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This study aimed to determine the bioavailability and pharmacokinetic parameters of sulfadiazine (SDZ) in channel catfish (Ictalurus punctatus) following oral gavage and intravenous injection. The healthy channel catfish were orally and intravenously administrated with SDZ solution at doses of 50 and 5 mg/kg, respectively. Plasma samples were determined by ultra-performance liquid chromatography with an ultraviolet detector. The results demonstrated that the concentration-time profile of SDZ after oral dosing was best described by a one-compartmental open model with first-order absorption. The absorption half-life (t1/2Kα ), the elimination half-life (t1/2Ke ), and the area under concentration-time profile (AUC0-∞ ) were estimated to be 0.87 h, 29.04 h, and 1311.72 mg.h/L, respectively. After intravenous administration, the concentration-time curve of SDZ conformed to a two-compartmental open model without absorption. The distribution half-life (t1/2α ), the elimination half-life (t1/2β ), the apparent distribution volume (Vss ), the total clearance (CL), and AUC0-∞ were calculated to be 0.19 h, 14.24 h, 0.36 L/kg, 0.018 L/h/kg, and 277.12 mg.h/L, respectively. Finally, the bioavailability was estimated to be 47.33%. This study will provide some useful information for the modification of the dosage form of SDZ in aquaculture, and is partly beneficial for appropriate use of SDZ in the future.

Introductions of invasive non-native species (and their subsequent impacts) are recognized as a major threat to native flora and fauna. This is especially true in island ecosystems such as the tropical island of Martinique. In 2018, one such aquatic invasive species, the suckermouth catfish Hypostomus robinii (Loricariidae), was reported for the first time in two of the islands rivers. H. robinii is a popular freshwater aquarium fish and native to tropical and sub-tropical South America. Since its initial discovery, a growing number of populations have been found, suggesting a larger distribution of this species through Martinique's hydrographic network. Here, we developed a novel survey technique (utilizing environmental DNA) and conducted a widespread survey across the island to assess the distribution of this invasive species. We were able to detect H. robinii in 22% of sites surveyed (18 out of 83) via our eDNA-based assay. The presence of these fish was confirmed using traditional trapping at 14 of these sites. Additionally, we used occupancy modeling to investigate the impact of different environmental covariates on the detection efficiency of the novel assay and the potential impacts of false positives and negatives. We highlight a decrease in the detection probability when water volume filtered increases. That said, the eDNA-based method proves a useful tool for the detection of this invasive fish species and monitoring its spread for management purposes.

A new species of the candiru genus Paracanthopoma is described from the floodplains of the Bananal Island, a transition area between the Cerrado and Amazon, in the Araguaia River basin, central Brazil. Paracanthopoma cangussu sp. nov. is distinguished from its congeners, Paracanthopoma parva and Paracanthopoma saci, by the presence of seven opercular odontodes, five dentary teeth, five median premaxillary teeth, and first dorsal-fin pterygiophore in a vertical through the centrum of the 23th or 24th vertebra. It is further distinguished from each congener by an exclusive combination of character states, comprising the number of vertebrae, number of precaudal vertebrae, number of dorsal procurrent caudal-fin rays, number of ventral procurrent caudal-fin rays, number of dorsal-fin rays, disposition of pores on the cephalic portion of the latero-sensory system, absence of an anterior process on the anterior margin of parieto-supraoccipital, number of dorsal-fin pteryigiophores and number of interopercular odontodes. Although vandelliines are known for being exclusively hematophagous, with guts gorged with blood, two cleared and stained specimens of P. cangussu sp. nov. had Chironomidae larvae (Insecta) on their guts. Because most specimens of P. cangussu sp. nov. were collected with stomachs filled with blood, it was hypothesized that the species feeds accidentally or occasionally on insects.

