Salinity stress can trigger a series of physiological changes. However, the mechanism underlying the response to acute salinity stress in Macrobrachium rosenbergii remains poorly understood. In this study, osmoregulation, physiological metabolism, antioxidant capacity, and apoptosis were examined over 96 h of acute salinity stress. Hemolymph osmolality increased with increasing salinity. After 48 h of salinity exposure, the glucose, triglycerides, total protein, and total cholesterol contents in two salinity stress groups (13 and 26‰ salinity) were significantly lower than those in the 0‰ salinity group. The highest levels of these parameters were detected at 6 h; however, superoxide dismutase (SOD), total antioxidant capacity (T-AOC), and malondialdehyde (MDA) were the lowest at 96 h in the 13‰ salinity group. The activity of immunity-related enzyme alkaline phosphatase (AKP) showed a decreasing trend with increasing salinity and remained at a low level in the 26‰ salinity group throughout the experiment. No significant differences were observed in aspartate aminotransferase (AST), alanine aminotransferase (ALT), or lysozyme (LZM) among the three treatments at 96 h. After 96 h of salinity treatments, the gill filament diameter significantly decreased, and a more pronounced terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL)-positive signal was detected in the 13‰ and 26‰ groups compared to that in the 0‰ group. Expression levels of apoptosis-related genes, including Cysteine-aspartic acid protease 3 (Caspase 3), Cysteine-aspartic acid protease 8 (Caspase 8), Cytochrome c (Cyt-c), tumor suppressor gene (P53), Nuclear factor kappa-B (NF-κB), and B cell lymphoma 2 ovarian killer (Bok) were significantly higher in the 26‰ salinity group than in the other groups at 24 h, but lower than those in the 0‰ salinity group at 96 h. Cyt-c and P53 levels exhibited a significantly positive relationship with MDA, AST, and LZM activity during salinity stress. In the 13‰ salinity group, Bok expression was significantly correlated with SOD, T-AOC, AKP, acid phosphatase, and LZM activity, whereas in the 26‰ group, the AST content was positively correlated with Caspase 8, Cyt-c, and P53 expression. A significant negative relationship was observed between Caspase 3 expression and catalase (CAT) activity. These findings provide insight into the mechanisms underlying the response to acute salinity stress and will contribute to improving M. rosenbergii aquaculture and management practices.

Through a 30-day experiment, this study investigated the effects of five photoperiods (0L:24D, 6L:18D, 12L:12D, 18L:6D, and 24L:0D) on the survival, enzyme activity, body color, and growth-related gene expression of redclaw crayfish (Cherax quadricarinatus) juveniles. The results showed that C. quadricarinatus juveniles under 18L:6D and 24L:0D photoperiods exhibited the highest survival rate, which was significantly higher than the survival rates of juveniles under the other three photoperiods (p < 0.05). However, the 0L:24D group had the highest final body weight and weight gain rate, significantly surpassing those of the 12L:12D, 18L:6D, and 24L:0D groups (p < 0.05). Regarding enzyme activity and hormone levels, juveniles under the 18L:6D photoperiod exhibited relatively higher activity of superoxide dismutase (SOD), acid phosphatase (ACP), and lysozyme (LZM) enzymes than those under other photoperiods, but their levels of melatonin and cortisol were relatively low. In addition, the 24L:0D group showed the highest malondialdehyde (MDA) content. Analysis of gene expression levels revealed that retinoid X receptor (RXR) and α-amylase (α-AMY) genes in C. quadricarinatus juveniles exhibited significantly higher expression levels under the 18L:6D photoperiod than those under the other four photoperiods (p < 0.05). With increasing daylight exposure, the body color of C. quadricarinatus changed from pale blue to yellow–brown. In summary, C. quadricarinatus juveniles achieved high survival rates, good growth performance, strong antioxidant stress response, and immune defense capabilities under an 18 h photoperiod. Therefore, in the industrial seedling cultivation of redclaw crayfish, it is recommended to provide 18 h of daily light. Further, the study demonstrated the ability to manipulate the body color of C. quadricarinatus through controlled artificial photoperiods. These findings provide essential technical parameters needed for the industrial cultivation of C. quadricarinatus juveniles.

