Trophic transfer of carbon nanofibers among eisenia fetida, danio rerio and oreochromis niloticus and their toxicity at upper trophic level

Abstract

Although the toxicity of carbon-based nanomaterials has already been demonstrated in several studies, their transfer in the food chain and impact on the upper trophic level remain unexplored. Thus, based on the experimental food chain “Eisenia fetida → Danio rerio → Oreochromis niloticus”, the current study tested the hypothesis that carbon nanofibers (CNFs) accumulated in animals are transferred to the upper trophic level and cause mutagenic and cytotoxic changes. E. fetida individuals were exposed to CNFs and offered to D. rerio, which were later used to feed O. niloticus. The quantification of total organic carbon provided evidence of CNFs accumulation at all evaluated trophic levels. Such accumulation was associated with higher frequency of erythrocyte nuclear abnormalities such as constricted erythrocyte nuclei, vacuole, blebbed, kidney-shaped and micronucleated erythrocytes in Nile tilapia exposed to CNFs via food chain. The cytotoxic effect was inferred based on the smaller size of the erythrocyte nuclei and on the lower “nuclear/cytoplasmic” area ratio in tilapia exposed to CNFs via food chain. Our study provided pioneering evidence about CNFs accumulation at trophic levels of the experimental chain, as well as about the mutagenic and cytotoxic effect of these materials on O. niloticus.