Effects of water pH on chromium toxicity to early life stages of the common carp ( Cyprinus carpio)

Abstract

Immediately after fertilization carp eggs were exposed to Cr(VI) concentrations of 3.9 and 9.6 μmol · l −1 at water pH 7.8 and 6.3. At regular intervals mortality, the incidence of spinal cord deformation, heart rate, tail movements, hatching success, whole body concentration of K, Na, Mg, Ca, and Cr, and ultrastructure of skin and gills were assessed. No effects of Cr on any of the examined parameters were observed at pH 7.8, while 9.6 μmol · l −1 Cr at pH 6.3 decreased total Na concentration of larvae, and increased mortality of the larvae. Skin of larvae (144-h) exposed to 9.6 μmol · l −1 at pH 6.3 showed increased numbers of mucus-secreting cells. The gill epithelium had a wrinkled appearance, and dark circle-shaped spaces, probably of mucus cells, were seen. After 240 h, the larvae were almost completely covered with mucus. In controls at pH 6.3 no significant changes of any of the above parameters were observed when compared to controls at pH 7.8.