Crucian Carp Research Articles

Survey of the fish fauna of the water bodies of the city of Kharkiv

The study of the biodiversity of urbanized landscapes, in the context of their permanent expansion, is becoming increasingly important as part of environmental management. The proposed review considers the history of the study and the results of modern research on the ichthyofauna of water bodies in and around the city of Kharkiv. The study includes data obtained during archeological excavations. The existing water fund is estimated as a habitat for fish in the city. We compiled a modern systematic list of the fish fauna, determined its place in the general zoogeographical zonation of the Palearctic, and analyzed the ecological and faunistic characteristics of the fish assemblages, which created a basis for a general assessment of the current state and prospects for changes in the fish community within the city. The state of recreational fishing in the waters of Kharkiv as the main type of utilization of fish resources on its territory is analyzed. The current fish fauna of the water bodies of Kharkiv and its environs consists of 32 species belonging to 31 genera, 11 families, 7 orders, and 4 superorders of bony fish, as well as one hybrid form of silver and bighead carps, whose abundance is maintained only by artificial introduction into water bodies outside Kharkiv with subsequent occasional migration to the city, and two diploid-polyploid hybridogenic complexes of fish of the genera Carassius and Cobitis, whose reproductive characteristics require further study. Five species have disappeared from the local fish fauna, i.e. four species of bony fish (common crucian carp Carassius carassius, Black Sea roach Rutilus frisii, asp Leuciscus aspius, Danilevsky's dace Leuciscus danilewskii) and the Ukrainian lamprey Eudontomyzon mariae, which used to live in the city or water bodies and watercourses of the adjacent territories. Thirteen fish species (41% of the total species composition) have a conservation status and require special measures for their protection according to national and international regulations. The share of non-native species in the ichthyofauna of Kharkiv is quite significant – eight species (22% of the total number of registered species and forms). The fish fauna of the city is dominated by freshwater fishes, limnophilic or indifferent to the current speed, with phytophilic or psammolithophilic portion spring and summer spawning, not belonging to any particular habitat.

Сравнительная характеристика состояния внутренних органов серебряного карася (Carassius auratus gibelio) в возрастном аспекте

The histological results of the study of the organs of larvae and mature individuals of the silver crucian carp Carassius auratus gibelio (Bloch, 1782) caught in the reservoirs of the Volga River delta are presented. Analysis the internal organs state and tissues helps to identify physiological disorders and pathologies. Thanks to the histological method, it becomes possible to study the structure of the body at the cellular and tissue level, to determine the development of the pathological process and the degree of damage. For pathomorphological evaluation, the liver, gills, kidneys, spleen, intestines and pancreas were examined in silver crucian carp of different ages. It was established that representatives of this species of different ages had identical pathological changes in the organs, but the degree of their manifestation was different: there was a tendency to increase the intensity of the pathology with age. 4 types of major pathological changes associated with metabolic disorders, necrotic damage to cells and tissues, circulatory disorders of organs and signs of hyperplasia were found. Sexually mature individuals had a higher level of pathological manifestations. To a greater extent, the gills, which are in direct contact with the environment, were damaged. The liver of the studied fish also had significant damage. The most frequently reported liver pathology was lipoid degeneration (vacuolar degeneration). Kidneys, intestines and spleen were characterized by degenerative and necrotic disorders. In the spleen of adults, granulomatous inflammation was found, which indicates infectious diseases. The same types of morphological changes were found in larvae and mature individuals, which indicates the nonspecific nature of the identified pathologies, which, as a rule, are associated with the adaptation of the organism to the prevailing living conditions.

