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Cyprinid herpesvirus 2 (CyHV-2) is a causative factor of herpesviral hematopoietic necrosis (HVHN) in farmed crucian carp (Carassius carassius) and goldfish (Carassius auratus). In this study, we analyzed the genomic characteristics of a new strain, CyHV-2 SH-01, isolated during outbreaks in crucian carp at a local fish farm near Shanghai, China. CyHV-2 SH-01 exhibited a high sensitivity to goldfish and crucian carp in our previous research. The complete genome of SH-01 is 290,428 bp with 154 potential open reading frames (ORFs) and terminal repeat (TR) regions at both ends. Compared to the sequenced genomes of other CyHVs, Carassius auratus herpesvirus (CaHV) and Anguillid herpesvirus 1 (AngHV-1), several variations were found in SH-01, including nucleotide mutations, deletions, and insertions, as well as gene duplications, rearrangements, and horizontal transfers. Overall, the genome of SH-01 shares 99.60% of its identity with that of ST-J1. Genomic collinearity analysis showed that SH-01 has a high degree of collinearity with another three CyHV-2 isolates, and it is generally closely related to CaHV, CyHV-1, and CyHV-3, although it contains many differences in locally collinear blocks (LCBs). The lowest degree of collinearity was found with AngHV-1, despite some homologous LCBs, indicating that they are evolutionarily the most distantly related. The results provide new clues to better understand the CyHV-2 genome through sequencing and sequence mining.

IL-22 is a critical cytokine of epithelial mucosal barrier. In humans, IL-22 signals through a heteroduplex receptor consisting of IL-22R and IL-10Rβ. In fish, IL-22 and its receptors homologues have been cloned in a number of species, however, no studies have been reported how the receptors are involved in IL-22 transduction. For this purpose, in this study we identified IL-22 and its soluble receptor IL-22BP and transmembrane receptors IL-22RA1 and IL-10R2 in Carassius cuvieri × Carassius auratus red var. (named WR-IL-22, WR-IL-22BP, WR-IL10R2 and WR-IL22RA1, respectively). WR-IL-22, WR-IL-22BP, WR-IL10R2 and WR-IL22RA1 were relatively conserved in the evolutionary process, sharing the same conserved domains as their higher vertebrate homologues. When the fish were infected with the Aeromonas hydrophila, the expression of WR-IL-22, WR-IL-22BP, WR-IL10R2 and WR-IL22RA1 were significantly induced in the gut. The co-IP assay showed that WR-IL-22 not only interacted with WR-IL-22BP, but also with WR-IL10R2 and WR-IL22RA1. When introduced in vivo, WR-IL-22 activated the JAK1-STAT3 axis and protected the gut mucosa from A. hydrophila infection. However, overexpression of WR-IL-22BP or knockdown of transmembrane receptors WR-IL10R2 and WR-IL22RA1 significantly inhibited the activation of WR-IL-22-mediated JAK1-STAT3 axis and promoted bacterial colonization in the gut. These results provided new insights into the role of IL-22 and its receptors in the gut mucosa barrier and immune response in teleost., Competing Interests: Declaration of competing interest The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

Polyploidy and subsequent diploidization provide genomic opportunities for evolutionary innovations and adaptation. The researches on duplicated gene evolutionary fates in recurrent polyploids have seriously lagged behind that in paleopolyploids with diploidized genomes. Moreover, the antiviral mechanisms of Viperin remain largely unclear in fish. Here, we elaborate the distinct antiviral mechanisms of two viperin homeologs (Cgviperin-A and Cgviperin-B) in auto-allo-hexaploid gibel carp (Carassius gibelio). First, Cgviperin-A and Cgviperin-B showed differential and biased expression patterns in gibel carp adult tissues. Subsequently, using co-immunoprecipitation (Co-IP) screening analysis, both Cg Viperin-A and Cg Viperin-B were found to interact with crucian carp (C. auratus) herpesvirus (Ca HV) open reading frame 46 right (ORF46R) protein, a negative herpesvirus regulator of host interferon (IFN) production, and to promote the proteasomal degradation of ORF46R via decreasing K63-linked ubiquitination. Additionally, Cg Viperin-B also mediated ORF46R degradation through autophagosome pathway, which was absent in Cg Viperin-A. Moreover, we found that the N-terminal α-helix domain was necessary for the localization of Cg Viperin-A and Cg Viperin-B at the endoplasmic reticulum (ER), and the C-terminal domain of Cg Viperin-A and Cg Viperin-B was indispensable for the interaction with degradation of ORF46R. Therefore, the current findings clarify the divergent antiviral mechanisms of the duplicated viperin homeologs in a recurrent polyploid fish, which will shed light on the evolution of teleost duplicated genes. [ABSTRACT FROM AUTHOR]

Predator-inducible defenses constitute a widespread form of adaptive phenotypic plasticity, and such defenses have recently been suggested linked with the neuroendocrine system. The neuroendocrine system is a target of endocrine disruptors, such as psychoactive pharmaceuticals, which are common aquatic contaminants. We hypothesized that exposure to an antidepressant pollutant, fluoxetine, influences the physiological stress response in our model species, crucian carp, affecting its behavioral and morphological responses to predation threat. We examined short- and long-term effects of fluoxetine and predator exposure on behavior and morphology in crucian carp. Seventeen days of exposure to a high dose of fluoxetine (100 µg/L) resulted in a shyer phenotype, regardless of the presence/absence of a pike predator, but this effect disappeared after long-term exposure. Fluoxetine effects on morphological plasticity were context-dependent as a low dose (1 µg/L) only influenced crucian carp body shape in pike presence. A high dose of fluoxetine strongly influenced body shape regardless of predator treatment. Our results highlight that environmental pollution by pharmaceuticals could disrupt physiological regulation of ecologically important inducible defenses. [ABSTRACT FROM AUTHOR]

Information about ploidy is important in both commercial and conservation aquaculture and fish research. Unfortunately, methods for its determination, such as karyology, determination of the amount of DNA in a cell using microdensitometry or flow cytometry and/or measuring erythrocytes in a blood smear can be stressful or even destructive. Some of these methods are also limited by the relatively large minimum size of the individual being measured. The aim of this study was to test a new low-stress method of determining ploidy by measuring the size of erythrocytes in the capillaries of a fish, including small individuals. First, we examined diploid and triploid loach (Cobitis sp.) and gibel carp, Carassius gibelio (Bloch, 1782), using flow cytometry and blood smears, with these results being used as a control. Subsequently, we measured the size of erythrocytes in the caudal fin capillaries of anesthetized fishes of known ploidy under a light microscope. For both the loaches and gibel carp, direct observation of the mean erythrocyte size in epithelial fin capillaries provided a consistent and reliable determination of ploidy when compared with the controls based on flow cytometry and blood smears. This new method allows for rapid determination of ploidy in living small fish, where collection of tissue using other methods may cause excessive stress or damage. The method outlined here simply requires the measurement of erythrocytes directly in the bloodstream of a live fish, thereby making it possible to determine ploidy without the need for blood sampling. The method described is sufficiently efficient, less demanding on equipment than many other procedures, can be used by relatively inexperienced personnel and has benefits as regards animal welfare, which is especially important for fish production facilities or when dealing with rare or endangered species. [ABSTRACT FROM AUTHOR]

