Effects of rutile titanium dioxide nanoparticles (nTiO2) on reproduction in the broadcast-spawning sea urchin Heliocidaris erythrogramma armigera

Despite increasing evidence of adverse effects of titanium dioxide nanoparticles (nTiO 2 ) on various biological processes, their impacts on many aquatic ecosystems, where nTiO 2 pollution is steadily increasing, remain largely unknown. For aquatic organisms with external fertilisation, reproductive stages are likely to be especially vulnerable to nTiO 2 toxicity, given that gametes and developing embryos are directly exposed to contaminants. Here, we investigated the effects of the rutile crystalline form of nTiO 2 at environmentally relevant concentrations of 5, 10 and 50 μg l -1 on reproduction in the sea urchin Heliocidaris erythrogramma armigera . We examined the key motility traits of sperm using computer-assisted sperm analysis and assessed fertilisation rates after exposure of gametes to nTiO 2 . Furthermore, we examined embryo survival in 2 distinct exposures to discern whether exposure of sperm to nTiO 2 prior to fertilisation or direct exposure of the developing embryos to nTiO 2 affects embryo survival. We found no significant effect of nTiO 2 on sperm motility, fertilisation success or embryo survival when embryos were directly exposed to nTiO 2 . However, embryo survival was reduced when sperm was exposed to nTiO 2 prior to fertilisation, highlighting the need for an extended assessment of the risk of nTiO 2 for this and other broadcast-spawning species.