Аналіз ураження коропових риб ендо- та ектопаразитами у рибогосподарських водоймах Одеської області

Purpose. Conducting an analysis of parasitic diseases of different age groups of carps grown in specialized fish farms of Odesa region under different forms of ownership for 2014–2023. Methodology. The paper presents the generalized results of studies carried out during planned test catches in specialized fish farms of various forms of ownership located in Odesa region. Parasitological studies were carried out according to the Bykhovska-Pavlovska method. The study included: visual inspection; excision of skin and muscle tissue; microscopy of scrapings from the surface of the body, fins and gills; microscopy of eye lenses; pathological autopsy, search for parasites in the body cavity; compression microscopy of internal organs and muscle tissue; intestinal dissection; gallbladder microscopy; dissection and microscopy of the swim bladder walls. At the same time, the parasitic species were identified, and the extensiveness and intensity of the invasion were calculated. Parasites were identified using identification keys. Findings. The study was conducted by employees of the ichthyopathology laboratory of the Institute of Fisheries of the National Academy of Sciences in laboratory conditions and at sampling sites in the period from 2014 to 2023. The objects of the study were different age groups of common carp (Cyprinus carpio), hybrids of silver and bighead carps (Hypophthalmichthys spp.), grass carp (Ctenopharyngodon idella) and crucian carp. Parasitological analysis showed that carp were most often affected by monogeneans, the prevalence (P) was 50.6% of the studied fish, and infestation intensity (II) was an average of 10 parasites per fish. In addition, a large percentage of infection was caused by ciliates with P of 24% P, II was 9 parasites per fish. Grass carp, in turn, were most affected by ciliates — P 56.3% with an average II — 16 parasites per fish and monogeneans — P 36.4% with an average II — 12 parasites per fish and trematodes — P 25.4% with II 8 parasites per fish. Grass carp was the most affected by crustaceans, the P was 46.6%, and the II was 3 parasites per fish, trematode P 16.6% with an average II of 10 parasites per fish. In Prussian carp, infestation by monogeneans was most often detected, which reached 75% with II — 5 parasites per fish. In the period of 2019-2023, carp was most often affected by monogeneans, where P was 29.3%, and II was 3 parasites per fish, also a high percentage of infection was due to ciliates 24%, II was 6 parasites per fish. Chinese carps, in turn, was most affected by trematodes — P 59.1% at II — 60 parasites per fish. Grass carp was the most affected by diplostoma, where P was 45.5% with an average II of 45 parasites per fish. Crucian carp was most affected by lernea. Based on the analysis of data on parasitic diseases of freshwater fish, it can be concluded that both in the period 2014‒2018 and 2019‒2023, fish were most often affected by monogeneans and infusoria, but in the period 2019‒2023, the infestation of silver and grass carps by diplostomes and postodiplostomes increased significantly. Originality. An analysis of parasitic diseases of carp grown in specialized farms of various forms of ownership, located in the Odesa region for the period of over the past ten years has been presented. The results of these studies can be used for parasitological monitoring of water bodies as well as control of the spread of ecto- and endoparasites. Practical value. The obtained results can be used for a timely understanding of trends in the spread of parasitic diseases and allows using the obtained material for parasitological monitoring of fish farms. Keywords: fish, carps, parasites, prevalence, infestation intensity.

Expression of prolyl hydroxylase domains, the upstream regulators of HIF, in the brain of the anoxia-tolerant crucian carp during anoxia-reoxygenation.

