Reaction To Acidity And Effects Of Food Change On The Golden Apple Snails At Different Developing Stages

Pomacea canaliculata,also known as golden apple snails,and which is worldly invasive species.Its strong ecological adaptability and fertility make it quickly establish a population,combined with a wide range of food,large food intake,fast feeding on crops,which threatens human health and ecosystem stability while causing great losses to agricultural production and the economy.There are a large number of reports on the biology and ecology of Pomacea canaliculata,However,the response to the environmental tolerance of different life stages of golden apple snails,the tolerance of different sex golden apple snails to acid stress,and the effects of food types of the metabolic characteristics of golden apple snails in different growth stages are not yet clear.Therefore,research in this area has far-reaching significance of further exploration of the life history strategy and ecological tolerance mechanism of the Pomacea canaliculata.The following aspects of research have been carried out based on this article:1.Different responses of the invasive golden apple snails at different life-history stages to acidic stressIn order to examine the differences in responses of the invasive golden apple snails at various life-history stages to acidic stress,the survival behavior and lethal effect of Pomacea canaliculata with shell height of 5,10,15,20,25,30,40,50 and 60 mm in the acidic environment were studied in this paper.When p H?4,the behavior of movement and spawning of Pomacea canaliculata was normal within seven days,and its reactions to the acid stress became stronger with the increase of acidity.The median lethal time(LT50)when p H2 was less than that when p H3.The LT50(22.95h)was the largest in the40 mm shell height group,while it(13.55h)was the smallest in the 60 mm shell height group.There were significant differences in mortality among different shell height groups(P<0.001)and among different time(P<0.001).The interaction between shell-height-effect and time-effect was also significant(P<0.001).When p H2,the mortality rates of Pomacea canaliculata with shell height of 40 mm at 24 h and 30 h were46.67%±11.5% and 53.33%±11.5%,respectively,which were both significantly lower than those in other groups.At p H3,the mortality of Pomacea canaliculata with a shell height of 60 mm was 86.67%±11.5% at 24 h.The mortality(66.67%±11.5%)of Pomacea canaliculata with shell height of 40 mm was lower than the other groups at30 h.However,the mortality of Pomacea canaliculata in the groups of 5mm,10 mm,20mm and 60 mm was 100.00%.Therefore,the variation of the snails' acid resistance was parabolic-shaped,with an increase following a decline along with the snail's developing process.2.Antioxidant enzyme activity and organ damage observation of male and female snails under acid stressIn this paper,the effects of antioxidant enzyme activities and liver damage in the livers of male and female Pomacea canaliculata at p H4,p H5 and p H6 for12 h,24h,48 h and 96 h were studied.The results showed that the SOD activity of male Pomacea canaliculata increased with the decrease of p H,and decreased first and then increased with the prolongation of stress time in p H4 environment,and decreased with the prolongation of stress time in p H5 and p H6 environment.The SOD activity of female Pomacea canaliculata decreased with increasing stress ti me in different p H environments.The CAT activity of male and female Pomacea canaliculata increased first and then decreased with p H stress in p H4 and p H5 environments,and the activity was highest at 48 h stress time.The MDA content of male Pomacea canaliculata increased with the increase of stress timeunder dif ferent p H treatments.The MDA content of female Pomacea canaliculata increased with the prolongation of stress time under the condition of p H4 treatment,and i ncreased first and then decreased with the stress time in p H5 environment,and decreased with stress time in p H 6 environment.The effects of different p H treatme nts of SOD activity,CAT activity and MDA content of the male and female Pomacea canaliculata were extremely significant(P<0.001).The effects of different stress time of SOD activity,CAT activity and MDA content of male and female Pomacea canalicu lata were also significant(P<0.001).PH and time and gender interactions,p H-time int eractions,and time-to-sex interactions were significant(P<0.001).The SOD activity,CAT activity and MDA content of male Pomacea canaliculata were higher than that of female Pomacea canaliculata in acid stress,indicating that the male Poma cea canaliculata were more severely oxidized after p H stress,and the degree of liver tissue damaged was larger than that of female Pomacea canaliculata,which indicated the acid resistance of male Pomacea canaliculata is weak.3.Effects of food types on metabolic characteristics of the invasive golden apple snails at different life-history stagesIn this paper,the digestive enzyme activities of Pomacea canaliculata with shell height of 10 mm,20mm,30 mm,40mm were studied after feeding on rice,spiodela polyrhiza,pistia stratiotes and water-hyacinths.The results show: The lipase,cellulase and amylase activities of Pomacea canaliculata feeded on spiodela polyrhiza with shell height of 10 mm and 30 mm were higher than the other shell-high groups.The lipase,cellulase and amylas activities of Pomacea canaliculata feeded on rice decreased during the growth and development period.By feeding on Pistia stratiotes and water-hyacinths,the activities of lipase,cellulose and amylase were increased first and then decreased with the growth and development period.The digestive enzyme activity of Pomacea canaliculata with shell height of 30 mm were all highest.The effect of food type on cellulase activity and amylase activity of Pomacea canaliculata at different developmental stages was extremely significant(P<0.001),and the effect on lipase activity was not significant(P>0.05).The effects of enzyme and amylase activity were extremely significant(P<0.001),and the interaction between shell height and food type was extremely significant(P<0.001).The contents of total phosphorus and total nitrogen in the water body of Pomacea canaliculata increased gradually with the growth and development.The ammonia nitrogen content in the water body of Pomacea canaliculata feeded on spiodela polyrhiza and rice also increased with the growth and development.The Pomacea canaliculata with shell height of 30 mm was feeded on pistia stratiotes and water-hyacinths,the ammonia nitrogen content in the water body of eichhornia crassipes changed with time,which was significantly higher than other shell height groups.The results showed that the digestive enzyme activity of Pomacea canaliculata in different developmental stages was closely related to their diet.