The spectrum is a key environmental factor, and light‐emitting diodes (LEDs) can influence the growth and development of crustaceans by altering the composition of the spectrum. This study conducted a 30‐day experiment to investigate the effects of five LED spectra (red, yellow, blue, green, and white light) on the growth, antioxidant and immune enzyme activities, stress hormone levels, and the expression of α‐amylase (α-AMY), ecdysone receptor (EcR) and retinoid X receptor (RXR) genes in juvenile redclaw crayfish (Cherax quadricarinatus). The results show that the survival rate of juveniles is markedly higher in the yellow and red‐light groups than in the other three groups (P < 0.05). The green light group exhibits the lowest survival rate, yet it demonstrates the highest weight gain rate and specific growth rate. Regarding enzyme activity and hormone levels, the yellow light group shows the lowest malondialdehyde content, with higher superoxide dismutase and acid phosphatase activity than the other groups; no significant differences are observed in lysozyme activity among the groups (P > 0.05). The melatonin content in the green and blue light groups is significantly higher than that in the other three groups (P < 0.01). In terms of growth gene expression, the expression of α-AMY, EcR, and RXR in juvenile C. quadricarinatus is regulated by the spectrum. In conclusion, when raised under the yellow light spectrum, juvenile C. quadricarinatus displays elevated survival rates, rapid growth, and robust antioxidant and immune defenses. This study provides important technical parameters for optimizing and enhancing the industrial cultivation of juvenile C. quadricarinatus.

17α-methyltestosterone (MT) is known for its ability to suppress ovaries and induce spermatogenesis; yet, its effects in crustaceans are underexplored. This study investigates the impact of varying MT concentrations on the gonadal development and intestinal microbiota of juvenile Macrobrachium rosenbergii. Feeds containing different MT doses were provided, and the sex ratios, histological observations, reproductive gene expression, and intestinal microbial composition were analyzed. The results revealed short-term feeding (60 days) of 1000 mg/kg MT resulted in the highest male ratio, while long-term feeding (150 days) of 500 mg/kg MT achieved the same outcome. Conversely, long-term feeding of 1500 mg/kg MT led to the lowest male ratio and retarded male germ cell development. An intestinal microbiota analysis showed that MT supplementation significantly increased microbial abundance and altered the intestinal microbial community structure. Additionally, MT suppressed the expression of female reproductive-related genes. This study provides insights into the effects of MT on reproductive development and gut microbiota in juvenile prawns, offering a valuable reference for the application of MT in crustacean aquaculture.

Povidone-iodine (PVP-I), a widely used aquaculture disinfectant, remains poorly understood in terms of sublethal toxicity and damage reversibility. This study employed Macrobrachium rosenbergii as the model organism to evaluate the acute toxicity and sublethal effects of PVP-I through a 4-day exposure experiment followed by a 7-day depuration period. Acute toxicity tests enabled the determination of 24–96 h median lethal concentrations (LC₅₀), with the 96 h LC₅₀ being 5.67 mg/L and the safe concentration (SC) being 1.37 mg/L. Based on this, three sublethal concentrations (1.14, 1.89, and 2.84 mg/L) were tested over a 4-day exposure followed by a 7-day depuration period. Investigated endpoints included gill ultrastructure, apoptosis, and antioxidant and immune-related gene expression. Subacute exposure at 1.89 and 2.84 mg/L induced mitochondrial vacuolization, upregulated apoptosis-related genes (Cyt-c, Caspase-3, Bok), and downregulated antioxidant gene expression (SOD, CAT, GSH-Px). The high-concentration group also showed sustained Toll-like receptor (Toll) gene overexpression and acid phosphatase (ACP) gene suppression. After depuration, antioxidant gene expression normalized; however, apoptotic markers in gill tissue remained impaired. Overall, high PVP-I concentrations cause irreversible gill damage via mitochondrial-mediated apoptosis, whereas lower concentrations (≤1.14 mg/L) allow for greater recovery. These results offer crucial toxicodynamic insights for safer PVP-I use and risk assessment in M. rosenbergii aquaculture.