Study On Propagating Ecology And Genetic Diversity Of The Golden Apple Snail (Pomacea Canaliculata)

The golden apple snails (Pomacea canaliculata) are big food fresh-water snail, and they live in tropical or Subtropical Region which are found in the Amazon Plain of South America. As a new breed source, the snails were introduced into Taiwan intentionally in 1981 and were transferred from Taiwan to Guangdong, and then it was spread to the national scale, in southern China it has become a serious pest of aquatic plants, rice specially. The report of the snails'damage came from the south of 30°N in China, which showed the harm extent had a positive correlation with temperature and propagation generation, a negative correlation with latitude. It deserves attention greatly because the snail is one of the most important intermediate host through infecting Angiostrongylus cantonensis both domestic animals and human as a cause of eosinophilic meningitis of human. The snails have made huge negative influence on ecological environment and economic activities.In this study, the snails were collected from Zhangzhou (Fujian),Zhuhai (Guangdong) and Suzhou (Jiangsu). Compare study on reproductive basis and genetic differentiation, including fecundity, mating selection, genetic diversity and genetic structure differentiation and so on, was carried out for different geographic populations, propagation generation and shell color of the snails. This study eventually provide theoretical basis for control the snails'harm and prevent from its spread. The main result and conclusion are as follows:1. Compare study on fecundity of different geographic populations of P. canaliculata. The single-pair mating method was used to analyze the snails'fecundity of different geographic and shell-color populations. The results indicated that there was difference to fecundity of different geographic populations, and the difference was significant between Fujian and Jiangsu in individual fecundity, and the difference was also significant between Guangdong and Jiangsu,Guangdong and Fujian in relative fecundity of female. Fecundity has insignificant difference for different shell-color populations of the snails. The spawning number is independent on individual size of the male and is positively related with individual size of the female. The snails'fecundity has close relationship with the factor, including environmental condition, food species and temperature and so on.2. Study on the analysis for the mating selection of different geographic populations of P. canaliculata. The snails'mating selection of different geographic populations was observed by using the marker method in vitro. The result showed that the snails from Guangdong preferred to mate each other within their population, but the snails from Fujian and Jiangsu preferred to mate among different populations; the finding given by test of the mating selection was the snails'mating belong to mixed type (no fixed mate), the mating rate among different shell-color snail was obviously higher than that of same shell-color; in general case, the female body size is larger than that of the male.3. The Analysis of the genetic law among different shell-color P. canaliculata. Study on the genetic law of the different color-shell snails by single-pair mating, which is existent in cultivating population in the Jiangsu province. The results showed that the yellow shell and black shell is a pair of relative properties, which is controlled by nuclear gene and have nothing to do with sex. The genetic law accord with Mendel's single factor separating Law. The research of wild population found that the shell-color difference of the snails was existent in nature, but the proportion taken up in different area was different. The snails'shell from Guangdong was mostly black, that was mainly yellow from Yunnan. Number of the yellow snail was more than that of the black in Fujian and Jiangsu population.4. Analysis of genetic diversity of different geographic populations of P. canaliculata by AFLP markers. Eight AFLP primer combinations, including E32M54, E42M61, E42M54, E45M62, E32M61, E32M62, E32M59 and E39M54, which were obtained by primer screening produced total 382 bands amplified (the percentage of polymorphic loci is 96.60%) from Fujian, Jiangsu and Guangdong populations, number of amplified loci produced by different primer combinations is 35-61 and their average value is 47.75. The proportion of polymorphic loci, Nei's index and Shannon's Information index from Fujian, Jiangsu and Guangdong were 85.08%, 84.82% and 79.06%; 0.2860, 0.2819 and 0.2710; 0.4308, 0.4259 and 0.4079, respectively. The three populations of P. canaliculata were in a higher level of genetic diversity, there is the highest genetic diversity within Fujian population and the lowest that within Guangdong population. Genetic distance is 0.0845-0.1017 among three populations, and that is the nearest between Fujian and Guangdong and is the farthest between Guangdong and Jiangsu. 21 specific sites, including 11, 4 and 6 from Fujian, Jiangsu and Guangdong population, were found in this study, respectively.5. Analysis of different shell-color of P. canaliculata. The proportion of polymorphic loci, Nei's index and Shannon's Information index from yellow and black snail were 92.41% and 93.72%; 0.3214 and 0.3327; 0.4819 and 0.4974, respectively. Comparing with the black snail, the yellow lose seven sites but their genetic diversity was still abundant.6. Analysis of t different genders of P. canaliculata. The proportion of polymorphic loci, Nei's index and Shannon's Information index from female and male snail were 94.76% and 91.36%; 0.3402 and 0.3222; 0.5068 and 0.4816, respectively. Comparing with the female snail, the male lose seven sites but their genetic diversity was still abundant.7. Study on genetic diversity of different geographic populations of P. canaliculata by ISSR markers. Three primers screened were made the amplification from three populations of P. canalicuata and 33 clear amplified loci were obtained, and their percentage of polymorphic loci is 93.94%. The proportion of polymorphic loci, Nei's index and Shannon's Information index from Fujian, Jiangsu and Guangdong were 69.70%, 63.64% and 48.48%; 0.2940, 0.2387 and 0.1903; 0.4247, 0.3536 and 0.2796, respectively. There is abundant genetic diversity among three populations, Fujian population has the highest genetic diversity and Guangdong population is the lowest that. Genetic distance is 0.1020-0.2158 among three populations, and its trend is same as AFLP among three populations.8. Comparison on preference to rice seedling among different geographic populations of P. canaliculata. Mainly crops endangered by snails is the rice seedling in south of china, the experiment indicated that the snails is omnivory, prefer to eat fresh and tender aquatic plants. In four different feeds, the rice seedling is negative selection; Azolla imbricata and Spirodela polyrrhiza, which are floating plants, is positive selection. Therefore, floating plants can be one kind of interim measures preventing rice seedling from the snails'endangering.