STUDIES ON STRESS RESPONSE OF AQUATIC ORGANISMS AND ASSESSMENT OF EFFECTS OF AQUATIC FACTORS THROUGH FOOD CHAIN

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In order to detect systematically responses of aquatic organisms to environmental factors effects of chemicals in the aquatic environment and genes expressed by those factors were studied using arsenate as a model chemical.1) High sensitive and resistant strains of Clamydomonas were isolated by using random insertion mutation method. The resistant strains scarecely accumulated arsenic. In the case of resistant strain, AR3, deleted a part of low affinity-phosphate transportor which incorporates competitively arsenate.It has been clarified that arsenic induces methylation in various kinds of aquatic organisms. The strain with high rate of incorporation of arsenate was incubated with arsenic and organic arsenic was analyzed by GC-MS.Dimethyl arsenic was detected in this Clamydomonas.2)In order to examine the mechanism of resistancy against arsenate incorporation of arsenate into Chironomus was examined. Upon treatment with 0.5mM arsenate body arsenic reached maximum at 6hr of incubation followed by gradual decrease. Incubation with 1.0mM arsenate resulted in rather small arsenic content. In Chironomus methylated arsenic compund was not detected. These results suggest that some detoxic mechanism other than methylation operates in this species.3)In marine mullusca arsenic is accumulated abundantly. Major arsenic compound, arsenobetaine was degraded by microorganisms into trimethylarsine oxide in the muscle of this organism.