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.

Current treatment strategies for parasitic infectious diseases in crucian carp primarily rely on chemotherapy. As a commonly used antiparasitic agent, deltamethrin (DEL) may have the potential adverse effects on external mucosa of fish such as gills. In this study, 180 healthy juvenile crucian carp (Carassius auratus) (average weight: 8.8 ± 1.0 g) were randomly divided into three groups for 28 days, which were immersed in 0 μg/L, 0.3 μg/L, and 0.6 μg/L of DEL, respectively. The results of histological analysis revealed that severe hyperplasia in the secondary lamellae of gills was observed, and the number of goblet (mucus-secreting) cells increased significantly after DEL immersion. TUNEL staining indicated that the number of apoptotic cells increased in crucian carp gill. At the molecular level, the mRNA expression analysis revealed significant upregulation of apoptosis (caspase 3, caspase 8, and bax), autophagy (atg5 and beclin-1), and immune response (lzm, muc5, il-6, il-8, il-10, tnfα, ifnγ, tgfβ, tlr4, myd88, and nf-kb), whereas tight junction-related genes (occludin and claudin12) were downregulated after DEL immersion, suggesting that DEL immersion altered innate immunity responses and promoted mucus secretion. Moreover, tandem mass tag (TMT)-based proteomics revealed that a total of 428 differentially expressed proteins (DEPs) contained 341 upregulated DEPs and 87 downregulated DEPs with function annotation were identified between the control and DEL groups. Functional analyses revealed that the DEPs were enriched in apoptotic process, phagosome, and lysosome pathways. Additionally, DEL immersion also drove gill microbiota to dysbiosis and an increase in potentially harmful bacteria such as Flavobacterium. Overall, this study showed that DEL elicited shifts in the immune response and changes in the surface microbiota of fish. These results provide new perspectives on the conventional anthelmintic concentration of DEL immersion disorder of the gill immune microenvironment in crucian carp and theoretical support for future optimization of their practical application.

Niclosamide (NIC) is a potent salicylanilide molluscicide/helminthicide commonly utilized for parasite and mollusc control in aquatic environments. Due to its persistent presence in water bodies, there is growing concern regarding its impact on aquatic organisms, yet this remains inadequately elucidated. Consequently, this study aims to assess the hepatotoxic effects and detoxification capacity of black carp (Mylopharyngodon piceus) in a semi-static system, employing various parameters for analysis. NIC was applied to juvenile black carp at three different concentrations (0, 10 and 50 μg/L) for 28 days in an environmentally realistic manner. Exposure to 50 μg/L NIC resulted in an increase in hepatic lysozyme (LYZ), alkaline phosphatase (ALP), and complement 4 (C4) levels while simultaneously causing a decrease in peroxidase (POD) activity. Additionally, NIC exposure exhibited a dose-dependent effect on elevating serum levels of LYZ, ALP, complement 3 (C3), C4, and immunoglobulin T (IgT). Notably, the mRNA levels of immune-related genes tnfα, il8, and il6, as well as nramp and leap2, were upregulated in fish exposed to NIC. RNA-Seq analysis identified 219 differentially expressed genes (DEGs) in M. piceus after NIC exposure, with 94 upregulated and 125 downregulated genes. KEGG and GO analyses showed enrichment in drug metabolism pathways and activities related to oxidoreductase, lip oprotein particles, and cholesterol transport at 50 μg/L NIC. Additionally, numerous genes associated with lipid metabolism, oxidative stress, and innate immunity were upregulated in NIC-exposed M. piceus. Taken together, these findings indicate that NIC has the potential to cause hepatotoxicity and immunotoxicity in M. piceus. This research offers important insights for further understanding the impact of molluscicide/helminthicide aquatic toxicity in ecosystems.

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.