Pendimethalin has been considered a moderately to extremely toxic compound for fish and aquatic organism. This study developed the determination of dynamic residual distribution for pendimethalin in crucian carp tissues (muscle, liver, kidney, gill, and blood) under semistatic exposure system by high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) method. The pendimethalin residues in various fish tissues increased initially and then decreased, and the residue amount of pendimethalin varied from tissue to tissue of crucian carp. Particularly, the pendimethalin accumulation in most fish tissues made significant decreases at two-time points. Pendimethalin was initially absorbed and enriched by fish body, and then partial pendimethalin was discharged into the outside environment through the metabolism function of crucian carp. The residue levels of pendimethalin distributed in crucian carp were ranked in the following decreasing order: liver > kidney > gill or muscle > blood, attributed to the fact that pendimethalin tends to accumulate in lipid-rich tissues of fish. Risk assessment results indicated that the chronic risk from dietary exposure to pendimethalin through crucian carp consumption for Chinese residents was acceptable, along with a lower estimated exposure dose (EED) than acceptable daily intake (ADI) and risk quotient (RQ) < 1. This study performed the first analysis for pendimethalin residual distribution in crucian carp tissues under semistatic exposure condition and provided a reference for pollution control and risk assessment of pendimethalin aimed at aquatic products. [ABSTRACT FROM AUTHOR]

The present study was performed to determine the effect of melatonin on cadmium accumulation and haematological parameters changes in females of Prussian carp (Carassius gibelio B.). The fish were exposed to a sublethal concentration of cadmium (0.4 and 4.0 mg/L) without or with melatonin implant (containing 18 mg melatonin hormone) for 1, 4, 7, 10 and 13 weeks. After the 7th week, Cd-exposed fish were divided into two groups. The first group of fish were subjected to depuration in clear water, while the second group remained exposed to the same concentrations of cadmium. After the 10th and 13th weeks of exposure the kidney, spleen, heart and blood were taken in order to determine the cadmium concentration and to analyse haematological parameters. The results of this study showed an increase in the concentration of cadmium in the tissues and blood in fish exposed to the highest dose (4.0 mg/L) of cadmium in water with a dependence on the exposure duration. Additionally, it was shown that melatonin administration reduced the cadmium concentration in the tissues and blood, and melatonin had a protective effect against cadmium accumulation. Moreover, the results showed a significant increase in blood parameters (RBC, Ht and Hb) in fish treated with the highest dose of cadmium. However, implantation of melatonin in cadmium-treated fish resulted in marked improvements in haematological parameters. Thus, melatonin can be a good implementation to alleviate, at least partially, the toxicity of cadmium. [ABSTRACT FROM AUTHOR]

Previous research has indicated that triploid crucian carp (3n fish) have preferential resistance to cadmium (Cd) compared to Carassius auratas red var. (2n fish). In this article, comparative research is further conducted between the 2n and 3n fish in terms of the immune response to Cd-induced stress. Exposure to 9 mg/L Cd for 96 h changed the hepatic function indexes remarkably in the 2n fish, but not in the 3n fish. In the serum of Cd-treated 2n fish, the levels of alanine amino transferase, aspartate aminotransferase, adenosine deaminase, and total bilirubin significantly increased, while the levels of total protein, albumin, lysozyme, and anti-superoxide anion radicals decreased demonstrating hepatotoxicity. By analysis of transcriptome profiles, many immune-related pathways were found to be involved in the response of 3n fish to the Cd-induced stress. Expression levels of the immune genes, including the interleukin genes, tumor necrosis factor super family member genes, chemokine gene, toll-like receptor gene, and inflammatory marker cyclooxygenase 2 gene were significantly enhanced in the hepatopancreas of the Cd-treated 3n fish. In contrast, the expression levels of these genes decreased in the 2n fish. This research provides a theoretical basis for polyploid fish breeding and is helpful for the ecological restoration of water due to pollution. [ABSTRACT FROM AUTHOR]

The aim of the present study was to test the hypothesis that predigesting commercial dry diets for fish with hydrochloric acid (HCl) can contribute to the reduction of the incidence of body deformities in a stomachless cyprinid species intensively reared under controlled conditions. Two different dry diets (Carpco Crumble by Coppens International and Aller Futura by Aller Aqua), their respective variants modified with HCl, and frozen larval chironomids (control diet) were fed as sole food sources to juvenile Carassius carassius in a recirculating aquaculture system at 25°C for 60 days. At the end of the experiment, visible body deformities occurred exclusively in the groups fed dry diets. The shares of deformities were significantly lower in fish groups fed the modified diets (6.1–13.2%) as compared to those fed the original ones (74.0–87.0%). Fish in the latter groups had significantly the highest condition factor values, which indicated a possible phosphorus deficiency. As evidenced by our results, predigesting commercial dry diets with HCl can be a useful method to mitigate the problem of body deformities occurring in intensively fed cyprinid species. [ABSTRACT FROM AUTHOR]

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The present study was conducted to investigate the volatile compounds profile of raw muscle between diploid (2n = 100) and triploid crucian carp (produced by hybridization from mating diploid crucian carp to allotetraploid, 3n = 150) cultured under the same conditions. Volatile compounds of crucian carp between ploidy were qualitatively analyzed by headspace solid-phase microextraction and gas chromatography-tandem mass spectrometry (HS-SPME-GC/MS). A total of 52 volatiles were identified in the two groups of crucian carp including 5 alcohols, 5 aromatics, 8 aldehydes, 1 ketone, 10 alkanes, 19 alkenes and 4 esters. No significant difference was observed in the total relative concentration between the two groups (P > 0.05). Based on the data of odor-active value (OAV ≥ 1), 10 odor-active compounds may mainly contribute to the overall odor, including 1-nonanol, 1-octen-3-ol, hexanal, decanal, octanal, 1-nonanal, p-cymene, styrene, limonene and tridecane. Triploid crucian carp had more odor-active compounds and higher total OAV value than that of diploid (P < 0.05). With the results of partial least squares discrimination analysis (PLS-DA) in total volatiles and odor-active compounds, the overall odor of triploid and diploid crucian carp was obviously different.

Previous research has indicated that triploid crucian carp (3n fish) have preferential resistance to cadmium (Cd) compared to Carassius auratas red var. (2n fish). In this article, comparative research is further conducted between the 2n and 3n fish in terms of the immune response to Cd-induced stress. Exposure to 9 mg/L Cd for 96 h changed the hepatic function indexes remarkably in the 2n fish, but not in the 3n fish. In the serum of Cd-treated 2n fish, the levels of alanine amino transferase, aspartate aminotransferase, adenosine deaminase, and total bilirubin significantly increased, while the levels of total protein, albumin, lysozyme, and anti-superoxide anion radicals decreased demonstrating hepatotoxicity. By analysis of transcriptome profiles, many immune-related pathways were found to be involved in the response of 3n fish to the Cd-induced stress. Expression levels of the immune genes, including the interleukin genes, tumor necrosis factor super family member genes, chemokine gene, toll-like receptor gene, and inflammatory marker cyclooxygenase 2 gene were significantly enhanced in the hepatopancreas of the Cd-treated 3n fish. In contrast, the expression levels of these genes decreased in the 2n fish. This research provides a theoretical basis for polyploid fish breeding and is helpful for the ecological restoration of water due to pollution.

Tryptophan (Trp) has received increasing attention in the maintenance of intestinal function. In this study, improved triploid crucian carp (ITCC) fed diets containing 6.35 g kg−1 Trp had higher average daily gain (ADG) and improved villus height (VH) and crypt depth (CD) in the intestine compared to the control group. To elucidate the potential mechanisms, we used RNA sequencing (RNA-seq) to investigate changes in the intestinal transcriptome and 16S rRNA gene sequencing to measure the intestinal microbiota in response to 6.35 g kg−1 Trp feeding in ITCC. Dietary Trp altered intestinal gene expression involved in nutrient transport and metabolism. Differentially expressed transcripts (DETs) were highly enriched in key pathways containing protein digestion and absorption and the AMPK signaling pathway. 16S rRNA sequencing showed that 6.35 g kg−1 Trp significantly increased the abundance of the genus Cetobacterium, and the Firmicutes/Bacteroidetes ratio at the phylum level (P < 0.05). In addition, bacterial richness indices (Simpson index) significantly increased (P < 0.05) community evenness in response to 6.35 g kg−1 Trp. In conclusion, appropriate dietary Trp improves the growth performance, and influences the intestinal flora of ITCC. This study might be helpful to guide the supply of dietary exogenous Trp in ITCC breeding.

