Abstract

The Atlantic purple sea urchin (Arbacia punctulata) is commonly found in shallow waters of the Western Atlantic Ocean from New England to the Caribbean. Sea urchins have played a major role in the study of toxicology, developmental biology, cell biology and more recently to exhibit actin in non-muscle cells.^1-4 In addition to their use in research, purple sea urchins are found in public aquaria exhibiting native species.

Tricaine methanesulfonate (MS-222) was used to determine anesthetic efficacy and sedation parameters of Atlantic purple sea urchins (A. punctulata) to include response to focal blunt stimuli, spine position, pseudopodia position, righting response and the ability to remain attached to a vertical surface. Physiologic and sedation parameters were evaluated on 11 individuals in each of three circumstances - unaltered aquarium water for physiologic normal behaviors, 0.4 g/L MS-222 and 0.8 g/L MS-222. Twenty-five urchins were collected from a natural habitat under the umbrella of a museum collection permit. Only animals weighing over 20 g were considered adequate for the purposes of this study. The animals were housed in a quarantine tank with water quality parameters similar to that of the natural collection site. Body weight, sex, and test diameter were recorded. Initial testing of 11 urchins for physiologic parameters was conducted in unaltered enclosure water to establish normal ranges for righting reflex and spine response to repeated focal blunt stimulus. Using a stock MS-222 solution of 10 g/L, buffered 1:1 with NaHCO₃, two anesthetic challenges were performed, each on 11 individuals chosen by a random number generator, at the lowest effective concentration based on in-house preliminary studies and twice the lowest effective concentration. The individuals undergoing the 0.8 g/L challenge were first immersed in a solution of enclosure water and NaHCO₃ as a control for potential sedative effects of the buffering agent. Tricaine methanesulfonate proved to be an effective sedative agent and an effective anesthetic agent for the Atlantic purple urchin at 0.4 g/L and 0.8 g/L, respectively. Sodium bicarbonate showed no measurable sedative effects. The anesthetic plane was quickly reversed with the transfer of each individual to an unaltered environment. Each individual was challenged in dorsal recumbency upon recovery and exhibited effort to right or righted. This study provides a baseline for sea urchin anesthesia and may be helpful for similar species and populations that are in need of anesthesia for surgical procedures or research.

To the authors' knowledge, this is the first reported study of sea urchin anesthesia. Data reported in this study represent an important step to the future of echinoderm anesthesia, medicine and research. Institutions with closed collections will more readily be able to medically and surgically manage patients as well as implant identification markers with limited stress to the animal and handlers.

Acknowledgements

We thank the North Carolina Museum of Natural Sciences (NCMNS), the Center for Marine Science and Technology (CMAST), Craig Harms, Brianne Phillips, Kent Passingham, Amy Brewbaker, Ashley Harrison-Jackson, Dina Ibrahim, and Brianna Nordstrom.

Literature Cited

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