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In nature, living organisms evolve unique functional components with mechanically adaptive compatibility to cater dynamic change of interface friction/lubrication. This mechanism can be used for developing intelligent artificial lubrication-regulation systems. Inspired by the muscle hardening-triggered lubrication of longsnout catfish , here we report a modulus adaptive lubricating hydrogel prototype consisting of top mucus-like hydrophilic lubricating layer and muscle-like bottom hydrogel that can stiffen via thermal-triggered phase separation. It exhibits instant switch from soft/high frictional state (~0.3 MPa, μ ~0.37) to stiff/lubricating state (~120 MPa, μ ~0.027) in water upon heating up. Such switchable lubrication is effective for wide range of normal loads and attributed to the modulus-dominated adaptive contact mechanism. As a proof-of-concept, switchable lubricating hydrogel bullets and patches are engineered for realizing controllable interface movements. These important results demonstrate potential applications in the fields of intelligent motion devices and soft robots. Stimuli responsive materials are interesting for applications in different technological fields, but realizing controllable surface friction-control based on the change of the modulus of a material is less investigated. Here the authors demonstrate a lubrication regulating strategy and prototype based on thermally triggered changes of the modulus of a hydrogel.

Plant protein (PP) sources are generally used in high levels in fish diets. Mostly, PP sources are deficient in taurine; hence, there is a need for its supplementation to fish fed high PP diets. Therefore, effects of dietary taurine were examined on growth performance, feed utilization, immunity, and antioxidant parameters of African catfish, Clarias gariepinus (B.). Fish (10.3 ± 0.4 g) were fed on diets (40% crude protein) containing different taurine levels of 0 (control), 10, 20, 30, or 40 g/kg diet for 12 weeks. Fish fed a taurine-free diet (the control) with high PP sources showed poor growth as compared with these fed taurine-enriched diets where taurine stimulatory effects were observed on fish growth and feed intake. Feed conversion ratio and fish survival rate were not significantly differed among different treatments. Fish fed taurine-enriched diets showed also higher levels of serum glucose, cholesterol, total protein, albumin, globulin, aspartate aminotransferase, alanine aminotransferase, alkaline phosphatase, urea, and creatinine over that fed the control diet. Furthermore, lysozyme and respiratory burst activities as well as superoxide dismutase and catalase activities were significantly elevated in fish fed taurine-enriched diets (P < 0.05) and their highest levels were observed in fish fed 30 g/kg diet. Additionally, taurine deposition in fish muscles was positively correlated with dietary taurine levels (P < 0.05). The present study concludes that taurine is a limiting factor for growth, immunity, and antioxidants responses of African catfish fed high PP-based diets and it should be incorporated in its diets with an optimum level of 20 g/kg diet.

Light microscopy, scanning electron microscopy, and proteomics analysis using high-resolution accurate mass spectrometry exhibit significant adaptive structural modifications and characteristic proteins in the adhesive organ (AO) of Pterygoplichthys disjunctivus, that could assist the adhesion of the fish to the substratum . The free surface of the epithelium of AO showed characteristic mound-like tubercles separated by deep furrows. These could enhance surface grip, and assist in creation of vacuum facilitating adhesion effectively. Spine-like unculi on the surface of the epithelium appear to assist clinging of the fish to the substratum as well as to scrape food particles for feeding. Taste buds located on the summit of mound-like tubercles could serve as adaptations to enhance their sensitivity in food selection and in environmental perception. Mucous and serous goblet cell secretions are believed to function as biological adhesives and protective surface lubricants. Proteomic analysis identified 285 differentially expressed proteins in the AO compared to those in the ventral and the dorsal skin. Out of these proteins in the AO, 80 proteins were significantly abundant. These were Periplakin, Desmoplakin, and Filamin A-like (adhesion related proteins); KRT8 and KRT19 (keratinization associated proteins); Myosin-7, Myosin light chain 13, and Tropomyosin 1 (proteins involved in cytoskeletal organization); and Apolipoprotein A1 and Complement Component 9 (proteins related to immune defense). Gene ontology analysis using Enrichr software revealed the enrichment of unique biological functions and pathways. This study provides a comprehensive understanding of the adaptive strategies that enable P. disjunctivus to thrive in turbulent hillstream environments. Additionally, the proteomic profile established in this study serves as a foundation for characterizing and comparing skin proteomes across teleost species.