Glutamine synthetase (GS) is a key enzyme that catalyzes the synthesis of glutamine from glutamate, which plays a role in the promotion of muscle cell growth and in improving the flavor of meats. In this study, a GS gene encoding 371 amino acids was cloned from triploid crucian carp and showed the highest level of similarity with the GS gene found in Cyprinus carpio. Meanwhile, GS was differentially expressed in different tissues, and its day–night expression changes showed obvious oscillation. Additionally, the effects of glutamate and glutamine on GS expression in muscle cells were investigated in vitro and in vivo. We found that its expression was obviously increased due to high levels of glutamate (2 mg/mL) but decreased by glutamine in vitro. However, it was significantly promoted by glutamate and glutamine in vivo, with an optimal concentration of 2%. Furthermore, the use of lysine–glutamate dipeptides as feed additives also had a positive influence on GS expression (the optimal concentration is 0.8%). Finally, we explored the effects of different protein levels and sources on the expression of GS, and the results demonstrated that GS had the highest expression at the 35% protein level, but no significant differences were observed in the different protein sources between the fish meal diet (FM) and the mixed diet comprising soybean meal and rapeseed meal (SM). This study sheds new light on the regulation of GS in teleost fish and provides new perceptions and strategies for the formulation of high-quality feed for triploid crucian carp.

Changes in the physiological and behavioral states of fish are affected by foreign substances. Therefore, fish need a certain adaptation period to eliminate the stress response. Herein, in order to determine the adaptation period, the bionic robot fish was used to obtain behavioral information about crucian carp, which was tested at five time points (1st, 7th, 14th, 21st and 28th day) within 28 days. First, the fear response and exploratory behavior of crucian carp affected by three-color bionic robot fish were explored. Then, according to the measurement results of the behavior, morphology, and feeding, and the physiological and biochemical properties of the crucian carp, a multi-parameter evaluation method was proposed to determine the adaptation period of the crucian carp under this monitoring mode. The results showed that more than 4 areas were occupied by crucian carp from the 21st day. From the 16th day, the number of crucian carp swimming with clear outlines gradually increased. The number of abnormal swimming occurrences decreased on day 13. More than 80% of the crucian carp body color returned to dark on the 23rd day. The crucian carp did not respond to food until day 19, when most of the crucian carp began to scramble for food. Food consumption reached more than two thirds on day 22. In addition, glucose and total protein leveled off after day 21, when mean hemoglobin levels were highest. Triglycerides showed a trend of first decreasing and then increasing. The pigmented area of the skin section gradually decreases and eventually stabilizes. In summary, it takes at least 23 days for the crucian carp to adapt to the influence of the bionic robot fish.

Unisexual lineages are commonly considered to be short-lived in the evolutionary process as accumulation of deleterious mutations stated by Muller's ratchet. However, the gynogenetic hexaploid gibel carp (Carassius gibelio) with existence over 0.5 million years has wider ecological distribution and higher genetic diversity than its sexual progenitors, which provides an ideal model to investigate the underlying mechanisms on countering Muller's ratchet in unisexual taxa. Unlike other unisexual lineages, the wild populations of gibel carp contain rare and variable proportions of males (1–26%), which are determined via two strategies including genotypic sex determination and temperature-dependent sex determination. Here, we used a maternal gibel carp from strain F to be mated with a genotypic male from strain A+, a temperature-dependent male from strain A+, and a male from another species common carp (Cyprinus carpio), respectively. When the maternal individual was mated with the genotypic male, a variant of gynogenesis was initiated, along with male occurrence, accumulation of microchromosomes, and creation of genetic diversity in the offspring. When the maternal individual was mated with the temperature-dependent male and common carp, typical gynogenesis was initiated that all the offspring showed the same genetic information as the maternal individual. Subsequently, we found out that the genotypic male nucleus swelled and contacted with the female nucleus after fertilization although it was extruded from the female nucleus eventually, which might be associated with the genetic variation in the offspring. These results reveal that genotypic males play an important role in the creation of genetic diversity in gynogenetic gibel carp, which provides insights into the evolution of unisexual reproduction. [ABSTRACT FROM AUTHOR]

Ultra-performance liquid chromatography (UPLC) was used to detect six fluoroquinolones (FQs) in live aquatic product sampled from the region surrounding the Dongting Lake in Hunan, China. Results showed that 8.3% of samples were contaminated with norfloxacin in the range of 4.5 to 10.3 µg/kg, and 7.3% of samples carried residual ofloxacin in the range of 6.7 to 76.0 µg/kg. One crucian carp sample was pefloxacin-positive, and one blunt snout bream sample was lomefloxacin-positive, and the level in these two samples were 18.3 and 25.1 µg/kg, respectively. Further, 3.1% of samples contained residues of enrofloxacin and (or) ciprofloxacin higher than their maximum residue limits. This survey demonstrated that banned drugs were occasionally used, and that enrofloxacin was occasionally used in excess in aquaculture in the surveyed area. [ABSTRACT FROM AUTHOR]

Phenotypic plasticity can be expressed as changes in body shape in response to environmental variability. Crucian carp (Carassius carassius), a widespread cyprinid, displays remarkable plasticity in body morphology and increases body depth when exposed to cues from predators, suggesting the triggering of an antipredator defense mechanism. However, these morphological changes could also be related to resource use and foraging behavior, as an indirect effect of predator presence. In order to determine whether phenotypic plasticity in crucian carp is driven by a direct or indirect response to predation threat, we compared twelve fish communities inhabiting small lakes in southeast Norway grouped by four categories of predation regimes: no predator fish, or brown trout (Salmo trutta), perch (Perca fluviatilis), or pike (Esox lucius) as main piscivores. We predicted the body shape of crucian carp to be associated with the species composition of predator communities and that the presence of efficient piscivores would result in a deeper body shape. We use stable isotope analyses to test whether this variation in body shape was related to a shift in individual resource use—that is, littoral rather than pelagic resource use would favor the development of a specific body shape—or other environmental characteristics. The results showed that increasingly efficient predator communities induced progressively deeper body shape, larger body size, and lower population densities. Predator maximum gape size and individual trophic position were the best variables explaining crucian carp variation in body depth among predation categories, while littoral resource use did not have a clear effect. The gradient in predation pressure also corresponded to a shift in lake productivity. These results indicate that crucian carp have a fine‐tuned morphological defense mechanism against predation risk, triggered by the combined effect of predator presence and resource availability. [ABSTRACT FROM AUTHOR]

The present study aims to explore the effects of oral astaxanthin administration on the growth performance and innate immunity of juvenile crucian carp (Carassius auratus). Juvenile crucian carps with a bodyweight of 40.06 ± 2.17 g were randomly assigned to four groups, i.e., one control group fed with a basic diet and three treatment groups fed with a diet that contains 200, 400 and 800 mg/kg astaxanthin. After 60 days of feeding, the groups fed with astaxanthin-containing diets had improved body weight gain rate; feed conversion ratio; intestinal digestive protease, lipase and amylase levels; serum superoxide dismutase, catalase, acid phosphatase, alkaline phosphatase and lysozyme activities; complement 3 and complement 4 levels; interleukin (IL)-10 and resistance to Aeromonas hydrophilia and reduced serum aspartate aminotransferase and alanine aminotransferase activities and tumour necrosis factor-α, IL-1β and IL-8 levels compared with those of the control group. Based on the efficiency of the oral administration of astaxanthin on the growth performance of juvenile crucian carps, the optimum dose of astaxanthin was 400 mg/kg. Results indicated that astaxanthin may be used as a dietary supplement for the crucian carp. [ABSTRACT FROM AUTHOR]

