Fish Tissues Research Articles

Enhancing aquaculture disease resistance: Antimicrobial peptides and gene editing

AbstractPrevious studies have demonstrated that CRISPR/Cas9‐mediated genome editing and transgenesis by integrating vector‐engineered antimicrobial peptide genes (AMGs) are effective to modulate the fish's innate immune system. To generalise the knowledge of AMG application in aquaculture, we recruited 544 data entries from a pool of empirical studies, which included 23 studies (two unpublished from our team) spanning 12 diseases. We systematically re‐processed and re‐analysed these data by harnessing a cross‐disease meta‐analysis. On aggregate, AMG‐genetic engineering aimed at enhancing disease resistance was shown to decrease the number of colony‐forming units of bacteria from fish tissues, increase post‐infection survival rates, and alter the expression of AMGs and immune‐related genes. Further, AMG pathogen‐combating activity was triggered within 2 h after infection and lasted 48 h. The overexpression of AMGs was highest in the spleen and skin, followed by the kidney and liver during this period. Typically, regardless of the type of AMGs, the synergistic expression of AMGs with IL‐10, IKβ, TGFβ, C3b and TLR genes in AMG‐integrated fish contributed to activating inflammatory/immune responses against pathogens. Our findings revealed that the efficiency of transgenic AMGs against pathogens was fish‐, pathogen‐ and AMG‐specific. Compared to bacteria, transgenic AMGs were less inhibitory to viruses and parasites. In addition, innovative CRISPR/Cas9‐based transgenesis enabling the site‐directed knock‐in of foreign genes at multiple loci was assessed for the enhancement of disease resistance in combination with other favourable fish‐production traits, including fast growth, sterility and enriched fatty‐acid content. Altogether, our findings indicated that AMGs as transgenes have substantial promise to modulate the fish's innate immune system and enhance disease resistance.

The Intra-Annual Variability of Immune System Organs and Lysozyme Content in Male Pike <i>Esox lucius</i> L.

The effect of the physiological state on the lysozyme concentration in the liver, kidney, spleen and serum, as well as the total amount of the enzyme in the organs, was studied in male pike Esox lucius L., 1758 under different conditions of the annual cycle. Multidirectional intra-annual dynamics of organ somatic indices and quantitative parameters of lysozyme in fish tissues and organs, depending on the temperature regime of the water body, was found. Despite significant changes in liver size and lysozyme concentration, the total amount of the enzyme in the organ, the lysozymic index, remained constant. A similar result was found in the spleen. When the influence of the temperature factor at low temperatures was minimized, the liver parameters changed to the opposite ones, while those in the kidney remained unchanged. Such a temperature regime did not affect the spleen parameters and the concentration of the enzyme in the serum. With significant differences between the liver and spleen in the enzyme concentration and size, their lysozymic indices were indicators of the same level. Stages of gonad maturity affected the liver index and the amount of lysozyme in the kidney, but the correlation of the kidney enzyme with maturity was not significant. The kidney lysozyme and the spleen parameters correlated with body mass without organs, although fish weight and length were not influencing factors. The size of the kidney, unlike the spleen, did not affect the enzyme in fish tissues. The liver and kidney enzyme concentrations and kidney lysozymic index were inversely correlated with liver size. A complex nature of the enzyme relationships in organs was revealed, at which the amount of lysozyme in one organ could affect the amount of the enzyme in the other. The relationship between the concentration of serum lysozyme and the morphophysiological parameters of fish under stable low temperature conditions in the water body was not found.

Hexavalent chromium induced oxidative, histopathological and hematological changes in snakehead fish, Channa punctatus

Aim: To evaluate the effect of hexavalent chromium on biochemical, hematological and histopathological responses and to assess its concentration in fish Channa punctatus. Methodology: Fishes were randomly distributed into Cr6+ treated groups, T1 (2 mg l-1), T2 (4 mg l-1), T3 (6 mg l-1), and one control (0 mg l-1) for 30 days exposure period. Potassium dichromate (K2Cr2O7) was used as source of Cr6+. The liver, kidney and blood were sampled after 10, 20 and 30 days intervals. Results: The significant (p < 0.05) increments in the concentration of hexavalent chromium and in the activities of enzymes (superoxide dismutase, catalase and glutathione reductase) as well as lipid peroxidation were recorded in the liver and kidney tissues of fish.However, the significant (p < 0.05) decline of reduced glutathione and total protein were noticed in both the tissues of fish. The red blood corpuscles count, hemoglobin and hematocrit significantly (p <0.05) decreased, while the white blood corpuscles count increased in blood of fish. Remarkably, the histopathological anomalies, pyknosis, hypertrophy and inflammation in liver and cavity reduction in renal tubules and glomerulus degenerative changes in kidney were prominently observed in fish. Conversely, the necrosis and vacuolization were observed in liver and kidney tissues of fish. Interpretation: The findings of the present study can be a useful tool as biomarkers for monitoring environmental pollution in aquatic ecosystem caused by hexavalent chromium. Key words: Biochemical, Biomarkers, Channa punctatus, Hematological, Hexavalent chromium, Histopathological

Genome-wide identification of TNF receptor-associated factors in Japanese flounder (Paralichthys olivaceus) and functional analysis of resistance to temperature and Edwardsiella tarda stress.

