The Role Of Sex Steroid Hormones In The Reproductive Process And Potential Ecological Control Strategies In Pomacea Canaliculata(Caenogastropoda: Ampullariidae)

The golden apple snail Pomacea canaliculata(Caenogastropoda: Ampullariidae)is an invasive species from South America.It has invaded China for more than 40 years,widely distributed in the Yangtze River Basin and the south,causing huge economic losses.At present,the scope of invasion continues to expand.There is a trend of invasion to the north of the Yangtze River,which poses a serious threat to China’s biodiversity protection,water ecological environment and food production security.The golden apple snail is a freshwater snail with stable hermaphroditism,gender and genotype.The rapid expansion is closely related to its vigorous reproductive ability.Sex hormone is the key factor to regulate reproduction.Starting from the reproductive process of P.canaliculata,this study studied the appearance.On one hand,the morphology of reproductive system during courtship,mating and oviposition are studied,on the other hand,the courtship,mating and oviposition behaviors are observed and recorded in detail sex steroid hormones in individual gonads during mating and dormancy,and to explore the role of sex steroid hormones in the reproduction of P.canaliculata.At the same time,by introducing endocrine disruptors Bisphenol A(BPA)and Tamoxifen(TAM),the specific function and action intensity of sex steroid hormones in the reproductive process of P.canaliculata are verified.Gas chromatography-mass spectrometry(GC--MS)is used to analyze and identify the effective chemical components that may secrete sex pheromones.The results of this study are helpful to reveal the regulation mechanism and key points of sex steroid hormones on the reproduction of P.canaliculata,and provide a scientific basis for exploring the development of new prevention and control technologies of P.canaliculata based on sex hormone interference blocking and sex pheromone induction.The main results are as follows:1.There are sex pheromones in the reproductive process of P.canaliculata.Through the observation and experiment of mating,mating and oviposition of P.canaliculata,there is a clear process of searching,locating and tracking between male and female snails during the mating period.There is information transmission between male and female snails,and some pheromone with gender orientation exists.However,the tracking effect is affected by the transmission medium and distance.Therefore,it can not be tracked the opposite sex for a long time and a long distance.And most of them are males who actively pursue females.In order to obtain mating opportunities,males are more excited and will have courtship actions such as dancing.2.Relationship between sex steroid hormones and reproductive process of P.canaliculata.The histological and enzyme-linked immunosorbent assay are used to analyze and compare the changes of gonadal morphology and the contents of various sex steroid hormones in the mating and dormant stages of P.canaliculata.The results show that the color and morphology of gonads in different cycles are different,and the fallopian tube has the unique function of packaging fertilized eggs,which has evolutionary advantages.Sex steroid hormones play an important role in the process of sex maintenance,gonadal differentiation,gametogenesis and release of P.canaliculata.According to the changes of gonadal morphology and the content of estradiol in testis and ovary in different periods,coupled with the changes of testosterone,serotonin,gonadotropin and other sex steroid hormones in the same period,it is found that estradiol plays a key role in the process of gametogenesis and reproduction of P.canaliculata.3.Effects of sex steroid hormones on the reproductive process of P.canaliculata.Bisphenol A and Tamoxifen are used as endocrine disruptors to study the response of sex steroid hormones to the interference of the endocrine system of P.canaliculata.The results show that the contents of various sex steroid hormones in P.canaliculata decrease significantly under high concentration and continuous Bisphenol A exposure;the feeding and movement behavior of P.canaliculata are blocked,the male’s initiative of courtship and mating is weakened,and the number of female snails laying eggs decreases,resulting in the reduction of the reproductive ability of P.canaliculata;there are also adverse risks in the gender differentiation of offspring.Tamoxifen can also significantly reduce the contents of various sex steroid hormones in the body of P.canaliculata,in which the contents of estradiol,progesterone,testosterone and serotonin decrease to a trace level;it leads to the obstruction of social behavior and sports behavior of P.canaliculata;the spawning number and hatching rate of female snails decrease significantly,which are not conducive to population stability.The response of sex steroid hormones of P.canaliculata to the interference of Bisphenol A and Tamoxifen proves that interfering with or blocking the secretion of sex hormones can evidently reduce the population of P.canaliculata.The next research needs to explore the interference mechanism of Bisphenol A and Tamoxifen,and find out the key factors in order to implement accurate interruption,so as to establish an efficient prevention and control technology of P.canaliculata.4.Origin and chemical constituents of sex pheromones in P.canaliculata.The chemical pheromone of P.canaliculata is extracted by extraction.We use gas chromatography-mass spectrometry(GC-MS)to separate and identify the chemical information components and analyze the possible "effective signal source" substances.The experiment preliminarily obtained some basic information of compounds,such as Indole and Hexadecanal.Considering the fact that these two compounds have typical strong odor and volatile characteristics,they may be one of the sex pheromones of P.canaliculata,which needs to be confirmed by further research.