FACTORS DETERMINING THE ACCUMULATION OF HEAVY METALS IN WILD ANIMALS -FROM A VIEWPOINT OF COMPARATIVE BIOLOGY-

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The present study aimed at making clear the body distribution, age- and sex-dependent accumulation of heavy metals in wild animals with various biological processes, and also at understanding the factors to determine those behavior and accumulation from a viewpoint of comparative biology. The following results were obtained in the period of 1994 and 1995 :1) The concentrations of essential elements in the body of wild animals were generally varied less in various biological processes due to the homeostasis when compared with non-essential elements. However, there found some exceptions in the inherent ecology and physiology of animal species. For example, it was noted that Fe concentrations in the liver of pinnipeds and cetaceans greatly varied according to the diving-capacity.2) On the other hand, concentrations of non-essential elements were found to be variable in the different biological processes. The greatest factor for this variation were arisen from the exposure to elements such … More as Hg and Cd which were retained greater in marime higher animals rather than terrestrial species. These toxic elements were retained greater in longer life organisms with age-dependent accumulation, but not so prominent in their transfer in the reproductive processes such as the breeding and lactating. Hg elimination was common in the process of molting, but Cd was a deal less. In case of Cd, the binding with metallothionein were likely to determine its variable residue level and toxic effects in wild animals.3) Organometallic compounds, paricularly Hg and Sn were also examined in wild animals. It was interestingly observed that open ocean waterbirds like albatross accumulated Hg with extraordinalily high concentrations. These species of seabirds were inferred to lose less Hg due to smaller frequency of molting and smaller capacity to metabolize the organic Hg into inorganic form. However, toxic effects of Hg have not been in these waterbirds, probably due to the detoxication by Se which was found with corresponding levels as Hg in their bodies. At the same time, the present study first detected butyltin compounds in marine mammals and waterbirds, and made clear the global dispersion of their contamination in the marine environment. Less