Abstract
ObjectivesIn search for methods of anesthesia of crustaceans, an implanted electrode into lobster and crayfish CNS enabled us to monitor signal propagation in the nerve system of animals undergoing different protocols.ResultsCooling (tap water 0°C, sea water -1,8°C) and anesthesia with MgCl2 (10%) were both discarded as anesthetic procedures because responses to external stimuli were still detectable under treatment. Contrarily, bubbling the aquarium water with CO2 can be considered a “partially successful” anesthesia, because signal propagation is inhibited but before that the animals show discomfort. The procedure of “electro-stunning” induces epileptic-form seizures in the crustacean CNS (lobster, crayfish), which overlay but do not mitigate the response to external stimuli. After several minutes the activity declines before the nervous system starts to recover. A feasible way to sacrifice lobsters is to slowly raise the water temperature (1°C min-1), as all electrical activities in the CNS cease at temperatures above ~30°C, whereas below this temperature the animals do not show signs of stress or escape behavior (e.g. tail flips) in the warming water.ConclusionCO2 is efficient to anaesthetize lobster and crayfish but due to low pH in water is stressful to the animals previous to anesthesia. Electrical stunning induces epileptiform seizures but paralyses the animals and leads to a reversible decline of nerve system activity after seizure. Electric stunning or slowly warming just before preparation may meet ethical expectations regarding anaesthesia and to sacrifice crustaceans.
Highlights
Besides for human consumption [1], crustaceans are used for scientific experiments (e.g. [2])
CO2 is efficient to anaesthetize lobster and crayfish but due to low pH in water is stressful to the animals previous to anesthesia
Some of the proposed methods for stunning, anaesthesia and killing were recently tested in crabs [9], but did not include direct measurements in the central nervous system
Summary
Besides for human consumption [1], (higher) crustaceans are used for scientific experiments (e.g. [2]). More than fifty years ago, Baker (1955) and Gunter (1960) proposed methods for “ethic” or “painless” killing of crabs and crayfish [3,4], which initiated a debate in the scientific community [5,6,7,8]. Some of the proposed methods for stunning, anaesthesia and killing were recently tested in crabs [9], but did not include direct measurements in the central nervous system. Crustaceans are well-established models for neurobiological research [10,11]. Studies reporting experimental research often provide succinct statements concerning preparative methods such as “animals were anesthetized on ice for 30 to 45 min” or “the nervous system was dissected out”, without indicating whether a state of anaesthesia had been reached
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