Sedative effects and stress-alleviating capabilities of four dietary plant-derived compounds on Procambarus clarkii.

In intensive aquaculture, post-larval Procambarus clarkii (the red swamp crayfish) are highly susceptible to stress — with oxidative stress as the primary form — induced by long-distance transport and high-density rearing, leading to substantial mortality and economic losses. Meanwhile, illegal use of diazepam to alleviate stress causes drug residues, threatening the safety of aquatic products. To address these industry challenges, this study selected four plant-derived compounds (isolated from plants) — gastrodin, matrine, paeonol, and eucalyptol — some of which have been proven to have sedative/stress-alleviating effects in other animals, and supplemented them into the diet of post-larval crayfish to explore their potential as natural alternatives to diazepam. A control group, four dietary supplement groups each at 20 mg/L, and a diazepam positive control group at 20 mg/L were established. After 21 days of rearing, which matches the pre-transport acclimation period for post-larvae, comprehensive evaluations were conducted through behavioral observation for sedative effect, antioxidant index determination, expression analysis of antioxidant-related genes (NRF2, HSP70, MT, FER), and intestinal section observation. The results showed that paeonol and eucalyptol exhibited both sedative effects and enhanced antioxidant capacity, and by regulating the activity of antioxidant enzymes such as catalase (CAT) and the expression of related genes, they improved the ability to alleviate stress; gastrodin only enhanced antioxidant capacity without significant sedative effects. No significant differences in growth performance were observed among all experimental groups and the control group. This study provides theoretical support for the healthy rearing of post-larval Procambarus clarkii, identifies that paeonol and eucalyptol have the potential to serve as alternatives to diazepam, and offers a feasible solution to reduce transport mortality and address diazepam abuse and drug residues.