The hypoxia-inducible factor (HIF) is considered key in the transcriptional response to low oxygen. Yet, the role of HIF in the absence of oxygen (anoxia) and in preparation for reoxygenation remains unclear. Recent studies suggest that mounting a HIF response may be counterproductive for anoxia survival. We here studied one of the champions of anoxia survival, the crucian carp (Carassius carassius), and hypothesized that expression of prolyl hydroxylase domains (PHDs; the upstream regulators of HIF) are upregulated to circumvent an energy-costly activation of HIF in anoxia and to prepare for reoxygenation. We measured whole brain mRNA and protein levels of the three isoforms PHD1, PHD2, and PHD3, coded for by multiple paralogs of the genes egln2, egln1, and egln3, using quantitative PCR and Western blotting in the brain of crucian carps exposed to 5 days normoxia or anoxia, and 5 days anoxia followed by 3 or 24 h of reoxygenation. The mRNA levels of most egln paralogs were increased in anoxia and upon reoxygenation, with egln3 showing the largest increase in mRNA level (up to 17-fold) and highest relative mRNA abundance (up to 75% of expressed egln). The protein level of all PHDs was maintained in anoxia and increased upon reoxygenation. We then explored PHD distribution in different brain regions and found PHD immunoreactivity to be associated with axonal branches and showing region-specific changes during anoxia-reoxygenation. Our results support an overall upregulation of egln under prolonged anoxia and PHDs upon reoxygenation in crucian carp, likely aimed at suppressing HIF responses, although regional differences are apparent in such a complex organ as the brain.NEW & NOTEWORTHY We report a profound upregulation of most egln paralog mRNA levels in anoxia and upon reoxygenation, with egln3ii showing the largest, a 17-fold increase, and highest relative mRNA abundance. The relative abundance of prolyl hydroxylase domain (PHD) proteins was maintained during anoxia and increased at reoxygenation. PHD immunoreactivity was localized to axonal branches with region-specific changes during anoxia-reoxygenation. These dynamic and regional changes in crucian carp, champion of anoxia tolerance, are most likely adaptive and call for further mechanistic studies.

Comparative analysis of nutrients in muscle and ovary between an improved fish and its parents

In previous studies, an allodiploid lineage (WR-F1-F5) was established by the distant hybridization of white crucian carp (Carassius cuvieri, WCC, ♀) and red crucian carp (Carassius auratus red var., RCC, ♂), an allodiploid fish (WR-II) was produced by WR-F1 (♀) × WCC (♂). In this study, the nutrients in the muscle and ovary of WR-II and its parents (WCC, RCC, and WR) were investigated, including protein, fat, amino acid, docosahexaenoic acid (DHA), moisture, and ash. The results showed that the protein content of WR-II in muscle and ovary (17.90 % and 25.60 % respectively) was higher than that of WR, and was significantly higher than that of WCC and RCC (p < 0.05). The fat content of WR-II in muscle and ovary (4.30 % and 5.31 % respectively) was higher than that of WR and was significantly higher than that of WCC and RCC (p < 0.05), and the muscle and ovary of WR-II showed rich DHA content (0.32 % and 0.54 % respectively) than that of WCC and RCC (p < 0.05). Fifteen amino acids were detected in WR-II and its parents, the total amino acid (TAA) content of WR-II in muscle and ovary (15.49 % and 18.43 % respectively) was significantly higher than that of WCC (p < 0.05), the delicious amino acid (DAA) content of WR-II in muscle and ovary (6.56 % and 8.29 % respectively) was different degrees higher than that of WCC, RCC, and WR. The moisture and carbohydrates of WR-II in muscle and ovary were lower than those in WCC and RCC. Furthermore, protein, fat, TAA, and DAA content in the ovary were significantly higher than those in muscle (p < 0.05), showing tissue differences in all detected fish. This study indicated that WR-II had the characteristics of high protein, high fat, high DHA, high TAA, high DAA, low moisture, and low carbohydrates, which provided theoretical support for its application.

Isomolar series methodology in sensory analysis of fish culinary products for HEALTHY-CAFE

The object of research is the technology of fish products for HELTHY-CAFE with regulated histamine content for the development of health food diets for the population. One of the most problematic places in the technology of food products from raw materials of aquatic origin is microbiological spoilage and, as a result, the formation and accumulation of HisA, which in a certain amount causes a toxic effect. In the course of the study, the methods of isomolar series, sensory analysis, and the study of quality indicators were used. The methodology chosen in the work allows to determine the optimal ratio of hydrocolloids in the system for maximum complexation with histamine in the technology of fish culinary products in gelatin fillings with a harmonious sensory profile and adjustable histamine content. The obtained results of the conducted research allow to state that the proposed method of determining the optimal ratio of sodium alginate and low-esterified pectin substances contributes to the development of a gelatinous filling for fish culinary products in order to ensure the harmonious flavor of ready-made fish dishes and contributes to the expansion of the range of fish products for HELTHY-CAFE with functional and preventive properties. This is due to the fact that taking into account the modern trends in nutrition regarding the safety, functionality, palatability, and attractiveness of fish food products made it possible, based on the method of isomolar series and sensory analysis, to scientifically substantiate the optimal ratio of plant biopolymers, to form requirements for the texture of gelatin filling in fish technology culinary products. On the basis of previous experimental studies, it was shown that the accumulation of histamine occurs more actively in sea fish, which made it possible to substantiate the choice of raw materials for the production of fish culinary products. Taking into account the main global trends in the development of aquaculture, it is proposed to use crucian carp as a raw material, as the main object of aquaculture in Ukraine. The low activity of the peptide hydrolase complex of the muscle tissue of the carp, compared to sea fish, contributes to the formation of a harmonious aromatic profile of fish culinary products, which corresponds to consumer expectations, and the use of natural hydrocolloids of vegetable origin to form a gelatinous structure provides functional properties to the food product and allows controlling the histamine content.

