RESUMO
Objective To anderstand the metagenesis of Oncomelania snails in the mountainous regions so as to control the spread of snails and the epidemics of schistosomiasis.Methods Observation spot was established at a typical snail habitat close to Puge county,Sichuan province from February 2008 to July 2009.Random sampling was applied to determine the place of each frame during the observation.All the snails in each frame were collected and numbers counted in the laboratory,with the number of mating pairs in each frame also observed.Snails being collected were measured for the body indices and the dissection was carried out to identify gender composition.survival status and the number of live snails in each frame counted.Line graphs of the body indices.mating pairs in each observed months,bar graphs of the snail density,proportions of gender together with the maturity of the snails in each month were drawn.Results The number of live snail existed the whole year and its density fluctuated.All the three kinds of body indices showed the same time trend and a dynamic circulation.The young snail existed all year around and arose constantly in proportion from May,becoming the dominant snailin October to replace the adult snails.The young and adult snails also showed a dynamic alternative.The gender composition showed no significant difference during each month.The number of the mating pairs was more on April.May and June annually,when were the snail's main multiplying stage.Conclusion In mountain area.the young snails existed through all the year while adult snails appeared to be dominantin each month except for October.Oncomelania snail showed a circular process of metagenesis which started in May and finished in October.The snail population presented a dynamic equilibrium.It was concluded that ecological studies on Oncomelania snail were extremely relevant,either to optimally apply the existing control measures or to develop alternative measures for snail control,ecologically or biologically.
RESUMO
Objective To analysis the spatial autocorrelation on the small-scale distribution of the genetic variation in the population of Oncomelania hupensis in Puge county, Sichuan province, using simple sequence repeat (SSR) marker. Methods 5 pairs of SSR primer were used to amplify the genomic DNA of Oncomelania hupensis, and the alleles with frequency ranging from 15% to 85% were used to calculate Moran' s I spatial autocorrelation coefficients in 14 distance band based on equal numbers of paired samples. Results A total of 274 alleles were scored by 5 pairs of SSR primer, the average polymorphic information content of the 274 alleles were 0.965 which indicated a high level of genetic diversity. 39 alleles showed different patterns of positive spatial autocorrelation of genetic variation, which was non-random spatial structure. When the distance band increased, the spatial auto-correlativity decreased based on the average Moran' s I value at 14 distance band. The alleles which showed a negative spatial autocorrelation were not found in any distance band. Conclusion The spatial distribution of the genetic variation of SSR showed positive spatial autocorrelation in the population of Oncomelania hupensis, and the spatial auto-correlativity decreased with the increase of distance band.
RESUMO
<p><b>OBJECTIVE</b>To explore the spatial distribution and elimination of Oncomelania hupensis in mountainous regions.</p><p><b>METHODS</b>Puge County in Tezi township was selected as the study site and the quadratus were placed randomly to investigate snail. The two sods with water were selected as the sites of snail elimination. One sod with area of 1000 m2 and mean density of 9.88 snails/0.11 m2 was selected as the trial group with 'heaping' method, and the other with area of 1000 m2 and mean density of 9.80 snails/0.11 m2 as the control group with sprinkling method. The molluscacidal effect of the two methods was compared by systematic sampling (5 m x 5 m). The sample size was 40 quadratus.</p><p><b>RESULTS</b>The snail distributed mainly in the sods with water, canals and farmlands. Among the three snail habitats, the area with snail was the most in the farmlands with relatively lower density of living snail; the next was the sods with water, with relatively higher density of living snail. Before killing snails, the rate of quadratus with snails was 87.50% in the trial site, and 82.50% in the control site. The mortality of snails was 3.89% in the trial site, and 4.16% in the control site. After three months, no living snails were found in the trial site, while in the control site, the rate of quadratus with snails (chi2 = 0.31, P > 0.05) and the mortality of snails (chi2 = 3.12, P > 0.05) did not decrease significantly, and the density of living snails only reduced by 8.88%.</p><p><b>CONCLUSION</b>The 'heaping' method is an efficacious measure for snail control.</p>