Channel Catfish Ictalurus Punctatus Research Articles

Interleukin-26 in channel catfish (Ictalurus punctatus): Molecular characterization and immune functional activity

IL-26 is a crucial inflammatory cytokine that participates in defending host cells against infections. We initially cloned and identified the cDNA sequences of interleukin (IL)-26 in channel catfish (Ictalurus punctatus). The open reading frame (ORF) of IpIL-26 was 537 bp in length, encoding 178 amino acids (aa). Constitutive expression of IpIL-26 was observed in tested tissues, with the highest level found in the gill and spleen. To explore the function of IpIL-26 in channel catfish, different stimuli were used to act on both channel catfish and channel catfish kidney cells (CCK). The expression of IpIL-26 could be up-regulated by bacteria and viruses in multiple tissues. In vitro, recombinant IpIL-26 (rIpIL-26) could induce the expression levels of inflammatory cytokines such as TNF-α, IL-1β, IL-6, IL-20, and IL-22 playing vital roles in defending the host against infections. Our results demonstrated that IpIL-26 might be an essential cytokine, significantly affecting the immune defense of channel catfish against pathogen infections.

Effects of different thermal methods and degrees on the flavor of channel catfish (Ictalurus punctatus) fillets: Fatty acids, volatile flavor and taste compounds

The effects of different thermal processing conditions on the flavor profiles of channel catfish were evaluated in terms of fatty acids, volatile flavor and taste compounds using steaming, boiling, roasting, and microwaving with different degrees. After thermal processing, 72 volatile organic compounds were detected, including 20 hydrocarbons, 5 ketones, 20 aldehydes, 7 heterocyclic compounds, 12 alcohols and others. Meanwhile, the contents of unsaturated fatty acids like oleic acid and linoleic showed a significant decline due to their heat-sensitive properties. With regard to taste compounds, thermal processing contributed to umami amino acids and free nucleotides conversion, with the initial glutamate and IMP contents of 15.87 and 164.91 mg/100 g in raw samples mainly increasing by 2.8–10.3 and 14.4–105.5 mg/100 g in processed ones. Compared to other methods, microwaving had limited effects on flavor compounds, and steaming and roasting had better performance to improve the flavor complexity of channel catfish.

Fugacity and kinetic models reveal specific-fate of geosmin in air-water-fish microcosm and channel catfish (Ictalurus punctatus)

Geosmin (GSM) is a ubiquitous odorant found in aquatic environments and organisms, with significant impacts on drinking water and aquaculture. However, its transfer from contaminated water to fish tissues is poorly investigated, resulting in limited information on its bioconcentration and environmental behavior. Fugacity and one-compartment models were developed to describe the fate, transformation, and transport of GSM in an air-water-fish system and analyze its uptake, distribution, and elimination kinetics in channel catfish (Ictalurus punctatus). The results showed that the fugacity model calculations indicated that 81.3 % of GSM was found in water for all microcosm. The primary mass transfer processes from water were water-air diffusion process (T21v) and that from water to fish (T2 f), with values of 67.3 and 22.54 μg/h, respectively. The emission rate (E2) and area (A2) in water parameters are most sensitive to GSM concentration, impacting the distribution and variance of contaminant concentration. Kinetic studies in fish revealed that GSM primarily accumulate in the muscle and skin, with the earthy-odor burden of fish contributed by the former, reaching 86.59 %. The uptake rate constant (kup), depuration rate constant (kde), and half-lives (t1/2) fell within the ranges of 0.737–3.534 L/(kg·h), 0.024–0.097 1/h, and 7.1–28.9 h, respectively. Bioaccumulation factors (BAFs) for GSM in fish skin, muscle, and liver tissues were 105.79, 61.71, and 51.22 L/kg, respectively. GSM was effectively depurated by other tissues within 72 h, while 18.16 % remained in skin. The liver demonstrated the most accurate curve (R2=0.97), followed by skin and muscle, with the gill showing the worst simulation. This work offers insights into understanding the fate and mass transfer flux of trace odorants in environmental and biological phases.