The aim of the present study was to create a suitable model of the glucose toxicity and elucidate the ability of zinc-binding proteins metallothioneins in the crucian carp Carassius auratus to reflect it. For that, fish was loaded by three waterborne concentrations of glucose (low (5.55 mM, LC), middle (55.5 mM, MC) or high (111 mM, HC)) for 21 days. The level of blood glucose, responses of metallothioneins, oxidative stress, DNA instability in the liver, as well as erythrocytes indices, cholinesterase activity in the brain and morphometric variables were evaluated. An increase in blood glucose levels (up to 3–5 times), glycated hemoglobin (HbA1c, only by the HC, by 55%), methemoglobin (by two times), oxyradicals (16-57%) and TBARS levels (up to 57%), frequency of the micronucleated erythrocytes, DNA fragmentation in hepatocytes, body mass and hepatosomatic indices and a decrease in metallothioneins concentration (40-74%), cholinesterase activity (~70%), total hemoglobin (by 18%) and red blood cells count (only after HC-treatment, by 47%) were detected. The lysosomal membrane stability, evaluated by the neutral red retention time, was affected by all studied concentrations of glucose (decreased by 58%). The most prominent changes were observed after the HC of glucose. CART analysis revealed the significant splitting parameters for studied group differentiation including HbA1c, lysosomal membrane stability and lipid peroxidation. We could consider the crucian carp is a useful model organism to perform DM studies and in the future, this fish model can help in mechanistic investigations and testing therapeutic interventions under glycemic states.

The release of hatchery-reared fish fry for restocking is important for the enrichment of fishery resources; however, the effective evaluation of the success rate of marking such fish is challenging. We exposed juvenile crucian carp (Carassius carassius) to a single concentration of SrCl2·6H2O for 5 d and evaluated the efficiency of Sr marking of the fish otoliths (sagittae, asterisci, and lapilli) using an electron probe micro-analyzer. Sr marking signatures formed a peak in all otolith types, with a marking success rate of 100%. The ratio of Sr to Ca in the lapilli and sagittae was higher than that in the asterisci. It took 2 d from the beginning of immersion to the deposition of Sr on the lapilli and sagittae, and the time delay for asterisci was 1 d. For the lapilli and sagittae, it took 16 d to terminate Sr marking and fully recover to the pre-marking Sr level, whereas it was 12 d for the asterisci. The application of the Sr dose had no effect on the survival or growth of the carp. This study demonstrated that the lapilli are the most suitable otolith type for Sr marking observations in crucian carp and provides a theoretical basis and technical support for carp restocking using the Sr marking approach.

Immersion vaccination relies on the response of fish mucosa-associated lymphoid tissues, the Crucian carp (Carassius auratus) and Grouper (Epinephelus coioides) were researched in this paper to examine local mucosal immune responses and associated humoral system responses following immersion vaccination. We administered 1.5 × 107 CFU/ml formalin-inactivated Vibrio harveyi cells and measured mucus and serum antibody titers as well as IgM, MHC II mRNA levels in immune organs. The mucosal antibody response preceded the serum response indicating a role for local mucosal immunity in immersion vaccination. IgM and MHC II mRNA levels were relatively greater for the spleen and head kidney indicating the importance and central position of systemic immunity. Expression levels were also high for the gills while skin levels were the lowest. IgM and MHC II mRNA levels were altered over time following vaccination and the hindgut, liver and spleen were similar indicating a close relationship, so the absolute value of r is used to analyze the correlation among different organs immunized. It can be inferred the existence of an internal immune molecular mechanism for Immune synergy hindgut-liver-spleen, from the peak time (14th day), the relative ratio of genes expression in the same tissues between the immunized grouper and the control group (26 times), and Pearson correlation coefficient (0.8<| r |<1). Injection challenges with live V. harveyi indicated that the relative protection rates for the crucian carp and Grouper was basically the same at 44.4% and 47.4%, respectively. It is believe that crucian carp may be used as a substitute for the valuable grouper in immunity experiment, just from aspect of the relative percent survival (RPS) and how it changes with time. But they were not consistent about the IgM mRNA expression between that of crucian carp and grouper after immersion the Vibrio vaccine. [ABSTRACT FROM AUTHOR]

Pengze crucian carp was pre‐frozen by liquid nitrogen and freezer, and then stored at −20/−40°C and −20°C, respectively, for 15–60 days. Effects of pre‐freezing methods and storage temperatures on the qualities of fish were investigated. The pH showed a "V" trend. The soluble myofibrillar protein content, hardness, springiness, cohesiveness, gumminess, chewiness, and resilience decreased. Thiobarbituric acid value, total volatile basic‐nitrogen value, thawing and cooking loss rates increased with the extending of storage period. LF‐NMR analysis indicated that the water‐protein connection became less tight. Moreover the qualities decline degrees were higher for freezer pre‐frozen than liquid nitrogen pre‐frozen, and higher for −20°C storage than −40°C storage. Accordingly, compared with conventional freezer pre‐freezing and storage, liquid nitrogen pre‐freezing and low temperature storage could inhibit the oxidation and degradation, and keep better water holding and textural properties of muscle. The present study showed a great potential application in aquatic products processing industry. Practical applications: In aquatic product enterprise, liquid nitrogen can be used to pre‐freeze fishes in seconds. And combined with low temperature storage, the oxidation and degradation of fish can be significantly inhibited. In addition, water holding capacity and textural properties of fish muscle can be better kept, and the shelf‐life of fish can be extended by several weekends in comparison with those of fishes pre‐frozen and stored in freezer. [ABSTRACT FROM AUTHOR]

Previously, a homodiploid goldfish-like fish (2 n = 100; GF-L) was spontaneously generated by self-crossing a homodiploid red crucian carp-like fish (2 n = 100; RCC-L), which was in turn produced via the distant hybridization of female koi carp (Cyprinus carpio haematopterus , KOC, 2 n = 100) and male blunt snout bream (Megalobrama amblycephala , BSB, 2 n = 48). The phenotypes and genotypes of RCC-L and GF-L differed from those of the parental species but were similar to diploid red crucian carp (2 n = 100; RCC) and goldfish (2 n = 100; GF), respectively. We sequenced the complete mitochondrial DNAs (mtDNAs) of the KOC, BSB, RCC-L, GF-L, and subsequent generations produced by self-crossing [the self-mating offspring of RCC-L (RCC-L-F2) to the self-mating offspring of RCC-L-F2 (RCC-L-F3) and the self-mating offspring of GF-L (GF-L-F2)]. Paternal mtDNA fragments were stably embedded in the mtDNAs of both lineages, forming chimeric DNA fragments. In addition to these chimeras, several nucleotide positions in the RCC-L and GF-L lineages differed from the parental bases, and were instead identical with RCC and GF, respectively. Moreover, RCC-L and GF-L mtDNA organization and nucleotide composition were more similar to those of RCC and GF, respectively, compared to parental mtDNA. Finally, phylogenetic analyses indicated that RCC-L and GF-L clustered with RCC and GF, not with the parental species. The molecular dating time shows that the divergence time of KOC and GF was about 21.26 Mya [95% highest posterior density (HPD): 24.41–16.67 Mya], which fell within the period of recent. The heritable chimeric DNA fragments and mutant loci identified in the mtDNA of the RCC-L and GF-L lineages provided important evidence that hybridizations might lead to changes in the mtDNA and the subsequent generation of new lineages. Our findings also demonstrated for the first time that the paternal mtDNA was transmitted into the mtDNA of homodiploid lineages (RCC-L and GF-L), which provided evidence that paternal DNA plays a role in inherited mtDNA. These evolutionary analyses in mtDNA suggest that GF might have diverged from RCC after RCC diverged from koi carp. [ABSTRACT FROM AUTHOR]

