Studies On The Induction Of Polyploid In The Giant Freshwater Prawn, Macrobrachium Rosenbergii

The giant freshwater prawn (Macrobrachium rosenbergii) is a kind of prawn with great economic value and is cultured very abroad. This freshwater prawn has been popular in Chinese Mainland due to its delicious taste and abundant nutrition since it was introduced here. Now the prawn has been one of the most important aquatic products in the freshwater cultivation. However, since the long-term artificially intensive aquaculture, that is the only way used for this prawn now in Chinese Mainland, is very easy to cause the problems such as being mature in advance , reducing of the body size and the weak resistance to adverse circumstance* so we researched on the polyploid induction of this prawn by cytological techniques so as to solve these problems. Generally the polyploids can grow fast and get a big size than the diploid, and they have stronger resistance to disadvantageous environment. Furthermore its taste is also nice. Here, I firstly investigated on the time of the extrusion of the first and the second polar bodies and of the first cleavage. Then I studied on the chromosome number of the wild type embryos of this prawn. On these basis, I successfully induced the tetraploidy embryos of the giant freshwater prawn by heat-shock and cytochalasin B(C.B) treatment.l.The investigation of the extrusion of the first and the second polar bodies and of the first cleavageThe time of the extrusion of the first and the second polar bodies and of the first cleavage were investigated by paraffin sections. We observed that the first polar body had been released when the oocyte matured physiologically. By 55 min after the insemination, the second polar body was released. The first cleavageoccurred approximately 210-230 min following insemination.2.The chromosome number of wild type embryoThe evaluation of the chromosome number showed that there are 118 chromosomes in wild type embryo.3.Tetraploidy induction by heat shockThe optimum condition of heat shock appeared to be at 210 min post-fertilization, treating for 1.5 min at 40℃, which could yield 35.86% tetraploidy embryos.4. Tetraploidy induction by Cytochalasin B treatmentUnder the condition of treatment with 1.0 mg/L C.B for 10 min at 230 min after fertilization, we obtained the maximum induction rate of tetraploid, 33.78%.