Long-term storage of oogonia and germ-line stem cells provides an alternative to the limitations associated with cryopreserving eggs of important fish species. These cell types are less vulnerable to the stresses of freezing. Cryopreservation has enormous potential for aquaculture advancement, but protocols must be developed for each species and cell type since its success hinges on various input factors. Blue Catfish Ictalurus furcatus were selected as the test species in this study because of the need to improve fry production of Blue Catfish ♂ × Channel Catfish I. punctatus ♀ hybrids, which can be facilitated by storing oogonia in gene banks. Our objective was to develop a freezing protocol for oogonia of this species. We tested different permeating and nonpermeating cryoprotectants, concentrations of these agents, and freezing rates. We proved that all three factors influenced postthaw recovery of oogonia. Of the permeating cryoprotectants, 1.0 M dimethyl sulfoxide resulted in the most live cells with the highest viability percentages, and adding 0.2 M lactose with 10% egg yolk further improved the results. There were also specific interactions in which the effects of concentration and freezing rate varied among the cryoprotectant treatments. The most effective freezing rate was −1.0°C/min, and cell viability was reduced at −2.5°C/min and −5.0°C/min. From these results, we propose adding 1.0 M dimethyl sulfoxide with 0.2 M lactose and 10% egg yolk to cryomedia and freezing it at a rate of −1.0°C/min. By developing a cryopreservation protocol for a commonly cultured catfish, this work may guide the development of protocols for other species of interest.

The bacterium Edwardsiella piscicida causes significant losses in global aquaculture, particularly channel (Ictalurus punctatus) × blue (I. furcatus) hybrid catfish cultured in the south-eastern United States. Emergence of E. piscicida in hybrid catfish is worrisome given current industry trends towards increased hybrid production. The project objectives were to assess intraspecific genetic variability of E. piscicida isolates recovered from diseased channel and hybrid catfish in Mississippi; and determine virulence associations among genetic variants. Repetitive extragenic palindromic sequence-based PCR (rep-PCR) using ERIC I and II primers was used to screen 158 E. piscicida diagnostic case isolates. A subsample of 39 E. piscicida isolates, representing predominant rep-PCR profiles, was further characterized using BOX and (GTG)5 rep-PCR primers, virulence gene assessment and multilocus sequence analysis (MLSA) targeting housekeeping genes gyrb, pgi and phoU. The MLSA provided greater resolution than rep-PCR, revealing 5 discrete phylogroups that correlated similarly with virulence gene profiles. Virulence assessments using E. piscicida representatives from each MLSA group resulted in 14-day cumulative mortality ranging from 22% to 54% and 63 to 72% in channel and hybrid fingerlings, respectively. Across all phylogroups, mortality was higher in hybrid catfish (p < .05), supporting previous work indicating E. piscicida is an emerging threat to hybrid catfish aquaculture in the south-eastern United States.

Hardhead catfish Ariopsis felis are a common marine catfish in the coastal waters of the Gulf of Mexico (GOM). The low economic value of this species has depressed interest and research, and although the species is known for its extremely low fecundity and large oocytes, little else is known about this catfish species. A total of 1230 samples across all months of the year from 2016 to 2018 resulted in 681 females, and analysis of gonado-somatic index (IG ) revealed 1% to be a clear cut-off indicating maturity. Females are considered capable of spawning from April to June when IG averaged 4-8%. Both atresia and post-ovulatory follicles were present in July, suggesting that spawning ends in July in the northern GOM. The 1% IG cut-off was used to designate maturity, and from that an L50 of 253 mm was estimated. Batch fecundity from 41 females estimated a mean batch size of 36 oocytes. Perhaps the most interesting finding was the presence of secondary growth stage oocytes (e.g., cortical alveoli) from July through November, well outside the spawning capable period. Furthermore, 78% of females had some early vitellogenic oocytes present during the non-spawning season, and the distribution of these relatively large (2-5 mm) oocytes did not change over time. The results here are not only important as reproductive biology information for a common and abundant species, but also present interesting and unusual patterns of non-spawning season oocyte development that is not commonly seen in Western Hemisphere subtropical fish species.

