Essential oil of Piper callosum, Piper hispidum and Piper marginatum (Piperaceae) possesses in vitro efficacy against monogeneans of Colossoma macropomum (tambaqui)

The in vitro efficacy of the essential oil of Piper callosum, Piper hispidum and Piper marginatum against monogeneans and the tolerance of Colossoma macropomum to these oils was assessed. Concentrations of these essential oils were tested, and two control groups were used: one with water from the cultivation tank only and the other with water from the cultivation tank + 70% alcohol, the solvent for these essential oils. For all the concentrations of P. callosum, 100% efficacy against Anacanthorus spathulatus, Notozothecium janauachensis, Mymarothecium boegeri and Linguadactyloides brinkmanni occurred after 5 min of exposure. At concentrations of 600 and 800 mg/L of P. hispidum, 100% in vitro efficacy occurred after 20 min of exposure. At concentrations of 200, 300 and 400 mg/L of P. marginatum, 100% efficacy occurred after 1 h of exposure. In the control groups using water from the tank + alcohol, the total immobilization of the monogeneans varied, while in the control groups with water from the cultivation tank, the total immobilization of monogeneans only occurred after 9 h of exposure. Little structural damage to the tegument of the parasites exposed to P. callosum, P. hispidum and P. marginatum was observed on scanning electron microscopy. The tolerance of C. macropomum for P. callosum, P. hispidum and P. marginatum was assessed and discussed. The results suggest that the essential oils of P. callosum, P. hispidum and P. marginatum possess high in vitro efficacy against monogeneans of C. macropomum and thus require testing in therapeutant baths for use in aquaculture.