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The catfishes are a group of economically important freshwater fish in China, which in recent years have suffered heavy losses as a result of bacterial outbreaks. In this study, we examined the diversity of the microbiome of infected skin mucus of yellow catfish (Pelteobagrus fulvidraco) and channel catfish (Ictalurus punctatus) and analyzed the bacterial pathogens. We found several common pathogenic bacteria, such as Aeromonas spp., Vibrio spp., Moraxella spp. and Proteus spp. present in both fish species, but with significantly different bacterial community structures. We isolated and cultured Aeromonas veronii and Proteus mirabilis and validated their infectivity in zebrafish (Danio rerio) and yellow catfish. Intraperitoneal injection of either bacteria into zebrafish, but not immersion, caused 100% mortality and ovary fragmentation. Yellow catfish was more sensitive than zebrafish with 100% mortality in the immersion challenges with A. veronii or P. mirabilis, and with a higher abundance of A. veronii in the P. mirabilis-challenged group compared to control. To our knowledge, this is the first study on the pathogenicity of P. mirabilis in yellow catfish, and the results will help to develop effective strategies for the disease prevention and control in catfish farming. more...

Coastal rivers and estuaries provide habitat and migratory corridors for freshwater estuarine-opportunists. We evaluated movement patterns of 61 blue catfish (Ictalurus furcatus) in the tidal York and Rappahannock rivers in Virginia, USA with acoustic telemetry from July 2015 to June 2016. To evaluate river-specific movements, we utilized a multistate Cormack–Jolly–Seber (CJS) model within a Bayesian framework to estimate probabilities of detection and transition (movement) among established salinity zones (i.e., tidal-fresh (0‰–0.5‰), oligohaline (>0.5‰–5‰), mesohaline (>5‰–18‰)). We considered flow as an environmental covariate. Despite high site fidelity in tidal-fresh zones, some individuals displayed movements into oligohaline and mesohaline habitats indicative of partial migration. Once downstream movement occurred, the probability of staying in the new salinity zone was higher than the probability of movements to other salinity zones. In the Rappahannock River only, movement upstream from mesohaline habitats was associated with below average flow. As flow increased, the probability of remaining in oligohaline and mesohaline zones increased. Our study shows blue catfish can move into downstream areas of tidal rivers with elevated salinities and that increased freshwater flow may allow them to remain in these habitats for extended durations. more...

This study compared growth performance between female and male transgenic channel catfish, Ictalurus punctatus, containing channel catfish growth hormone full-length cDNA driven by the ocean pout antifreeze protein promoter, opAFP-ccGH, the rainbow trout metallothionein promoter, rtMT-ccGH, or both constructs, and their non-transgenic siblings in earthen ponds at 16 and 48 months of age. Body weight between the transgenic and their non-transgenic siblings differed (P 0.05). In the case of non-transgenic GH siblings, males were larger than females at both 16 and 48 months of age (P more...

Abstract The skeleton of Siluriformes is characterized by several autapomorphies, including secondary absence, extreme modification, and purported fusion of several ossifications. Although well documented in adults, information on skeletal development in catfishes is relatively sparse and typically focused on particular regions of the skeleton (e.g., Weberian apparatus). To further our understanding of the siluriform skeleton, I document the development of the entire skeleton in two ictalurid species, Ictalurus punctatus (channel catfish) and Noturus gyrinus (tadpole madtom) from five days pre-hatch to adult. I reexamine the homologies of bones previously hypothesized to represent compound elements in catfishes as well as an additional element only known to occur in some ictalurids. Development of the skeleton is complete in I. punctatus at 22.4 mm SL and almost complete in N. gyrinus (except dorsal- and anal-fin distal radials) at 14.1 mm SL. No signs of ontogenetic fusion were observed in any of the purported compound elements. Previous hypotheses of the homology of these elements and of additional ossifications are reviewed in light of developmental information obtained herein. No dermal parietal component is present at any stage in the so-called parieto-supraoccipital. The bone is the supraoccipital which ossifies from two lateral centers of ossification which later fuse, rather than from a median center. The 'posttemporo-supracleithrum' originates from a single center of ossification and represents the supracleithrum. The posttemporal is present in ictalurids and many other catfishes as a canal-bearing bone between the supracleithrum and the pterotic, a bone sometimes identified as the extrascapular. The extrascapular is missing in catfishes. Ictalurids have an additional dermal bone above the posttemporal, which is either an independently ossifying fragment of the posttemporal or a neoformation restricted to some members of this family. The single chondral bone of the pectoral girdle originates from a single center of ossification that represents the coracoid. The scapula is missing in catfishes. Dorsal-fin distal radial 2 is absent in catfishes and the foramen of dorsal-fin spine 2 is formed from modifications to the base of the fin-ray itself. Unlike loricarioid catfishes, the urohyal of ictalurids originates solely as an ossification of the sternohyoideus tendons. The anteriormost infraorbital element ossifies from a single center of ossification around the infraorbital sensory canal and represents the lacrimal. The antorbital is missing in catfishes. Finally, skeletal development of I. punctatus is compared to that available for other otophysans, including the cypriniforms Danio rerio and Enteromius holotaenia and the characiform Salminus brasiliensis. more...

The genus Henneguya is the second largest within the class Myxosporea, which infects marine and freshwater fish. One hundred Clarias gariepinus specimens were collected alive from a branch of the Nile River in Kafrelsheikh, Egypt. Microscopic and molecular procedures were used to describe how Henneguya fusiformis infects the ovaries of C. gariepinus. The infected fish showed no pathogenic changes except for macroscopic creamy whitish nodules in their ovaries with the highest prevalence during the spring season. The mature spores are spindle-shaped. The total spore length, spore body length and width are 53.4 ± 0.8 (52.5–54.3) µm, 29.8 ± 0.5 (29.2–30.4) µm and 6.5 ± 0.3 (6.1–6.9) µm, respectively. The spore anterior end consisted of two equal polar capsules, located in a tandem position, each one measuring 4.2 × 2.1 µm. The polar filament formed a coil with 6–8 turns. The measurement of the spore end with two extended processes was 24.3 ± 0.4 (23.9–24.8) µm. Phylogenetic analyses of the 18S ribosomal RNA gene sequence revealed that H. fusiformis are clustered together with other myxobolids that are histozoic in channel catfish, Ictalurus punctatus, and Asian Redtail catfish, Hemibagrus nemurus” (Clariidae) in the United States and Malaysia, respectively. To the best of our knowledge, this is the first record of H. fusiformis in Egypt. Additionally, our study is the first record of H. fusiformis in the ovaries of C. gariepinus. more...

