Immersion in clove oil with and without ethanol does not result in consistent anesthesia in mystery snails (Pomacea bridgesii)

Objective: To evaluate clove oil (CO) as an immersion anesthetic agent in mystery snails (Pomacea bridgesii). Methods: Initial pilot trials evaluated CO (0.2 to 1 mL/L) and CO combined with ethanol (CO-E; 0.05 to 4 mL/L and 10 to 50 mL/L) in 40 mystery snails. Subsequently, a randomized, blinded, complete crossover study compared CO 0.5 mL/L and CO-E 0.5 and 10 mL/L in 28 snails. Results: CO 0.5 mL/L resulted in 11 of 24 anesthetized with a median time to anesthesia of 30 minutes (20 to 85 minutes), time to first movement of 89 minutes (9 to 175 minutes), time to full recovery of 325 minutes (168 to 1,200 minutes), and median heart rate of 30 beats/min (20 to 40 beats/min). CO-E 0.5 mL/L and 10 mL/L resulted in 9 of 21 anesthetized. Adding ethanol to the CO immersion bath did not produce any significant differences in anesthetic parameters compared with CO alone. However, CO-E resulted in a 21% mortality rate (5 of 24) compared to 5% (1 of 21) with CO treatment. Gill necrosis was evident in all snails that died following CO-E anesthesia. Conclusions: CO is a safe but inconsistent anesthetic agent for mystery snails at 0.5 mL/L, whereas CO 0.5 mL/L combined with ethanol 10 mL/L is not a safe anesthetic protocol in this species. Clinical Relevance: While CO is frequently used interchangeably with eugenol, it is less effective than eugenol as an anesthetic in mystery snails, and combining it with ethanol resulted in high mortality.