Blue catfish alloherpesvirus (BCAHV) is a novel virus isolated from the blue catfish (Ictalurus furcatus). To date, the ultrastructure, virulence and immunogenicity of BCAHV have not been reported. Given the importance of blue catfish in producing channel ♀ (I. punctatus) × ♂ blue (I. furcatus) catfish hybrids and the increasing demand for hybrid catfish in the US catfish industry, the susceptibility of blue, channel and hybrid catfish to BCAHV was assessed. Further, the cross-protective potential of BCAHV against Ictalurid herpesvirus 1 (IcHV1) was investigated in channel and hybrid catfish that survive BCAHV exposure. Neutralization assays revealed BCAHV is refractive (neutralization index [NI] = 0) to anti-IcHV1 monoclonal antibody Mab 95, compared to IcHV1 (NI = 1.8). Exposure of blue catfish fingerling to 1.3 × 105 TCID50 /L BCAHV produced cumulative mortality of 51.67 ± 0.70% and pathologic changes similar to those of channel catfish virus disease. No mortality was observed in channel or hybrid catfish. Twenty-eight days post-challenge, surviving channel and hybrid catfish were exposed to 9.4 × 104 TCID50 /L IcHV1 (LC50 dose), resulting in 100% relative per cent survival compared to naive cohorts. These data provide baseline information for BCAHV and lay the groundwork for future studies. Data also identify BCAHV as a potential vaccine candidate against IcHV1. Based on host range and immunogenicity evaluations, in addition to genome sequence data from previous studies, BCAHV should be given consideration as a new species of Ictalurivirus.

The Southern catfish (Silurus meridionalis) is a nocturnal and benthic freshwater fish endemic to the Yangtze River and its tributaries. In this study, we constructed a chromosome-level draft genome of S. meridionalis using 69.7-Gb Nanopore long reads and 49.5-Gb Illumina short reads. The genome assembly was 741.2 Mb in size with a contig N50 of 13.19 Mb. An additional 116.4 Gb of Bionano and 77.4 Gb of Hi-C data were applied to assemble contigs into scaffolds and further into 29 chromosomes, resulting in a 738.9-Mb genome with a scaffold N50 of 28.04 Mb. A total of 22,965 protein-coding genes were predicted from the genome with 22,519 (98.06%) genes functionally annotated. Comparative genomic and transcriptomic analyses revealed a rod-dominated visual system which was responsible for scotopic vision. The absence of cone opsins SWS1 and SWS2 resulted in the lack of ultraviolet and blue violet sensitivity. Mutations at key amino acid sites of RH1.1, RH1.2 and RH2 resulted in spectral tuning good for dim light vision and narrow colour vision. A higher expression level of rod phototransduction genes than that of cone genes and higher rod-to-cone ratio led to higher optical sensitivity under dim light conditions. In addition, analysis of the genes involved in eye morphogenesis and development revealed the loss of some conserved noncoding elements, which might be associated with the small eyes in catfish. Together, our study provides important clues for the adaptation of the catfish visual system to the nocturnal and benthic lifestyles. The draft genome of S. meridionalis represents a valuable resource for studies of the molecular mechanisms of ecological adaptation.