This study isolated CFI gene from Pelteobagrus fulvidraco and named it PfCFI. The cDNA of PfCFI is 2374 bp long, including a 52 bp 5′ untranslated sequence, a 222 bp 3′ untranslated sequence, and an open reading frame (ORF) of 2100 bp encoding polypeptide consisting of 699 amino acids. Phylogenetic analysis revealed that the PfCFI was closely related to CFI of Ictalurus punctatus. Real-time quantitative reverse transcription-PCR (qRT-PCR) analysis indicate that there is the PfCFI gene which expressed in all the rest of tested tissues in varied levels, and mainly distributed in liver and least in heart. The reseachers induce the expressions level of PfCFI gene in liver, spleen, head kidney and blood at different points in time after challenged with lipopolysaccharide (LPS), and polyriboinosinic polyribocytidylic acid (poly I:C), respectively. Together these results suggested that CFI gene plays an important role in resistance to pathogens in yellow catfish immunity. more...

Sustainability of channel catfish, Ictalurus punctatus ♀ × blue catfish, Ictalurus furcatus ♂ hybrid aquaculture relies on new innovative technologies to maximize fry output. Transplanting spermatogonial stem cells (SSCs) from blue catfish into channel catfish hosts has the potential to greatly increase gamete availability and improve hybrid catfish fry outputs. Cryopreservation would make these cells readily accessible for xenogenesis, but a freezing protocol for blue catfish testicular tissues has not yet been fully developed. Therefore, the objectives of this experiment were to identify the best permeating [dimethyl sulfoxide (DMSO), ethylene glycol (EG), glycerol, methanol] and non-permeating (lactose or trehalose with egg yolk or BSA) cryoprotectants, their optimal concentrations, and the best freezing rates (−0.5, −1.0, −5.0, −10 °C/min until −80 °C) that yield the highest number of viable type A spermatogonia cells. Results showed that all of these factors had significant impacts on post-thaw cell production and viability. DMSO was the most efficient permeating cryoprotectant at a concentration of 1.0 M. The optimal concentration of each cryoprotectant depended on the specific cryoprotectant due to interactions between the two factors. Of the non-permeating cryoprotectants, 0.2 M lactose with egg yolk consistently improved type A spermatogonia production and viability beyond that of the 1.0 M DMSO control. The overall best freezing rate was consistent at −1 °C/min, but similar results were obtained using −0.5 °C/min. Overall, we recommend cryopreserving blue catfish testicular tissues in 1.0 M DMSO with 0.2 M lactose and egg yolk at a rate of either -0.5 or −1 °C/min to achieve the best cryopreservation outcomes. Continued development of cryopreservation protocols for blue catfish and other species will make spermatogonia available for xenogenic applications and genetic improvement programs. more...

Cathelicidins are a class of antimicrobial peptides (AMPs) known to possess rapid and direct antimicrobial activities against a variety of microorganisms. Recently identified cathelicidins derived from alligator and sea snake were found to be more effective in inhibiting microbial growth than other AMPs previously characterized. The ability of these two cathelicidins along with the peptides, cecropin and pleurocidin, to protect channel catfish (Ictalurus punctatus, Rafinesque) and hybrid catfish (I. punctatus ♀ × blue catfish, Ictalurus furcatus, Valenciennes ♂) against Edwardsiella ictaluri, one of the most prevalent pathogens affecting commercial catfish industry, was investigated. Cathelicidin-injected fish (50 µg ml-1 fish-1 ) that were simultaneously challenged with E. ictaluri through bath immersion at a concentration of ~1 × 106 CFU/ml had increased survival rates compared with other peptide treatments and the infected control. Bacterial numbers were also reduced in the liver and kidney of channel catfish and hybrid catfish in the cathelicidin treatments 24 hr post-infection. After 8 days of challenge, serum was collected to determine immune-related parameters such as bactericidal activity, lysozyme, serum protein, albumin and globulin. These immune-related parameters were significantly elevated in fish injected with the two cathelicidins as compared to other peptide treatments. These results indicate that cathelicidins derived from alligator and sea snake can stimulate immunity and enhance the resistance to E. ictaluri infection in channel catfish and hybrid catfish. more...

Proliferative gill disease (PGD) caused by the myxozoan Henneguya ictaluri is one of the most damaging diseases affecting U.S. catfish aquaculture. In channel and hybrid catfish, continuous exposure to the actinospore stage of the parasite elicits a destructive branchitis, impairing osmoregulatory and respiratory function. Mortality can reach 100% in severe outbreaks. Despite similarities during acute stages of infection, research indicates arrested development in hybrid catfish, evinced by reduced H. ictaluri sporogenesis and comparably less parasite DNA in hybrid tissues across the developmental timeline. To assess these findings at the pond level, 18, 0.4‐ha ponds were stocked (3,000 fish/pond) with channel (n = 9) or hybrid (n = 9) catfish fingerlings and maintained as monoculture systems for three production cycles, with clean harvests and restocking as warranted. Water was collected monthly for quantitative polymerase chain reaction (qPCR) estimations of H. ictaluri DNA, and sentinel fish were utilized to estimate PGD severity. By the second year, H. ictaluri DNA in hybrid systems was significantly reduced, and PGD lesions in sentinel fish were negligible. Assessment of parasite loads in fish harvested at the termination of the study revealed H. ictaluri DNA in channel catfish to be an order of magnitude higher than hybrid catfish. These results support previous work suggesting that the production of hybrid catfish may reduce PGD incidence in U.S. catfish aquaculture. more...

