食物連鎖における有害物質の移行 Ｖ ヒメダカにおけるカドミウムの排出

Abstract

Two series of rearing experiments were undertaken for the check of accumulation and ex-cretion of cadmium (Cd) on Himedaka Oryzias latipes. In one of two series, 10 fish of Himedaka (average length, weight, and contont of Cd were 2cm, 0.2g, and 0.25ppm, respectively)took 3-10 ppm of Cd in each body within 20-24h ofrearing in the experimental solution including 1.1 ppm of Cd. In other series, during the rearing of 10 fish of Himedaka in the pure solution, 15, 000 of Artemia salina LINNAEUS having 19 ppm of Cd were fed into the pure water for 20 min. In the case of 5h, two feeding of 15, 000 of the Artemia into the pure solution, 3 ppm of Cd was accumulated in the fish body. The Anemia as the feeding material, which had 19 ppm of Cd in the body, contained 2-4 ppm of Cd. By using both Cd-accumulated fish, the rate of Cd excretion was examined in the pure water after 72h of rear-ing. In both accumulations of Cd via branchial and via oral, the excretion of Cd occured im-mediately after the transfer of fish into the pure water. The excretion of Cd was especially ob-served as the decrease of letter L curve on the fish containing above 3 ppm of Cd. The concentra-tion of Cd in the fish body decreased to 1-3 ppm after 72h of rearing with pure water, Cd accumulated via oral intake excreted outside the fish body much faster than that of via branchial accumulation. The rate of fatality was lower in the fish with oral intake than that of branchial intake, even if the content of Cd in the body was the same at both intakes. The rate of fatality was also low in the Himedaka which contained high amount of Fe in the body.