Dietary supplementation of mineral nanoparticles for channel catfish (Ictalurus punctatus).

This study evaluated the supplementation of iron and copper nanoparticles in channel catfish diets and their influences on growth and health. A comparative feeding trial was carried out for 9weeks to evaluate combinations of iron and copper nanoparticles: only iron nanoparticles (IronNP), only copper nanoparticles (CopperNP), CopperNP + IronNP, and a control diet supplemented with inorganic iron and copper (FeSO4 and CuSO4). After a 9-week feeding trial, growth performance, hematological parameters, whole-body proximate composition, and intestinal microbiota were evaluated, and fish were subjected to a bacterial challenge against Edwardsiella ictaluri to evaluate the contribution of the experimental treatments to fish health status. No statistical differences were detected for catfish fed the various diets in terms of production performance or survival after bacterial challenge. The hematocrit and RBC counts from fish fed the diet containing copper nanoparticles were significantly lower than the control group. A higher relative abundance of gram-positive bacteria was found in the digesta of catfish fed diets containing copper nanoparticles. Furthermore, in the context of hematology, iron nanoparticles did not impact the blood parameters of channel catfish; however, reduced hematocrits were observed in fish fed the copper nanoparticle diet, which lacked supplemental dietary iron, thus reinforcing the importance of dietary iron to catfish hematopoiesis. Nonetheless, additional studies are needed to investigate the effects of dietary copper nanoparticle supplementation in catfish diets to better illuminate its effects on the intestinal microbiota.

Impact of hook choice, fish size, and water temperature on hooking depth, injury, and postcapture physiology in Channel Catfish

AbstractObjectiveCatch‐and‐release angling is an oft‐practiced conservation tool involving the release of captured game fish either due to harvest regulations or conservation ethic on the part of the angler. Central to this practice is the assumption that released fish survive; however, a large body of work has shown that postrelease mortality can occur, especially if fish are injured during the capture process. In this study, we examined hooking location, bleeding, injury rates, and postcapture physiology in Channel Catfish Ictalurus punctatus, a popular game fish species.MethodsA total of 83 Channel Catfish were angled from a lake in southern Illinois using conventional rod‐and‐reel techniques with one of four hook types (J‐hook, shiner, circle, and octopus). Captured fish were then assessed for hooking depth, bleeding, and injury. Subsequently, a subset of 40 fish were additionally held for 4 h in submerged totes before being tested for reflex responsiveness and undergoing a blood biopsy for glucose and lactate levels.ResultCircle and octopus hooks reduced hooking depth in Channel Catfish compared with J‐hooks and tended to reduce postcapture bleeding as well. Postholding physiological results showed no effect of hook type on blood lactate or glucose levels, and reflex impairment was very rare (only a single fish was impaired for any reflexes 4 h postcapture).ConclusionOverall, the results of this study suggest that the use of circle hooks reduce the likelihood of deep hooking and injury in Channel Catfish, though Channel Catfish, at least in the short term, were physiologically resilient to the effects of capture.

Reversible Sterilization of Channel Catfish via Overexpression of Glutamic Acid Decarboxylase Gene.