The complete germline repertoires of the channel catfish,Ictalurus punctatus, T cell receptor (TR) loci, TRAD, TRB, and TRG were obtained by analyzing genomic data from PacBio sequencing. The catfish TRB locus spans 214 kb, and contains 112 TRBV genes, a single TRBD gene, 31 TRBJ genes and two TRBC genes. In contrast, the TRAD locus is very large, at 1,285 kb. It consists of four TRDD genes, one TRDJ gene followed by the exons for TRDC, 125 TRAJ genes and the exons encoding the TRAC. Downstream of the TRAC, are 140 TRADV genes, and all of them are in the opposite transcriptional orientation. The catfish TRGC locus spans 151 kb and consists of four diverse V-J-C cassettes. Altogether, this locus contains 15 TRGV genes and 10 TRGJ genes. To place our data into context, we also analyzed the zebrafish TR germline gene repertoires. Overall, our findings demonstrated that catfish possesses a more restricted repertoire compared to the zebrafish. For example, the 140 TRADV genes in catfish form eight subgroups based on members sharing 75% nucleotide identity. However, the 149 TRAD genes in zebrafish form 53 subgroups. This difference in subgroup numbers between catfish and zebrafish is best explained by expansions of catfish TRADV subgroups, which likely occurred through multiple, relatively recent gene duplications. Similarly, 112 catfish TRBV genes form 30 subgroups, while the 51 zebrafish TRBV genes are placed into 36 subgroups. Notably, several catfish and zebrafish TRB subgroups share ancestor nodes. In addition, the complete catfish TR gene annotation was used to compile a TR gene segment database, which was applied in clonotype analysis of an available gynogenetic channel catfish transcriptome. Combined, the TR annotation and clonotype analysis suggested that the expressed TRA, TRB, and TRD repertoires were generated by different mechanisms. The diversity of the TRB repertoire depends on the number of TRBV subgroups and TRBJ genes, while TRA diversity relies on the many different TRAJ genes, which appear to be only minimally trimmed. In contrast, TRD diversity relies on nucleotide additions and the utilization of up to four TRDD segments. more...

The papaya and pineapple are the major agricultural food products in Thailand. Their by-products contain protease enzyme, papain and bromelain, which can breakdown proteins. The objective of this study was to investigate the growth performances of channel catfish (Ictalurus punctatus) fed with feed mixed with pineapples juice (PA) and dried papaya peel (PP) in a recirculating aquaculture system (RAS). Three experimental feeds controlled at 25% isonitrogenous formulation containing 5 ml/kg feed PA, 5 g/kg feed PP, mixed PP-PA (5 ml/kg) feed pineapple juice mixed with 5 g/kg feed papaya peel (PP-PA) and a commercial control feed were fed to catfish for 90 days. Each treatment had 3 replicates. The channel catfish (5 g/fish) were allocated in 12 (1 x 1 x 1 m) placed in RAS concrete tanks. The water quality in this research was within the recommended nets levels by the Pollution Control Department, Thailand. The results showed that weight gain, length gain, average daily gain, feed conversion efficiency and protein efficiency ratio was highest in catfish fed with PP and which was significantly different (p < 0.05) from control. The survival rate of all treatments was not significantly different (p > 0.05). In conclusion, 5 g of dried papaya peel mixed in the 1 kg of diet could be applied for channel catfish culture to improve growth performances. more...

Catfish Ictalurus spp. are subjected to stressful conditions during harvest, which may be linked to fillet coloration and quality. Poor water quality in ponds, socks or hauling tanks, as well as handling stress, have been suggested to cause red fillets in catfish; however, chronic exposure has not resulted in red fillets. Short‐term occurrences of extreme poor water quality, particularly low dissolved oxygen, high carbon dioxide and high temperature, may occur in ponds or during harvest. Therefore, market‐sized Channel Catfish Ictalurus punctatus were acutely exposed (12 hr) to one of the three water quality treatments while confined during a simulated socking procedure and evaluated for stress responses by means of change in blood parameters and fillet quality. In fish subjected to the extreme treatment, hematocrit, plasma cortisol, glucose and lactate levels increased, with 22% mortality, indicating highly stressful conditions. In fish subjected to moderate and typical (control) treatments, cortisol increased but a lack of change or decrease in glucose and lactate indicated minimal anaerobic metabolism. Only one red fillet was produced by the extreme treatment and two by the typical treatment; therefore, the results suggest red fillets are not a product of poor water quality compounded by handling during harvest. more...

To determine the role of piscine anti-viral cytotoxic cells, we analyzed the response of channel catfish to Ictalurid herpesvirus 1, commonly designated channel catfish virus (CCV). Peripheral blood leukocytes (PBL) from catfish immunized with MHC-matched, CCV-infected G14D cells (G14D-CCV) showed marked lysis of G14D-CCV but little to no lysis of uninfected allogenic (3B11) or syngeneic (G14D) cells. Expansion of effectors by in vitro culture in the presence of irradiated G14D-CCV cells generated cultures with enhanced cytotoxicity and often broader target range. Cytotoxic effectors expressed rearranged TCR genes, perforin, granzyme, and IFN-γ. Four clonal cytotoxic lines were developed and unique TCR gene rearrangements including γδ were detected. Furthermore, catfish CTL clones were either CD4+/CD8- or CD4-/CD8-. Two CTL lines showed markedly enhanced killing of G14D-CCV targets, while the other two lines displayed a broader target range. Collectively, catfish virus-specific CTL display unique features that illustrate the diversity of the ectothermic vertebrate immune response. more...