Characteristics of CD4-1 gene and its immune responses against Aeromonas veronii infection by activating NF-κB signaling in Qihe crucian carp Carassius auratus

CD4-1 found in bony fish contains four extracellular immunoglobulin (Ig)-like domains similar to that of mammalian CD4, which is crucial for the activation of CD4+ helper T-cell. However, there is limited knowledge regarding the molecular markers, immune functions and regulation mechanism of CD4-1 in teleosts due to their vast diversity. In this study, we cloned and characterized two isoforms of Qihe crucian carp CD4-1, designated as CaCD4-1.1 and CaCD4-1.2. We further explored their expression responses upon stimulation with Aeromonas veronii, and the regulation of their immune responses against A. veronii by NF-κB. The ORF of CaCD4-1.1 and CaCD4-1.2 cDNA encoded 477 and 466 amino acids, respectively. Both proteins contained seven conserved cysteine residues in the extracellular domain, and a CCC motif in their cytoplasm, respectively. However, CaCD4-1.1 exhibited a relatively limited similarity with CaCD4-1.2 in the ectodomain. The quantitative real-time polymerase chain reaction (qRT-PCR) analysis revealed that the mRNA expression of CaCD4-1.1 and CaCD4-1.2 exhibited differential constitutive expression across all examined tissues. Furthermore, the expression level of CD4-1.2 was higher than that of CD4-1.1 in the gills, head kidney, and spleen of Qihe crucian carp subjected to A. veronii challenge, while it was lower in the trunk kidney. Inhibition of NF-κB activity resulted in a decrease in the expression levels of CD4-1.1 and CD4-1.2 mRNA in the gill, while inducing an increase in expression levels in the spleen, in accordance with the observed ultrastructural changes in both organs. Interestingly, the impact of NF-κB on the mRNA expression level of CD4-1.1 appears to be stronger than that of CD4-1.2. Our results suggest that CaCD4-1.1 and CaCD4-1.2 could be expressed on T cells and antigen-sampling cells that exhibit similar characteristics to mammalian M cells, respectively, and differentially regulated by NF-κB in adaptive immune responses against bacterial infection. This research contributes to a better understanding of the crucial role of CD4-1 in the immune response of Qihe crucian carp and provide novel insights for the prevention and treatment of fish diseases in aquaculture.

The Irkutsk focus of opisthorchosis (to the 40th Anniversary of the discovery)

The purpose of the research is to summarize our own and literature data on the Irkutsk focus of opisthorchosis.Materials and methods. The materials (mollusks, cyprinids and muskrat) were collected in the reservoirs of the Biryusa River basin. Mollusks were identified using the key by Ya. I. Starobogatova et al. (2004). The fish were studied for metacercariae of the trematode Opisthorchis felineus using the conventional compression method according to the recommendations and using the method of digestion with artificial gastric juice.Results and discussion. According to our own and literature data, there is a focus of mixed type opisthorchosis in the Taishetsky District, the Irkutsk Region, in which the final hosts of the parasite are wild animals, namely, the muskrat, along with domestic animals (cats) and humans. The first intermediate host is Opisthorchophorus troscheli. The second intermediate hosts are four fish species (roach, dace, crucian carp, and bream); minnow and tench were not infected with Opisthorchis sp. Mapping of current data has showed its distribution in the Biryusa River basin. The current state of knowledge for the Irkutsk focus of opisthorchosis shows that a comprehensive research plan is needed with the participation of scientific and regulatory institutions of the Irkutsk Region and Taishetsky District.

