Putative Nociceptive Responses in a Decapod Crustacean: The Shore Crab (Carcinus maenas).

Simple Summary: Nociceptors detect damaging stimuli and send signals to the central nervous system (CNS) about potential injury, which can give rise to pain. Crustaceans, such as shore crabs, are widely used in science and aquaculture. Understanding whether they can experience pain is essential for improving their welfare. One key criterion for assessing pain is the presence of nociceptors. This study investigated the existence of nociceptors in shore crabs by examining the CNS response to two types of potentially noxious stimuli, i.e., mechanical and chemical or acetic acid. Using electrophysiological equipment, the crabs' CNS activity was measured when different parts of its body, such as the soft tissues of the claws, antennae, and legs were stimulated. The results suggest that the crabs responded to both mechanical and chemical stimuli, indicating the existence of putative nociceptors in these areas. Interestingly, responses to physical stimuli were shorter and more intense than the chemical stimuli, which elicited a longer response. The antennae responded only to the chemical stimuli with no discernable response to touch. Although further research is needed to fully understand pain in crustaceans, this study provides important information on the perception of tissue damage in a crustacean. Nociceptors are receptors that detect injurious stimuli and are necessary to convey such information from the periphery to the central nervous system. While nociception has been extensively studied in various taxa, there is relatively little electrophysiological evidence for the existence of nociceptors in decapod crustaceans. This study investigated putative nociceptive responses in the shore crabs, specifically their response to mechanical and noxious chemical stimuli. Extracellular multi-unit electrophysiological recordings were conducted from the anterior ganglion and the circumesophageal connective ganglia to assess nociceptive responses. Soft tissues at the joints of the chelae, antennae, and walking legs were stimulated using acetic acid (noxious stimulus) and von Frey hairs (mechanical stimulus), while nearby ganglion activity was recorded. The results indicate the existence of nociceptors in the tested areas, with mechanical stimuli eliciting shorter, more intense neural activity compared with acetic acid. Although acetic acid triggered responses in all areas, the antennae and antennules did not respond to mechanical stimuli. Though we acknowledge the challenges of conducting in vivo electrophysiological recordings, future research should focus on further characterizing nociceptor activity because the results suggest the presence of nociceptors. [ABSTRACT FROM AUTHOR]