Effects of Four Light Colors on Physiology, Antioxidant Enzyme Activity, Shell Pigmentation, and Genes Associated with Body Color Formation in Procambarus clarkii

Light plays a critical role in the physiology and pigmentation of aquatic animals. Regulating the light environment of aquatic animals offers insights into healthy aquaculture practices. In this study, Procambarus clarkii were reared under four different light colors—white (WL), red (RL), blue (BL), and green (GL)—for 21 days, with four replicates per light color. Morphological characteristics did not differ among light treatments. However, significant differences were observed in hemolymph cortisol levels and tyrosinase activity across different tissues (hemolymph, muscle, hepatopancreas) among groups (RL > BL > GL > WL). Hepatopancreatic CAT activity in WL was significantly higher than that in GL and BL, whereas hepatopancreatic MDA content was highest in BL. Regarding chromatic parameters, the yellow color of the RL cephalothorax cuticle and the red color of the muscle were more pronounced than in WL, The chela cuticle of GL is darker than RL, while the red color of the chela cuticle was more pronounced than in WL.. For pigment content, cephalothorax cuticle astaxanthin content in BL was significantly higher than that in other light color groups, while abdominal cuticle astaxanthin content was lowest in BL. Chela cuticle astaxanthin content in RL was significantly higher than that in WL, and chela cuticle astaxanthin and lutein contents in WL were significantly lower than those in BL and GL. Compared with WL, hepatopancreatic glutathione S-transferase P1 (GSTP1) mRNA expression significantly decreased under colored light, whereas NinaB mRNA expression significantly increased under RL and BL. These results indicate that light color does not affect the morphological characteristics of P. clarkii but significantly modulates oxidative stress responses, physiological status and energy metabolism. Different light colors may mediate carotenoid transport and deposition by regulating the expression of GSTP1, NinaB, leading to specific chromatic differences in different body parts of P. clarkii. Comprehensive analysis revealed that the red light environment exerted a more positive effect on enhancing the body color of P. clarkii. This study provides a reference for revealing the mechanism of light color regulating crustacean physiological function and pigmentation and optimizing aquaculture model.