The impact of dietary protein and lipid levels on the growth performance, feed utilization, and serum biochemical indices of Furong crucian carp was examined. Five hundred and forty carp (2.35 ± 0.08 g) were randomly assigned to nine groups and fed diets with three different protein levels (30.0, 35.0, and 40.0%) and three different lipid levels (4.0, 7.0, and 10.0%) for 60 days. The current findings revealed that the interaction effect between dietary lipid and protein levels exhibited significance for the final average weight (FAW), weight gain rate (WGR), specific growth rate (SGR), feed efficiency (FE), energy deposition rate (EDR), whole-fish energy, ash, and fat content (p < 0.05). Specifically, there was a significant reduction in FAW, WGR, and SGR with increasing dietary fat supplementation. Conversely, FE, EDR, and protein efficiency ratios were significantly decreased with increasing dietary protein levels (p < 0.05). Furthermore, serum albumin and globulin levels exhibited significant increases in response to dietary lipid inclusion (p < 0.05). The findings collectively indicate that Furong crucian carp fed a diet comprising 4% lipid and 30% protein exhibited the optimal growth and feed utilization. Conversely, excessive protein and lipid supplementation were detrimental to growth and resulted in the aggravation of metabolic disorders.

In this study, juvenile crayfish hatched from the same population were cultured in different growing environments: pond (D1), paddy field (D2), and aquaculture barrel (D3), and fed for 60 days. Crayfishes were selected randomly, females and males, 50 tails each from six groups (D1-♀, D1-♂, D2-♀, D2-♂, D3-♀, D3-♂) to measure the following morphological traits: full length (X₁), body length (X₂), chelicerae length (X₃), chelicerae weight (X₄), cephalothorax length (X₅), cephalothorax width (X₆), cephalothorax height (X₇), eye spacing (X₈), caudal peduncle length (X₉), and caudal peduncle weight (X₁₀). We found that the coefficient of variation (CV) of X₄ was the largest in each culture mode, and males (28.58%~38.67%) were larger than females (37.76%~66.74%). The CV of X₄ of crayfish cultured in D1 and D2 was larger than that of D3. All traits except X₈ were positively correlated with body weight (p < 0.05). After pathway analysis, we found that X₄, X₅, X₇, and X₁₀ were significantly correlated with the body weight of D1-♀; the equation was Y_D1-♀ = −29.803 + 1.249X₄ + 0.505X₅ + 0.701X₇ + 1.483X₁₀ (R² = 0.947). However, X₂, X₄, and X₆ were significantly correlated with the body weight of D1-♂; the equation was Y_D1-♂ = −40.881 + 0.39X₂ + 0.845X₄ + 1.142X₆ (R² = 0.927). In D2-♀, X₁, X₄, X₅, and X₁₀ were significantly correlated with body weight; the equation was Y_D2-♀ = −12.248 + 0.088X₁ + 1.098X₄ + 0.275X₅ + 0.904X₁₀ (R² = 0.977). X₄ and X₅ played a major role in the body weight of D2-♂ with the equation: Y_D2-♂ = −24.871 + 1.177X₄ + 0.902X₅ (R² = 0.973). X₃ and X₁₀ mainly contributed to the body weight of D3-♀ with the equation: Y_D3-♀ = −22.476 + 0.432X₃ + 3.153X₁₀ (R² = 0.976). X₁ and X₄ mainly contributed to the body weight of D3-♂ with the equation: Y_D3-♂ = −34.434 + 0.363X₁ + 0.669X₄ (R² = 0.918). Comparing the pathway analysis with the gray relation analysis, we could conclude that the traits most correlated with body weight in D1-♀ were X₁₀ and X₇; in D1-♂, X₆; in D2-♀, X₁₀, X₁, and X₅; in D2-♂, X₅; in D3-♀, X₁₀; and in D3-♂, X₄ and X₁.