The confinement of transgenic fish is essential to prevent their escape and reproduction in natural ecosystems. Reversible transgenic sterilization is a promising approach to control the reproduction of transgenic fish. Therefore, the present study was conducted to develop a reversibly sterile channel catfish (Ictalurus punctatus) via the transgenic overexpression of the goldfish (Carassius auratus) glutamic acid decarboxylase (GAD) gene driven by the common carp (Cyprinus carpio) β-actin promoter to disrupt normal gamma-aminobutyric acid (GABA) regulation. Three generations of GAD-transgenic fish were produced. All studied generations showed repressed reproductive performance; however, this was not always statistically significant. In F1, 5.4% of the transgenic fish showed a sexual maturity score ≥ 4 (maximum = 5) at five years of age, which was lower (p = 0.07) than that of the control group (16.8%). In the spawning experiments conducted on F1 transgenic fish at six and nine years of age, 45.5% and 20.0% of fish spawned naturally, representing lower values (p = 0.09 and 0.12, respectively) than the percentages in the sibling control fish of the same age (83.3% and 66.7%, respectively). Four of six pairs of the putative infertile six-year-old fish spawned successfully after luteinizing hormone-releasing hormone analog (LHRHa) therapy. Similar outcomes were noted in the three-year-old F2 fish, with a lower spawning percentage in transgenic fish (20.0%) than in the control (66.7%). In one-year-old F2-generation transgenic fish, the observed mean serum gonadotropin-releasing hormone (GnRH) levels were 9.23 ± 2.49 and 8.14 ± 2.21 ng/mL for the females and males, respectively. In the control fish, the mean levels of GnRH were 11.04 ± 4.06 and 9.03 ± 2.36 ng/mL for the females and males, respectively, which did not differ significantly from the control (p = 0.15 and 0.27 for females and males, respectively). There was no significant difference in the estradiol levels of the female transgenic and non-transgenic fish in the one- and four-year-old F2-generation fish. The four-year-old F2-generation male transgenic fish exhibited significantly (p < 0.05) lower levels of GnRH and testosterone than the control fish. In conclusion, while overexpressing GAD repressed the reproductive abilities of channel catfish, it did not completely sterilize transgenic fish. The sterilization rate might be improved through selection in future generations.

Supplementation of Mangiferin to a High-Starch Diet Alleviates Hepatic Injury and Lipid Accumulation Potentially through Modulating Cholesterol Metabolism in Channel Catfish (Ictalurus punctatus).

Starch is a common source of carbohydrates in aqua feed. High-starch diet can cause hepatic injury and lipid accumulation in fish. Mangiferin (MGF) can regulate lipid metabolism and protect the liver, but there is limited research on its effects in fish. In the present study, we investigated whether MGF could ameliorate high-starch-induced hepatic damage and lipid accumulation in channel catfish. The channel catfish (Ictalurus punctatus) were fed one of four experimental diets for eight weeks: a control diet (NCD), a high-starch diet (HCD), an HCD supplemented with 100 mg/kg MGF (100 MGF), and an HCD supplemented with 500 mg/kg MGF (500 MGF). The results demonstrated that the weight gain rate (WGR) (p = 0.031), specific growth rate (SGR) (p = 0.039), and feed conversion efficiency (FCE) (p = 0.040) of the 500 MGF group were significantly higher than those of the NCD group. MGF supplementation alleviated liver damage and improved antioxidant capacity (T-AOC) compared to those of the HCD group (p = 0.000). In addition, dietary MGF significantly reduced plasma glucose (GLU) (p = 0.000), triglyceride (TG) (p= 0.001), and low-density lipoprotein cholesterol (LDL) (p = 0.000) levels. It is noteworthy that MGF significantly reduced the plasma total cholesterol (TC) levels (p = 0.000) and liver TC levels (p = 0.005) of channel catfish. Dietary MGF improves cholesterol homeostasis by decreasing the expression of genes that are involved in cholesterol synthesis and transport (hmgcr, sqle, srebf2, sp1, and ldlr) and increasing the expression of genes that are involved in cholesterol catabolism (cyp7a1). Among them, the largest fold decrease in squalene epoxidase (sqle) expression levels was observed in the 100 MGF or 500 MGF groups compared with the HCD group, with a significant decrease of 3.64-fold or 2.20-fold (p = 0.008). And the 100 MGF or 500 MGF group had significantly decreased (by 1.67-fold or 1.94-fold) Sqle protein levels compared to those of the HCD group (p = 0.000). In primary channel catfish hepatocytes, MGF significantly down-regulated the expression of sqle (p = 0.030) and reduced cholesterol levels (p = 0.000). In NCTC 1469 cells, MGF significantly down-regulated the expression of sqle (p = 0.000) and reduced cholesterol levels (p = 0.024). In conclusion, MGF effectively inhibits sqle expression and reduces cholesterol accumulation. The current study shows how MGF supplementation regulates the metabolism and accumulation of cholesterol in channel catfish, providing a theoretical basis for the use of MGF as a dietary supplement in aquaculture.

