Oncomelania quadrasi, the vector snail of
Schistosoma japonicum in the Philippines, is said to have been found in waters ranging from pH 6.2 to pH 7.8 and on soils ranging from pH 4.6 to pH 7.2 (Pesigan
et al., 1958) . On the pH range conditioning the activity and survival of
O. nosophora, however, very few reports are available.
As to the effect of sea water on the survival of Oncomelania snails, Muto
et al. (1915) and Nagao
et al. (1918) noted that when snails were submerged into sea water experimentally all of them died within 49 hours and 4 to 6 days, respectively. Practically, the habitat of
O. nosophora in Suzunuma district of Shizuoka Prefecture was flooded with sea water in July 1917 and as a result of this almost all snails were found dead (Muto
et al., 1918) . The present report gives data concerning the effect of pH and salinity on the extruding responce and survival of
O. nosophora.
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