Exposure to Waterborne nTiO₂ Reduces Fertilization Success and Increases Polyspermy in a Bivalve Mollusc: A Threat to Population Recruitment

Fertilization success is crucial for the population recruitment of an organism. However, little is known about the threat of nanoparticles (NPs) to the fertilization of broadcast spawners. Therefore, the effects of nTiO₂ on fertilization success, polyspermy rate, sperm velocity, gametic DNA damage, sperm-egg collision probability, gamete fusion, and oocyte ultrastructure were investigated in a broadcast spawning bivalve, Tegillarca granosa. The results obtained show that fertilization success significantly decreased, whereas polyspermy risk markedly increased upon nTiO₂ exposure. In addition, nTiO₂ exposure led to a significant reduction in sperm swimming velocity, which would subsequently constrain gamete collisions. In addition, nTiO₂ exposure resulted in a significant decline in gamete fusion per collision along with aggravated DNA damage in gametes. Furthermore, ultrastructural analysis illustrated the attachment of nTiO₂ to the oocyte surface, which subsequently resulted in microvillus disassociation and plasma membrane damage. In conclusion, the results obtained suggest a significant threat from NP pollution to the recruitment of broadcast spawning invertebrates.