Use of electroencephalogram (EEG) to optimize stunning efficiency and animal welfare in commercial catfish production

The welfare of farmed fish has gained increasing attention during recent decades, and as technological advances have facilitated measurements of brain activity in fish, the slaughter process has been highlighted as an area for assessment and potential improvement. Here, we used electroencephalograms (EEG) to assess brain activity in channel catfish (Ictalurus punctatus), and used commercial slaughter practices to guide optimization of stunning conditions in a laboratory setting. Following in-air electro-stunning at processing plants, individual fish responses to the shock varied based on EEG and corresponding ventilation measurements prior to physical euthanasia. Results from laboratory experiments showed stunning efficacy is dependent on shock duration and the location where electrodes contact fish. Electrodes contacting the head for 1 s using 50 Hz 132 AC VRMS, with a current >380 mARMS, caused immediate loss of consciousness lasting 10–40 s. When the exposure period was prolonged to 6 s, recovery time was significantly longer, ranging from 45 to 240 s (mean 125 s). If the electrodes contacted the body instead of the head, shock delivered for 6 s resulted in a shorter recovery time of 0–100 s (mean 48 s). These findings highlight that shock duration and electrode position are important when stunning channel catfish and presumably other fishes, and indicate the time from stunning to killing should be kept as short as possible.

Dietary betulinic acid alleviates high carbohydrate diet-induced hepatic de novo lipogenesis through AMPK signaling and improves liver health in channel catfish (Ictalurus punctatus)

A high carbohydrate diet (HCD) induced excessive hepatic de novo lipogenesis, which caused metabolic disorder and impaired the health of fish species. Betulinic acid (BA) has been applied to ameliorate fatty liver and anti-inflammatory in mammals. Here, we investigated the effects of dietary BA supplementation on HCD-induced hepatic de novo lipogenesis and liver health in channel catfish (Ictalurus punctatus). The catfish were fed with three diets: NCD (18 % carbohydrate), HCD (36 % carbohydrate), HCD+BA (36 % carbohydrate with 150 mg/kg BA). After an 8-week feeding trial, we found that dietary BA decreased hepatosomatic index (HSI) and condition factor (CF) without affecting the growth of channel catfish fed HCD. Dietary BA significantly reduced the HCD-induced excessive lipid accumulation (oil red O area, TG content, and de novo lipogenesis gene expression, P < 0.05). Moreover, we found that dietary BA prevented hepatic lipid accumulation via activating phosphorylation of adenosine monophosphate-activated protein kinase (AMPK) and inhibiting sterol regulatory element-binding protein 1 (SREBP1) (P < 0.05) in liver of channel catfish fed HCD. Besides, we also found that dietary BA significantly prevented HCD-induced liver damage, as confirmed by liver H&E staining, reduced inflammation biomarkers (ALT, AST, hydroxyproline, α-sma and tgf-1β), downregulated expression of ER stress-related genes (eif2a, bip, atf4, xbp1) (P < 0.05). Overall, the present study indicated that dietary BA inclusion attenuated hepatic de novo lipogenesis, improved liver inflammation and reduced ER stress in channel catfish fed HCD.

Direct and pleiotropic effects of antimicrobial peptide transgene integration on reproductive, growth regulating, and non-coding loci in channel catfish (Ictalurus punctatus)