Accurate, unbiased phenotypic performance of progeny is critical for the development of fish‐breeding programs, and identification of possible environmental factors affecting phenotypes is an important aspect of genetic analysis. Catfish progeny can be produced by either natural pond‐spawning or hormone‐induced strip‐spawning. We determined the effects of pond‐spawning versus strip‐spawning on fingerling weight, harvest weight, and carcass yield of channel catfish, Ictalurus punctatus, progeny. Progeny from 65 pond‐spawned full‐sib families and 29 strip‐spawned full‐sib families were reared in separate family tanks, then tagged as fingerlings, and then stocked communally in earthen ponds and harvested at ~17 months posthatch. A sample of fish from each full‐sib family was measured for carcass yield. Fingerling weight was not affected by sex or spawning type. Harvest weight was higher for males than for females and higher for pond‐spawned fish than for strip‐spawned fish. Carcass yield was higher for females than for males and higher for pond‐spawned fish than for strip‐spawned fish. Results indicate that strip‐spawning had substantial negative effects on progeny harvest weight and carcass yield. Accounting for the effect of strip‐spawning in breeding programs and the potential effects of strip‐spawning on commercial catfish production should be determined. more...

This study evaluated dietary protein concentrations and replacing fish meal with porcine meat and bone meal (PMB) for pond‐raised fingerling channel catfish, Ictalurus punctatus. Three diets were formulated to have 28, 32, or 35% protein using soybean meal, cottonseed meal, and fish meal as the main protein sources, respectively. A fourth diet contained 32% protein with fish meal being replaced with PMB. Analyzed protein concentrations were 29.7, 31.9, 34.4, and 31.1% on 90% dry matter basis, respectively. Small fingerlings (average initial weight: 2.0 g/fish) were stocked in 20 earthen ponds (0.04 ha) at 172,970 fish/ha and were fed once daily to apparent satiation for 98 days. There were no significant differences in total diet fed, gross yield, final weight, feed conversion ratio, survival, or condition factor among diets. There were also no significant differences in ammonia‐N, nitrite‐N, chlorophyll a, or desirable zooplankton concentrations in pond water of fish receiving different diets. Results show that a diet containing about 30% protein can support optimum growth of pond‐raised channel catfish fingerlings of 2 g and larger in fertilized ponds fed once daily to apparent satiation. PMB can completely replace fish meal in a 32% protein diet. Economic analysis suggests considerable cost savings by replacing fish meal with PMB and reducing protein concentrations in channel catfish fingerling diets. more...

Although a concerted effort in catfish nutrition research in the United States did not begin until the late 1950s/early 1960s, the genesis of both the catfish industry and catfish nutrition research is rooted in studies conducted early in the 20th century. Thus, a historical view delineating the progression of channel catfish, Ictalurus punctatus, nutrition from 1900 to the present is given. Notable nutrition research programs, as well as significant events and accomplishments, will be examined. more...

This study investigated the effects of dietary lysolecithin on growth performance, feed utilization and metabolic responses of channel catfish (Ictalurus punctatus). Fish (initial weight: 14.77 ± 0.45 g) were randomly fed one of five practical diets supplemented with graded levels of lysolecithin (0, 125, 250, 375 and 500 mg/kg) in quadruplicate groups for 10 weeks. Results showed that no significant differences in weight gain, condition factor and viscerosomatic index among all the treatments. Fish fed diet supplemented with 250 mg/kg lysolecithin had significantly decreased feed conversion ratio and significantly increased protein efficiency ratio compared to that fed the control diet. The group with 250 mg/kg of dietary lysolecithin had higher protein and lower lipid contents in the whole body, and lower lipid content in the liver than those in the control group. Groups supplemented with 250–500 mg/kg of dietary lysolecithin had significantly higher gastric and intestinal lipase activities than the control group. Dietary lysolecithin at the level of 250 mg/kg significantly increased the activities of Na⁺, K⁺‐ATPase, alkaline phosphatase, total antioxidative capacity, total superoxide dismutase, glutathione peroxidase and catalase and significantly decreased the content of malondialdehyde compared to the control diet. In conclusion, dietary supplementation of lysolecithin could confer benefits of feed utilization, body composition and antioxidative capacity of channel catfish. more...

Intestinal microbiota contributes health of living organisms. Florfenicol is an approved antimicrobial (AM) prescribed for several bacterial fish diseases. The present study investigated the extent to which florfenicol modulates intestinal microbial populations of channel catfish (Ictalurus punctatus). Florfenicol was administered orally to catfish at a standard therapeutic dose (10–15 mg/kg of body weight for 10 days), and the intestinal contents were collected and the 16S rRNA was subjected to Illumina sequencing. Alpha diversity analysis indicated that florfenicol significantly decreased microbiota richness and diversity. Beta diversity reflected a clear separation had occurred between the florfenicol‐fed and control groups. Results indicated a significant increase in the abundance of phylum Proteobacteria (98.97% vs. 79.35% of the population) and decrease in phyla Firmicutes and Bacteroidetes (0.72% and 0.29% vs. 18.04% and 2.53%, respectively) in the florfenicol‐fed fish in comparison with the control fish. At the genus level, unclassified Enterobacteriaceae and Escherichia populations increased in the florfenicol group. In contrast, Plesiomonas, Aeromonas, Lactococcus, Clostridium sensu stricto, Romboutsia, Klebsiella, Turicibacter and Lactobacillus decreased in florfenicol‐fed fish in comparison with the control fish, indicating that intestinal microbiota of catfish was substantially modulated by florfenicol administration. Knowledge of changes in gut microbiota during medicated feed administration is important to improve fish performance and disease management and could enable the development of alternative therapeutic strategies. more...