Effects of Vitamin E on Immune Response, Antioxidant Capacity, and Liver Tissue Structure of Crucian Carp under Acute Cold Stress

The purpose of this study was to investigate the effects of vitamin E addition to the water column on immune response, antioxidant capacity, and liver tissue structure of crucian carp (Carassius auratus) under acute cold stress. Crucian carp was placed in the aqueous solution of control group (E1), negative control group (E2), and 100 mg/L vitamin E (E3) and cooled from 20 to 5°C by cold acclimation intelligent cooling device. Samples were taken at three temperature points of 20, 10, and 5°C, respectively, and the samples were detected and analyzed. The results showed that the content of each index increased under acute cold stress. The contents of white blood cell, red blood cell, hemoglobin, platelet, lysozyme, and glutathione peroxidase in E3 treatment group were significantly lower than those in E1 and E2 treatment groups ( P &lt; 0.05 ). The contents of cholinesterase, alkaline phosphatase, acid phosphatase, hydrogen peroxide, superoxide anion, superoxide dismutase, peroxidase, and malondialdehyde in E3 treatment group were significantly lower than those in E1 and E2 treatment groups ( P &lt; 0.01 ). Under acute cold stress, the liver tissue structure of crucian carp also changed, such as hepatocyte vacuolization, and the damage degree of E3 treatment group was lower than that of E1 and E2 treatment groups. In summary, the addition of vitamin E in water to treat crucian carp can reduce the harm caused by acute cold stress to its body and provide a theoretical reference for the application of vitamin E in water to alleviate fish stress.

Heavy metal baselines in cyprinidae of the Han River: a decade-long study on bioaccumulation trends and species-specific sensitivities

Despite numerous urban pollution sources, research on aquatic species bioaccumulation in the Han River is scarce. In this longitudinal study, we assessed baseline heavy metal (HM) concentrations in Cyprinidae, a major freshwater fish family in the Han River. Specifically, were evaluated copper (Cu), total mercury (THg), cadmium (Cd), lead (Pb), and chromium (Cr) levels in the muscle of common carp, crucian carp, and barbel steed. Common carp had the highest HM accumulation, with baseline concentrations of Cu, THg, Cd, Pb, and Cr at 0.877, 0.060, 0.003, 0.032, and 0.178 mg/kg, respectively. Larger fish exhibited greater bioaccumulation, with THg levels significantly correlated with fish length (correlation coefficients: 0.57 (p < 0.05)–0.74 (p < 0.001)). Notably, Cr accumulated more extensively in fish muscle than Pb, and the metal selectivity index (MSI) of THg in barbel steed was 2–3 times higher than in other fish species. The baseline concentrations determined in this study can serve as identifiers of the initial point of abnormal HM bioaccumulation in fish and provide foundational data for future long- or short-term fish monitoring.

Correction: Xu et al. Effects of Replacing Dietary Fish Meal by Soybean Meal Co-Fermented Using Bacillus subtilis and Enterococcus faecium on Serum Antioxidant Indices and Gut Microbiota of Crucian Carp Carassius auratus. Fishes 2022, 7, 54

In the original publication [...]

