Fertilization and larval development in sea urchins following exposure of gametes and embryos to cadmium

Abstract

The gametes and embryos of three sea urchin species were exposed to cadmium chloride at concentrations ranging from 10⁻⁸ M to 10⁻³ M. When zygotes were reared in the presence of Cd²⁺, skeletal differentiation displayed some severe abnormalities or was suppressed, as a function of Cd²⁺ level. The embryotoxic action of Cd²⁺ was inversely related to salinity and to Ca²⁺ concentration. Cadmium-exposed larvae displayed similar abnormalities if Cd²⁺ was present throughout development or only after hatching, while pre-hatching exposure produced no developmental defects. No aberrations in mitotic figures were observed in cleaving eggs following acute exposure to Cd²⁺. The pretreatment of sperm or eggs did not affect the ensuing development of embryos, both for acutely toxic Cd²⁺ levels (up to 10⁻²M), and for prolonged exposures in relatively low Cd²⁺ levels. The fertilization rate was differently affected depending on whether sperm or eggs were pretreated;i.e., the exposure of eggs to Cd²⁺ promoted fertilization at relatively high Cd²⁺ levels. If sperm was exposed to Cd²⁺, a depression of fertilizing capacity was observed at high Cd²⁺ levels, while lower Cd²⁺ levels, displayed an opposite action, resulting in an increase in fertilization rate after prolonged sperm exposure.