Channel catfish farming is the most important warm water aquaculture in the United States and is very important to the rural economy. This study's objective was to investigate the kinetics of the enzymatic hydrolysis of catfish by-product. Channel catfish (Ictalurus punctatus) by-products (heads and frames) were collected from local catfish processing plant. Papain, ficin, bromelain, neutrase, alcalase, protamex, novo-proD and thermolysin were used for hydrolysis. Proteolytic activities of those proteases were examined at different hydrolysis temperature, proteases cost for reaching certain degree of hydrolysis was predicted. Degree of hydrolysis (DH) of the hydrolysates and hydrolysis kinetics were studied. Emulsifying and foaming property and stability of selected hydrolysates were evaluated. Results indicated that thermolysin had the highest activity (8.2 × 108 Azocoll U/g and 5.6 × 106 Azocasein U/g) at 70 °C. The highest DH of the hydrolysates were observed in 120 min with the concentration of 80 AzU/g for all enzymes. Ficin (80 AzU/g) was the most efficient in hydrolyzing the by-product (DH reaching 71%) in 120 min at 30 °C. The hydrolysis curves fit the Peleg model well with R2 higher than 0.91. This study provides important engineering information for choosing proteases and processing conditions for optimization of efficiency, yield and economy. more...

FOXO proteins are a subgroup of the forkhead family of transcription factors that play crucial roles in lifespan regulation. In addition, FOXO proteins are also involved in immune responses. After a systematic study of FOXO genes in channel catfish, Ictalurus punctatus, seven FOXO genes were identified and characterized, including FOXO1a, FOXO1b, FOXO3a, FOXO3b, FOXO4, FOXO6a and FOXO6b. Through phylogenetic and syntenic analyses, it was found that FOXO1, FOXO3 and FOXO6 were duplicated in the catfish genome, as in the zebrafish genome. Analysis of the relative rates of nonsynonymous (dN) and synonymous (dS) substitutions revealed that the FOXO genes were globally strongly constrained by negative selection. Differential expression patterns were observed in the majority of FOXO genes after Edwardsiella ictaluri and Flavobacterium columnare infections. After E. ictaluri infection, four FOXO genes with orthologs in mammal species were significantly upregulated, where FOXO6b was the most dramatically upregulated. However, after F. columnare infection, the expression levels of almost all FOXO genes were not significantly affected. These results suggested that either a pathogenesis-specific pattern or tissue-specific pattern existed in catfish after these two bacterial infections. Taken together, these findings indicated that FOXO genes may play important roles in immune responses to bacterial infections in catfish. more...

A study was conducted in earthen ponds to investigate the effects of available lysine (AL) concentrations in 28 and 32% protein diets on production and processing characteristics, proximate composition, and lysine concentrations in the fillet of channel catfish, Ictalurus punctatus. Diets were formulated to contain 28% protein with 1.22 and 1.43% AL, and 32% protein with 1.43 and 1.63% AL, which were equivalent to 4.37, 5.1, 4.46, and 5.1% AL of protein, respectively. Fingerlings with a mean initial weight of 32 g/fish were stocked into 20 ponds (0.04 ha) at 19,760 fish/ha. Fish were fed once daily to apparent satiation for 181 days. No significant differences were observed for total diet fed, net yield, weight gain, survival, or fillet proximate composition among dietary treatments. However, the 28% protein with low AL diet (1.22% AL of diet or 4.37% AL of protein) resulted in significantly lower carcass and fillet yield and fillet lysine level compared with fish fed the 28% protein diet with 1.43% AL (5.1% AL of protein) and 32% protein diets with 1.43 and 1.63% AL (4.47 and 5.1% AL of protein). Results suggest 1.43% AL of diet is adequate for both 28 and 32% protein diets for optimum growth, processing yield, and lysine retention in fillets for pond‐raised channel catfish. more...

Recently, a skin ulcerative disease caused by Vibrio mimicus has led to heavy economic losses in catfish, including yellow catfish, southern catfish, and Zhengchuan catfish in China. Currently, there was no effective method of controlling the outbreak of this disease. In this study, the bacterial isolates were obtained from dying channel catfish and identified as V. mimicus, which consist of formalin-inactivated V. mimicus (antigen). After first immunization, four weeks later, fishes were exposed to V. mimicus and the immune response was analyzed: Fish survival, respiratory burst activity of blood leukocytes, serum agglutination titers, and lysozyme activity, every week (during four weeks). Survival was up 90%. Respiratory burst activity of blood leukocytes, serum agglutination titers, and lysozyme activity were determined at 1, 2, 3, and 4 weeks after primary immunization. Immunization of channel catfish protected hosts against V. mimicus infection with a survival percentage of more than 90%. Respiratory burst activity of blood leukocytes was not affected by vaccination. Serum agglutination titer and lysozyme activity were significantly increased after immunization, in comparison with un-vaccinated control fish. The obtained results indicated that vaccination is an effective method to control the outbreaks of V. mimicus through regulation of the humoral immune response. Key words: Vibrio mimicus, catfish, skin ulcer, vaccine. more...

Cryopreservation of genetic material can become an important tool for user groups in imperiled fishes, wild fisheries, aquaculture, and biomedical research. Persistent challenges within aquatic species cryopreservation are standardization and reliable collection of diverse, high quality samples. The overall goal of this study was to work with different user groups and cryopreserve sperm on-site at their facilities to evaluate the uses and challenges of a mobile laboratory with high-throughput and quality control capabilities comparable to those of a specialized centralized facility. The objectives were to demonstrate collection and cryopreservation of sperm of: 1) large-bodied freshwater Blue Catfish (Ictalurus furcatus) for aquaculture; 2) small-bodied freshwater Xiphophorus for biomedical and imperiled repository development, and 3) saltwater Red Snapper (Lutjanus campechanus) for wild fisheries research. Over the course of this project, the mobile laboratory traveled more than 4,000 km collecting germplasm from more than 650 male fishes. A total of 136 Blue Catfish were processed in 2015 and 2016 resulting in a total of 6,146 0.5-mL French straws. A total of 521 males from 11 different species in the genus Xiphophorus were processed over 4 d in 2015 resulting in a total of 488 0.25-mL French straws. And, a total of 17 Red Snapper males were processed during 2015 resulting in a total of 316 0.5-mL French straws. This is the first development of a mobile laboratory with high-throughput capability for aquatic species. User groups would no longer be limited to germplasm resources that can only be shipped as samples or transported as live animals to a central cryopreservation facility. Mobile laboratories create opportunities to collect higher quality germplasm, provide access to new species, and enable direct cooperation, including training, with a wide variety of user groups and applications. more...

