A survey of abnormalities was carried out on 5567 C. pyrrhogaster, which were collected in spring and autumn of 1995 in the same area of Japan as that surveyed earlier (in 1981 and 1985). As before, male and female individuals were afflicted in roughly equal proportions and cases of papilloma occurred in 1.6%. However, fewer incidences of limb-, finger-, and toe-abnormalities were recorded. The highest figure was in the autumn collection, but even then only 0.6% of all animals showed morphological abnormalities of the appendages. It is suggested that improvements in water quality and greater environmental awareness by the public could be responsible for the drop in abnormalities.
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