Antimicrobial peptides (AMPs) show promise in enhancing resistance against pathogens. Previously, we integrated two AMP genes, cathelicidin (Cath) from alligator (Alligator mississippiensis or Alligator sinensis) and cecropin (Cec) from moth (Hyalophora cecropia), into the channel catfish (Ictalurus punctatus) genome. This study examines the efficacy of exogenous AMP gene integration in improving bacterial resistance in transgenic channel catfish and assesses the direct and pleiotropic effects of gene replacement/knockout on survival and growth based on insertion site. Transgenic Cath- and Cec-expressing fish exhibited similar or higher survival rates (P ​> ​0.05) compared to controls during the initial culture. Integration of the Cec transgene doubled the survival rate when challenged with Edwardsiella ictaluri, with knock-in (KI) of Cath further increasing bacterial resistance. Coupling Cec KI with mstn knockout (KO) increased survival 3-fold after E. ictaluri infection and growth by 50% at 4 months post-fertilization (mpf). However, random integration of Cec had a minimal effect on disease resistance and did not enhance growth. Random integration of Cath increased survival 2.5-fold and 4-fold against E. ictaluri and Flavobacterium covae, respectively, without affecting growth. Cath KI at the lh locus increased survival 4-fold when challenged with F. covae and reduced growth by 10% (P ​> ​0.05) at 24 mpf, whereas Cath KI coupled with mc4r KO resulted in a 2.5-fold increase in survival following F. covae infection compared with controls, and increased growth by 80% at 3 mpf. Simultaneous KI of Cath and Cec, along with KO of mc4r and mstn, increased survival 4-fold against E. ictaluri, while increasing growth by 50% at 3 mpf. Dual insertion of AMP genes yielded the greatest resistance to disease. These direct and pleiotropic effects may increase comprehension and societal acceptance of genetic engineering in aquaculture.

Hypothalamic transcriptome response to simulated diel earthen pond hypoxia cycles in channel catfish (Ictalurus punctatus).

Commercial culture of channel catfish (Ictalurus punctatus) occurs in earthen ponds that are characterized by diel swings in dissolved oxygen concentration that can fall to severe levels of hypoxia, which can suppress appetite and lead to suboptimal growth. Given the significance of the hypothalamus in regulating these processes in other fishes, an investigation into the hypothalamus transcriptome was conducted to identify specific genes and expression patterns responding to hypoxia. Channel catfish in normoxic water were compared with catfish subjected to 12 h of hypoxia (20% oxygen saturation; 1.8 mg O2/L; 27°C) followed by 12 h of recovery in normoxia to mimic 24 h in a catfish aquaculture pond. Fish were sampled at 0-, 6-, 12-, 18-, and 24-h timepoints, with the 6- and 12-h samplings occurring during hypoxia. A total of 190 genes were differentially expressed during the experiment, with most occurring during hypoxia and returning to baseline values within 6 h of normoxia. Differentially expressed genes were sorted by function into Gene Ontology biological processes and revealed that most were categorized as "response to hypoxia," "sprouting angiogenesis," and "cellular response to xenobiotic stimulus." The patterns of gene expression reported here suggest that transcriptome responses to hypoxia are broad and quickly reversibly with the onset of normoxia. Although no genes commonly reported to modulate appetite were found to be differentially expressed in this experiment, several candidates were identified for future studies investigating the interplay between hypoxia and appetite in channel catfish, including adm, igfbp1a, igfbp7, and stc2b.NEW & NOTEWORTHY Channel catfish are an economically important species that experience diel episodic periods of hypoxia that can reduce appetite. This is the first study to investigate their transcriptome from the hypothalamus in a simulated 24-h span in a commercial catfish pond, with 12 h of hypoxia and 12 h of normoxia. The research revealed functional groups of genes relating to hypoxia, angiogenesis, and glycolysis as well as individual target genes possibly involved in appetite regulation.

TLR7 in channel catfish (Ictalurus punctatus) is expressed in the endolysosome and is stimulated by synthetic ssRNA analogs, imiquimod, and resiquimod.

Toll-like receptors (TLRs) are pivotal pattern recognition receptors (PRRs) and key mediators of innate immunity. Despite the significance of channel catfish (Ictalurus punctatus) in comparative immunology and aquaculture, its 20 TLR genes remain largely functionally uncharacterized. In this study, our aim was to determine the catfish TLR7 agonists, signaling potential, and cellular localization. Using a mammalian reporter system, we identified imiquimod and resiquimod, typical ssRNA analogs, as potent catfish TLR7 agonists. Notably, unlike grass carp TLR7, catfish TLR7 lacks the ability to respond to poly (I:C). Confocal microscopy revealed predominant catfish TLR7 expression in lysosomes, co-localizing with the endosomal chaperone protein, UNC93B1. Furthermore, imiquimod stimulation elicited robust IFNb transcription in peripheral blood leukocytes isolated from adult catfish. These findings underscore the conservation of TLR7 signaling in catfish, reminiscent of mammalian TLR7 responses. Our study sheds light on the functional aspects of catfish TLR7 and contributes to a better understanding of its role in immune defense mechanisms.

