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Low temperature is a critical factor restricting the growth and survival of aquatic animals, but research on the mechanism of response to low temperature in Cherax destructor is limited. C. destructor is one of the most important freshwater crustaceans with strong adaptability in Australia, and it has been commercialized gradually in recent years. Here, growth indicators, antioxidant parameters, anti-stress gene expression, and transcriptome sequencing were used on crayfish following 8 weeks of low-temperature acclimation. The results showed that weight gain, length gain, and molting rates decreased as the temperature decreased. The activity of antioxidant enzymes decreased, while the content of antioxidant substances and the expression of anti-stress genes increased. Transcriptome sequencing identified 589 differentially expressed genes, 279 of which were upregulated and 310 downregulated. The gene functions and pathways for endocrine disorders, glucose metabolism, antioxidant defense, and immune responses were identified. In conclusion, although low-temperature acclimation inhibited the basal metabolism and immune ability of crayfish, it also increased the antioxidant substance content and anti-stress-gene expression to protect the organism from low-temperature damage. This study provided molecular insights into the study of low-temperature responses of low-temperature-tolerant crustacean species.

Ammonia nitrogen is an important source of water pollution that severely limits the development of aquaculture. Macrobrachium nipponense is widely cultivated due to its delicious meat, strong reproductive ability and short reproductive cycle, but the problems caused by germplasm degradation are becoming increasingly concerning.Hybridization is an efficient means to solve this problem. In this study, the parental population, Dianshan Lake (DS) and the hybrid population, DS ♀ × CD (Changjiang, CJ ♂ × Dongting, DT ♀ [SCD]) were exposed to 0, 1 or 10 mg/L total ammonia nitrogen (TAN) for 28 days. Our results indicated that the number of gill-positive cells and the apoptosis rate of the two groups showed an upward trend with the ammonia nitrogen concentration increased. The ammonia metabolism-related substance levels and the detoxifying enzyme activities in the gills of shrimp in the SCD group exposed to 10 mg/L of TAN were significantly higher than shrimp in the DS group (p < 0.05). As the TAN concentration increased, the respiratory-related genes displayed a downward trend and the nitrogen metabolism-related genes presented an upward trend.Our results suggest that the SCD population had a stronger detoxifying capacity and a greater stress resistance ability than the DS population when subjected to the same concentration of ammonia nitrogen stress.

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