Anesthesia in echinoderms: an experimental study of efficacy based on behavioural and cellular stress responses

• Main Author: Carter, Jillian
• Format: Text
• Language: unknown
• Published: Memorial University of Newfoundland 2023
• Subjects: Cucumaria frondosa
• Online Access: https://research.library.mun.ca/15978/

While invertebrates make up most of the biodiversity on Earth, they remain understudied and have received limited attention relative to vertebrates when it comes to the complex issues of anesthesia. There is a knowledge gap that exists about whether and how invertebrates feel emotions or pain, therefore, animal care committees are often ambiguous on the need for anesthetics while performing experimental procedures on invertebrate taxa. Most of the anesthetics currently used for invertebrates have been adapted from protocols developed for vertebrates, under the unverified assumption that they are effective in blocking pain and/or reducing stress. For this reason, the focal species chosen for this study was a member of Echinodermata, the most closely related invertebrate phylum to vertebrates. In this study, four anesthetics that are currently used in the literature were tested for their efficacy, based on behavioural and cellular responses used to quantify stress levels in Cucumaria frondosa. The anesthetic agents that were tested include: ethanol, clove oil, MS-222 and MgCl₂. The behavioural metrics included reaction to a physical stimulus after anesthesia to test for immobilization, and measurements of cloacal respiration rate at the beginning and end of the anesthetizing procedure to test for a stress response. The cellular metrics included terminal counts and measurements of coelomocytes, which are known to spike during perceived threats in the focal species. Ethanol was not effective as an anesthetic as it evoked behavioural and cellular stress responses. MgCl₂ and clove oil were promising anesthetic agents but responses suggest that higher concentrations or longer exposures may be required. MS-222 seemed to have the most promise but was perhaps too harsh/potent based on the ambiguous behavioural response. This work highlights the complexity in finding effective invertebrate anesthetics, and that more research is needed to confirm the efficacy of the chemicals tested and explore alternate ones.