The article substantiates the expediency of improving of technological methods of processing unprofitable small fish and expanding of the food products range from them. It proposes enriching of the flesh of freshwater fish with trace elements by adding chelate complexes based dietary supplements to salt or brine during the salting of raw materials. The kinetics of penetration of the chelate complexes micronutrients based dietary supplement into the muscle tissue of crucian carp was researched using the method of electronic paramagnetic resonance (EPR). The salting was performed using three methods. In the first, dry method of salting the fish was mixed with sodium chloride NaCl with the addition of a chelate complex based dietary supplement in the amount of 20–25% and 0.1% of the weight of raw material, respectively. In the second, brine method the fish was salted in brine, which was a solution of sodium chloride NaCl in the amount of 2 kg of salt per 1 kg of raw material. The amount of the chelate complex based dietary supplement was 0.1% of the weight of raw material. In the third method, the salting was performed in brine with the same concentrations of sodium chloride and dietary supplement, but the fish raw material was previously treated with ultrasound. The salting of fish lasted for 6 days. The distribution of Mn ions in the plane (i, j) was researched. The kinetics of penetration of the trace element into the volume of crucian carp muscle tissue was researched using the EPR method. The kinetics of Mn2+ ions distribution in the researched muscle tissue samples and the tomograms of these surfaces were determined. The values of the area under the EPR spectrum were normalized to the values of the area under the maximum EPR signal. In the dry salting method the signal from the liquid in which the raw material was during the salting was selected as the maximum EPR signal; and in the brine method the signal from the brine sample was selected as the maximum EPR signal. It is noted that the kinetics of penetration of the trace element is determined by the area of contact of the raw material with the diffusing substances and the method of intensification of the internal transfer of these substances inside the raw material. It was found that in the brine method and in the brine method with pre-sonication, the amount of trace element in the depth of the crucian carp muscle tissue varied within the error margin. This indicates the homogeneity of distribution of the trace element of the chelate complex based dietary supplement in these methods of salting. [ABSTRACT FROM AUTHOR]

The addition of heavy protein to aquafeed causes low digestibility, high cost and significant nitrogen pollution in the water. The addition of protease is an effective way of improving protein absorption, but few proteases have been developed specifically for aquafeeds. The hydrolysis efficiency of protease additives for plant protein in the neutral gut environment and their synergy with endogenous proteases has not been sufficiently investigated. In this study, the performance of the recombinant neutral protease rNpI as an aquafeed additive to reduce the raw protein materials in the diet of Carassius carassius during 56 days of growth was evaluated. rNpI effectively hydrolysed soya bean protein isolates (SPI) with a high degree of hydrolysation and a high small‐peptide yield. The rNpI‐treated SPI exhibited a notable antioxidant activity, which benefited fish health. In vitro digestibility indicated that rNpI complemented trypsin in SPI digestion better than papain or Alcalase. The growth trial showed that the addition of rNpI could warrant a reduction in the crude protein and gross energy of feed while producing a lower feed‐conversion rate (FCR) and better growth performance. Crucian that were fed an RM‐wheat‐E diet (5.5% rapeseed meal and 5% wheat reduction) showed the best performance, with the lowest FCR and highest weight gain. These results indicate that rNpI could be an effective additive for the aquafeed industry and could provide economic benefits by reducing aquafeed protein requirements and nitrogen emissions. This study provides novel information and strategies for additive protease use and development in aquafeed. [ABSTRACT FROM AUTHOR]

Owning to the extreme difficulty in identifying the primary generation (G0), the common ancestor of various twin-tail goldfish strains remains unclear. However, several authors have hypothesized that this ancestor may have been the crucian carp (Carassius auratus). Previously, we generated an experimental hybrid goldfish (EG) from the interspecific hybridization of red crucian carp (Carassius auratus ♀, RCC) × common carp (Cyprinus carpio ♂, CC). Unlike either parent, EG possessed twin caudal fins similar to those of natural goldfish (Carassius auratus , NG). The genetic characteristics of EG, as well as the mechanisms underlying its formation, are largely unknown. Here, we identified the genetic variation in the chordin gene that was associated with the formation of the twin-tail phenotype in EG: a stop codon mutation at the 127th amino acid. Furthermore, simple sequence repeat (SSR) genotyping indicated that, among the six alleles, all of the EG alleles were also present in female parent (RCC), but alleles specific to the male parent (CC) were completely lost. At some loci, EG and NG alleles differed, showing that these morphologically similar goldfish were genetically dissimilar. Collectively, our results demonstrated that genetic variations and differentiation contributed to the changes of morphological characteristics in hybrid offspring. This analysis of genetic variation in EG sheds new light on the common ancestor of NG, as well as on the role of hybridization and artificial breeding in NG speciation. [ABSTRACT FROM AUTHOR]

Prussian Carp Carassius gibelio, also referred to as Gibel Carp, is a destructive aquatic invasive species, recently found in Alberta, Canada. Three-pass electrofishing is a potential approach to control some aquatic invasive fish species in stream habitats. The objectives of this study were to 1) determine the efficacy of this strategy to control Prussian Carp in connected streams and 2) assess whether population size or the distance to the introduction site would influence removal success. We sampled sites by using electrofishing in tributaries of the Red Deer River in both the summer and fall and detected Prussian Carp at all sites before removal, with >90% probability of detection of this species within the first 120 m of electroshocking efforts. Overall, we were not successful at removing Prussian Carp from the sample sites, and we found that abundances of Prussian Carp were significantly higher postremoval. Removal success related significantly to distance to the introduction site, suggesting that removal may be useful in targeted situations close to the edge of the invasion front. [ABSTRACT FROM AUTHOR]

The objective of this study was to determine growth parameters, such as age–length and length–weight relationships, as well as condition factors and sex ratio, of the Carassius gibelio (Bloch, 1782) population in Lake Marmara (western region of Turkey), which is one of the most important fishing areas. Fish were caught on a monthly basis by gillnets and trammel nets (mesh size 10–50 mm) between March 2012 and February 2013. A total of 1058 specimens (809 females and 249 males) were examined. The female–male ratio was 1:0.31. The maximum age was determined as VI and V for females and males, respectively. The total length of females and males ranged from 10.0 to 27.5 cm and from 10.2 to 24.0 cm, respectively. Their weight varied from 17.1 to 378.4 g and from 17.7 to 244.9 g, respectively. Length–weight relationship parameters were a = 0.014 and b = 3.040 for females and a = 0.015 and b = 3.039 for males. Von Bertalanffy growth parameters of the C. gibelio population were as follows: L∞ = 35.86 cm, k = 0.189 year−1, t0 = −1.238 years. Minimum and maximum condition factors were 1.56 for females in October and 1.82 in May and 1.67 for males in September and 1.94 in January. [ABSTRACT FROM AUTHOR]

The object of this work is to investigate the effects of emodin and curcumin on Pengze crucian carp. Fish was, respectively, fed Control diet and supplementation of 50 mg/kg emodin (EM group) and curcumin (CU group) with 4 repetitions each group (20 fish per cage). Our results indicated that the growth was unaffected by diets, whilst whole‐body lipid content was detected to remarkably decrease in EM group. Two additives exerted positive impacts on antioxidant system through elevation of antioxidant enzymes activities and antioxidants content. The improvement of intestinal antioxidant property appeared to be associated with up‐regulating expression of antioxidant genes through nuclear factor erythroid 2‐related factor 2 (Nrf2) activation. Moreover, intestinal inflammatory response was suppressed in EM and CU groups through inhibition of Toll‐like 4 receptor (TLR4) signalling pathway and pro‐inflammatory cytokine genes expression, and it may be related to the regulation of antioxidant system and overexpression of interleukin‐10. Afterwards, intestinal barrier function was enhanced in EM and CU groups by inducing the expression of tight junction protein genes. These results revealed that emodin and curcumin exerted positive benefits on the health of Pengze crucian carp by enhancing antioxidant capacity, suppressing inflammatory response and improving intestinal barrier function. [ABSTRACT FROM AUTHOR]

