Study On The Chromosome And Polyploid Induction In Some Penaeid Shrimps

Penaeid shrimps are very important commercial species in the marine aquaculture industry and their production has been increasing in the world. But the supply of shrimps is still not enough to satisfy consumer need because of the overfishing of wild stock and the serious viral diseases in shrimp-farming. The sustainable aquiculture of shrimp becomes more and more important. But because of a lack of knowledge on fundamental aspects of their biology, progress in penaeid genetics and biotechnology research is slow. In cytogenics, there is little research undertaken on the chromosome number, structure, composition and chromosome manipulation in shrimp. A careful study of shrimp chromosomes is not only useful to taxonomy and evolution studies of crustacean, but also essential to its genetic and breeding researches for the shrimp aquaculture. In this paper, we studied the chromosome, ploidy manipulation and gene location using chromosome preparation, flow ctyometery, fluorescence microscopy, histological methods, electronic microscopy and fluorescence in situ hybridization. High qualitative somatic and meiotic chromosomes from embryo, larvae and adult of three shrimps: Metapenaeus ensis, Litopenaeus vannamei and L. stilymstris were obtained. The somatic chromosomes were prepared from embryo, nauplius larvae and adult tissues including ovaries and testes. The testis lobes contained both meiotic and mitotic cells, so diploid and haploid chromosomes can be obtained. Diploid chromosomes can be observed in ovaries of M ensis, but the majority of the chromosomes in testes and ovaries were the 揹ot?shapes. The chromosome number of M ensis is 2n=78,n39, preliminary results of karyotype is 40M+1OSM+I4ST+14T0 L. vannamei and L. stilyrostris have the same diploid chromosome number 2n=88. Using of DNA of chicken erythrocyte (2.3 Opg/2c) as a standard, diploid nucleus DNA content of M ensis was measured from the blood, ovaries, muscle and gills, by flow cytometer (Patarc- PCAII). DNA content of Mensis is 4.025 pg/2c and the ratio to that of chickens is 1.75. The genome size was compared in four species shrimps L. stilyrostris, Marsupenaeus japonicus, M ensis and. Fenneropenaeus chinensis by flow cytometery. The L. stilyrastris have the largest genuine size, it is 1.48 times to M japonicus, 1.61 to M ensis, and 1.65 to F chinensis. We presumed DNA lose may occur in the Penaeoidae evolution. Fluorescence in situ hybridization (FISH) is a promising technique used in cytogenetic researches at tI~ molecular level. It regards to such fields as gene localization, sex identification, chromosome vriation, and interspecies hybridization. In this paper, FISH was attempted in shrimp. I 8SrRNA gene was applied into localization in two chromosomes of Chinese shrimp F chinensis, which not only enriched the cytogenetic studies of shrimps but also provided implication for genome maping. Microsatelate sequence (AG) ~ was also been localized in I Ochromosomes of F chinensis. The triploid of three species tropical shrimps: M japonicus, P monodon, and M ensis were induced by heat shock, cold shock and 6-DMAE Optima] condition of temperature shock was determined in the Mjaponicus and F monodon. The eggs were spawn at about 28C,cold shock treatment at 5-9C for 10-20 mm duration initiated at different time 6-I 8mm after fertilization. 68.52% and 84.70% triploid nauplii were produced in M japonicus and P monodon.. 6-DMAP was used to induce triploid in M japonicus. P. monodon, and M ensis with 400-600 pmol/L 6-DMAP for 15-20mm initiated at 6-18 mm after spawning, the induction rate was 52.42%, 59.990/...