title: Morphological and ecological studies on Lymnaea natalensis the snail vector of Fasciola gigantica in Egypt.
abstract: Lymnaea natalensis were collected from several localities in Giza Governorate (El-Mansouria, Kafr Hakim and The Nile). The collected snails were examined for cercarial shedding and measurement of shell was carried out using a virner caliper. A total of 217 Lymnaea was collected from all habitats and 24 snails were found to shed Fasciola gigantica cercariae with infection rate 11.1%. The ratio of shell height to shell width (H/W) ranged 1.7-2.1. The ratio between length of aperture to shell height (A/H) was almost constant ranged 0.7-0.8. While the ratio between length of aperture and shell width (A/W) ranged from to 1.8. There was a significant positive correlation between shell height and both shell width and length of aperture (p<0.001). The same relation was clearly indicated between shell width and length of aperture. Also, when the aperture length increased the ratio between height and width increased (p<0.05). While, the following ratios (H/W), (A/H) and (A/W) remained somewhat constant irrespective to the number of whorls. There was a positive correlation between number of whorls and each of aperture length, shell length and shell height. On maintaining L. natalensis in different pH values, the results showed that at pH 3 and pH 11, all snails maintained at these pH values died after one day of maintenance. While snails survived and laid eggs in the range of pH 5-9.
authors.affiliation: Medical Malacology Laboratory, Theodor Bilharz Research Institute, Imbaba, Giza, Egypt.
authors.forename: Shadia M
authors.initials: SM
authors.lastname: el-Dafrawy
mesh_terms: D000818:Animals; D004199:Disease Vectors; D004534:Egypt; D005209:Fasciola / Q000502:physiology*; D005211:Fascioliasis / Q000635:transmission; D006863:Hydrogen-Ion Concentration; D008195:Lymnaea / Q000033:anatomy & histology / Q000469:parasitology* / Q000502:physiology