| 论文摘要： |
The ionic composition of water is important for all fish. In the present study, the effects of total hardness and Ca2+:Mg2+ ratio on early life stages of rare minnows (Gobiocypris rarus), a promising laboratory fish in China, were evaluated. Paired parent fish were transferred to spawning aquaria (16 L) containing water at different total hardness and Ca:Mg ratios, and their offspring were further cultured at 25 +/- 1 degrees C and 12:12-h light:dark photoperiod. Fertilization rates were not affected by total hardness to 480 mg L-1 CaCO3, but egg size decreased with increasing total hardness. Ca:Mg ratios less than 1:20 or greater than 8:1 had adverse influences on hatching, feeding, development, larval growth, and survival. Embryos and larvae incubated in Mg2+- and Ca2+-deficient waters exhibited high malformation rates and high mortality. Our results demonstrate that rare minnows can adapt to a wide range of total hardness and Ca:Mg ratios, although an imbalance between Ca2+ and Mg2+ in water is toxic to this species. To increase the comparability and usefulness of test results, we recommend the use of reconstituted or drinking water of defined total hardness and Ca:Mg ratio for the culture and toxicity testing of rare minnows. |
