Effects of mercury accumulation on the electrophoretic patterns of the serum, haemoglobin and eye lens proteins of Tilapia mossambica (Peters)

Abstract

Two test concentrations of mercury (0.01 and 0.04 ppm) were used for studies on the uptake of mercury by the tissues and alteration in the electrophoretic patterns of blood serum, haemoglobin and eye lens proteins. Haemoglobin showed an increase in protein in the faster moving band. Significant changes were seen in the patterns of serum protein with respect to number, mobility and intensity of the protein fractions in the fish exposed to higher concentration of mercury (0.04 ppm). The patterns of eye lens protein were quite constant throughout the period of exposure. Short-term experiments on the fish serum electrophoresis were carried out using higher concentrations of mercury in the medium (0.4, 0.6 and 0.8 ppm). These were just below the lethal level. Sampling was done at 3, 24, 48 and 72 h intervals. From 24 h onwards there was a significant increase in the intensity of the lower mobility bands and there was a decrease in the higher mobility bands. After 48 and 72 h, a distinct extra band was seen between the first two fast-moving bands at all the three high concentrations of mercury used. These patterns were very similar to the pattern observed with the lower concentration of mercury in the medium (0.04 ppm) after the 11th week exposure period, which was found to affect the survival or growth potential of the fish. This study shows that exposure to a large amount of mercury over a short period has an effect similar to small amounts over a long period. The serum electrophoretic patterns obtained after 48 and 72 h exposures to sublethal concentrations of mercury, and which were similar to the one obtained in 0.04 ppm mercury concentration after the 11th week exposure period, can be regarded as the "stress pattern" of T. mossambica serum. The use of fish blood morphology as a biological index of water quality has been indicated.