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Organotin compounds have been used as anti-fouling reagents having high toxicity to aquatic organisms. In this study, in order to assess the toxic effects of triphenyltin on fish, potential activities of chymotrypsinogen and trypsinogen in the liver of red sea bream, Pagrus major, and the activities of chymotrypsin and trypsin in the intestine were determined. The red sea bream were exposed to triphenyltin ranging from 0.13μg/l to 3.23μg/l for up to 8 weeks. The potential activities of chymotrypsinogen and trypsinogen in the liver of exposed fish were much lower than those in the control fish, whereas the active forms of these enzymes in the intestine were not affected by the exposure to triphenyltin. The feeding activity of fish exposed to tiphenyltin of 3.23μg/l was depressed. The results of the relationship between diet amounts given and enzyme activities suggested that starvation caused a remarkable decrease in the potential activities of the zymogens in the liver, suggesting the depression of potential activities of the zymogens in the liver of exposed fish was not caused by the change in feeding activity of fish but by the toxic effects of triphenyltin. The potential activities of the zymogens were influenced by the exposure to triphenyltin of 0.13μg/l for 4 weeks.

The effects of cadmium exposure on the concentrations of blood plasma electrolytes (sodium, potassium, calcium, and magnesium) in the carp Cyprinus carpio and the girella Girella punctata were examined. In the carp, all four electrolytes examined decreased significantly after 24-h exposure to 0.3mg Cd/l. The total calcium concentration in plasma decreased significantly during the camdium ex-posure. The depression of the total calcium concentration in plasma depended on the ambient cadmium concentration. The total magnesium concentration in plasma increased significantly after a transient decrease. In the girella, the plasma concentrations of sodium and total magnesium increased significantly and the concentrations of potassium and total calcium showed a tendency to decrease during the exposure to 10mg Cd/l. However, the decrease of the total calcium and potassium concentrations in plasma did not necessarily depend on the cadmium concentration in the seawater. The results of the study suggest that cadmium of high concentrations could increase the electro-lyte permeability of the apical plasma membrane of the obsorption site, and that the uptake of potassium and calcium from water into the body of fish could be particularly inhibited by lower cadmium concentrations.

The Cd toxicity and its accumulation for two species of marine fish were examined at various growth stages. Girella Glarella punctata and goby Chasmichtys dolichognatus fish. The 96-h LC50 for girella at the first growth stage when the mean body weight was 0.18g was 15.7mg/l and this value was considerably lower compared with 25.1, 27.1 and 29.7mg/l in the later three stages. Cd accumulated in juveniles weighing about 0.2-0.3g in the highest concentration for 96h while the concentration in thefish weighing over about 1.0g remained constant. Goby was found to enhance prominently the tolerance to Cd, i.e. the 96-h LC50 increased from 5.5mg/l at 0.021g of mean body weight to 30.5mg/l at 0.211g. The Cd concentration in exposed gobies decreased markedly with the growth in the early juvenile stage and remained a constant level in adult. Those results indicate that girella and goby enhanced markedly their tolerance to Cd in their early juvenile stages, and they had a particular period when this metal was highly concentrated in acute exposure.

To know a physiological role of vitamin in the development of fish eggs, changes in the con-tents of ascorbic acid, pantothenic acid, biotin, niacin and vitamin B6, and activities of glutamic oxaloacetic transaminase (GOT) and glutamic pyruvic transaminase (GPT) in developing rainbow trout eggs were determined. The ascorbic acid content rapidly decreased by half level on third day after fertilization, thereafter the vitamin tended to decrease during development. The sac fry, when a substantial amount of the yolk had disappeared, retained the ascorbic acid and was about one fourth of that of the initial eggs. The amounts of thiamine, pantothenic acid and biotin were reduced by half during the course of development, while niacin content tended to increase after hatching. The amounts of vitamin B6 decreased by about 45% during the course of the development. Some variation of the composition were found: the concentration of pyridoxal decreased appreciably, while those of pyridoxal 5'-phosphate, pyridoxamine 5'-phosphate and pyridoxamine increased in the course of development. The activities of GOT and GPT were very low in the early stages of development. After hatching, the activities of the vitamin B6 enzymes increased greatly.

Cadmium accumulation and its effect on calcium metabolism in girellas were studied during 24 weeks of exposure to sublethal cadmium levels (25 to 250μg Cd/l) in filtered sea water. After the 24 weeks of exposure, the fish were reared in clean sea water for 10 weeks and the removal of cadmium from the bodies was investigated. A large amount of cadmium was accumulated in the livers and kidneys during the exposure. Cadmium levels in the gills and intestines reached to the maximum amount within 8 weeks and remained constant thereafter. Cadmium contents in the gills and intestines decreased remark-ably after the end of the exposure period. The 4 week exposure of girellas to cadmium caused a depression of the serum calcium concentrations in proportion to the cadmium levels in the test water. However, there was no difference between the serum calcium concentrations of the ex-posed fish and those of the control after 16 weeks. Calcium contents in the kidneys after the 24 week exposure showed a tendency to decrease in proportion to the cadmium levels in the test water. The exposure to cadmium had no effect on the calcium contents in the livers, intestines, gills, muscles and vertebrae.