Distribution of Oncomelania quadrasi in waters in the Philippines
Tanaka, H.; Santos, M.J.; Matsuda, H.; Hambre, R.S.; Iwanaga, Y.; Shimomura, H.; Blas, B.L.; Santos, A.T.
Japanese Journal of Experimental Medicine 48(3): 193-202
1978
ISSN/ISBN: 0021-5031 PMID: 713127 Document Number: 128192
The horizontal and vertical distribution of O. quadrasi, the intermediate snail host of Schistosoma japonicum, was studied in standing and running water habitats using the filter paper sampling method. In the 3 streams surveyed, Vicob-Malaigang stream, Juber creek and Gacao south main canal, snail density was highest at the margin of the water in the sloping bank and in the near-by wet bank. The density of snails became lesser at the higher portion of the moist bank. Snails were also found in the water plants growing from the bank and shallow places close to the bank. In the running water habitat only a few snails were noted on the surface or at the bottom of water. In a shallow Gacao pond with little standing vegetation and where the water is 20 cm at its deepest, no snails were noted although they were abundant in the sloping bank and few in the steep bank. In a portion of the huge water-logged area in Sab-a Basin, it was noted that snails were many in a near-by stream, some in boggy area and only a few at a deep watery portion where only standing vegetation was dense. In a huge water-logged area in Tabontabon, snails were densely accumulated along the moist banks, less only on the surface of accumulated floating vegetation and none below the surface of the floating vegetation, and decreased by the distance from the bank following a regression line between log density and the distance. The density in the moist bank was reduced to 1/10 at a distance of 50 m from the bank. Thus O. quadrasi is not so aquatic in habitat as was presumed before, although it must be more aquatic than O. nosophora in Japan.