Simple SummaryPhysiological measures were examined during stunning of three commercially important crustacean species: crab, crayfish, and shrimp in an ice slurry or with electroshock. Neural circuits for sensory-central nervous system (CNS)-cardiac response and sensory-CNS-skeletal muscle were examined. Heart rate of shrimp was the most affected by both stunning methods, followed by crayfish, then crabs. Ice slurry and electroshocking may paralyze crabs, but neural circuits are still functional; however, in shrimp and crayfish the neural responses are absent utilizing the same protocols. The use of stunning methods should vary depending on species and slaughter method. Interpretation of behavioral signs should be supported by further research into related physiological processes to objectively validate its meaning.AbstractStunning of edible crustaceans to reduce sensory perception prior and during slaughter is an important topic in animal welfare. The purpose of this project was to determine how neural circuits were affected during stunning by examining the physiological function of neural circuits. The central nervous system circuit to a cardiac or skeletal muscle response was examined. Three commercially important crustacean species were utilized for stunning by immersion in an ice slurry below 4 °C and by electrocution; both practices are used in the seafood industry. The blue crab (Callinectes sapidus), the red swamp crayfish (Procambarus clarkii), and the whiteleg shrimp (Litopenaeus vannamei) responded differently to stunning by cold and electric shock. Immersion in ice slurry induced sedation within seconds in crayfish and shrimp but not crabs and cardiac function was reduced fastest in shrimp. However, crabs could retain a functional neural circuit over the same time when shrimp and crayfish were nonresponsive. An electroshock of 10 s paralyzed all three species and subsequently decreased heart rate within 1 min and then heart rate increased but resulted in irregularity over time. Further research is needed to study a state of responsiveness by these methods.

Simple SummaryThe purpose of this project was to determine how neural circuits were affected during warming by examining sensory neurons, the neuromuscular junction, and the cardiac function and behavior of the commercially important crustacean species, the red swamp crayfish (Procambarus clarkii). Various rates of heating at 1 °C/min, 12 °C/min, or 46 °C/min to 80 °C as well as placing crayfish directly in boiling water were examined. Sensory nerves and the neuromuscular junction will stop working at 44 °C within two minutes. The heart ceases functioning fastest (within 10 s) when placing the crayfish directly in boiling water, which is the quickest method to kill them while minimizing exposure to noxious stimuli.AbstractThis project determined how neural circuits are affected during warming by examining sensory neurons, the neuromuscular junction, and the cardiac function and behavior of the commercially important crustacean species, the red swamp crayfish (Procambarus clarkii). Rapid inactivation of neural function in crustaceans prior to slaughter is important to limit exposure to noxious stimuli, thus improving animal welfare. This study demonstrated that as a crayfish is warmed at 1 °C/min, the heart beat stops at 44 °C. When temperature is rapidly increased, at 44 °C synaptic transmission at the neuromuscular junction ceases and primary sensory neurons stop functioning. Even though animals do not respond to stimuli after being warmed to 44 °C, if sensory neurons are returned to 20 °C saline after two minutes, they may regain function. Conversely, the neuromuscular junction does not regain function after two minutes in 44 °C saline. Examining behavior and heart rate while warming at 1 °C/min, 12 °C/min, or 46 °C/min to 80 °C indicated that at approximately 40 °C the heart rate is altered. Within 10 s at 80 °C, the heart stops with the highest heating rate. Directly placing crayfish in boiling water stopped the heart quickest, within 10 s, which likely represents denaturing of the tissue by heat. Using an impedance measure to detect a heartbeat may also be influenced by movements in the denaturing process of the tissue. A rapid increase in the temperature of the crayfish above 44 °C is key to limit its exposure to noxious stimuli.