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Seasonal changes in toxicity of Kokai River water to a freshwater shrimp (Paratya compressa improvisa) were monitored from 1989 to 1993. A 4-d toxicity test was conducted three times a week from April to August from 1989 to 1993 to measure mortality. Seventeen pesticides were analyzed during the biological monitoring. Expected shrimp mortalities were calculated by adding mortalities caused by each insecticide at the measured concentrations. Shrimp mortalities increased in late May to mid-June and could be attributed to additive effects of insecticides such as pyridaphenthion, malathion, and fenobucarb. Mortalities decreased toward the end of June but increased again from July to mid-August and could be attributed to insecticides such as diazinon or fenobucarb, which drifted directly into the river after aerial pesticide spraying on paddy fields. High mortalities decreased rapidly after heavy rains in August.

1. The larvae of mayflies (Baetis thermicus) that lived in a metal-contaminated river (the river Ashio in Tochigi, Japan) were collected and the concentrations and distributions of several heavy metals in mayflies were compared with those collected from another metal-contaminated river (the river Mazawa in Yamagata, Japan). 2. Distribution profiles of multi-elements in the supernatant of the mayflies were determined simultaneously on a gel filtration column by the HPLC-atomic emission spectrometry method. 3. Sharp cadmium and copper peaks of comparable intensities were observed at slightly different retention times. 4. The copper peak increased at the expense of cadmium peak by stepwise additions in vitro of cupric ions, the replacement being at a molar ratio of Cu/Cd = 5.35. 5. The replacement of cadmium with copper induced shifts of the sulfur and absorbance peaks at 254 and 280 nm to the original copper peak, indicating that cadmium and copper were bound to the same protein separately.

1. 1. The larvae of mayflies (Baetis thermicus) that inhabited a metal-contaminated river (the river Mazawa in Yamagata, Japan) were collected and the concentrations of several heavy metals in mayflies were compared with those inhabiting a river not contaminated with metals. 2. 2. Cadmium, copper and zinc in mayflies of the contaminated river were 13.4, 18.4 and 15.6 times higher in concentration than those in the non-contaminated river. 3. 3. Distributions of the three metals in the supernatants of the larvae collected from the contaminated and non-contaminated rivers were determined by HPLC-atomic emission spectrometry with inductively coupled argon plasma. 4. 4. Cadmium and copper in the supernatant of the larvae collected from the contaminated river were sequestered by metal-binding components induced for the respective metals, while zinc seemed to be bound loosely to native components.

1. 1. The midge larva ( Chironomus yoshimatsui ) exposed to cadmium (10 μg Cd/ml) for 2 days was histochemically stained with benzothiazolylazo-β-naphthol. 2. 2. A large portion of cadmium taken up by the larvae was distributed to the digestive tract, epithelial tract and fat bodies. 3. 3. Cadmium accumulated in the fat bodies was discharged slowly relative to cadmium in the tract contents when the larvae were placed in control water. 4. 4. Glycogen in the fat bodies of cadmium-exposed larvae was insensitive to PAS staining.

1. Gibels were exposed to cadmium in their aquarium at a concentration of 10 μg Cd/l for up to 39 weeks. 2. Distributions of cadmium, copper and zinc in the liver soluble fraction were determined along with sulfur by high performance liquid chromatography-inductively coupled argon plasma-atomic emission spectrometry. 3. Cadmium was sequestered by the two major isoforms of gibel metallothionein as in the case of cadmium injected intraperitoneally into gibel. 4. Several peaks with cadmium, copper, zinc and sulfur were observed other than the two major isoforms and their relative ratios were different between the control and cadmium-exposed fishes.