SPERMIOTOXICITY AND EMBRYOTOXICITY OF HEAVY-METALS IN THE ECHINOID PARACENTROTUS-LIVIDUS

Spermio- and embryotoxicities of Cu, Ag, Cd, and Hg were investigated in Paracentrotus lividus, the dominant echinoid species of the Mediter ranean. Spermiotoxicity was studied by assessing the effects of sperm exposure on fertilization rate (FR) as well as on the induction of tra nsmissible damages to the offspring. Embryotoxicity was studied by ass essing developmental defects in larvae exposed to the tested metals th roughout their development. Sperm exposures resulted in significant de creases of FR, depending on both metal concentration and duration of t he exposure. Lowest spermiotoxic concentrations recorded when sperm we re exposed for 75 min to the metals were 10(-7) M Hg(II), 10(-6) M Ag( I), 10(-5) M Cu(II), and 10(-5) M Cd(II). Tested metals did not exert any transmissible damage to spermatozoa that could result in larval ma lformations in the offspring, even for concentrations that dramaticall y reduced FR. Single-element exposures of embryos for 72 h resulted in developmental defects whose occurrence and severity showed a steep do se dependence, indicating that once a threshold is reached, any furthe r increase in toxicant concentration rapidly enhances the impairment o f target function(s). Those observations suggest the involvement of a saturable protective mechanism. Lowest observed embryotoxic concentrat ions of the metals were 10(-7) M Hp(II), 2.5 X 10(-7) M Ag(I), 5 X 10( -7) M Cu(II), and 10(-5) M Cd(II) and are in the range of concentratio ns reported in heavily polluted marine environments. Thus, the possibi lity of impairment of echinoid development actually exists in metal-co ntaminated marine environments, possibly threatening echinoid populati ons in those environments.