Diseases of crucian carp (Carassius auratus) are closely related to intestinal parameters. Enterococcus faecalis has strong colonization ability in the intestinal tract, and produces natural antibiotics, bacteriocin, and other bacteriostatic substances, which can effectively inhibit some pathogenic bacteria and improve the intestinal microenvironment. This study aimed to assess the effects of E. faecalis YFI-G720 which was isolated from the intestinal of crucian carp on the growth, immunity, intestinal health, and disease resistance of crucian carp. Fish (48.16 ± 0.55 g) were fed four diets, commercial diet or diet containing E. faecalis at 105 CFU/g (EF1), 106 CFU/g (EF2), or 107 CFU/g (EF3) for 28 days. The results showed that supplementation of E. faecalis significantly improved the weight gain ratio (WGR) and the specific growth rate (SGR) compared with control group (p < 0.05). Intestinal mucosal epithelial cells in EF2 were intact and normal, but there was obvious vacuolation in CG. Compared with CG, serum C3 and IgM in EF2 were significantly increased at the end of the experiment (p < 0.05), and serum alkaline phosphatase was significantly higher in all experimental groups (p < 0.05). Among studied immune-related genes, expression was detected by qPCR, C3, IgM, and IL-1βwere upregulated in all experimental groups to varying degrees from 14 days, with highest expression in EF2 at 28 days. Intestinal microbiota structure analyzed through high-throughput sequencing, and the results showed that the relative abundance of Aeromonas and Acinetobacter decreased while Cetobacterium increased in all experimental groups, with the greatest changes in EF2. Challenge tests showed that fish fed E. faecalis were more resistant to Aeromonas veronii (p < 0.05). In conclusion, dietary E. faecalis YFI-G720 at 106 CFU/g can improve the health status, immune parameters, intestinal microbiota composition, and disease resistance of crucian carp.

Background: Melanocortin-3 and -4 receptors (MC3R and MC4R), G protein-coupled receptors, play vital roles in the regulation of energy homeostasis. To understand the functions of mc3r and mc4r in the energy homeostasis of red crucian carp ( Carassius auratus red var., RCC), we cloned mc3r and mc4r , analyzed the tissue expression and localization of the genes, and investigated the effects of knockout of mc3r ( mc3r +/- ) and mc4r ( mc4r +/- ) in RCC., Results: The full-length cDNAs of RCC mc3r and mc4r were 1459 base pairs (bp) and 1894 bp, respectively. qRT-PCR indicated that mc3r and mc4r were profusely expressed in the brain, but lower expressed in the periphery tissues. ISH revealed that mc3r and mc4r were located in NPP, NPO, NAPv, NSC, NAT, NRL, NLTl, and NLTp of the brain, suggesting that mc3r and mc4r might regulate many physiological and behavioral aspects in RCC. To further verify the roles of mc3r and mc4r in energy homeostasis, the mc3r +/- and mc4r +/- fish were obtained by the CRISPR/Cas9 system. The average body weights, total lengths, body depths, and food intake of mc4r +/- fish were significantly higher than those of mc3r +/- and the normal wild-type (WT) fish, but there was no difference between the mc3r +/- and WT fish, indicating that the RCC phenotype and food intake were mainly influenced by mc4r but not mc3r . Interestingly, mc4r +/- fish displayed more visceral fat mass than mc3r +/- and WT fish, and mc3r +/- fish also exhibited slightly more visceral fat mass compared to WT. RNA-seq of the liver and muscle revealed that a large number of differentially expressed genes (DEGs) differed in WT vs. mc3r +/- , WT vs. mc4r +/- , and mc3r +/- vs. mc4r +/- , mainly related to lipid, glucose, and energy metabolism. The KEGG enrichment analysis revealed that DEGs were mainly enriched in pathways such as steroid biosynthesis, fatty acid metabolism, fatty acid biosynthesis, glycolysis/gluconeogenesis, wnt signaling pathway, PPAR signaling pathway, and MAPK signaling pathway, thereby affecting lipid accumulation and growth., Conclusion: In conclusion, these results will assist in the further investigation of the molecular mechanisms in which MC3R and MC4R were involved in the regulation of energy homeostasis in fish., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2024 Huang, Deng, Yang, Tang, Fan, Zhou, Tao and Liu.)

Aeromonas salmonicida is an ancient fish pathogen. Lysozymes are important molecules in the innate immune system that fight bacterial infections. The expression characteristics of C-type lysozyme in crucian carp infected with A. salmonicida and its antibacterial effect against A. salmonicida had not been investigated. Thus, we used bioinformatics to analyze the gene and protein characteristics of C-type lysozymes in crucian carp. Changes in C-type lysozyme expression before and after crucian carp infection with A. salmonicida were detected, and the in vitro antibacterial effect of recombinant carp C-type lysozyme on A. salmonicida was validated. The results showed that the coding DNA sequence region of the lysozyme gene sequence was 438 bp long, encoding 145 amino acids and containing two conserved catalytic sites: Glu53 and Asp69. Phylogenetic analysis revealed that crucian carp C-type lysozymes clustered with Cyprinus carpio lysozyme C. After crucian carp were infected with A. salmonicida , the gene and protein expression of C-type lysozymes in the liver, spleen, kidney, and hindgut were significantly upregulated, with the liver showing the highest upregulation that was 15 times higher than that in the uninfected group. In addition, recombinant C-type lysozyme exhibited significant antibacterial activity against A. salmonicida , with an average inhibition zone radius of 0.92 cm when using 40 μg recombinant lysozyme. In conclusion, this study reveals the important role of C-type lysozymes in the innate immune response of crucian carp and provides a theoretical basis for preventing crucian carp infection with A. salmonicida ., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2024 The Authors.)

Our study aimed to test whether fluoxetine impairs learning in fish and whether this potential impairment is reversible. Learning efficiency, with no aversive stimuli, of the Carassius carassius was analysed under different pharmaceutical conditions: (i) fish cultured without antidepressant (control), (ii) fish exposed to fluoxetine for 21 days (fluoxetine), and (iii) fish exposed to fluoxetine for 21 days and then cultured without fluoxetine for another 21 days (recovery). We exposed animals to environmental concentrations (360 ng L -1 ) of antidepressant. The learning rate was measured by timing how long it took the individual fish to find food and start feeding, six days in a row. The control and recovery fish took significantly less time to start eating over the six days. Control fish start eating 14 times faster than the fluoxetine fish. Fluoxetine can significantly affect learning and 21-day recovery period is not enough to fully restore the original learning abilities., Competing Interests: Declaration of Competing Interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests:Malgorzata Grzesiuk reports financial support was provided by National Science Centre Poland., (Copyright © 2023 Elsevier B.V. All rights reserved.)

