Research On Effects Of Heavy Metals On Physiology And Ecology Of Cynoglossus Semilaevis Gǖnther

To help define the tolerance of marine environmental stress exerted by heavy metals, embryos, newly hatched larvae, 10-20days after hatching larvae,20-30 days after hatching larvae of Cynoglossus semilaevis Giinther^a kind of high-valued recreationally and commercially harvested flatfishes found along the coast line of China, which grows fast and is an ideal candidate for aquaculture development and stock enhancement programs--were incubated at different levels of copper, mercury, lead, zinc and cadmium solutions, respectively. Embryos incubated at 0.01 mg/L, 0.08 mg/L, 0.1mg/L copper solutions showed low hatching rate, which significantly different from the control (P<0.05), other heavy metals didn't affect the hatching rate of embryos notably, but the newly-hatched larvae in all heavy metals' solutions exhibited significant difference from the control for the high deforming rate. 0.125 mg/L, 0.25 mg/L, 0.5 mg/L cadmium could boost the development speed of embryos, other metals retarded the hatching course by 2⁷ h. Malformation of embryos caused by the metals were observed during the experiment, which different from each other, such as monothphmia, cyclopia, embryo death, larvae have V-shaped, S-shaped, L-shaped vertebral abnormality, the larvae can't hatched from the embryos, and so on. The 50% lethal concentration and safety concentration of these metals of 24 h,48 h,72 h and 96h for newly hatched larvae, 10-20 days after hatching larvae,20-30 days after hatching larvae are calculated to help establish water criterion and protect marine environment. Larvae were sensitive to metals at high concentrations, many died soon after entering the solution. The abnormal larvae affected by the metals showed the curled vertebra and inconsistent swimming behavior.1-year-old Cynoglossus semilaevis Gunther were exposed to 0.1×10^-6mg/L lead,zinc,cadmium,copper solutions for 29 days and 10 days respectively in laboratory.Behavioral alteration has been detected: jerky, uncoordinated, spontaneous and slow movement, boeotian irritability was observed for fish in cadmium and copper solutions as the experiment processed, but different in fish in lead and zinc solutions. Effects of lead,zinc,cadmium,copper on the morphology of gill, kidney, liver and brain were investigated using routine histological technique and light microscope analysis. Cadmium and copper caused more serious lesion: gill lamellae structure completely damaged, pillar cells, mucus cells and chloride cells were not seen; accumulation of numerous droplets of fat and necrosis of hemopoietic tissue in liver; tubular necrosis and hyperplastic tubular cells were seen in kidney. Lead and zinc caused balloonlike appearance in gill basi-lamellae epithelium, shortage in mucus cells and hypertrophy of chloride cells, accumulation of fat droplets in hepatic cells, necrosis of blood cells in kidney and damaged tubules and tubular cells with hyperplasia and hypertrophy. Lesion in spleen and brain were not detected. Combination of abnormal behavior and histological lesion might be an useful way to monitor the heavy metals pollution in marine environment and artificial rearing offish.Histological alterations and Na+-K+-ATPase activity changes in gill of Cynoglossus semilaevis Gunther induced by subchronic copper exposure at different levels were studied in laboratory by combinding light and transmission electron microscope techniques and biochemistry methods. Lesion caused by copper in gill included epithelial changes such as lifting, rupture(vacuols), lamellar fusion, hyperplasia and cellular hypertrophy; mucus cells increased , rupture of pilar cells system, erythrocyte congestion, and so on. Hytrophy and hyperplasia of chloride cells and epithelial cells increased the thickness of the water-blood barrier, which indicated severe impairment of ion regulation and gas transfer of fish exposed to copper. The results of the study indicate that histology is a successful tool capable of revealing sensitively and selectively even the sublethal effects of heavy metals on the environment and aquatic biota. Na+-K+-ATPase activity decreased significantly as the copper concentration increased, showed significant difference from the control (P^ 0.05). Fish exposed to 150 u.g/L exhibited behavioral alteration: uncoordinated and jerky swimming behavior, slow movement and reaction to exterior stimulus wasobserved after 12 days exposure. As the sensitivity and dose-depended relationship between the Naf-K+-ATPase activity and copper concentration in water, it has the potential to be a bio-indicator for copper pollution in aquaculture and marine environment.Routine histological methods and electron microscope technique were combined to investigate the lesion and the changes of several functional enzymes in liver of Cynoglossus semilaevis Giinther after subchronic copper exposure 15 days. The liver experienced variable changes caused by copper: hepatocytes decreased in diameter with abnormal or necrotic nucleus, cytoplasm showed vacuols and accumulation of lot of glycogen, ribosomes fell off the endoplastic reticulum into the cytoplasm, mitochondria enlarged with abnormal shape such as round cake and dumbbell, sinusoids and bile canaliculus damaged with decrease in quatity which indicated an turbulence in fat metabolism, lysosomes manifolded, and so on. Glutamate-oxaloacetate transaminase (GOT), glutamate-pyruvate transaminase (GPT), succinate dehydrogenase(SDH), antioxidant enzymes catalase(CAT), glutathione peroxidase(GSH-Px), superoxide dismutase(SOD), glutathione reductase(GR) activity changes were investigated in vivo in liver following 15 days of copper administration. The specific activities of antioxidant enzyme CAT , GSH-Px and GR was strongly reduced by copper exposure. Meanwhile SOD and GPT activity were strongly stimulated in contrast, whereas the GOT and SDH activity were stimulated notably by 37.5u.g/L copper exposure. As far as the 150 ug/L is concerned, the enzyme activity all decreased slightly. These data suggest that copper in fish hepatocytes altered cell membrane structure and concomitantly induced some perturbation in the liver function. As CAT, GSH-Px, GR activity decreased with the elevated copper concentration in water and the dose-depengded relation to copper concentration, these enzymes would be effective bio-indicators for copper pollution in marine and aquaculture environment.