Amino-nanopolystyrene exposures of oyster (Crassostrea gigas) embryos induced no apparent intergenerational effects.

Early life stages (ELS) of numerous marine invertebrates mustcope with man-made contaminants, including plastic debris, during their pelagic phase. Among the diversity of plastic particles, nano-sized debris, known as nanoplastics, can induce effects with severe outcomes in ELS of various biological models, including the Pacific oyster Crassostrea gigas. Here, we investigated the effects of a sub-lethal dose (0.1 µg mL-1) of 50 nm polystyrene nanobeads (nano-PS) with amine functions on oyster embryos (24 h exposure) and we assessed consequences on larval and adult performances over two generations of oysters. Only a few effects were observed. Lipid analyses revealed that first-generation (G1) embryos exposed to nano-PS displayed a relative increase in cardiolipin content (+9.7%), suggesting a potential modification of mitochondrial functioning. G1-larvae issued from exposed embryos showed decreases in larval growth (-9%) and lipid storage (-20%). No effect was observed at the G1 adult stage in terms of growth, ecophysiological parameters (clearance and respiration rates, absorption efficiency), or reproductive outputs (gonadic development, gamete quality). Second generation (G2) larvae issued from control G1 displayed a significant growth reduction after G2 embryonic exposure to nano-PS (-24%) compared to control (as observed at the first generation), while no intergenerational effect was detected on G2 larvae issued from G1 exposed embryos. Overall, the present experimental study suggests a low incidence of a short embryonic exposure to nano-PS on oyster phenotypes along the entire life cycle until the next larval generation.

Nanopolystyrene beads affect motility and reproductive success of oyster spermatozoa (Crassostrea gigas).

Oysters are keystone species that use external fertilization as a sexual mode. The gametes are planktonic and face a wide range of stressors, including plastic litter. Nanoplastics are of increasing concern because their size allows pronounced interactions with biological membranes, making them a potential hazard to marine life. In the present study, oyster spermatozoa were exposed for 1 h to various doses (from 0.1 to 25 µg mL-1) of 50-nm polystyrene beads with amine (50-NH2 beads) or carboxyl (50-COOH beads) functions. Microscopy revealed adhesion of particles to the spermatozoa membranes, but no translocation of either particle type into cells. Nevertheless, the 50-NH2 beads at 10 µg mL-1 induced a high spermiotoxicity, characterized by a decrease in the percentage of motile spermatozoa (-79%) and in the velocity (-62%) compared to control spermatozoa, with an overall drop in embryogenesis success (-59%). This major reproduction failure could be linked to a homeostasis disruption in exposed spermatozoa. The 50-COOH beads hampered spermatozoa motility only when administered at 25 µg mL-1 and caused a decrease in the percentage of motile spermatozoa (-66%) and in the velocity (-38%), but did not affect embryogenesis success. Microscopy analyses indicated these effects were probably due to physical blockages by microscale aggregates formed by the 50-COOH beads in seawater. This toxicological study emphasizes that oyster spermatozoa are a useful and sensitive model for (i) deciphering the fine interactions underpinning nanoplastic toxicity and (ii) evaluating adverse effects of plastic nanoparticles on marine biota while waiting for their concentration to be known in the environment.