Novel insights into the inhibitory effect of pterostilbene targeting Aeromonas hydrophila virulence

The overuse of antibiotics in aquaculture brings a range of problems. Therefore, novel approaches alternating antibiotics are urgently needed. Strategies targeting bacterial virulence have become one of the routes developing drugs against bacterial infections. Here, we found that pterostilbene (PSE) could inhibit the activity of aerolysin (AerA) and disrupt quorum sensing (QS) at sub-inhibitory concentrations. Molecular docking and dynamics simulation assays were performed to predict the binding mode and binding sites of AerA-PSE complex. Then we confirmed that PSE bound to the sites of Val189 and Ile302 and prevented AerA forming heptamer with transmembrane pores. In addition, PSE could protect to A549 cells and the channel catfish (Ictalurus punctatus) against AerA mediated cell injury and mortality infected with A. hydrophila. The findings demonstrated that targeting bacterial virulence could be a promising measure identifying agents against A. hydrophila infections.

Transcriptome analysis revealed potential mechanisms of channel catfish growth advantage over blue catfish in a tank culture environment.

Channel catfish (Ictalurus punctatus) and blue catfish (Ictalurus furcatus) are two economically important freshwater aquaculture species in the United States, with channel catfish contributing to nearly half of the country's aquaculture production. While differences in economic traits such as growth rate and disease resistance have been noted, the extent of transcriptomic variance across various tissues between these species remains largely unexplored. The hybridization of female channel catfish with male blue catfish has led to the development of superior hybrid catfish breeds that exhibit enhanced growth rates and improved disease resistance, which dominate more than half of the total US catfish production. While hybrid catfish have significant growth advantages in earthen ponds, channel catfish were reported to grow faster in tank culture environments. In this study, we confirmed channel fish's superiority in growth over blue catfish in 60-L tanks at 10.8 months of age (30.3 g and 11.6g in this study, respectively; p < 0.001). In addition, we conducted RNA sequencing experiments and established transcriptomic resources for the heart, liver, intestine, mucus, and muscle of both species. The number of expressed genes varied across tissues, ranging from 5,036 in the muscle to over 20,000 in the mucus. Gene Ontology analysis has revealed the functional specificity of differentially expressed genes within their respective tissues, with significant pathway enrichment in metabolic pathways, immune activity, and stress responses. Noteworthy tissue-specific marker genes, including lrrc10, fabp2, myog, pth1a, hspa9, cyp21a2, agt, and ngtb, have been identified. This transcriptome resource is poised to support future investigations into the molecular mechanisms underlying environment-dependent heterosis and advance genetic breeding efforts of hybrid catfish.

Plasma and tissue transferrin and ferritin, and gene expression of ferritin, transferrin, and transferrin receptors I and II in channel catfish Ictalurus punctatus fed diets with different concentrations of inorganic or organic iron.

Ferritin, transferrin, and transferrin receptors I and II play a vital role in iron metabolism, health, and indication of iron deficiency anaemia in fish. To evaluate the use of high-iron diets to prevent or reverse channel catfish (Ictalurus punctatus) anaemia of unknown causes, we investigated the expression of these iron-regulatory genes and proteins in channel catfish fed plant-based diets. Catfish fingerlings were fed five diets supplemented with 0 (basal), 125, and 250 mg/kg of either inorganic iron or organic iron for 2 weeks. Ferritin, transferrin, and transferrin receptor I and II mRNA and protein expression levels in fish tissues (liver, intestine, trunk kidney, and head kidney) and plasma were determined. Transferrin (iron transporter) and TfR (I and II) genes were generally highly expressed in fish fed the basal diet compared to those fed the iron-supplemented diets. In contrast, ferritin (iron storage) genes were more expressed in the trunk kidney of fish fed the iron-supplemented diets than in those fed the basal diet. Our results demonstrate that supplementing channel catfish plant-based diets with iron from either organic or inorganic iron sources affected the expression of the iron-regulatory genes and increased body iron status in the fish.