An integrative taxonomic analysis combining mitochondrial cytochrome oxidase subunit I sequences, morphology, colour pattern and two species delimitation approaches revealed the existence of five lineages within the Natal mountain catfish, Amphilius natalensis, in southern Africa. These lineages are separated by substantial genetic divergences (1.6%-9.46%), and they can be consistently distinguished from one another based on a combination of morphology and colour pattern differences. Additionally, the lineages are allopatrically distributed and confined to isolated river systems draining discrete mountain ranges, which makes gene flow among them unlikely. One of these lineages is A. natalensis s.s., which is confined to the uMngeni and Tukela river systems in KwaZulu Natal (KZN) Province in South Africa. The other four lineages represent new species to science which are described as Amphilius zuluorum sp. nov., endemic to the uMkhomazi River system in KZN, Amphilius engelbrechti sp. nov., endemic to the Inkomati River system in Mpumalanga Province in South Africa, Amphilius marshalli sp. nov., endemic to the Pungwe and Lower Zambezi river systems in Zimbabwe and Mozambique, and Amphilius leopardus sp. nov., endemic to the Ruo River in Malawi. The results show that Amphilius laticaudatus which is endemic to the Buzi River system in Zimbabwe and Mozambique, belongs to the A. natalensis s.l. complex. A redescription of A. laticaudatus is presented and an updated identification key for the mountain catfishes of southern Africa is provided.

A new long-snouted Corydoras species is described from two tributaries of the rio Manuripe and a tributary of the rio Madre de Dios, rio Madeira basin, Peru. Corydoras fulleri can be distinguished from its congeners by having the following features: (I) branch of the temporal sensory canal at sphenotic, which gives rise to the supraorbital canal, with two pores; (III) upper tooth plate of branchial arch with three series of teeth; (III) area at the corner of the mouth, ventral to the maxillary barbel, with a small fleshy flap; (IV) two moderate-sized dark brown or black blotches on caudal-fin base, one on its lateral portion and another one on its dorsal portion, blotches variably diffuse and/or fused with each other; (V) absence of a dark brown or black stripe transversally crossing the orbit; (VI) a longitudinal dark brown or black stripe on postdorsal region of flank midline, variably fused with the lateral peduncular blotch, some specimens with slender, longitudinally elongated, dark brown or black blotch on flank midline, forming a dash-like marking, stripe or dash-like blotch diffuse in some specimens; and (VII) region around dorsal-fin origin generally lacking dark brown or black blotch, or displaying diffuse blotch. This article is protected by copyright. All rights reserved.

BACKGROUND Cucumber plants suffer from a serious threatening disease, downy mildew, throughout the growing seasons irrespective of the weather temperature. The causal agent, Pseudoperonospora cubensis, tends to evolve rapidly upon sequential applications of chemical fungicides and generate new progeny possessing tolerance to such fungicides. Glycoproteins represent an environmentally safe alternative for chemically synthetized fungicides and do not trigger fungicide resistance. We studied the antifungal activity of four glycoproteins namely soybean β-conglycinin, chickpea vicilin, duck egg ovomucin and catfish p22 against P. cubensis. Ten commercial fungicides of different chemical groups were used as positive controls of glycoprotein treatments. RESULTS The results revealed that soybean β-conglycinin and catfish p22 glycoproteins possess significant antifungal activity against P. cubensis. The amount of disease suppression caused by β-conglycinin and p22 was comparable to the highly efficient chemical fungicides containing copper oxychloride, cymoxanil and fosetyl Al as active ingredients. Vicilin and ovomucin were less efficient biocides as they gave moderate suppression of disease severity. However, all tested glycoproteins provided full protection for the newly emerged cucumber leaves. Microscopic examination of glycoprotein-treated leaves inferred the ability of catfish p22 and soybean β-conglycinin to disrupt the integrity of sporangial cell walls of P. cubensis rendering them non-viable compared to untreated ones. Expression levels of total phenolic compounds and the antioxidant enzymes catalase, superoxide dismutase and peroxidase were elevated upon glycoproteins application, which infers their involvement in disease suppression. CONCLUSION This report emphasizes the direct and indirect roles of glycoproteins in safe management of cucumber downy mildew disease. © 2021 Society of Chemical Industry.

