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.

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.

Real-time quantitative PCR (qPCR) is a key technique for elucidating the mechanisms underlying environmental stress responses in aquatic animals, and its accuracy relies heavily on stable reference genes for data normalization. In this study, histopathological examination revealed alterations in the gill, hepatopancreas, and muscle tissues of Procambarus clarkii following NH₃ stress. Based on transcriptomic screening and reference genes reported in the literature, 13 candidate reference genes were selected. Their expression levels in 8 different tissues before and after NH₃ stress were detected using qPCR, and their stability was systematically evaluated using multiple algorithms, including geNorm, NormFinder, BestKeeper, Delta CT and RefFinder. The results identified 60S ribosomal protein L13a (RPL13a), ribosomal protein S18 (RPS18) and eukaryotic translation initiation factor 4A (EIF4A) as the three most stable candidates under NH₃ stress, whereas the traditionally used reference genes beta-actin (β-actin) and glyceraldehyde 3-phosphate dehydrogenase (GAPDH) showed relatively low stability under these conditions. geNorm pairwise variation analysis indicated that the inclusion of a third reference gene could further improve normalization. Validation using four NH₃-responsive genes showed that (RPL13a + RPS18) and (RPL13a + RPS18 + EIF4A) yielded similar log₂ fold-change estimates, supporting their use as normalization options under the tested conditions. It is worth noting that RPL13a remains highly stable across four conditions: different embryonic developmental stages, different ovarian developmental stages, tissues from both males and females, and following infection with white spot syndrome virus (WSSV). These findings contribute to the selecting and validating reference genes for qPCR analyses in Procambarus clarkii under the specific experimental conditions evaluated in this study.