As one economically important fish in the southeastern Himalayas, the giant devil catfish (Bagarius yarrelli) has been known for its extraordinarily large body size. It can grow up to 2 m, whereas the non-Bagarius sisorids only reach 10–30 cm. Another outstanding characteristic of Bagarius species is the salmonids-like reddish flesh color. Both body size and flesh color are interesting questions in science and also valuable features in aquaculture that worth of deep investigations. Bagarius species therefore are ideal materials for studying body size evolution and color depositions in fish muscles, and also potential organisms for extensive utilization in Asian freshwater aquaculture. In a combination of Illumina and PacBio sequencing technologies, we de novo assembled a 571-Mb genome for the giant devil catfish from a total of 153.4-Gb clean reads. The scaffold and contig N50 values are 3.1 and 1.6 Mb, respectively. This genome assembly was evaluated with 93.4% of Benchmarking Universal Single-Copy Orthologs completeness, 98% of transcripts coverage, and highly homologous with a chromosome-level-based genome of channel catfish (Ictalurus punctatus). We detected that 35.26% of the genome assembly is composed of repetitive elements. Employing homology, de novo, and transcriptome-based annotations, we annotated a total of 19,027 protein-coding genes for further use. In summary, we generated the first high-quality genome assembly of the giant devil catfish, which provides an important genomic resource for its future studies such as the body size and flesh color issues, and also for facilitating the conservation and utilization of this valuable catfish. more...

In the metric “Relative Impact Potential” (RIP), the functional response (FR) of a non‐native species can be compared with that of a native analogue and combined with the species abundance to predict its environmental impact. Here, using the River Guaraguacu (Brazil) as a case study, this methodology was implemented to identify the impacts of the non‐native channel catfish Ictalurus punctatus (Rafinesque) compared with a native species Rhamdia quelen (Quoy & Gaimard) towards small prey fish. Both species exhibited Type II FRs, but handling times were lower for I. punctatus, resulting in a greater maximum feeding rate in this species. Consequently, an RIP > 1 was found, indicating that I. punctatus represents a superior impact to prey compared with its native analogue. These results demonstrate that I. punctatus is a potential threat to small endangered fish species; therefore, policies to avoid escapes from aquaculture should be created and the abundance of I. punctatus controlled. more...

The Channel Catfish Ictalurus punctatus is an important ecological, recreational and aquaculture species. In both natural and pond culture systems, Channel Catfish are periodically exposed to acute increase in temperature, especially in the summer, which may induce a stress response. With the effects of global climate change, the impact of rising temperatures on aquatic systems is expected to be exacerbated in the future. Hence, there is the need to understand the physiological mechanisms controlling the thermal stress response in fish. Acid–base, haematological, osmotic and metabolic regulations were investigated following acute temperature increase from 28°C to either 32°C or 36°C at a rate of 2°C/hr to assess the physiological response of Channel Catfish to temperature increase. Blood was sampled 1 hr after treatment temperatures were reached. When temperature increased from 28 to 32°C, blood bicarbonate (HCO3-) decreased while cortisol, partial pressure of carbon dioxide (pCO₂) and glucose increased. When temperature increased from 28 to 36°C, blood pH, HCO3-, chloride, total proteins and mean corpuscular haemoglobin concentration decreased while cortisol, pCO₂, haematocrit, haemoglobin, glucose, lactate, mean corpuscular volume and mean corpuscular haemoglobin all increased. The changes observed are characteristic of acute stress responses in fish and suggest that acute temperature increases to both 32 and 36°C are physiologically stressful to Channel Catfish. more...

Although cortisol is considered the main glucocorticoid involved in regulating stress in fish by elevating the serum glucose, the presence of serum corticosterone and whether its level can be used as an indicator for fish stress activation and reflect the degree of fish stress remains to be determined. To comprehensively and accurately evaluate the performance of two glucocorticoids after stress, in this study, seven of the most common stressors (ammonia nitrogen, high-temperature, acid, alkali, Aeromonas hydrophila, and salinity) in aquaculture were selected. The levels of serum corticosterone, cortisol, and glucose were detected within 48 h, and then the dynamic changes were analyzed. In addition, the kidneys were collected to detect the expression of corresponding proteins involved in corticosterone and cortisol synthesis (3 β-HSD and CYP17A1) for further exploration. From the results obtained, the content of serum corticosterone was about 100 times higher than that of cortisol, and it was found that corticosterone and cortisol showed different dynamic changes within 48 h among the seven kinds of stress. In the subsequent detection of glucose, it was found that the dynamic shift in glucose was not consistent with the dynamic changes of corticosterone or cortisol entirely but seemed to be caused by the combination of the two. In the follow-up protein expression detection, we found that corticosterone seemed to respond to stress earlier. Therefore, it is concluded that the responses of corticosterone and cortisol to stress are independent, corticosterone may be more sensitive in the current seven acute stresses, and then they regulate glucose together to resist stress. The study aimed to fill the vacancy of corticosterone in fish research and provide a reference for the complete evaluation of fish stress degree. more...

Objective: Determine the main food components of the catfish, their seasonal variability and according to the sex of the organism. Methodology: In total, 143 stomachs of catfish were examined. In the analysis of the stomach content, the detected organisms were determined until the taxonomic order rank. It was analyzed the seasonal and sex feeding variability. Results: The total annual trophic spectrum for catfish consisted of 13 items, of which only the order Ephemeroptera reached the category as a frequent food. In the winter season the catfish consumed significantly more food compared to the other seasons and there was no difference in the amount consumed by females and males (p>0.05). Implications: This information is relevant to highlight the importance of the biological integrity of the terrestrial site surrounds the reservoir, which is a source of food for the catfish. Conclusions: Catfish channel in the Venustiano Carranza Dam is a generalist species (13 alimentary items). There was a difference in the amount of food consumed between the seasons of the year; however there was no difference between the sexes. more...