The cultural and ecological importance of fork-tailed catfish, Neoarius graeffei, in northern Australia is linked to its energy stores, or how fat fish are. Water resource development that alters river flow has the potential to impact the energy stores of fork-tailed catfish. We investigated the influence of flow and habitat on the energy reserves of fork-tailed catfish during the dry season in an intermittent wet–dry tropical river using data collected in three years with different flow volumes from a variety of habitats, i.e. different mesohabitats (tributary, main-channel) and pool sizes. Julian day was included to describe seasonal trends. We used mesohabitat and pool size to reveal where fork-tailed catfish had the most energy reserves and flow-year and Julian day to reveal when reserves were greatest. Body condition and the quantity of intramuscular and coelomic fat were used to describe energy reserves. Predictive models created for each metric revealed that fork-tailed catfish body condition and intramuscular fat were greater in years following moderate to high wet-season flow, smallest in a year following very low flows and decreased as the dry season progressed. Coelomic and intramuscular fat of fork-tailed catfish was also lower in smaller pools. There was no association between mesohabitat and energy store. These when and where hydro-ecological patterns highlight the importance of wet season flows and groundwater-fed refuge pools for fork-tailed catfish energetics in this wet–dry tropical river. Intermittent rivers flowing through wet–dry tropical savanna habitats are under increasing threat globally and the results of the present study illustrate how flow variation may impact on biota and influence their continued survival and functional roles.

In a recent expedition to the rio Grande basin, a tributary of the rio Parana in southern Brazil, individuals of the armoured catfish genus Hypostomus with a peculiar and beautiful colour pattern composed of pale vermiculations on the head and four to five horizontal stripes on the flanks were collected. Initially, the specimens were identified as a colour morph of the pale-spotted H. margaritifer. However, when we compared their partial cytochrome C oxidase subunit I (COI) mitochondrial gene to sequences of some typically pale-spotted H. margaritifer, the striped specimens were genetically distinct. Further analysis of the striped individuals revealed that they are the poorly known but valid species Hypostomus variipictus, which was described by Ihering in 1911 from the rio Pardo, a tributary of the rio Grande, upper rio Parana basin, in Sao Paulo State, Brazil. Since its descriptions, no robust taxonomic work has been published concerning this species. In this study, the newly sampled population was compared to the original description and to the holotype of H. variipictus, providing the foundation for a complete redescription, proper diagnosis, and first live colour illustration and description of the previously hidden H. variipictus.

Background Channel catfish farming is very important aquaculture in the Southern states of United State. However, huge amounts of by-products are generated from catfish fillet processing industries. The by-products (mostly heads and bone frames) are excellent sources of proteins. Currently, catfish by-product has little value, and is regarded as a 'waste', which if not utilized properly would cause serious environmental pollution. Therefore, to find a way to utilize those by-products is critical for the economy of aquaculture. Method Protein isolates were extracted from the mixture of catfish by-products (heads and frames) with different alkaline conditions (pH 7.5-11) and made into protein gels. Secondary structures of extracted protein isolates were studied. Microbial transglutaminase (MTGase, 0-4 U/g of proteins) was incorporated to improve gel structure. Gelling, physicochemical, textural and thermal properties of protein gels treated with/without MTGase were investigated. Protein pattern changes of MTGase treated protein gels were studied and the microstructures of protein gels were analyzed. Results Alpha-helicity of protein isolates made at pH 11 was 21.5% lower than that extracted at pH 8.5. Storage modulus (G') of protein gel decreased with the increasing in extraction pH (pH > 9) of the corresponding protein isolate. MTGase treatment exhibited significant effect on denaturation temperature and enthalpy of protein gels. Excessive MTGase (> 2 U/g) could weaken the gel structure. Conclusion Protein isolates can be extracted from catfish by-products and made into protein gels which is a value-added product. This article is protected by copyright. All rights reserved.

