STUDIES ON THE TETRAPLODY INDUCTION IN THE GIANT FRESHWATER PRAWN,MACROBRACHIUM ROSENBERGII

Triploicl organisms are advantageous in agricultural breeding due to their rapid growth rate and more delicious meat. Tetraploid animals are also valuable because of their fertility and capacity of producing triploidy by crossing with normal diploid. The giant freshwater prawn Macrobrachium rosenbergii is an important aquaculture species in China. The intensive breeding, which is widely used, may cause many problems, such as prematurity, being smaller in size, etc. Triploid induction may be a solution to solve these problems. Present study showed that the first polar body was released when the oocyte matured physiologically and the second polar body was extruded about 55 mins after fertilization. After the synapsis of male and female pronuclei, the first cleavage occurred around 210-230 mins following fertilization. Furthermore the tetraploidy embryos of this prawn were successfully induced by heat-shock and cytochalasin B(C.B)treatment. The tetraploid embryos of the prawn could be obtained by induction with either heat shock or C. B. The optimum condition of heat shock appeared to be at 210 minutes post-fertilization, duration for 1.5 minutes at 40℃ ,which could yield 35.86% tetraploidy embryos. While treated with 1 .0mg/L C. B for 10 minutes at 230 minutes after fertilization, the maximum rate of tetraploid(33.78% )was obtained.