ABSTRACT
Objective To study the distribution of Oncomelania hupensis snails in mountainous regions and the dynamic charaeteristics of the distribution.Methods An environment calledLanbaoclosed to Puge County.Sichuan Provinee WaS selected as the study field.Random sampling was designed to determine the investigation sites.The snails were collected and the hying snaila were identified by the method of dissection in the laboratory.The distribution of snails was analyzed by some statistical indices,such as mean,variance and so on.Then the negative binomial distribution.log-normal distribution and exponential distribution were fitted to the snail data by the method of maximum likelihood estimation to explore the snail distribution in different time.Results The negative binomial distribution was fitted well to the snail data in April,May,July,August,September,November in 2008,and no distribution was fined to the snail data in June,October.December in 2008 and February in 2009.Conclusions The distribution of Oncomelania hupensis in mountainous regions is not simple negative binomial distribution,but pwbably a dynamic process and an uncertain distribution.
ABSTRACT
Objective To explore a possible method for determining the appropriate sample size of Oncomelania hupensis in the marshland and lake regions. Methods Four bottomlands were selected randomly along the Qiupu River in Guichi District, Anhui Province. Oncomelania snails were surveyed carefully in these bottomlands and brought back to the laboratory to judge whether they were alive or not with mild water. All the data of Oncomelania hupensis were doubly input into the EpiData software and checked for the errors. Repeated sampling was performed in the four databases according to different sample sizes by using SAS software and the corresponding snail density was also calculated. According to the values of sample size and corresponding snail density, sample size-snail density absolutely changing curve and relatively changing curve were drawn to determine the appropriate sample size of snail survey. Results The appropriate sample sizes of snail survey were 40,200,100 and 200 frames in Gutan bottomland, Caizi bottomland, Qiupu bottomland and Ouyang bottomland, respectively. Conclusion Sample size-snail density absolutely changing curve and relatively changing curve could provide some instructions for choosing the appropriate sample size during the process of snail survey in the marshland and lake regions.
ABSTRACT
Objective To study the impact of vegetation changes on the distribution of Oncomelania hupensis in the marshland and lake regions.MethodsA bottomland from the 14 bottomlands along the Qiupu River in the Guichi District,Chizhou City,Anhui Province was selected,and a 50 m?50 m area of uniform vegetation was choosed as the research field.Low-grass group,boundary-grass group,hay group and control group were designed to represent four types of vegetation's status and the snail density,soil temperature and soil moisture were surveyed half a month after the design.The change of Oncomelania hupensis's distribution due to the vegetation change was analyzed statistically.ResultsThe snail density of the hay group was nearly 0 with high soil moisture and low soil temperature.The snail density of the low-grass group was obviously decreased(32.1/0.1 m2),and the snail density of the boundary group slightly increased,which had no statistical significance compared with the snail density of the control group.ConclusionsOncomelania hupensis moves from the low-grass group to the boundary group after the vegetation is cut down,which changes the distribution of snail.Hay group is the worst environment for Oncomelania hupensis to survive and the method of cut-overlay grass may be used to improve the effect of molluscicide.
ABSTRACT
Objective To explore morphologic variations and their spatial correlation among Oncomelania hupensis populations from the mainland of China. Methods Twenty-seven snail populations from ten provinces were collected. The morphologic indices of shells and geographic distances between the snail spots were measured respectively, and the morphologic variations among snail populations and the correlations between morphologic variations and geographical distances were analyzed. Results The median of Euclidean distances was 3.24 (95% CI: 2.88-3.81) among 20 snail populations of O.h.hupensis including a snail population from Guangxi Province, and was 3.15 (95% CI: 2.86-3.76) excluding the Guangxi snail population; the median was 1.69 (95% CI: 1.33-2.27) among 6 populations of O.h.robertsoni. Whether including a snail population from Guangxi Province or not, the median among O.h.robertsoni was less than that among O.h.hupensis (P0.05). The correlation coefficient was 0.2655 for O.h.hupensis including a snail population from Guangxi Province, 0.2567 not including it; and was 0.3121 for ribbed-shell population. Conclusions Morphologic variation among O.h.hupensis is bigger than that among O.h.robertsoni, and morphologic variation among ribbed-shell populations is bigger than that among smooth-shell populations. There is significant spatial structure among ribbed-shell snail populations of Oncomelania hupensis distributed in the mainland of China.