Copaifera oleoresins as a novel natural product against acanthocephalan in aquaculture: Insights in the mode of action and toxicity

Abstract

Tambaqui Colossoma macropomum is the main South American fish in continental aquaculture. However, its production has been hampered by acanthocephalan Neoechinorhynchus buttnerae. In this study, we evaluated the antiparasitic potential of five oleoresins (ORs): Copaifera duckei, Copaifera pubiflora, Copaifera reticulata, Copaifera paupera and Copaifera multijuga, as a novel treatment against N. buttnerae, describing their mode of action by histology of the parasite and their toxicity to the host. In in vitro assays, parasites were exposed to three concentrations (0.0467, 0.0934 and 0.1868 mg/ml) of ORs. At the lowest concentration tested (0.0467 mg/ml), none of the ORs had a significant effect on acanthocephalans (p > .05). At the intermediate concentration (0.0934 mg/ml), C. duckei, C. pubiflora and C. reticulata were significantly (p < .05) more effective than C. paupera and C. multijuga. At the highest concentration (0.1868 mg/ml), all species of Copaifera resulted in 100% mortality of the parasites after 24 hr, except C. multijuga. Acanthocephalans killed by the ORs showed generalized vacuolization in the tissues with abnormal accumulation of fluid (remarkable body swelling). We were able to relate the antiparasitic effect of ORs to their composition (ORs with highest concentration of diterpenes were most effective). In toxicity testing, tambaqui were exposed to the three most effective ORs (C. duckei, C. pubiflora and C. reticulata). All were classified as moderately toxic. In vitro and in vivo tests showed that Amazon ORs have the potential to be included in a list of products for therapeutic purposes in aquaculture.