Study On Killing Action Of Salt Solution On The Egg Mass Of Pomacea Canaliculata

Pomacea canaliculata, one of the 100 most harmful invasive species, causes a series of problems in agricultural production, ecological environment and the pathophoresis of parasitosis. However, efficient methods of killing P. canaliculata, which is related to the invasive mechanism and current methods, have not been available at present. This study probes into the theory and feasibility of using salt solution to kill the egg mass of P. canaliculata, aiming at finding a new, targeting, practical and environmentally friendly way of preventing and controlling P. canaliculatas. The results are as follows.1. Eggs of P. canaliculata are covered with a type of protective, transparent grume which can be dissolved in water. The biuret reaction of the grume is positive while the Bial reaction is negative, showing that the grume contains proteins but without sugar.2. Under the principle that salt solution of high concentration can salt-out the protein and cause the cell to lose water, the experiment of killing the egg mass is carried out by using such 7 different salt solution as Calcium chloride (CaCl2), Calcium nitrate [Ca(NO3)2], Magnesium chloride (MgCl2), Sodium chloride (NaCl), Sodium sulfate (Na2SO4), Sulfurous acid (Na2SO3), Sodium bisulfate (NaHSO4). The result shows that:(1) CaCl2, Ca(NO3)2 and MgCl2 can kill the egg mass effectively with the Median Lethal Concentration (LC50) in 15 days of 9.89g/L, 13.92g/L and 15.09g/L, respectively; (2) NaCl, Na2SO4 and Na2SO3 are less effective, with the LC50 in 15 days of 25.93g/L,26.95g/L and 26.46 g/L, respectively; (3) The effect of NaHSO4is not significant.3. To understand the effect of killing the egg mass of P. canaliculata in practice, in different time periods after applying CaCl2 solution, the egg mass are flushed with fresh water for 1 minute. The results show that:(1) 12 hours after applying CaCl2 solution, no significant difference is found in the death rate between the 1-minute flushing group and the no-flushing group. (2) The results of the outdoors experiments show that the death rate of the egg mass increases as the concentration of CaCl2 solution increases:When the concentration reaches 40g/L, the death rate goes up to (93.33±2.89)%(Mean±SE) (Y=1.5238X+26.763,df=6, r2=0.8685, p<0.001). All the results indicate that the CaCl2 solution can kill the egg mass of p. canaliculata effectively even in rainy day. Therefore, it is effective to use CaCl2 solution to kill the egg mass of P. canaliculata.