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

本研究旨在弄清不同生物学过程的野生动物体内重金属的分布、与年龄和性别相关的积累，并从比较生物学的角度了解决定这些行为和积累的因素。结果表明：1)与非必需元素相比，由于动态平衡，在各种生物过程中，野生动物体内必需元素的浓度变化一般较小。然而，在动物物种的固有生态和生理方面也发现了一些例外。例如，人们注意到，鳍足类和鲸目动物肝脏中的铁浓度随潜水能力的不同而有很大差异。造成这种差异的最大因素是接触…等元素更多的As、Hg和Cd在海生高等动物中保留得更多，而不是陆生物种。这些有毒元素在具有年龄依赖性积累的长寿生物中保留得更多，但在繁殖和哺乳等生殖过程中的转移不那么突出。在蜕皮过程中，汞的清除很常见，但镉的清除要少得多。对于Cd，与金属硫蛋白的结合可能决定其在野生动物中的可变残留水平和毒性效应。3)在野生动物中也检测了有机金属化合物，特别是汞和锡。有趣的是，人们观察到信天翁等公海水鸟积累的汞浓度非常高。据推测，这些种类的海鸟由于较少的蜕皮频率和较小的将有机汞代谢成无机形式的能力而损失较少的汞。然而，汞的毒性作用在这些水鸟身上没有，可能是由于硒的解毒作用，在它们的体内发现了与汞相应的水平。同时，本研究首次在海洋哺乳动物和水鸟中检测到丁基锡化合物，并明确了其污染在海洋环境中的全球扩散。较少

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