Abstract

Spermio - and embryotoxicities of Hg were investigated in Echinothorix diadema, the dominant echinoid species of the Red sea (Jeddah coast). Spermiotoxicity was studied by assessing the effects of sperm exposure on fertilization rate (FR). Sperm exposures indicated a significant decreases of FR, depending on both metal concentration and duration of exposure. The lowest spermiotoxic concentrations recorded were 5-7 mM when sperm were exposed for 30 min to the metal. The time – dependence of toxicity was short, a 5-min exposure to the toxic concentration of 10-12 mM HgCl2 was sufficient to provoke sperm disability, while 20-30 min, completely inhibited sperm fertilization capacity. Embryotoxicity was studied by assessing the kinetics of first egg cleavage and developmental defects in larvae exposed to the tested metal throughout their development. Studies were carried out on unfertilized and fertilized eggs with the purpose of testing the role of fertilization membrane against the metal. Metal exposure of embryos for 72 hr resulted in developmental defects whose occurrence and severity showed steep dose dependence. Some malformations, such as an exogastrula, deformed larvae and other abnormal forms were induced.

Key words: TOXCIITY, MERCURY, THE SEA–URCHIN, GAMETES, EMBRYOS