Mitochondrial damage and activation of NLRP3 induced by Yersinia ruckeri infection play an important role in the occurrence of diffuse acute inflammation of channel catfish (Ictalurus punctatus)

Yersinia ruckeri, as a facultative intracellular pathogen, can cause two different infection phenotypes of fish. An important phenotype is diffuse acute inflammation (DAI), which is mainly characterized by systemic hemorrhage and multiple tissues damage. Another phenotype is enteric redmouth symptom (EM) with predominantly digestive system damage, while slight damage to other tissues and organs. At present, the causes and mechanisms of heterogeneity of Y. ruckeri infection are not clear. According to our previous research and related bioinformatics analysis, it is suggested that the heterogeneity of infection of Y. ruckeri may be related to the activation of intracellular pattern recognition receptor (NLRP3). Furthermore, combined with the transmission electron microscope observation and ultrastructural pathological analysis of DAI and EM phenotypes, it is hypothesized that Y. ruckeri infection may mediate the occurrence of DAI by inducing mitochondrial damage and activation of NLRP3. In this study, we established DAI and EM phenotypes of channel catfish (Ictalurus punctatus) through the artificial infection experiment. Subsequently, we observed the pathological changes and characteristics of different tissues in DAI and EM phenotypes, such as liver, spleen, kidney, intestine and gill. In addition, the mitochondrial damage of head kidney mediated by Y. ruckeri infection was confirmed by transmission electron microscope observation. Furthermore, by detecting the expression of proinflammatory factors and related pattern recognition receptors in various tissues, we preliminarily clarified the molecular characteristics of immune response in DAI and EM phenotype fish. Moreover, the head kidney macrophages isolated from DAI and EM were observed through transmission electron microscope, and the expression levels of NLRP3, Caspase-1 and IL-1β were detected. Finally, the correlation between mitochondrial damage induced by Y. ruckeri infection and NLRP3 signal transduction was preliminary revealed. Taken together, our results showed that the inflammatory DAI phenotype of fish mediated by Y. ruckeri infection is closely related to mitochondrial damage and NLRP3 activation, which will provide theoretical basis for further study on the pathogenic mechanism of Y. ruckeri infection and clinical diagnosis of the disease, and also provide some insights into the role of NLRP3 in the natural immunity of aquatic animals.

Susceptibility of Delta Select and Delta Control Channel Catfish lines to experimental Edwardsiella ictaluri and Edwardsiella piscicida infection

AbstractObjectiveThe Delta Select line of Channel Catfish Ictalurus punctatus was established in 2006 and has undergone five generations of genetic selection, specifically targeting increased growth rate and carcass yield, and was released to U.S. catfish farmers in 2020. While improvements in growth rate and carcass yield have been confirmed, performance for other important production traits has yet to be evaluated. Infectious disease, particularly bacterial infections caused by Edwardsiella spp., cause significant economic losses to catfish producers in the southeastern United States. Given the economic consequences of these bacterial pathogens, experimental infectivity trials were conducted comparing susceptibility to Edwardsiella spp. between the Delta Select line and a randomly bred line of Channel Catfish originating from the same base population (Delta Control line).MethodsTwenty‐six full‐sib families from each line were used in infectivity trials consisting of a high and a low dose of E. ictaluri (immersion challenge: high dose = 1.6 × 107 CFU/mL, low dose = 8.0 × 106 CFU/mL) and E. piscicida (intracoelomic challenge: high dose = 6.3 × 105 CFU/fish, low dose = 1.9 × 105 CFU/fish).ResultThe high challenge dose resulted in the highest mortality for both pathogens (p &lt; 0.001), regardless of selection line. There was no significant difference in cumulative percent mortality between the Delta Select and Delta Control lines following the E. ictaluri challenge at either dose (p = 0.55). Delta Selects had reduced mortality (p &lt; 0.001) in response to E. piscicida challenge compared with the Delta Controls, regardless of dose.ConclusionThese results indicate that selection for increased growth rate and carcass yield in the Delta Select Channel Catfish line did not negatively impact resistance to E. ictaluri while potentially improving resistance to E. piscicida.