Lipid accumulation mechanism of Amphora coffeaeformis under nitrogen deprivation and its application as a feed additive in Carassius auratus aquaculture

BackgroundAmphora coffeaeformis, a unicellular diatom, can significantly accumulate lipids under nitrogen (N) limitation. However, the molecular mechanism underlying lipid accumulation in A. coffeaeformis remains unknown and its application development is lagging.ResultsThis work analyzed the lipid composition of A. coffeaeformis under N deprivation and investigated its mechanism underlying lipid accumulation using RNA-seq. The results showed that the total lipid content of A. coffeaeformis increased from 28.22 to 44.05% after 5 days of N deprivation, while the neutral lipid triacylglycerol (TAG) content increased from 10.41 to 25.21%. The transcriptional profile showed that N deprivation induced wide-ranging reprogramming of regulation and that most physiological activities were repressed, while the upregulation of glycerol-3-phosphate acyltransferase directly determined TAG accumulation. Moreover, we explored the effect of A. coffeaeformis as a food additive on the lipid composition of crucian carp. The results showed that the contents of unsaturated fatty acids in the meat of fish supplemented with A. coffeaeformis were significantly increased, indicating its potential application in animal nutrition for improving meat quality indicators.ConclusionThe findings shed light on the molecular mechanisms of neutral lipid accumulation and revealed the key genes involved in lipid metabolism in A. coffeaeformis. Moreover, we also confirmed that A. coffeaeformis can be used as feed additive for improving the lipid composition of crucian carp meat, which provided evidence for the biotechnology application of this high-oil microalgae.

Polybrominated diphenyl ethers in aquatic products of Guangzhou city, South China: Accumulation, distribution and health risk

Studies have shown that consuming aquatic products is the primary pathway for human uptake of polybrominated diphenyl ethers (PBDEs). This study collected seven types of aquatic products eaten in Guangzhou City. Gas chromatography‒mass spectrometry (GC/MS) was used to investigate eight PBDE congeners to analyze their concentration, distribution, and potential risk. The concentration of PBDEs in aquatic products ranged from 1.92 to 91.11 ng/g lw, with BDE–209, BDE–99, and BDE–154 as the predominant PBDE congeners. Moreover, the concentrations and congener profiles of these contaminants vary in aquatic products. The highest accumulation level was found in shrimp and clams, primarily attributed to dietary habits, metabolic capacity, and accumulation of xenobiotics. According to the dietary questionnaire, the total consumption of aquatic animals was 82.64 g/day, with a significant non-carcinogenic risk to consumers in Guangzhou at higher levels of consumption (HI ≥ 1). Therefore, the maximum allowable daily consumption of grass carp, crucian carp, tilapia, Japanese seaperch, shrimp, clam and crab is 33.33, 55.00, 67.50, 44.44, 41.67, and 51.67 g/day, corresponding to daily intake frequencies of 5, 8, 10, 6, 6, 7, and 5 times/month, respectively. Our results could provide reasonable dietary advice for humans.

Physiological and Transcriptome Analysis Reveal the Regulation Mechanism Underlying the Muscle Quality Effect of Dietary Schisandra chinensis in Triploid Crucian Carp (Carassius auratus).

Schisandra chinensis (sc) is generally demonstrated to improve antioxidant and immune functions in mammal. The present study through physiological and transcriptome analysis revealed alterations in muscle metabolisms of triploid crucian carp (Carassius auratus) cultured at different concentrations of S. chinensis diets (sc0, sc0.125%, sc0.25%, sc0.5%, sc1%, sc2%) after 8weeks. The serum antioxidant enzyme activities analysis showed that dietary S. chinensis could reduce oxidative stress and increase organismic antioxidant capacity. Meanwhile, the detected results of muscle components presented that the amino acids and two flavor nucleotides of GMP and IMP significantly elevated while muscle crude lipid significantly reduced in S. chinensis feeding groups. In addition, springiness, chewiness, and fiber density in S. chinensis feeding groups muscle were significantly upregulated while muscle fiber diameter and area showed an opposite trend. By comparative transcriptome analysis of the muscles, functional enrichments of differentially expressed genes showed that multiple terms were related to purine metabolism, glycerolipid metabolism, regulation of actin cytoskeleton, and peroxisome. Finally, some key hub genes such as egln, gst, ggct, su1b, pi3kr4, myh9, lpl, gcdh, mylk, and col4a were identified by weighted gene co-expression network analysis. Taken together, our findings facilitate the understanding of the molecular basis underlying the muscle quality effect of dietary S. chinensis in triploid crucian carp, which provides valuable insights into the nutritional strategies of the aquaculture industry.

