Effects of calcium and copper exposure on lipogenic metabolism, metal element compositions and histology in Synechogobius hasta

The present study was conducted to evaluate the effects of calcium (Ca) and copper (Cu) exposure on growth performance, metal element composition, enzymatic activities and histology in Synechogobius hasta and tested the hypothesis that Ca could protect against Cu-induced toxicity in the fish species. Three hundred sixty S. hasta (initial mean weight 22.6 ± 0.2 g, mean ± SEM) were stocked in 18 circular fiberglass tanks (water volume: 300 l), 9 of which were pre-exposed to Ca at a rate of 600 mg Ca/l for 10 days and then exposed to concentrations of 0, 77 and 154 μg Cu/l for 30 days. Another 9 tanks were cultured in natural seawater (no extra Ca addition) for 10 days and then exposed to concentrations of 0, 77 and 154 μg Cu/l for 30 days. Both Ca exposure and then waterborne Cu exposure influenced the accumulation of metal elements (Cu, iron, zinc and manganese) in several tissues (muscle, intestine, gill, liver and spleen), changed hepatic lipogenic metabolism and induced histological alterations in liver, gill and spleen. In general, Ca exposure seemed to mitigate the severity of Cu-induced mortality and histopathological injuries, indicating that Ca exposure had the capacity to decrease Cu toxicity in S. hasta. To our knowledge, it is the first study involved in the effects of Ca and Cu exposure on hepatic lipogenic metabolism and metal element compositions in a wide range of tissues and organs in fish, which provides new insight into the protective effect of Ca on toxic metal elements in fish.