Eugenol, menthol, and benzocaine as anesthetic and antiparasitic treatments for Cheirodon interruptus (Ostariophysi: Characidae)

Abstract

Anesthetics such as benzocaine, eugenol, and menthol are commonly used in fish in sustainable aquaculture practices. There is growing interest in exploring their beneficial antiparasitic properties. Cheirodon interruptus is a small native freshwater baitfish widely used in Argentina, South America. There is limited literature on the effects of different anesthetic and antiparasitic agents in C. interruptus. Thus, the aim of the present study was to evaluate the anesthetic and antiparasitic effects of benzocaine, eugenol and menthol in C. interruptus. A total of 165 C. interruptus adults were collected from a natural stream of the Salado River basin, Buenos Aires, Argentina. Fish were divided in 15 groups (n = 10) and exposed to different treatments: eugenol 10, 20, 50, 80 and100 mgL−1; benzocaine 20, 50, 80, 110 and140 mgL−1 and menthol 25, 50, 75, 100 and 125 mg L−1. Based on the idea that a good anesthetic induces sedation in less than 180 s and allows recovery in less than 300 s, results indicated that 20 mg L−1 eugenol, 125 mg L−1 menthol and 80 mg L−1 benzocaine meet the requirements for use as good anesthetics in C. interruptus. In addition, their antiparasitic effects were evaluated by assessing differences in the mean abundance of the monogenean Diaphorocleidus sp. Most of concentrations tested showed differences in the mean abundance of Diaphorocleidus sp. Eugenol 20 mg L−1 and benzocaine 80 mg L−1 decreased the parasite mean abundance, whereas menthol 125 mg L−1 showed no significant differences with the controls.