Induction of gynogenesis and effects of ultraviolet irradiation on ultrastructure of sperm of the Zhikong scallop Chlamys farreri
Effects of ultraviolet (UV) irradiation on genetic inactivation and ultrastructure of sperm were examined in the scallop Chlamys farreri. UV irradiation of sperm for 30 s at a UV intensity of 256 erg/mm2 per s was the optimum dose to achieve haploid gynogenesis on the basis of observations on rate of cleaved eggs, chromosome constitutions and flow cytometry analysis of the larvae. The rates of cleaved eggs and development of D-shaped larvae decreased with increasing irradiation time, while the survival rate of trochophore larvae improved at UV exposure longer than 20 s, suggesting the presence of a ‘Hertwig effect’ in the gynogenesis of C. farreri. Electron microscopy showed clear destruction of the acrosome, cytoplasmic membrane, nuclear envelope, mitochondrial cristae, and flagellum in the UV-irradiated sperm. Moreover, an irradiation duration of 30 s caused decondensation of sperm chromatin. Abnormalities in these structures might affect the ability of sperm to fertilize the eggs.