A Comparison of Buffered Tricaine Methanesulfonate (MS-222) and Isoeugenol Anesthesia for Caudal Fin Clipping in Zebrafish (Danio rerio).

The purpose of this study was to compare the safety and efficacy of buffered tricaine methanesulfonate (MS-222) and isoeugenol for the anesthesia of zebrafish undergoing caudal fin clipping. Eighty 9 mo Danio rerio (AB strain) zebrafish were allocated to one of 2 equal groups: buffered MS-222 (168 mg/L, n = 40) or isoeugenol (20 mg/L, n = 40). The time to induction of anesthesia was significantly shorter in the isoeugenol group (141 ± 70 s) than in the MS-222 group (207 ± 103 s). The time to recovery from anesthesia was also shorter in the MS-222 group (373 ± 125 s) than in the isoeugenol group (491 ± 176 s). No obvious displays of distress or aversion to anesthesia were observed in either group. No difference was detected in the proportion of zebrafish that became anesthetized with either drug. One male zebrafish in the buffered MS-222 group was found dead at the 1-h post-procedural monitoring time point, but there was no difference between groups in the proportion of fish that survived anesthesia to the end of experiment. In conclusion, the safety and efficacy of buffered MS-222 (168 mg/L) and isoeugenol (20 mg/L) was similar for zebrafish undergoing anesthesia for caudal fin clipping.