MTOR signaling pathway regulates embryonic development and rapid growth of triploid crucian carp

Triploid crucian carp is a new breed of aquaculture with rapid growth characteristics. However, its growth regulation mechanism has not yet been elucidated. In this study, our results show that the expression levels of mTOR signaling pathway-related genes (AKT1, AKT2, AKT3, mTOR, 4E-BP1 and S6K1) are higher in the muscle and intestine tissues of triploid crucian carp than those of diploid red crucian carp. Embryos of triploid crucian carp exhibit a faster growth rate comparing to red crucian carp. And in muscle effect stage, the mRNA levels of mTOR signaling pathway related genes in triploid crucian carp are higher than red crucian carp, except for AKT2. Inhibition of mTOR activity with rapamycin leads to slower embryonic development and the eliminated expression of mTOR in the embryos of neurula, muscle effect, and eye pigmentation stages. Conversely, overexpression of the upstream gene AKT2 can promote the development of zebrafish embryos and affect the expression of mTOR signaling pathway. These data highlight the significant role of mTOR signaling pathway in regulating fish embryonic development and rapid growth, and might offer new insights and avenues for exploring fish embryonic development, improving fish growth.

Effect of chronic deltamethrin exposure on brain transcriptome and metabolome of juvenile crucian carp.

Deltamethrin (Del), a widely administered pyrethroid insecticide, has been established as a common contaminant of the freshwater environment and detected in many freshwater ecosystems. In this study, we investigated the changes in brain transcriptome and metabolome of crucian carp after exposure to 0.6 μg/L Del for 28 days. Elevated MDA levels and inhibition of SOD activity indicate damage to the antioxidant system. Moreover, a total of 70 differential metabolites (DMs) were identified using the liquid chromatography-mass spectrometry, including 32 upregulated and 38 downregulated DMs in the Del-exposed group. The DMs associated with chronic Del exposure were enriched in steroid hormone biosynthesis, fatty acid metabolism, and glycerophospholipid metabolism for prostaglandin G2, 5-oxoeicosatetraenoic acid, progesterone, androsterone, etiocholanolone, and hydrocortisone. Transcriptomics analysis revealed that chronic Del exposure caused lipid metabolism disorder, endocrine disruption, and proinflammatory immune response by upregulating the pla2g4, cox2, log5, ptgis, lcn, and cbr expression. Importantly, the integrative analysis of transcriptomics and metabolomics indicated that the arachidonic acid metabolism pathway and steroid hormone biosynthesis were decisive processes in the brain tissue of crucian carp after Del exposure. Furthermore, Del exposure perturbed the tight junction, HIF-1 signaling pathway, and thyroid hormone signaling pathway. Overall, transcriptome and metabolome data of our study offer a new insight to assess the risk of chronic Del exposure in fish brains.

Enrichment and distribution of 3,6-dichlorocarbazole in red crucian carp (Carassius auratus) and its hepatotoxicity

Polyhalogenated carbazoles (PHCZs) are a class of organohalogen compounds where the hydrogen atom on the carbazole ring is replaced by a halogen atom. In recent years, PHCZs have drawn increasing concern due to their persistence, dioxin-like toxicity, bioaccumulation, potential ecological hazards and widespread occurrence in the environment. Current research on the enrichment and depuration of PHCZs in biological tissues and organs is insufficient, and the liver toxicity is unclear. Herein, to understand the enrichment and elimination of 3,6-DCCZ in fish tissues and organs as well as the hepatotoxicity, we exposed the red crucian carp to 20 and 100 μg/L of 3,6-DCCZ for 20 days followed by a depuration period of 10 days. The 3,6-DCCZ enrichment in each organ tissue was classified from high to low: brain > liver, intestine, gill > muscle. For depuration, 3,6-DCCZ was quickly excreted in the various organs of the red crucian carp; however, the liver depuration was slow, with the concentration of 3,6-DCCZ was maintained at 0.25–0.35 μg/g. 3,6-DCCZ exposure at both tested concentrations induced oxidative stress in red crucian carp, causing lipid peroxidation and DNA damage, as well as some histopathological changes in the liver, such as cell vacuolization, nucleus pyknosis, nucleus pleomorphism, no nucleus areas. Additionally, the 3,6-DCCZ exposure at higher concentration (100 μg/L) caused more serious damage and abnormal lipid metabolism in the red crucian carp liver.

