Acrosome Reaction of Sperm in the Mud Crab Scylla serrata as a Sensitive Toxicity Test for Metal Exposures.

In order to test the sensitivity of the sperm cell of the mud crab Scylla serrata to heavy metals, the toxic effects of Ag⁺, Cd²⁺, Cu²⁺, and Zn²⁺ on the acrosome reaction (AR) were studied by artificially inducing the AR of sperm exposed to heavy metals, counting the AR rates by light microscopy, and observing structural changes in sperm by transmission electron microscopy. The AR in S. serrata occurs at two stages. The first stage (ARI) is the eversion of the subacrosomal material. The second stage (ARII) is the ejection of the acrosomal filament. The results showed the EC₅₀ values of the AR based on (ARI + ARII)% for Ag⁺, Cd²⁺, Cu²⁺, and Zn²⁺ were 10.02, 2.14, 13.69, and 2.21 μg/L, and the EC₅₀ values based on ARII % of Ag⁺, Cd²⁺, Cu²⁺, and Zn²⁺ were 1.96, 0.20, 1.46, and 0.34 μg/L. The order of toxicity is Cd²⁺ > Zn²⁺ > Cu²⁺ > Ag⁺ based on the percentage of reacted sperm at the second stage. Sperm cells exposed to heavy metals showed an increased rate of swelling, shape irregularities, and the acrosomal filament of some sperm cells was, crooked, ruptured, and even dissolved. The AR of the sperm cell from S. serrata is more sensitive to the tested heavy metals compared to sea urchin sperm cell toxicity tests. [ABSTRACT FROM AUTHOR]