 16 species of penaeid shrimps : Fenneropenaeus chinensis (2n = 88), Penaeus monodon (2n = 88), Fenneropenaeus penicillatus(2n = 88), Penaeus semisulatus(2n = 90), Farfantepenaeus aztecus(2n = 88), Litopenaeus setiferus (2n = 90), Farfantepenaeus duorarum(2n = 88), Marsupenaeus japonicus (2n = 86), Fenneropenaeus merguiensis (2n = 88), Penaeus esculentus (2n = 88), Litopenaeus vannamei(2n = 88), Litopenaeus stylirostris (2n = 88), Trachypenaeus curvirostris (2n = 70 =42m+10sm+12st+6t), Metapenaeus ensis (2n = 78), Xiphopenaeus kroyeri(2n = 78) and Sicyonia ingentis(2n = 64). Among these species, 11 species are the first estimates studied by our group. The somatic chromosomes were obtained from embryo, nauplius larvae, other larvae and adult tissues including antennal gland, branchia, ovaries and testis. The gastrula provided the best chromosomes, the embryos were treated in 0.04% colchicine for 1-1.5hr and then placed in 0.7%(w:w) KCl 30-50min and fixed with fresh Carnoy's solution (methanol: acetic acid =3:1) for 2hr, fixative was change twice in the course. Air-drying preparation stained with 2-5% Giemsa solution with a phosphate buffer (pH=7.0) were microscopically observed. Phase contrast and fluorescence microscopy proved to be useful tools for the purpose of observation. Meiotic chromosomes were prepared from testis lobes. The living adult shrimps were injected with 0.1-0.3ml of 0.2%(w:w) colchicine solution, the testis dissected out after 5-6hr, dip in 0.7%(w:w) 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, but the majority of the chromosomes in testis and ovaries were the dot shape. Better chromosome morphology was found in gastrula and nauplius larvae, most of the chromosomes in penaeids are metacentric and sub-telocentric or telocentric. But it is difficult to define karyotype due to the very small size in individual chromosome and the change in different tissues or preparation.