Impact of noise on the behaviour and biochemical parameters of the crayfish Cherax quadricarinatus and Cherax destructor

Anthropogenic noise is widely acknowledged as a pollutant at the global level. Exposure to intense noise can result in hearing damage, physiological stress and behavioural changes. Crayfish, which have great commercial value and high resilience to various stresses, can serve as effective models for assessing the acoustic impact on behavioural dynamics and biochemical parameters indicative of stress conditions. The aim of this study was to evaluate the effect of acoustic stimulus (1-s linear sweep, from 1 to 20 kHz, repeated for 45 min) on the behavioural and biochemical responses of two species of crayfish, Cherax destructor and Cherax quadricarinatus. Sixty individuals (30 C. destructor, 30 C. quadricarinatus), divided into groups of three, were randomly assigned to test or control conditions in tanks equipped with a synchronized audio-video system. Behavioural events (number of fights, encounters, tail flips and acoustic signals) and motility states (velocity, distance moved, angular velocity) were considered, as well as some haemolymphatic parameters (enzymatic activities, pH, osmolality and total protein). Our results showed that exposure to noise significantly increased in both species the number of fights, whereas no significant changes were found in the number of encounters and tail flips. Significant increases in acoustic signals emitted were observed in C. quadricarinatus, while a decrease was noted in C. destructor. The parameters of movement velocity and distance moved increased in both species. Conversely, angular velocity significantly decreased only in C. quadricarinatus. In terms of haemolymphatic parameters, alkaline phosphatase, esterase and peroxidase activity significantly decreased in specimens exposed to noise in both species. pH, osmolality and total protein did not show significant differences. This research contributes to the broader knowledge of the potential negative effects of anthropogenic noise on the health status of these animals and could represent a further approach to assessing farm welfare.