Goldfish have been subjected to over 1,000 y of intensive domestication and selective breeding. In this report, we describe a highquality goldfish genome (2n = 100), anchoring 95.75% of contigs into 50 pseudochromosomes. Comparative genomics enabled us to disentangle the two subgenomes that resulted from an ancient hybridization event. Resequencing 185 representative goldfish variants and 16 wild crucian carp revealed the origin of goldfish and identified genomic regions that have been shaped by selective sweeps linked to its domestication. Our comprehensive collection of goldfish varieties enabled us to associate genetic variations with a number of well-known anatomical features, including features that distinguish traditional goldfish clades. Additionally, we identified a tyrosine-protein kinase receptor as a candidate causal gene for the first well-known case of Mendelian inheritance in goldfish--the transparent mutant. The goldfish genome and diversity data offer unique resources to make goldfish a promising model for functional genomics, as well as domestication. [ABSTRACT FROM AUTHOR]

Normally, fish will decrease food intake or even stop feeding during the winter. In previous studies, two widely cultured gibel carp strains (strain A and strain F) showed differences in lipid and glucose metabolism. Therefore, we hypothesized that the physiological changes during the overwintering period would be different between the two strains. Thus, the two strains were starved for 77 days, after which the levels of glucose and lipid metabolism, ER stress, autophagy, and apoptosis were determined. The starvation increased hepatic glycogenolysis and fatty acid β-oxidation but suppressed lipogenesis in both strains overwintering. Considering the effects of genotype, strain F had higher levels of ER stress and autophagy but lower levels of apoptosis than strain A, suggesting that strain F might be more resistant to overwintering starvation. The interactions between strains and starvation periods were observed in plasma triglyceride contents and the mRNA levels of pyruvate kinase (pk), sterol regulatory element binding protein 1 (srebp1), activating transcription factor 4 (atf4), and autophagy protein 12 (atg12). In conclusion, long-term starvation during winter could induce hepatic glycogenolysis and fatty acid β-oxidation but suppress lipogenesis, ER stress, autophagy, and apoptosis in gibel carp, and strain F may be more resistant to starvation during winter. Taken together, these results discovered the responses to prolonged starvation stress during winter in two strains of gibel carp and could provide information for genotype selection, especially for selecting strains better adapted to winter. [ABSTRACT FROM AUTHOR]

Chemokine receptor cxcr4 and its ligand cxcl12 have evolved two paralogs in the teleost lineage. In this study, we have identified four duplicated cxcr4 and cxcl12 genes from hexaploid gibel carp, Carassius gibelio , respectively. Cgcxcr4b s and Cgcxcl12a s were dynamically and differentially expressed in immune-related tissues, and significantly up-regulated in head kidney and spleen after crucian carp herpesvirus (Ca HV) infection. Blocking Cxcr4/Cxcl12 axis by injecting AMD3100 brought more severe bleeding symptom and lower survival rate in Ca HV-infected fish. AMD3100 treatment also suppressed the up-regulation of key antiviral genes in head kidney and spleen, and resulted in more acute replication of Ca HV in vivo. Consistently, the similar suppression of up-regulated expression of key antiviral genes were also observed in CAB cells treated by AMD3100 after poly(I:C) stimulation. Finally, MAPK3 and JAK/STAT were identified as the possible pathways that Cg Cxcr4s and Cg Cxcl12s participate in to promote the antiviral response in vitro. [ABSTRACT FROM AUTHOR]

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The northern section of the Caspian Sea is an important fishery for Kazakhstan. In the present study, a total of 606 individuals of 13 fish species were collected. For each of Abramis brama, Alosa saposchnikowii, Atherina boyeri caspia, Carassius auratus, Clupeonella cultriventris, Cyprinus carpio, Liza aurata, Leuciscus aspius, Rutilus rutilus caspius, Sander lucioperca, Sander marinus, and Sander volgensis 50 individuals were examined whilst 6 individuals of Siluris glanis were examined. The nematode parasite Anisakis schupakovi was found in all fish species except Liza aurata, Carassius aurata, Cyprinus carpio and Rutilus rutilus at intensities ranging from 1 to 1197 parasites per infected fish. Trematodes of family Diplostomidae were also isolated from all fish except Alosa saposhnikowii, Clupeonella cultriventris and Sander marinus at intensities ranging from 1 to 242 parasites per infected fish. Other parasites found included the nematodes Porrocaecum reticulatum, Contracecum sp, Camallanus sp and Eustrongylus excisus; the cestodes Neogryporhynchus cheilancristrotus, Bothriocephalus opsariichthydis; the monogenean parasites Mazocraes alosa, Ancyrocephalus paradocus, Gyrodactylus spp, Ligophorus vanbenedenii and Dactylogyrus spp; and the crustacean parasites Ergasilus sp. and Synergasilus sp. In addition one unidentified species of nematode and a bivalve of the genus Unio was recovered from Rutilus rutilus caspius. There was no association between Fulton's condition index and intensity of parasite infection. [ABSTRACT FROM AUTHOR]

Lactic acid bacteria (LAB) are commonly applied to fish as a means of growth promotion and disease prevention. However, evidence regarding whether LAB colonize the gastrointestinal (GI) tract of fish remains sparse and controversial. Here, we investigated whether Lacticaseibacillus casei ATCC 393 (Lc) can colonize the GI tract of crucian carp. Sterile feed irradiated with 60Co was used to eliminate the influence of microbes, and 100% rearing water was renewed at 5-day intervals to reduce the fecal–oral circulation of microbes. The experiment lasted 47 days and was divided into three stages: the baseline period (21 days), the administration period (7 days: day −6 to 0) and the post-administration period (day 1 to 19). Control groups were fed a sterile basal diet during the whole experimental period, whereas treatment groups were fed with a mixed diet containing Lc (1 × 107 cfu/g) and spore of Geobacillus stearothermophilus (Gs, 1 × 107 cfu/g) during the administration period and a sterile basal diet during the baseline and post-administration periods. An improved and highly sensitive selective culture method (SCM) was employed in combination with a transit marker (a Gs spore) to monitor the elimination of Lc in the GI tract. The results showed that Lc (

The pentraxin family is an evolutionarily conserved group that plays an important role in innate immunity. C-reactive protein (CRP) and serum amyloid P component (SAP) are classical members of the short pentraxins and are known to be the major acute phase proteins. In this work, we have cloned a novel pentraxin fusion protein, WR-PTXF, from Carassius cuvieri × Carassius auratus red var. In fish, the biological function of PTXF is essentially unknown. For this purpose, we report the identification and analysis of WR-PTXF and elucidate its role in the antibacterial innate immunity. WR-PTXF contains 224 amino acids and shares 79.8% and 23.0% sequence identities with crucian carp CRP and SAP, respectively. Blast analysis shows that WR-PTXF and goldfish PTXF had the highest similarity (97.3%). WR-PTXF is expressed in multiple tissues and is upregulated by Aeromonas hydrophila infection. WR-PTXF contains a short pentraxin domain and recombinant WR-PTXF protein (rWR-PTXF) can bind the A. hydrophila in a concentration-dependent manner. Further, rWR-PTXF displays apparent bacteriostatic activity against A. hydrophila in vitro by enhancing the uptake of the bound bacteria by host phagocytes. When introduced in vivo, rWR-PTXF not only protects the gut mucosa but also limits the colonization of A. hydrophila in systemic immune organs. Consistently, knockdown of WR-PTXF significantly promotes bacterial dissemination in the tissues of host. These results indicate that WR-PTXF is a classic pattern recognition molecule that exerts a protective effect against bacterial infection., Competing Interests: Declaration of competing interest The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

Background: It has been reported that antibiotic enrofloxacin can impair reproductive function of mammals, induces multi-generational oscillatory effects on reproduction of Caenorhabditis elegans, and disturbes endocrine system in grass carp., Objectives: This study aims to explore the effect of short-term enrofloxacin exposure on sex steroid hormones biosynthesis in Carassius auratus var. Pengze through assessing the contents of growth hormone (GH), thyroid hormone 4 (T 4 ), estradiol (E 2 ) and testosterone (T) in plasma, and investigating sex steroid hormones biosynthesis based on targeted metabonomics analysis, and determining expression level of some important genes, gonadotropin-releasing hormone (gnrh), gonadotropin hormone 1-β (gth1-β), gonadotropin hormone 2-β (gth2-β) and cyp19a1a in hypothalamus-pituitary-ovary axis (HPOA)., Results: We found that short-term exposure of enrofloxacin disordered contents of E 2 and T in plasma of fish determined by ELISA detection, T content elevation and E 2 content decline, which was confirmed by the following data from targeted metabonomics analysis of plasma. The metabonomic results showed that both T and its upstream intermediate products during the process of sex steroid hormones biosynthesis in fish were increased significantly, but E 2 content was decreased markedly. At the exposure 24 h of enrofloxacin, expression of gnrh in hypothalamus, gth1-β and gth2-β in pituitary were promoted. Meanwhile GH and T 4 contents in plasma, two inducers of sex steroid hormones synthesis, were augmented, which indicated that sex steroid hormones biosynthesis was improved. However cyp19a1a expression in ovary was repressed, and content of estriol (E 3 ) was upregulated. These data suggested that enrofloxacin promoted sex steroid hormones biosynthesis and conversion of E 2 to estriol (E 3 ), but inhibited the conversion of T to E 2 . Finally, content of E 2 was declined sharply., Discussion: Animal specific antibacterial enrofloxacin is widely detectable in aquatic ecosystem, exposure of the agent can induce adverse effects on plants and animals. This study firstly evidenced induction of disruption of sex steroid hormones by enrofloxacin in fish, which indicates enrofloxacin is an endocrine disruption compound that can induce endocrine disruption of animals, including fish., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

