The Study Of Cadmium And Lead Toxicity On The Chinese Mitten-handed Crab, Eriocheir Sinensis

With the development of agriculture and industry, much of contamination including Cd⁺ and Pb⁺ was discharged into water system, which seriously endangered the growth and survival of aquatic animals, which seriously endangered the growth, survival, idioplasm and farming of hydrobiology. In this study, Chinese Mitten-handed crabs(Eriocheir sinensis) were chosen as the reserch object. The growth of the crab, Cd-metallothioneins of crab, the impact of Pb²⁺ on the ultrastructure of hepatopancreas, the effect of heavy metals on digestive enzymes and metabolizable enzymes and the influence of heavy metal on DNA single strand break were studied. The main contents and results were summarized as the following:1. The acute toxicity and joint toxicity test of Pb²⁺ Cd²⁺ to Eriocheir sinensisThe results showed that the LC50 of 48h, 72h and 96h for cadmium to Eriocheir sinensis were 6.83mg/L ,3.98mg/Land 2.23mg/L respectively. The safe concentrations of cadmium was 0.22 mg/L for the crabs. Those for lead were 197.14mg/L , 171.31mg/L and 143.59mg/L , respectively, and the safe concentrations of lead for crabs was 14.36mg/L. The toxicity of cadmium was much higher than that of the lead. In addition, It also indicated that the joint toxicity of Cd²⁺ and Pb²⁺ was obviously synergistic by evaluation using marking additive index.2. The effect of different heavy metal levels on the growth and the digestive enzymes activities of hepatopancreas on Eriocheir sinensisIn this part, the results showed that the death rate of crabs treated with the Pb²⁺ of the lowest concentration, which is 17.1%, while that of crabs under the joint toxicity of the two metals, which is 40.0%. The reseults demonstrated that the changes of digestive enzymes activities in hepatopancreas were different. Different level heavy metal inhibit the pepsin enzymes activities except low level of Pb²⁺. The inhibition effect could be noted on activities of trypsin enzymes. Low level of Pb²⁺ increased amylase and cellulose enzymes activities, while high level Pb²⁺ inhibitedamylase enzymes activities but increased cellulose enzymes activities.3. The effect of Pb²⁺Cd²⁺on the activity of enzymes acetylcholinesterase (AChE),lactate dehydrogenase (LDH) and glutathione-S- transferases (GST) of the Eriocheir sinensisIn this chapter, the effects of cadmium, lead and mixture of both metals on the Chinese Mitten-handed crabs was investigated. The indicative parameters of toxicity were the activity of the enzymes acetylcholinesterase (AChE), lactate dehydrogenase (LDH) and glutathione-S- transferases (GST). Cadmium, lead and mixture of both metals influenced AChE, LDH and GST of hepatopancreas after an exposure of 96h. The result indicated that different level heavy metal increased GST activity before 48h, but inhibited its activity after 48h. Low level cadmium and lead all increased AChE activity at first but inhibited its activity after 48h exposure. High level cadmium and the mixture of heavy metal inhibited AChE activity. LDH activity represent single change. That is to say, the activity of LDH failed during 96h.4. The effect of Pb²⁺ exposure on the ultrastructure of hepatopancreas in theEriocheir sinensisAfter an experimental exposure of Pb²⁺ (15 mol/L) for 30 days, the effects of Pb²⁺ on ultrastructure of the hepatopancreas cells of the Eriocheir sinensis were studied. The result showed that the nuclear membrane changed from spreading all over the place to disintegrated, and the penetration of the mitochondrial outer membrane and inner membrane was changed. The mitochondria showed swelling and vacuolating. Mitochondrial cristae partly disintegrated, then, fully disintegrated. Besides, the Pb²⁺ exposure affected the gross form and the structure of the rough endoplasmic reticulum (RER). At first, the RER became the different size dvesicles,then ,the ribosomes on the little vesicles began to fall, and finally, the RER turned to the concentric round lamellar structures. But the smooth endoplas micreticulum(SER)increase dmarkedly. In...