Aquaculture offers great potential for fish production in Lake Chapala, but reports of heavy metal contamination in fish have identified a main concern for this activity. In the present study, cultures of the species Cyprinus carpio and Ictalurus punctatus were grown in a net cage in Lake Chapala. The patterns of heavy metal accumulation (Cu, Zn, Cd, Hg, Pb, As) in muscle and liver were monitored in order to evaluate the level of metal incorporation in the fish. Estimates of weekly metal intake (EWI) were made based on the results of the concentrations in edible parts of fish of commercial size. The patterns of metal bioaccumulation between tissues and species showed that liver had a higher concentrating capacity for Zn, Cu, Cd, and Pb. In contrast, similar concentrations of Hg and As were found in the liver and muscle tissue. According to the EWI estimates, the heavy metals in these cultured fish do not represent a risk for human consumption. more...

Blue Catfish Ictalurus furcatus have been introduced into many of Kansas reservoirs since 1972. They ranked sixth in terms of favorite fish to catch and target among licensed Kansas anglers in 2013 despite limited management. Blue Catfish were sampled and aged from two reservoirs located on the northern and western periphery of their current distribution.Fish were sampled using experimental gill nets, low frequency electrofishing, and float lines. Ages were assigned to a subset of captured fish by a panel of three independent readers examining a thin section cut from the articulating surface of a pectoral spine. Rapid growth was observed in Lovewell Reservoir with Blue Catfish reaching 659-mm by age 6. Growth of Blue Catfish was slower in Wilson Reservoir (552-mm by age 6) but comparable to other populations in the United States. Recruitment of stocked fish was variable but more consistent in Lovewell Reservoir. Year classes established by stockings that contained larger individuals at greater densities were more prevalent in both populations. These results demonstrate inconsistent recruitment patterns of Blue Catfish population development when stocked in large reservoirs. more...

Tra catfish (Pangasianodon hypophthalmus), also known as striped catfish, is a facultative air-breather that uses its swim bladder as an air-breathing organ (ABO). A related species in the same order (Siluriformes), channel catfish (Ictalurus punctatus), does not possess an ABO and thus cannot breathe in the air. Tra and channel catfish serve as great comparative models for investigating possible genetic underpinnings of aquatic to land transitions, as well as for understanding genes that are crucial for the development of the swim bladder and the function of air-breathing in tra catfish. In this study, hypoxia challenge and microtomy experiments collectively revealed critical time points for the development of the air-breathing function and swim bladder in tra catfish. Seven developmental stages in tra catfish were selected for RNA-seq analysis based on their transition to a stage that could live at 0 ppm oxygen. More than 587 million sequencing clean reads were generated, and a total of 21,448 unique genes were detected. A comparative genomic analysis between channel catfish and tra catfish revealed 76 genes that were present in tra catfish, but absent from channel catfish. In order to further narrow down the list of these candidate genes, gene expression analysis was performed for these tra catfish-specific genes. Fourteen genes were inferred to be important for air-breathing. Of these,HRG,GRP, andCX3CL1were identified to be the most likely genes related to air-breathing ability in tra catfish. This study provides a foundational data resource for functional genomic studies in air-breathing function in tra catfish and sheds light on the adaptation of aquatic organisms to the terrestrial environment. more...

Establishment and range expansion of non-native species in novel habitats depend on their energetic requirements and food availability. Knowledge of growth and metabolic rates of non-native fishes at various food levels is particularly critical to inform models that assess their invasion potential. We compared growth rates, body condition and metabolic rates of juvenile blue catfish (Ictalurus furcatus), an invasive species in many lakes, coastal rivers and estuaries throughout the Eastern USA, at three ration levels: ad libitum (3.5% of fish body mass/d), two-third ad libitum and one-third ad libitum. All fish survived the entire duration of the experiment (4 months) regardless of ration level. Blue catfish exhibited routine metabolic rates similar to those of other benthic fishes but below the more active species. Mean growth rates were lower at reduced ration levels, but we found no evidence of ration size effect on body condition or metabolic rates. Blue catfish therefore appear to have mechanisms that enable them to survive low rates of food intake for long periods, indicating the potential of this invasive species to become established in habitats with low prey availability. more...

Hypervirulent Aeromonas hydrophila (vAh) is an emerging pathogen in freshwater aquaculture that results in the loss of over 3 million pounds of marketable channel catfish, Ictalurus punctatus, and channel catfish hybrids (I. punctatus, ♀ x blue catfish, I. furcatus, ♂) each year from freshwater catfish production systems in Alabama, U.S.A. vAh isolates are clonal in nature and are genetically unique from, and significantly more virulent than, traditional A. hydrophila isolates from fish. Even with the increased virulence, natural infections cannot be reproduced in aquaria challenges making it difficult to determine modes of infection and the pathophysiology behind the devastating mortalities that are commonly observed. Despite the intimate connection between environmental adaptation and plastic response, the role of environmental adaption on vAh pathogenicity and virulence has not been previously explored. In this study, secreted proteins of vAh cultured as free-living planktonic cells and within a biofilm were compared to elucidate the role of biofilm growth on virulence. Functional proteolytic assays found significantly increased degradative activity in biofilm secretomes; in contrast, planktonic secretomes had significantly increased hemolytic activity, suggesting higher toxigenic potential. Intramuscular injection challenges in a channel catfish model showed that in vitro degradative activity translated into in vivo tissue destruction. Identification of secreted proteins by HPLC-MS/MS revealed the presence of many putative virulence proteins under both growth conditions. Biofilm grown vAh produced higher levels of proteolytic enzymes and adhesins, whereas planktonically grown cells secreted higher levels of toxins, porins, and fimbrial proteins. This study is the first comparison of the secreted proteomes of vAh when grown in two distinct ecological niches. These data on the adaptive physiological response of vAh based on growth condition increase our understanding of how environmental niche partitioning could affect vAh pathogenicity and virulence. Increased secretion of colonization factors and degradative enzymes during biofilm growth and residency may increase bacterial attachment and host invasiveness, while increased secretion of hemolysins, porins, and other potential toxins under planktonic growth (or after host invasion) could result in increased host mortality. The results of this research underscore the need to use culture methods that more closely mimic natural ecological habitat growth to improve our understanding of vAh pathogenesis. more...