Combining Ability of Female Channel Catfish, Ictalurus punctatus, and Male Blue Catfish, I. furcatus, for Early Growth Performance of Their Progeny

The hybrid between the female channel catfish (Ictalurus punctatus) and the male blue catfish (I. furcatus) is the best genetic type currently available for commercial catfish farming due to their superior traits. However, further genetic improvements can be achieved by selecting parents with increased combining abilities. Twenty female channel catfish and twelve male blue catfish were crossed in a partial factorial mating design, resulting in forty hybrid families. These families were evaluated for early growth in three different rearing systems, including ponds and aquaria. The early growth performance of hybrid catfish was significantly (p &lt; 0.05) affected by the additive gene action of the female parent and the male parent. There were genotype–environment or genotype–age interactions affecting the combining abilities, both the amount and the type of genetic variation. Dam GCA was significant in all environments/ages; however, sire GCA was variable, and SCA was not significant. These findings suggest that reciprocal recurrent selection for growth could potentially improve the performance of F1 hybrid catfish.

Microbiota of laboratory channel catfish skin mucosa and aquaria water exposed to chloramine-T trihydrate.

Here, we describe the skin mucosa microbiome of channel catfish (Ictalurus punctatus) before and after exposure to chloramine-T trihydrate. We also describe the aquaria water microbiome after the post-treatment period. These data provide a unique baseline description of skin mucosa and aquaria water microbiome from catfish reared in research aquaria.

Exploring the nutritional value of corn fermented protein as a replacement for soybean meal in diets for juvenile channel catfish (Ictalurus punctatus): Impacts on production performance, intestinal health, and disease resistance

The use of corn fermented protein (CFP) can be a promising alternative ingredient to replace soybean meal (SBM) in aquafeeds, because of its attractive price and constant supply. In this study, the apparent digestibility of CFP was evaluated with channel catfish (Ictalurus punctatus), followed by a comparative feeding trial in which dehulled, solvent extracted SBM in the control diet was incrementally replaced with graded levels of CFP. A slight but significantly higher apparent protein digestibility coefficient was observed for SBM (91%) compared to CFP (89%). However, phosphorus and lipid were twice as available from CFP than SBM. A 60-day feeding trial was conducted, testing the gradual replacement of SBM by CFP on an equalnitrogen basis at 0, 25, 50, 75, and 100%. Channel catfish juveniles (∼11.6 g) were stocked in 30 aquaria (30 fish/ 110-L tank; n = 6) operating as a recirculating system and offered the experimental diets to apparent satiation twice daily. No differences were observed for hepatosomatic index, survival, or serum superoxide dismutase and lysozyme activities. Also, no treatment effects were observed for whole-body protein, ash, and protein conversion efficiency. However, weight gain, feed efficiency, intraperitoneal fat, and whole-body lipid were significantly affected by the dietary treatments with CFP able to replace up to 40 to 58% of the SBM in the diet while providing similar fish performance and body composition as fish fed the control diet. Digesta samples from the posterior segment of the intestine were subjected to DNA extraction, followed by 16S rRNA gene (V3-V4 region) sequencing to profile the intestinal microbiota. A higher relative abundance of Aeromonas spp. was observed for fish fed the control diet. The remaining fish from the feeding trial were challenged with Edwardsiella ictaluri, and cumulative survival was monitored for 21 days. Survival after the bacterial challenge gradually increased as the inclusion levels of CFP increased in the diets, with the 100% replacement treatment being significantly different from the control diet. In conclusion, CFP is a promising alternative plant protein ingredient with high protein and phosphorus digestibility, and it can replace up to 40 to 58% of the SBM in feed formulations for juvenile channel catfish based on weight gain and feed efficiency while potentially increasing disease resistance against E. ictaluri.