Observations of the effect of zinc on the gametes and various development phases of Arbacia lixula

The action of various concentrations of zinc on different phases of development of Arbacia lixula L. has been observed. The following concentrations were used in the experiment: 0.01, 0.1, 1 and 10 mg l^-1; these concentrations were tested on unfertilized eggs, sperms, fertilized eggs and adult individuals. It was found that after 96 h a 0.01 mg l^-1 concentration reduces the mobile sperm percentage compared with the control group. At concentrations of 0.1, 1 and 10 mg l^-1 no mobile sperm were found after 96 h. Compared with the control group, the action of zinc on unfertilized eggs was to increase the percentage of eggs showing signs of cytolisis after 12, 36 and 60 h. In the case of fertilized eggs it was found that with a concentration of 0.01 mg l^-1 the P₅ pluteus stage was attainable; the percentage of forms reaching that stage was less than in the control group. At 0.1 mg l^-1 only a very low percentage of eggs could reach the P₅ pluteus stage; concentrations of 1 and 10 mg l^-1 are incompatible with the normal development of an egg. Adult individuals kept in aquaria with 1 mg l^-1 zinc showed no signs of suffering after 20 d. Gametes are proposed as the appropriate material for carrying out bioassays.