This study identified the parasitic species in juvenile freshwater finfishes during the fattening stage, from a fish farm located in the Zona da Mata (MG), southeastern Brazil, and revealed both macro and microscopical lesions in fish gills. A total of 172 juvenile fishes of different species (Oreochromis niloticus, Ictalurus punctatus, Ctenopharyngodon idella, Cyprinus carpio, Astyanax bimaculatus and Brycon amazonicus) were transported to a laboratory in São Paulo city. The fish were sedated and then euthanized for parasitological analysis. All fish were infected by at least one parasite species. Ten different species of parasites were identified: Apiosoma sp., Epistylis sp., Ichthyobodo sp., trichodinids, Piscinoodinium pillulare, Ichthyophthirius multifiliis, Tetrahymena sp., monogeneans, Centrocestus formosanus metacercariae, and Dermocystidium sp. The best management practices and lack of sanitary control were also discussed. Resumo Este trabalho identificou espécies parasitas em peixes de produção juvenis de água doce, durante a fase de engorda, oriundos de uma piscicultura da Zona da Mata (MG), na região sudeste do Brasil, além das lesões de brânquias, causadas tanto macro quanto microscopicamente. Um total de 172 peixes juvenis de diferentes espécies (Oreochromis niloticus, Ictalurus punctatus, Ctenopharyngodon idella, Cyprinus carpio, Astyanax bimaculatus e Brycon amazonicus) foram transportados para um laboratório na cidade de São Paulo. Os peixes foram anestesiados e eutanasiados para análise parasitológica. Todos os peixes estavam acometidos por pelo menos uma espécie de parasito. Dez diferentes espécies de parasitos foram identificadas: Apiosoma sp., Epistylis sp., Ichthyobodo sp., tricodinídeos, Piscinoodinium pillulare, Ichthyophthirius multifiliis, Tetrahymena sp., monogeneas, metacercárias de Centrocestus formosanus e Dermocystidium sp. As boas práticas de manejo e inadequado controle sanitário também foram discutidos. more...

The objective of this study was to investigate the bioavailability (BA) and pharmacokinetics (PK) of doxycycline (DC) in channel catfish (Ictalurus punctatus) following a single intravenous injection at 5 mg/kg and a single oral administration at 50 mg/kg at 24°C. The calculation of PK parameters was based on the software 3P97. The plasma samples were determined using ultra-performance liquid chromatography. Following oral administration, the multiple-peak phenomenon presented in concentration vs. time curve of DC at 2 h (107.01 mg/L), 8 h (55.07 mg/L), and 72 h (15.10 mg/L), respectively. The compartmental model cannot simulate the oral concentration vs. time profile beside a non-compartmental model. The calculated parameters of the elimination rate constant (λz), the elimination half-life (t1/2λz ), and the area under the concentration vs. time curve (AUC0-144) were 0.037 1/h, 18.91 h, and 2255.45 μg.h/mL, respectively. After intravenous administration, the concentration vs. time profile of DC was best described by a two-compartmental open model without absorption. The parameters of the distribution rate constant (α), the distribution half-life (t1/2α), the elimination rate constant (β), the elimination half-life (t1/2β), the apparent distribution volume at steady state (Vss), the total clearance (Cl) and the area under the concentration vs. time curve (AUC0-∞) were 2.79 1/h, 0.25 h, 0.042 1/h, 16.51 h, 300.00 mL/kg, 14.00 mL/h/kg, and 364.99 μg.h/mL, respectively. For the calculation of BA values at the same condition, the data obtained from intravenous injection were also iterated based on a non-compartmental model, and the corresponding parameters of λz, t1/2λz , Vz, Cl, and AUC0-144 were 0.019 1/h, 36.26 h, 480.00 mL/kg, 9.10 mL/h/kg, and 514.45 μg.h/mL, respectively. However, there was a considerable difference in the same parameter when calculated by compartmental and non-compartmental approaches. Finally, the medium BA value of DC was evaluated to be 43.84%. This study provides future studies with a framework for determining the BA of DC in the development of a new formulation and provides information on the appropriate use of DC in aquaculture. more...

The Chinese Longsnout catfish Leiocassis longirostris (L. longirostris) is one of the most economically important freshwater catfish in China. It is a valuable model for studies on sexual dimorphism, comparative and conservation biology since its wild resources have declined sharply. However, there is lack of high-quality chromosome-level genome information for comparative genomic analysis and genome evolutionary studies. Therefore, we constructed the first high-quality chromosome-level reference genome for L. longirostris using a combined strategy of BGI-SEQ500, Nanopore, and Hi-C technologies. The assembled genome of L. longirostris contained a total length of 703.19 Mb with 389 contigs, and an N50 size of 4.29 Mb. Using the Hi-C data, we finally successfully generated 82 chromosome-level scaffolds anchored onto 26 chromosomes with a total length of 685.53 Mb (97.44% of the total genome sequences), ranging in size from 17.36 Mb to 43.97 Mb. A total of 23,708 protein-coding genes were identified in the L. longirostris genome, and up to 97.73% of L. longirostris genes were functionally annotated. In addition, the genome contained 239.11 Mb (33.99% in the total genome) repetitive sequences and 6,303 non-coding RNAs. The phylogenetic analysis indicated that the divergence time between L. longirostris and their closest relative species Pelteobagrus fulvidraco was approximately 26.6 million years. Collinearity analyses showed 26 chromosomes of L. longirostris displayed high homology with the corresponding scaffold (≥3M) of P. fulvidraco and the corresponding chromosomes of the Ictalurus punctatus. The high-quality reference genome of L. longirostris was assembled for the first time and will pave a way for genome-scale selective breeding, genome comparisons and evolution investigations. more...