Essential oil of Piper marginatum (Piperaceae) against monogeneans, and its hematological and histopathological effects on Colossoma macropomum

Abstract Purpose This study investigated the anthelmintic efficacy of therapeutic baths with the essential oil of Piper marginatum against the monogeneans Anacanthorus spathulatus, Notozothecium janauachensis, Mymarothecium boegeri and Linguadactyloides brinkmanni in Colossoma macropomum, and its hematological and histopathological effects on this fish. Methods Six therapeutic baths with 100 mg/L of the essential oil of P. marginatum and two control groups (water from the cultivation tank and water from the cultivation tank + 70% alcohol) were used for 20 min every two days. Results The therapeutic baths with 100 mg/L of the essential oil of P. marginatum had efficacy of 42.8% against monogeneans of C. macropomum gills. Toxicity was low for C. macropomum, because there were few physiological and histopathological changes that did not compromise the functioning of the gills of this fish. Conclusion Short therapeutic baths with 100 mg/L of the essential oil of P. marginatum had low efficacy for controlling monogeneans in C. macropomum and thus cannot be recommended.