Background Recently, fatty fish have been utilized as a potential approach for the fabrication of surimi products, with the yield of fatty fish surimi being > 10 000 tons in 2019. However, the gelling properties of catfish surimi can be influenced by intermuscular lipid. Lipase could effectively enhance the gel quality of catfish surimi gels, although the chemical forces involved in gel formation and alteration in lipid and protein oxidation status are not well understood. The present study investigated the gelation-enhancing effects of lipase on catfish surimi based on changes in chemical oxidation interactions. Results The addition of 7.5 g kg-1 lipase significantly increased the hydrophobic interactions and disulfide bond contents, both of which facilitated gel formation, in surimi gels. The 2-thiobarbituric acid reactive substance and carbonyl concentrations demonstrated that lipase promoted lipid and protein oxidations. Furthermore, an appropriate dose of malondialdehyde accelerated protein oxidation, thereby resulting in the covalent cross-linking of proteins. Consequently, the gel strength increased from 55.72 to 127.71 g × cm with lipase contents of up to 7.5 g kg-1 , and strong chemical cross-linking and a compact network were observed via sodium dodecyl sulfate polyacrylamide gel electrophoresis and scanning electron microscopy. However, excessive oxidation led to the degeneration of the gel matrix. A schematic mechanism, mainly based on the chemical changes, is proposed. Conclusion The present study revealed the gelation mechanism of catfish surimi gels with lipase, and suggested that lipase treatments may be an effective approach for improving the textural properties of fatty fish surimi gels. © 2021 Society of Chemical Industry.

Environmental disasters affecting Brazilian rivers have been frequent recently, especially involving mining activities. Two recent dam-rupture events suddenly released millions of cubic meters of iron tailings downstream into two major Brazilian watersheds. These events generated major losses to the environment and human life. Additionally, the biodiversity in both watersheds was still incompletely known. Two new species of the armoured catfish genus Hypostomus were discovered in the Rio Paraopeba and surrounding rivers of the Rio São Francisco Basin. The species share some main characteristics including a depressed body, large dark spots on a clearer background and the absence of keels on flanks. However, while one species (Hypostomus freirei sp. n.) has a large mandibular ramus and numerous slender teeth, the other (Hypostomus guajupia sp. n.) has a shorter mandibular ramus and few robust teeth. The discovery of these two new mid-sized fish species emphasizes the presumption that the effects of major environmental disasters cannot be fully estimated as local biodiversity is not completely known. This discovery in a recently devastated area also shows that tough environmental laws for the protection, supervision and mitigation of major impacts are urgently needed in developing countries.

Two specimens of Micromyzon akamai, an eyeless and miniaturized species previously known only from the deep channels of the eastern Amazon basin in Brazil, are reported from the Curaray River, a tributary of the Napo River in Ecuador. The new specimens are the first records of Micromyzon in the headwaters of the Amazon River and the first records of M. akamai outside Brazil. External morphological characters and a phylogenetic analysis of cytochrome c oxidase I (coI) gene support the identification of the new specimens as M. akamai. Nevertheless, the new specimens also indicate that some features previously hypothesized to be apomorphic for M. akamai are intraspecifically variable.

Bacillary necrosis is a problematic disease in farming of Mekong striped catfish (Pangasianodon hypophthalmus). The pathogenic bacterium is Edwardsiella ictaluri, causing numerous white spots in swelled liver, kidney and spleen. An alternative to antibiotic treatment and vaccine is to select for improved genetic resistance to the disease that requires to establish a proper challenge test. Here, four challenge tests of Mekong striped catfish against E. ictaluri are reported proposing 3 days of acclimatization of test fish prior to the challenge, with restricted water level in the test, keeping a temperature of 26°C. In the challenge, cohabitant shedders should be released directly into the test tank and make up around ⅓ of the fish, and bacteria should be added directly to water. The last two experiments, with the highest mortality, suggest that any factor involving the dead cohabitants should be removed and that additional experimentation should focus on bacteria (density) and timing for addition of bacteria to water. Genetic analyses revealed that resistance to bacillary necrosis tested in replicated tanks in the same experiment can be considered the same genetic trait.