RESUMEN
Objective To observe the morphological changes in the testes and ovaries of adult 12th-generation Oncomelania hupensis bred for 12 winters in Weishan Lake areas. Methods The offspring of the adult O. hupensis snails bred in the Weishan Lake that were originated from the Yangzhou section of the Yangtze River was defined as the experiment group, while uninfected, adult O. hupensis snails captured from the marshland of the Yangzhou section of the Yangtze River served as the control group. Snails were dissected and intact testicular and ovarian specimens were sampled, routinely fixed, dehydrated, embedded, polymerized in an oven and sliced on an ultramicrotome. The sections were visualized under a transmission electron microscope, and the ultrastructure of the snail gonad was compared between the experiment and control groups. Results Transmission electron microscopy showed “9 + 2” microtubules on the transverse sections of the tails of sperm cells in the testes of male snails in the control group, with triangular acrosomes and spiral, dense nuclei seen in the tip, while in the experiment group, the “9 + 2” microtubules disappeared on the transverse sections of the tails of sperm cells in the testes of male snails, with low chromatin density found in the tip. Transmission electron microscopy revealed clear nucleolus and nuclear membranes in the ova of female snail ovaries, and displayed yolk body, liposomes and endoplasmic reticulum in the cytoplasm, bilayer twists of nuclear membrane and a uniform nucleolus in the control group, while in the experiment group, smooth nuclear membrane and unclear nucleolus were observed in the ova of female snail ovaries, with few contents seen within cells. Conclusions Following breeding for 12 winters in the Weishan Lake, the 12th-generation O. hupensis snails fail to fully adapt to the natural environment in northern China, and the remarkable changes in the ultrastructure of the snail gonad may be a cause of gradual decline and even extinction of O. hupensis in the Weishan Lake areas.
RESUMEN
Objective To explore the shape change characteristics of Oncomelania hupensis snail shell after the snails being passively migrated into Shandong intake area of the South-to-North Water Diversion Project. Methods The snails raised on the Dushan island in Weishan Lake region were captured,and 115 the first filial generation snails and 107 the second filial generation ones were selected. The length and width of shells and apertures,and the labial ridge thickness of those snails were measured,the longitudinal rib number of snail spiral was counted,and 107 parental snails were chosen as controls. Results The labial ridge thickness of the filial generation snail was significantly reduced with the increase of algebras,and the labial ridge thickness among the 3 generations had a significant difference(P<0.01). Both the length of snail shell and the width of snail apertures were de-creased,while the width of snail shell,the length of snail apertures,the multiplication product of snail aperture’s length and width and the longitudinal rib number of snail spiral were all increased. Conclusion The body size of Oncomelania snails in Weishan Lake region becomes smaller,and their shells become thinner,which indicates that the environment of the lake region is not suitable for snail breeding,and the snails have natural decay tendency with the extension of time.
RESUMEN
To understand the possibility of schistosomiasis transmission on the East Route Project of the South-to-North Water Diversion Project, a survey of endemic status of schistosomiasis in Weishan Lake area was conducted. A cluster sampling of 2086 boatmen were screened with DDIA Kit, and the positive ones were examined with Kato-Katz technique. Meanwhile, a questionnaire survey about schistosomiasis control was carried out to collect the data about the boatmen's general information and knowledge , attitude and practice (KAP). The results showed there were no schistosomiasis patients. However, there exist potential risk factors for schistosomiasis transmission because of the bad hygiene habits and the poor knowledge of schistosomiasis prevention in boatmen.