Toxicity Effects Of Water-borne Cadmium On Cypridopsis Vidua (Crustacean Ostracoda)

China has vast territory, including large of waters, but many researchers found that most of all have some degree of water pollution, many of them seriously suffered heavy metals pollution with the development of industries and agriculture, which affected the normal activities of human. Therefore, it is quite important to find an effective biology to monitor water environmental protection and environmental resources to provide a theoretical basis for rational use. In recent years, the use of aquatic biology to monitor the health of the water environment has become a very popular and practical way. The author chose Cypridopsis vidua (Muller O F,1776), a comprehensive ostracoda, as an investigative object to investigate the damage of organism and the effects of toxicity of Cd2+by the mean of the experiments of acute toxicity and subacute toxicity colligate with microscopic and submicroscopic observation. The data of this experiment would supply some theoretical evidences in using water organisms as water environmental evaluation.一Acute toxic effects of Cd2+on C. vidua (Crustacean Ostracoda)The toxic effects of Cd+on C. vidua and its intestinal ultrastructure were studied with a static renewal system in this paper. The results indicated that the LC5o values of cadmium for C. vidua were 5.00,2.01,0.46 and 0.14 mg/L at 24,48,72 and 96 h exposure respectively, and the safe concentration range of cadmium for long-term survival of C. vidua was less than 0.014 mg/L. It is nearly three times higher than the national standard value of Cd2+concentration for water quality in fish production: <0.005 mg/L (Water Quality Standard for Fisheries of China, GB11607-89), and slightly higher than the national standard for the relevant water quality type V<0.01 mg/L (National Surface Water Environmental Quality Standard, GB3838-2002). This suggested that C. vidua had a very high tolerance to Cd2+pollution, and the process of toxicity effects of Cd2+is slow in this specie body. So Cd2+has much more opportunity to enrich in C. vidua, and enters the food chain through this animal predated. A significant turning point was found at 72 h for the half-lethal concentration of Cd2+on C. vidua (see Figure 1)with the prolonging of experimental time, namely, the change in the curve of the LC50 value for Cd2+was gradually parallel to the time axis, which indicated that the remaining survival ostracods had a high tolerance to Cd2+and some kind of detoxification mechanism on Cd2+might emerge in the organism. Therefore, these results would provide a frame of reference for exploring the mechanism of the toxicity of Cd2+and detoxification mechanism.二Subacute toxic effects of Cd2+on C. vidua(Crustacean Ostracoda)Ostracoda, a small crustacean, haven't gills to exchange air. With hard, waxy and chitinous exoskeleton, the ions hardly penetrated the body from skin, so the gastrointestinal tract become the majority way of Cd2+into the body. Therefore, the structure of gastrointestinal tract was chosen to observe in the subacute experiment.1. Effects on the structure of microscope observations on intestinal cells of C. viduaIn order to find toxicity effects of water-borne cadmium on C. vidua's gastrointestinal tract and other organs, two groups between the fatal concentration gradients and survival concentration gradients were set in the subacute toxic experiment at the basis of acute toxic experiment. The results showed that the structures of ostracoda changed in different concentrations in the subacute fatal toxicity. The morphous of ostracoda had obviously changed during subacute toxicity for 7 days in water-borne cadmium. It appeared time effect and dose effect. Compared with the controls, as following time and dose, the majority injury was gastrointestinal tract, another was multilayer cellular formations. In the high concentrations(5 mg/L), the number of dead increased quickly, the injury of gastrointestinal tract became seriously, even fractured and broke down. Multilayer cellular formations fell off in some content. There were many liquid droplets and vacuoles. During the toxic experiment, the injury of gastrointestinal tract was quite obvious during a week, from completed structure to breakdown. The other group, near the security concentration, the structures also had some changed, below the security concentration, the structures basely kept completed, however, after surpassing SC, the structures also damaged in some content, but during a week, there wasn't dead animals, the structures nearly kept regular. This result indicated that Cd2+mainly destroyed C. vidua's gastrointestinal tract because Cd2+couldn't get into C. vidua's body through skin or mucous membrane except gastrointestinal tract as a result of C. vidua's hard exoskeleton.2. Effects on the ultrastructure of electron microscope observations on intestinal cells of C. viduaAnother two concentrations(0.004 and 0.064 mg/L)near the safety concentration were chosen and a blank was set for subacute toxic experiment for a week. The ultrastructure results showed the different degree of structure damages were found on the cell membrane, cytoplasm, organelle, etc., which was becoming worse with the increasing of the Cd2+concentrations. Compared to the controls, in the low concentration, the external membrane expanded slightly, the gap between cells extended, many karyotins gathered; In the high concentration, the internal and external membranes were injuried seriously, even breakdown, karyotin also gathered and fractured, many vacuoles in endoplasmic reticulum appeared, the number of mitochondrion decreased.