Abstract: Cypridopsis vidua is one of the few ostracods which can surrive from heavy pollution water. The toxic effects of Cd²⁺ on C. vidua and its intestinal ultrastructure were examined using a static renewal system. The LC₅₀ values for cadmium in 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 of Cd²⁺ for long-term C. vidua survival was less than 0.014 mg/L. To observe the structure changes of its intestinal, four Cd²⁺ concentrations were set up, and two of them were below the safe concentration of Cd²⁺ (0.001 and 0.004 mg/L) and the other concentrations were above its safe concentration (0.016 and 0.064 mg/L). The experiment lasted for 7 days. When microstructure of C. vidua was observed, the gastrointestinal orga- nization was not damaged below the safe concentration; while the degree of injury showed a certain amount of time and dose effects in 24-72 hours above the safe concentration, and some structures among those surviving animals were slightly recovered in 7 days under same concentration. Sub-microscopic analysis of intestinal cells of C. vidua in two concentrations (0.004 and 0.064 mg/L) groups showed, different degrees of structure damage were found in the cell membrane, cytoplasm and organelles, which worsened with increasing Cd²⁺ con- centrations. Among these cellular structures, the damage to the membrane system of the cell was especially serious.

Key words: Ostracoda, Cd²⁺, acute toxicity, intestinal ultrastructure