Combined toxicities of tributyltin and polychlorinated biphenyls on the development and hatching of Japanese medaka (Oryzias latipes) embryos via in ovo nanoinjection

Tributyltin (TBT) and polychlorinated biphenyls (PCBs) are typical organic pollutants that co-exist in the aquatic environment. Despite increasing awareness of their combined impacts, knowledge about their potential interactive effects remains limited. In this study, we investigated the effects of TBT-PCBs mixtures on the survival, development, and hatching of embryos of Japanese medaka (Oryzias latipes). Our goal was to assess the interactive effects of TBT and PCBs on early-life-stage fish. We used in ovo nanoinjection to simulate the maternal transfer process and to control exposure doses at 0, 7.5, 15, 30 ng/g-egg (for both toxins). A factorial design (4 × 4) corresponding to the above doses was used to define the formulation of mixtures. Results showed that injection of mixtures of TBT and PCBs into fertilized eggs caused significantly elevated rates of mortality, yolk-sac shrinkage, swim-up failure, and deformities of medaka embryos/larvae. TBT and PCBs interacted synergistically to induce the above developmental abnormalities. In contrast, exposure to only TBT increased the hatching times of embryos, whereas exposure to only PCBs decreased the hatching times. The dose ratios, dose levels, and interactive effect of TBT and PCBs in a mixture played significant roles in determining the final impact on time-to-hatching. Our results suggested that in ovo exposure to a mixture of TBT and PCBs may interact synergistically to induce developmental abnormalities in fishes.