This study was performed to determine the effects of dietary microencapsulated carvacrol (MC) on growth, resistance to A. hydrophila, and intestinal health parameters including intestinal bacteria, intestinal morphology and intestinal cytokines, in Pengze crucian carp (Carassius auratus var. Pengze). Fish were divided into four groups. Each group was fed a different diet for 56 days (a control diet or diets supplemented with 200, 400, or 600 mg/kg of MC). Our results indicate that MC had no effect on growth but significantly decreased A. hydrophila infection-associated mortality rates at 400 and 600 mg/kg and the lowest mortality was present at 600 mg/kg. The intestinal health of fish receiving the control diet was compared with that of the group receiving 600 mg/kg MC. High-throughput sequencing showed that MC increased the abundance of phylum Fusobacteria. It also increased the abundance of the genus Cetobacterium and decreased those of Flavobacterium and Pseudomonas. Light microscopy and transmission electron microscopy images support the ability of MC to improve the integrity of the lamina propria, increase microvilli height, and strengthen tight junctions, especially in the foregut. An ELISA assay indicated that levels of intestinal pro-inflammatory cytokines, including tumor necrosis factor-α and interleukins-1β, were reduced, whereas the level of the anti-inflammatory cytokine interleukins-10 was increased of fish administered dietary MC. We conclude that carvacrol promotes intestinal bacteria composition, intestinal morphology status and reduces intestinal inflammatory, which enhances resistance to A. hydrophila in Pengze crucian carp.

Bacillus spp. as probiotics have been widely used in the aquaculture industry. This study was designed to investigate the dietary supplementation of Bacillus cereus QSI-1 with quorum quenching activity, on intestinal barrier and expression levels of innate immune genes. After 14 d of feeding, fish fed with Bacillus cereus QSI-1 exhibited a significant down-regulated gene expression of TNF, IL-8, and IL-10 in the intestinal mucosa, but up-regulated tight junction (TJ) proteins zonula occludens-1 (ZO-1) and occludin and adaptor protein myeloid differentiation factor 88 (MyD88) transcription. This is an indication that Bacillus cereus QSI-1 could enhance intestinal barrier function and activate the non-specific immune system of Crucian carp. At the end of the feeding trial, the Crucian carps in each group were anally infected with A. hydrophila YJ-1. The results showed that Bacillus cereus QSI-1 could prevent the inflammatory response caused by A. hydrophila infection. Histological (integrity of intestinal villi) and qPCR analyses suggested that Bacillus cereus QSI-1 could improve the intestinal barrier function. Taken together, these findings indicate that Bacillus cereus QSI-1 could increase the intestinal epithelial barrier function and innate immune function, and also has the potential to be an alternative agent instead of antibiotics in feed supplements in aquaculture.

Abstract Gut microbiota are known to play an important role in health and nutrition of the host and have been attracting an increasing attention. Farming of new lineages of grass carp and crucian carp has been developed rapidly as these species were found to outperform indigenous ones in terms of growth rate and susceptibility to diseases. Despite this rapid development, no studies have addressed the characteristics of their gut microbiota as a potential factor responsible for the improved characteristics. To reveal whether microbiomes of the new lineages are different from indigenous ones, and therefore could be responsible for improved growth features, intestinal microbiota from the new lineages were subjected to high‐throughput sequencing. While the phyla Firmicutes, Fusobacteria and Proteobacteria were representing the core bacterial communities that comprised more than 75% in all fish intestinal samples, significant differences were found in the microbial community composition of the new linages versus indigenous fish populations, suggesting the possibility that results in the advantages of enhanced disease resistance and rapid growth for the new fish lineages. Bacterial composition was similar between herbivorous and omnivorous fish. The relative abundance of Bacteroidetes and Actinobacteria was significantly higher in omnivores compared to that of herbivores, whereas Cetobacterium_sp. was abundant in herbivores. We also found that the gut microbiota of freshwater fish in the Dongting lake area was distinct from those of other areas. Network graphs showed the reduced overall connectivity of gut bacteria in indigenous fish, whereas the bacteria of the new fish lineage groups showed hubs with more node degree. A phylogenetic investigation of communities by reconstruction of unobserved states inferred function profile showed several metabolic processes were more active in the new lineages compared to indigenous fish. Our findings suggest that differences in gut bacterial community composition may be an important factor contributing to the rapid growth and high disease resistance of the new fish lineages.

At present, the role of erythrocyte magnesium in the respiratory processes of fish (and other animals) under conditions of stress load is not known. This article presents the results of research on change in the concentration of magnesium in erythrocytes under the action of stressors of different quality and quantity for bream (Abramis brama L.), silver crucian carp (Carassius auratus gabelio Bloch) and tench, (Tinca tinca L.) in Rybinsk Reservoir. The concentration of magnesium ions was analyzed on an atomic absorption spectrometer AAS-1 manufactured by Carl Zeiss (Germany) in the absorption regime in an air-acetylene flame. For the first time, the dependence of the change in magnesium concentration in erythrocytes on the intensity of the stress load of different nature on the example of fishes was revealed. Weak and moderate strength effects (low doses of epinephrine, norepinephrine, small changes in water temperature, saline injection, prick into the abdominal cavity, short-term removal of fish from the water, short-term keeping of fish in a limited volume of water) increased the concentration of magnesium in erythrocytes up to 2.5 times. At the same time, an increase in the affinity of hemoglobin for oxygen and a decrease in oxygen consumption were observed. However, strong stressors such as catching, transporting fish to the laboratory (representing complex effects of hypoxia, limited water volume, mechanical effects, etc.), as well as a sharp and large change in water temperature, high doses of adrenaline reduced the concentration of magnesium in erythrocytes 3 times. At the same time, the hemoglobin affinity for oxygen decreased and oxygen absorption increased. However, before the death of fish (from exhaustion), with a low level of magnesium in erythrocytes the affinity of hemoglobin for oxygen increased and the intensity of gas exchange decreased. The research conducted allow us to consider the change in the concentration of magnesium ions in erythrocytes – which are positive modulators of the affinity of hemoglobin for oxygen – in fish exposed to stress as one of the mechanisms for reducing the gas exchange intensity for weak and medium short-term stress effects and increasing it for strong short-term ones. Especially important is the role of erythrocyte magnesium as a molecular mechanism for reducing oxygen uptake and, consequently, increasing anabolism and, thus, increasing the growth and development of animals under the action of mild, short-term stressors, i.e. with eustress. In addition, the concentration of magnesium in erythrocytes can serve as an indicator of the state of fish. A high level of this cation in erythrocytes (1.5–2.0 times higher and more than normal) is characteristic for strong, healthy animals in a state of eustress or physiological stress, and extremely low values of this indicator (1.5–2.0 and more times below the norm) are an indicator of reversible or permanent ill-being (distress or pathological stress). Weakened, exhausted animals are not capable of a response to eustress or physiological stress. The possible causes of low magnesium concentrations in human erythrocytes are discussed.