标题：Observations on the distribution of freshwater mollusca and chemistry of the natural waters in the south-eastern Transvaal and adjacent northern Swaziland
摘要：An extensive survey of the molluscan fauna and of the chemistry of the freshwaters of the Eastern Transvaal Lowveld has revealed no simple correlation between the two. The waters fall into four fairly distinct and geographically associated groups chiefly characterized by their calcium and magnesium content. The frequency of the two intermediate hosts of bilharziasis was found to be roughly proportional to the hardness of the water but as the latter, in this area, is associated with altitude and this again with temperature and stream gradient it is thought highly probable that the distribution of these snails is the result of the interaction of a complex of factors. None of the individual chemical constituents in any of the waters examined is regarded as outside the tolerance range of these snails. It is also concluded that under natural conditions this area would have had few waterbodies suitable for colonization by these snails but that the expansion of irrigation schemes has created ideal conditions for their rapid establishment throughout the area. Full text Full text is available as a scanned copy of the original print version. Get a printable copy (PDF file) of the complete article (6.1M), or click on a page image below to browse page by page. Links to PubMed are also available for Selected References . 389 390 390-1 390-3 390-5 390-7 390-9 391 392 393 394 395 396 397 398 399 400
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