An Exploration of Alternative Anesthesia in the Difficult-to-Anesthetize New Zealand Freshwater Snail Potamopyrgus Antipodarum

An effective method for anesthesia is important in terms of minimizing pain and discomfort for research organisms and negative emotions associated with the perception of inflicting pain for the researchers who perform necessary but invasive procedures as part of live-animal studies. Here, I focus on developing a more effective anesthesia method for Potamopyrgus antipodarum, a New Zealand freshwater snail that is an important model system in ecology and evolution. The best available anesthesia method for P. antipodarum, exposure to menthol crystals,only results in successful anesthesia for ~50% of exposed snails. My first objective was to investigate alternative anesthesia approaches: beer, ethanol, Listerine, benzocaine, and clove oil, but none of these methods proved effective. One possible barrier to successful anesthesia outcome may be the ability of P. antipodarumto deploy its operculum, a secreted hard structure that covers the opening of the shell. I investigated this possibility by surgically removing the opercula of a group of snails and comparing the anesthesia outcome to snails with intact opercula. Operculum status did not significantly affect anesthesia success, pointing to other mechanisms underlying variation in anesthesia efficacy. One such potential mechanism is genetic background, which I investigated by comparing the anesthesia outcomes of snails from distinct genetic backgrounds. This study revealed marked variation in anesthesia success across genetically distinct snail lineages, emphasizing that genetic variation likely is a major determinant of menthol anesthesia effectiveness.