The peripheral tissue pacemaker is responsive to light and other zeitgebers, especially food availability. Generally, the pacemaker can be reset and entrained independently of the central circadian structures. Studies involving clock-gene expressional patterns in fish peripheral tissues have attracted considerable attention. However, the rhythmic expression of clock genes in skeletal muscle has only scarcely been investigated. The present study was designed to investigate the core clock and functional gene expression rhythms in crucian carp. Meanwhile, the synchronized effect of food restrictions (short-term fasting) on these rhythms in skeletal muscle was carefully examined. In fed crucian carp, three core clock genes (Clock, Bmal1a, and Per1) and five functional genes (Epo, Fas, IGF1R2, Jnk1, and MyoG) showed circadian rhythms. By comparison, four core clock genes (Clock, Bmal1a, Cry3, and Per2) and six functional genes (Epo, GH, IGF2, Mstn, Pnp5a, and Ucp1) showed circadian rhythms in crucian carp muscle after 7-day fasting. In addition, three core clock genes (Clock, Per1, and Per3) and six functional genes (Ampk1a, Lpl, MyoG, Pnp5a, PPARα, and Ucp1) showed circadian rhythms in crucian carp muscle after 15-day fasting. However, all gene rhythmic expression patterns differed from each other. Furthermore, it was found that the circadian genes could be altered by feed deprivation in crucian carp muscle through the rhythms correlation analysis of the circadian genes and functional genes. Hence, food-anticipatory activity of fish could be adjusted through the food delivery restriction under a light–dark cycle. These results provide a potential application in promoting fish growth by adjusting feeding conditions and nutritional state.

Red swamp crayfish (Procambarus clarkii) is one of the most important aquaculture species in China. Frequent outbreaks of diseases seriously threatened the sustainable development of the industry. It is necessary to understand the causes of disease and study the mechanism of disease resistance in P. clarkii. In this paper, the pathogenic bacteria causing head ulcers in juvenile P. clarkii were found and identified as Citrobacter freundii, which can cause severe pathological changes in the hepatopancreas and intestines of juvenile P. clarkii. Detection of humoral immune factors revealed that PO activity and lysozyme activity of infected P. clarkii were significantly enhanced at 15 and 20 dpi, respectively. Transcriptome analysis was conducted of hepatopancreas from normal and diseased P. clarkii after C. freundii injection, as well as bacteria-free control of P. clarkii. It was found that DEGs are rich in NF-κB, oxidative phosphorylation, JAK/STAT, Leukocyte transendothelial migration, MAPK, and PPAR signaling pathway. These pathways are related to immune modulation, metabolism, and pathogen clearance. Meanwhile, immune-related genes such as Gip, nfyA, psmD13, and FGFR were significantly highly expressed in the normal group, which was verified by qRT-PCR results, suggesting that they may be the key regulatory genes for juvenile P. clarkii resistance to C. freundii. This study will help to elucidate the molecular mechanism of the immune response of P. clarkii to C. freundii. The results are instructive for the prevention and treatment of P. clarkii diseases and for further understanding of the invertebrate immune system.

Background/Objectives: Procambarus clarkii is an important freshwater aquaculture species in China which has the characteristics of rich nutrition and delicious taste. However, the expansion of aquaculture scale, germplasm degradation, and other problems that have become increasingly prominent seriously restrict the sustainable development of the crayfish industry. Genetic improvement is an urgent need for the crayfish aquaculture industry, and selective breeding is an important way to improve the crayfish varieties. Methods: We established full-sibling family populations of the red swamp crayfish and performed whole-genome resequencing of the F3 family-selected red swamp crayfish population and wild red swamp crayfish populations from four regions of Hunan Province (Nanx, Mil, Caish, and Wangc). Results: The results showed that there was a clear separation between the wild population and the family population, and the decline rate was slightly faster in the wild population than that of the family breeding population. There was local gene flow between family populations, as well as gene flow between Mil, Caish, and families. In addition, 52 SNP loci related to body weight traits were identified by genome-wide association analysis, and the candidate gene WIPF1 related to growth was screened out. Conclusions: We established a line selection population of red swamp crayfish and obtained more stable candidate lines. In addition, this study identified Wiskott–Aldrich syndrome protein-interacting protein family member 1 (WIPF1) as a candidate gene related to body weight for the first time. The results provide a theoretical basis for exploring the growth mechanism of P. clarkii and carrying out in-depth genetic improvement.