Fish transportation, a routine operation in aquaculture, can induce immune responses in fish, potentially affecting their health. Nevertheless, the immune response mechanisms involved in microRNAs (miRNAs) under transport stress remain unclear. Therefore, we investigated the immune response strategy of miRNAs in intestines of hybrid yellow catfish under transport stress via physiological, biochemical and RNA-seq analysis. We found that transportation induced innate immune response of intestines characterized by significant increases in alkaline phosphatase, acid phosphatase, lysozyme, and complement 3 level. Meanwhile, 50 differentially expressed miRNAs were identified and comprehensive analysis of miRNA-mRNA sequencing showed their targets genes involved in 9 immune-related pathways. Notably, the miRNAs involved in immune regulation, such as miR-29a/b, miR-106, miR-454-3p and miR-455, were notably upregulated following the induction of transport stress, while miR-196a-5p was significantly downregulated. In addition, their corresponding target genes such as tkt , mafg , arap2 , nfatc2 , egr2 and wnk4 showed opposite expression trends, suggesting that these genes may be the key immunomodulatory targets of corresponding miRNA. Here, we focused on the regulatory function of miR-455 and its predictive target genes egr2 . Double luciferase assay revealed that miR-455 might exist binding site in the 3’-UTR sequence of egr2 mRNA. Interestingly, silencing miR-455 under transport stress led to the increase of intestinal egr2 expression, affected intestinal immune and inflammation responses, and caused intestinal tissue damage and abnormal secretion of mucous substances. In conclusion, transport stress triggered intestinal immune response, and multiple miRNAs played important role in immune response, among which miR-455 might be an important biomarker. These findings not only improve the understanding of the immunomodulatory function of miRNA in fish, but also provide a theoretical basis for screening potential regulatory targets under transport stress. Graphical abstract

The present study assessed the effects of methionine, lysine, and tryptophan on the growth performance, amino acid composition, and immune-related gene expression of basa catfish ( Pangasius bocourti ). Fish (n = 260; initial weight = 10.00 ± 1.00 g) were fed eight isonitrogenous (30%) diets, each containing different combinations of tryptophan (Trp), methionine (Met), and lysine (Lys) (A0: no amino acids, A1: Trp, A2: Lys, A3: Met, A4: Trp + Met, A5: Lys + Trp, A6: Met + Lys, A7: Lys + Trp + Met, 6 g/kg each) for 10 weeks. The experiment consisted of eight treatments, each with three replicates (n = 15/replicate). After the 10-week feeding trial, the fish were intraperitoneally injected with 0.2 mL of Streptococcus iniae for a 14-day bacterial challenge. Following the feeding trial and bacterial challenge, growth parameters, insulin-like growth factor-I, haematological profile, blood biochemistry, interleukin-6, and interleukin-10 revealed that amino acid supplementation significantly improved both growth and immune response in all treatments except A0. Significant differences were observed in crude protein and amino acid profiles across treatments. Interleukin-10 levels were significantly elevated in all treatments except in the positive control (+ve A0). Compared to the positive control, interleukin-6 levels were significantly reduced (P < 0.05) in all treatments. Superoxide dismutase and catalase activity increased in response to the bacterial challenge, while malondialdehyde levels gradually decreased. The A7 diet (Lys + Trp + Met: 6 g/kg) yielded the most favourable results, enhancing the immune response, which may further support the commercial production of Pangasius bocourti .

Background/Objectives: North African catfish (Clarias gariepinus) and bighead catfish (Clarias macrocephalus) play crucial roles in Thai aquaculture. Although significant growth disparities exist among these species, the genetic factors underlying these differences are still unknown. This study aimed to identify GH1 gene polymorphisms, in North African and bighead catfish populations across Thailand and Laos. Methods: Sequencing, phylogenetic, and clustering analyses were performed to assess genetic diversity, selection patterns, and lineage differentiation of catfish partial GH1 fragment. Results: Six alleles of the studied fragment of GH1 gene were identified; they differed at 33 variable sites within intron 2, located between the conserved regions at the 3′ end of exon 2 and the 5′ end of exon 3. At the population-level, GH1 exhibited low heterozygosity (mean Ho = 0.043 ± 0.023; He = 0.059 ± 0.028). Bayesian clustering analyses identified two distinct genetic clusters, corresponding to North African and bighead catfish, apart from the bighead population in Laos, indicating their distinct genetic origins. Evidence of purifying selection was observed in both species. Phylogenetic analysis indicated the presence of lineage-specific alleles in the GH1 gene. Conclusions: These findings provide valuable insights into GH1 polymorphisms in commercially important catfish species and may help to develop future breeding programs aimed at enhancing aquaculture productivity.

