ESTOGENIC ACTIVITY OF RIVERWATER AND FEMINIZATION OF WILD CARP IN JAPAN

摘要

Endocrine disruptors (EDs) have been suspected to cause feminization of wild fish in rivers of the UK, the US and Japan. Although the estrogenic activity was detected in many Japanese river waters, what this signifies in terms of feminization of fish is unclear. This study examined feminization of wild common carp (Cyprinus carpio) living in the rivers in terms of vitellogenin induction and occurrence of the testicular abnormality. Among 551 male carp that were captured, 26.1% exceeded 0.1μg/mL of plasma vitellogenin. The testis of the male carp was apparently and histologically observed. Abnormality of the testis was identified from 12.9% of the male carp. Occurrence of vitellogenesis and testicular abnormality in the wild male carp differed among the locations. To understand the cause of difference in the locations, correlation analysis of the occurrence of vitellogenesis and the testicular abnormality was conducted based on the concentrations of 4-toctylphenol, nonylphenol, bisphenol A, 17 b-estradiol (ELISA) and estrogenic activity of river water and sediment. A positive relationship between the average estrogenic activity of the river water and the ratio of the male carp whose serum vitellogenin was detected, which implies that increase in the estrogenic activity increases the ratio of the male carp whose serum vitellogenin concentrations exceed 0.1μg/mL. However, less significant relation was observed between the estrogenic activity of the river water and occurrence of the testicular abnormality of the male carp. This difference might be derived from the following reasons: the estrogen-like activity of water can reversiblely induce vitellogenin in adult male carp, while abnormality of testis of the male carp might be caused by complex factors and during crucial embryonic period. The vitellogenesis in the wild male carp due to the estrogenic activity of river water seemed more frequently occurs than the case of exposure of the male carp to the estrogenic activity of secondary effluent. This suggests acceleration of induction due to food-web route in river waters.