The indiscriminate use of deltamethrin in agriculture and aquaculture can lead to residues increased in many regions, which poses negative impacts on intestinal health of aquatic organisms. Although the potential toxicity of deltamethrin have recently attracted attention, the comprehensive studies on intestinal injuries after chronic deltamethrin exposure remain poorly understood. Herein, in a 28-day chronic toxicity test, crucian carp expose to different concentrations of deltamethrin (0, 0.3, and 0.6 μg/L) were used as the research object. We found that the morphology changes and increased goblet cells in intestinal tissue, and the extent of tissue injury increased along with the increasing exposure dose of deltamethrin. Additionally, the genes expression of antioxidant activity (Cu/Zn superoxide dismutase (Cu-Zn SOD), glutathione peroxidase 1 (GPX1), and catalase (CAT)), inflammatory response (tumor necrosis factor alpha (TNFα), interferon gamma (IFNγ), and interleukin 1 beta (IL-1β)), and tight junctions (Claudin 12 (CLDN12), and tight junction protein 1 (ZO-1)) dramatically increased. Meanwhile, the apoptosis and autophagy process were triggered through caspase-9 cascade and autophagy related 5 (ATG5)- autophagy related 12 (ATG12) conjugate. Besides, chronic deltamethrin exposure increased the amount of Proteobacteria and Verrucomicrobiota, while decreased Fusobacteriota abundance, resulting in intestinal microbiota function disorders. In summary, our results highlight that chronic exposure to deltamethrin cause serious intestinal toxicity and results in physiological changes and intestinal flora disturbances.

More and more evidences proved that deltamethrin (Del) exposure induced adverse effects and damaged immune function to the aquatic animals in the parasite killing process with increasing insecticide application. However, little is currently known of the negative effect on mucosal immunity, especially in gills tissue. Therefore, this study was aimed to reveal the tissue injury and immunotoxicity in the gill of gibel carp following acute deltamethrin exposure. The LC50 of deltamethrin on gibel carp at 96 h was determined to be 6.194 μg/L, and then juvenile gibel carp (Carassius auratus gibelio) (8.8 ± 1.0 g) were exposed to four Del exposure groups (0.61, 1.22, 2.44, and 4.88 μg/L) for 12 h and 24 h. We measured the lysozyme (LYZ) contents and myeloperoxidase (MPO) activities and found that with increased concentration of Del exposure, the LYZ contents were found to increase in the 1.22 μg/L Del group initially significantly and then gradually significantly decrease in the 4.88 μg/L Del group. And the activities of MPO were significantly lifted in a dose-dependent manner. The histological analysis showed that Del exposure caused serious desquamation and necrosis in the surface of epithelial cells, accompanied by interlamellar cellular mass degenerative. In addition, the mucous cells were significantly decreased in the high Del concentration group (2.44 μg/L and 4.88 μg/L Del group) by AB-PAS staining. Additionally, totally 2857 DEGs (including 1624 up-regulated and 1233 down-regulated genes) were identified between the control group and 4.88 μg/L Del exposure group using transcriptional analysis. Among these, some genes involved in innate immune molecules, complement activation, apoptosis-related molecules, cytokine, and adaptive immune molecules, were also down-regulated. Importantly, we found immune system process and tumor necrosis factor receptor (superfamily) binding pathways were downregulated based on the GO and KEGG enrichment analysis. Meanwhile, we detected the expression of pro-inflammatory cytokines (TNF-α, IFN-γ, IL-1β, and IL-8), anti-inflammatory cytokines (TGF-β), LYZ, IgM, and Hsp70 in the gills tissue at 12 h and 24 h after Del exposure, which were consistent with our sequencing results. Collectively, these results demonstrated that the gills injury and immunotoxicity were induced by Del exposure and provided novel insight for explaining to some extent why Del-exposure fish are more susceptible to concurrent or secondary viral or bacterial infections.

To investigate whether Mandarin fish developed oxidative stress after being domesticated with artificial feed, we conducted a series of experiments. Oxidative stress is an important factor leading to diseases and aging in the body. The liver integrates functions such as digestion, metabolism, detoxification, coagulation, and immune regulation, while the gills are important respiratory organs that are sensitive to changes in the water environment. Therefore, we used the liver and gills of Mandarin fish as research materials. The aim of this study was to investigate the effects of short-term artificial feed domestication on the expression of oxidative stress genes and the changes in oxidative-stress-related enzyme activity in the liver and gills of Mandarin fish. We divided the Mandarin fish into two groups for treatment. The control group was fed with live bait continuously for 14 days, while the experimental group was fed with half artificial feed and half live bait from 0 to 7 days (T-7 d), followed by solely artificial feed from 7 to 14 days (T-14 d). The experimental results showed that there was no difference in the body weight, length, and standard growth rate of the Mandarin fish between the two groups of treatments; after two treatments, there were differences in the expression of genes related to oxidative stress in the gills (keap1, kappa, gsta, gstt1, gstk1, SOD, and CAT) and in the liver (GPx, keap1, kappa, gsta, gstt1, gr, and SOD). In the liver, GPx activity and the content of MDA were significantly upregulated after 7 days of domestication, while in the gills, SOD activity was significantly upregulated after 7 days of domestication and GPx activity was significantly downregulated after 14 days of domestication. These results suggest that artificial feed domestication is associated with oxidative stress. Moreover, these results provide experimental basic data for increasing the production of aquaculture feed for Mandarin fish.

Background: Classification of the Acanthocephala, a clade of obligate endoparasites, remains unresolved because of insufficiently strong resolution of morphological characters and scarcity of molecular data with a sufficient resolution. Mitochondrial genomes may be a suitable candidate, but they are available for a small number of species and their suitability for the task has not been tested thoroughly. Methods: Herein, we sequenced the first mitogenome for the large family Rhadinorhynchidae: Micracanthorhynchina dakusuiensis. These are also the first molecular data generated for this entire genus. We conducted a series of phylogenetic analyses using concatenated nucleotides (NUC) and amino acids (AAs) of all 12 protein-coding genes, three different algorithms, and the entire available acanthocephalan mitogenomic dataset. Results: We found evidence for strong compositional heterogeneity in the dataset, and Micracanthorhynchina dakusuiensis exhibited a disproportionately long branch in all analyses. This caused a long-branch attraction artefact (LBA) of M. dakusuiensis resolved at the base of the Echinorhynchida clade when the NUC dataset was used in combination with standard phylogenetic algorithms, maximum likelihood (ML) and Bayesian inference (BI). Both the use of the AA dataset (BI-AAs and ML-AAs) and the CAT-GTR model designed for suppression of LBA (CAT-GTR-AAs and CAT-GTR-NUC) at least partially attenuated this LBA artefact. The results support Illiosentidae as the basal radiation of Echinorhynchida and Rhadinorhynchidae forming a clade with Echinorhynchidae and Pomporhynchidae. The questions of the monophyly of Rhadinorhynchidae and its sister lineage remain unresolved. The order Echinorhynchida was paraphyletic in all of our analyses. Conclusions: Future studies should take care to attenuate compositional heterogeneity-driven LBA artefacts when applying mitogenomic data to resolve the phylogeny of Acanthocephala. Graphical

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.