In the present study, juvenile striped catfish (Pangasianodon hypophthalmus), a freshwater fish species, have been chronically exposed to a salinity gradient from freshwater to 20 psu (practical salinity unit) and were sampled at the beginning (D20) and the end (D34) of exposure. The results revealed that the intestinal microbial profile of striped catfish reared in freshwater conditions were dominated by the phyla Bacteroidetes, Firmicutes, Proteobacteria, and Verrucomicrobia. Alpha diversity measures (observed OTUs (operational taxonomic units), Shannon and Faith’s PD (phylogenetic diversity)) showed a decreasing pattern as the salinities increased, except for the phylogenetic diversity at D34, which was showing an opposite trend. Furthermore, the beta diversity between groups was significantly different. Vibrio and Akkermansia genera were affected differentially with increasing salinity, the former being increased while the latter was decreased. The genus Sulfurospirillium was found predominantly in fish submitted to salinity treatments. Regarding the host response, the fish intestine likely contributed to osmoregulation by modifying the expression of osmoregulatory genes such as nka1a, nka1b, slc12a1, slc12a2, cftr, and aqp1, especially in fish exposed to 15 and 20 psu. The expression of heat shock proteins (hsp) hsp60, hsp70, and hsp90 was significantly increased in fish reared in 15 and 20 psu. On the other hand, the expression of pattern recognition receptors (PRRs) were inhibited in fish exposed to 20 psu at D20. In conclusion, the fish intestinal microbiota was significantly disrupted in salinities higher than 10 psu and these effects were proportional to the exposure time. In addition, the modifications of intestinal gene expression related to ion exchange and stressful responses may help the fish to adapt hyperosmotic environment

Background The striped catfish, Pangasianodon hypophthalmus , is a freshwater and benthopelagic fish common in the Mekong River delta. Catfish constitute a valuable source of dietary protein. Therefore, they are cultured worldwide, and P. hypophthalmus is a food staple in the Mekong area. However, genetic information about the culture stock, is unavailable for breeding improvement, although genetics of the channel catfish, Ictalurus punctatus , has been reported. To acquire genome sequence data as a useful resource for marker-assisted breeding, we decoded a draft genome of P. hypophthalmus and performed comparative analyses. Results Using the Illumina platform, we obtained both nuclear and mitochondrial DNA sequences. Molecular phylogeny using the mitochondrial genome confirmed that P. hypophthalmus is a member of the family Pangasiidae and is nested within a clade including the families Cranoglanididae and Ictaluridae. The nuclear genome was estimated at approximately 700 Mb, assembled into 568 scaffolds with an N50 of 14.29 Mbp, and was estimated to contain ~ 28,600 protein-coding genes, comparable to those of channel catfish and zebrafish. Interestingly, zebrafish produce gadusol, but genes for biosynthesis of this sunscreen compound have been lost from catfish genomes. The differences in gene contents between these two catfishes were found in genes for vitamin D-binding protein and cytosolic phospholipase A 2 , which have lost only in channel catfish. The Hox cluster in catfish genomes comprised seven paralogous groups, similar to that of zebrafish, and comparative analysis clarified catfish lineage-specific losses of A5a , B10a, and A11a . Genes for insulin-like growth factor (IGF) signaling were conserved between the two catfish genomes. In addition to identification of MHC class I and sex determination-related gene loci, the hypothetical chromosomes by comparison with the channel catfish demonstrated the usefulness of the striped catfish genome as a marker resource. Conclusions We developed genomic resources for the striped catfish. Possible conservation of genes for development and marker candidates were confirmed by comparing the assembled genome to that of a model fish, Danio rerio , and to channel catfish. Since the catfish genomic constituent resembles that of zebrafish, it is likely that zebrafish data for gene functions is applicable to striped catfish as well.

Abstract In this study, striped catfish larvae were gradually exposed to the increase of different salinities, and then they reached the levels of 0, 5, 10, 15, and 20 psu after 10 days, followed by heat shock at 39 °C to determine stress tolerance. After the 10-day experiment, the survival rate of fish exposed to the 20 psu treatment was only 28.6 ± 4%, significantly lower than that of the other treatments. The results showed that the osmolality of the whole-body (WB) homogenate was gradually and significantly increased with salinity elevation, except in fish exposed to freshwater and 5 psu treatments, while there were no significant changes in WB Na+/K+-ATPase activity. Digestive enzymatic activities, i.e., pepsin, α-amylase, alkaline phosphatase, and leucine alanine peptidase (leu-ala) generally increased with salinity, but not aminopeptidase and trypsin. Lysozyme and peroxidase activities increased in fish larvae exposed to 15 and 20 psu. These increases proportionally improved growth performance, with the lowest and the highest final weights observed in fish reared at 0 psu (0.08 ± 0.03 g/larvae) and 20 psu (0.11 ± 0.02 g/larvae), respectively, although the average growth recorded at 20 psu could be biased by the high mortality in this group. Occurrence of skeleton deformities, such as in caudal vertebrae and branchiostegal rays, was significantly higher in fish exposed to the higher osmotic conditions (15.0 ± 1.2% and 10.3 ± 2.1% respectively at 0 psu vs. 31.0 ± 2.9% and 49.0 ± 5.6%, respectively at 15 psu). After the 12.5-h heat shock, survival rates significantly differed between treatments with the highest survival observed in fish submitted to 5 psu (68.9%), followed by those exposed to 0 (27%) and 10 (20%) while all fish died at 15 psu. These findings suggest that the striped catfish larvae could be reared in salinity up to 5 to 10 psu with a higher survival and tolerance to thermal stress when compared to fish maintained in freshwater.