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(M/MF203) Influence of sublethal copper concentrations on the energy metabolism of different fish species. van der Ven, Karlijn1, De Boeck, Gudrun1, Gorissen, Wim1, Blust, Ronny1, 1 ABSTRACT- Different freshwater fish, under identical exposure conditions, show species specific differences in resistance to copper. However, the mechanisms underlying these differences are not well understood. We examined differences in sublethal effects of waterborne copper on two freshwater fish: the rainbow trout (Oncorhynchus mykiss) and common carp (Cyprinus carpio). These species were selected because of their differences in hypoxia tolerance since copper can cause respiratory problems. Acute toxicity studies have shown that the most hypoxia sensitive species, the rainbow trout, is more sensitive to copper intoxication compared to the hypoxia tolerant common carp. When exposed to sublethal copper concentrations, the critical swimming speed (Ucrit) of both species decreased. The Ucrit of the rainbow trout recovered but the common carp did not, not even after one month of exposure. Respiration rates dropped in the beginning of the exposure for the carp and showed a slow recovery. In contrast, rainbow trout showed a significant increase in O2-consumption. The discrepancy between swimming capacity and respiration rates indicated that the decreased Ucrit is not only caused by the capacity for O2-uptake, but also by the capacity to allocate and/or depress energy usage for certain physiological processes. To verify this assumption, blood O2- and CO2-levels and electrolytes were monitored through indwelling catheders during copper exposure. The results indicate that blood O2-levels dropped for the carp, while they remained constant for trout. Furthermore osmoregulatory disturbances appeared to be more important in the case of the trout than that of the carp. The combined effect of copper exposure on the Ucrit with the effect on blood physiology and respiration rates indicates that differences in hypoxia tolerance might explain differences in sensitivity to copper exposure. Key words: copper, trout, carp, physiology |