Tumor necrosis factor α1 (TNFα1) administration can disrupt barrier function and attenuate redox defense in midgut of red crucian carp (Carassius auratus red var)

TNFα belongs to superfamily of tumor necrosis factor that can exert the pleiotropic effort in a large quantity of biological processes, including immune homeostasis, intracellular modulation and etiopathogenesis, but its regulatory role in mucosal immune regulation of fish is unclear. Currently, this study aimed to evaluate the immunoregulatory function of TNFα1 on gut barrier in teleost fish. In this study, TNFα1 sequences were identified from red crucian carp (RCC, Carassius auratus red var). The high-level expression of RCC-TNFα1 mRNA was detected in gill among all the isolated samples. Then, RCC-TNFα1 expression increased dramatically in immune-related tissues after A. hydrophila infection and in cultured fish cells after lipopolysaccharide (LPS) treatment. RCC-TNFα1 fusion protein was generated and purified in vitro. RCC receiving RCC-TNFα1 perfusion showed an increased levels of villi fusion and edema in injured midgut with the fuzzy appearance. In addition, The mRNA expressions of tight junction (TJ) genes, mucin genes and redox sensitive genes decreased sharply in TNFα1-treated midgut in comparison with those of the control (P < 0.05), whereas the expression levels of apoptotic genes involved in caspase signals and unfolded protein response (UPR) attained the dramatic increase. These results demonstrated that RCC-TNFα1 stimulation could impair midgut structural integrity and immune function by induction of antioxidant collapse and apoptotic activation.

Mechanisms for improving the quality of crucian carp (Carassius auratus) by short-term low-salinity treatment revealed by UPLC-MS and GC–MS

Mechanisms for improving the quality of crucian carp (Carassius auratus) by short-term low-salinity treatment revealed by UPLC-MS and GC–MS

Improvement of non-specific immunity, intestinal health and microbiota of crucian carp (Carassius auratus) juvenile with dietary supplementation of Bacillus coagulans BC1

Establishing beneficial intestinal microbiota using autochthonous probiotics is a promising approach for disease control and growth regulation during fish rearing. Therefore, it is crucial to identify indigenous probiotics with high application potential in aquaculture. In this study, we screened Bacillus coagulans BC1, a strain with strong application potential. After a comprehensive safety assessment, diets containing varying doses of BC1 were formulated and administered to crucian carp. Subsequently, a feeding experiment was conducted to evaluate non-specific immune response, intestinal structure, microbiota, and challenge protection rate. The results demonstrate that oral supplementation of BC1 can lead to tissue-dependent upregulation of various serum immune enzymes and IgM levels, while significantly enhancing the expression of IL-1β, IL-10, TNF-α, and TGF-β in various organs of crucian carp (p < 0.05). The BC1 diet effectively promoted intestinal morphology in crucian carp and improved resistance to Aeromonas veronii TH0426 infection. Intestinal microbiota analysis revealed that the oral addition of BC1 significantly changed the intestinal microbial community structure of crucian carp but did not clearly affect intestinal microbial diversity. Oral administration of BC1 significantly improved the relative abundance of Cetobacterium in the intestines of crucian carp; reduced the abundance of opportunistic pathogens such as Bacteroides, Vibrio and Aeromonas and effectively regulating the nutrient metabolism in intestinal microbiota. These results indicate that BC1 could regulate immune function, effectively improving the intestinal morphology and intestinal flora structure and function of crucian carp, and therefore is a potential candidate strain for aquatic feed additives.