Tumor necrosis factor receptor-associated factors (TRAFs), as the signaling mediators of the tumor necrosis factor (TNFR) superfamily, toll-like receptors (TLR) and interleukin-1 receptor (IL-1R) superfamily, can activate downstream signal transduction pathways and play an important role in the body's immune process. In this study, six TRAF genes, namely PoTRAF2a, PoTRAF2b, PoTRAF3, PoTRAF4, PoTRAF6 and PoTRAF7, were identified and annotated in Japanese flounder by using bioinformatics methods. Phylogenetic analysis confirmed that TRAF genes can be divided into seven groups. Analysis of motif composition and gene structure demonstrated that all PoTRAF members were evolutionarily conserved. The expression patterns of PoTRAF genes were then further investigated in six different developmental stages and eleven tissues of healthy fish, and it was found that there were spatial and tissue specificities among the members. To investigate the immune response of Japanese flounder to abiotic and biotic stresses, we further analyzed the expression profile of PoTRAFs after temperature stress and pathogen challenge. The result showed that PoTRAF3 and PoTRAF4 were observably differentially expressed under temperature stress, indicating that they were involved in the immune response after temperature stress. The expression of PoTRAF2a, PoTRAF2b and PoTRAF4 was significantly different after E. tarda infection, suggesting that they might have antibacterial effects. These results would help to clarify the molecular roles of PoTRAF genes in the regulation of immune and inflammatory responses in Japanese flounder.

An attenuated strain of cyprinid herpesvirus 2 as a vaccine candidate against herpesviral hematopoietic necrosis disease in gibel carp, Carassius auratus gibelio.

Herpesviral hematopoietic necrosis disease causes by cyprinid herpesvirus 2 (CyHV-2) infection is a high mortality disease that leads to great economic damage to gibel carp, Carassius auratus gibelio aquaculture. In this study, an attenuated strain of CyHV-2 G-RP7 was achieved by subculture on RyuF-2cells derived from the fin of Ryukin-variety goldfish and GiCF cells derived from fin of gibel carp. As the attenuated vaccine candidate, there are no clinical symptoms of gibel carp that immersion or intraperitoneal injection with G-RP7 strain. The protection rates of G-PR7 to gibel carp by immersion and intraperitoneal injection were 92% and 100%, respectively. In the test for virulence reversion, the candidate was propagated through gibel carp six times by intraperitoneal injection with kidney and spleen homogenate of the inoculated fish. During in vivo passages in gibel carp, no abnormality and mortality of the inoculated fish were observed, and the virus DNA copies maintain a low level from the first passage to the sixth passage. The dynamic of virus DNA in each tissue of G-RP7 vaccination fish increased within 1, 3, and 5 days post-immunization, and subsequently decreased and stabilized within 7 and 14 days. In addition, the increase of anti-virus antibody titer was detected both immersion and injection immunization fish 21 days after vaccination by ELISA. These results demonstrated that G-RP7 can be a promising live attenuated vaccine candidate against the disease.

Traumatic endophthalmitis following injury by a fish: A rare case report and review of literature

A 26-year-old male presented with decreased vision in left eye (OS) following an attack by a fish while swimming in a pond. His best corrected visual acuity (BCVA) was hand movements in OS and 20/20 in right eye (OD). Fundus examination and ultrasonography B-scan confirmed the presence of traumatic endophthalmitis in OS. Wound exploration confirmed the presence of a foreign body near limbus, which was removed and found to be a cartilaginous fish tissue measuring 4.5 millimeters in length. Pars plana vitrectomy was performed, and intravitreal antibiotics were administered. The case highlights a rare form of ocular injury and its management.

A Comprehensive Review on the Deleterious Effects of Heavy Metal Bioaccumulation on the Gills and Other Tissues of Freshwater Fishes

Heavy metals can be harmful to aquatic organisms when exposed for a short (acute) or long (chronic) period. They have made a tremendous contribution to human welfare, but they also have considerable negative impacts on organisms that are not their targets. Runoff and groundwater leaching from a range of hazardous metals have a significant risk of contaminating aquatic habitats that pass through industrial or agricultural areas, which could directly threaten freshwater life, especially delicate animals like fish. Fish are the most well-known model for determining the extent of aquatic pollution. Since fish play a significant part in the food chain, the investigation into how toxic metals affect fish might help determine whether or not metals have harmful impacts on human health. This review attempted to consolidate all available scientific findings on the accumulation and uptake of various heavy metals (As, Hg, Cd, Cu, Cr, and Pb) as well as the overall histopathological changes caused by long-term exposure to sublethal doses of these heavy metals on the gills and other tissues of the freshwater fishes. Keeping in mind the above facts, in this review, an effort has been made to elucidate the deleterious impact of metals on the gills of freshwater fishes.

Influence of fertilizers on physiological functions of fishes

Fertilizers are strong pollutants in the surrounding water environment. These substances get into the water environment through the groundwater during the spraying of crops under agricultural cultivation. The toxicity of fertilizers influences growth, physiology, and a hemato-biochemical profile and causes serious changes in some tissues of aquatic organisms, including fish, which has also proved to be true in our research. From the mentioned effects, hematological parameters serve as important biomarkers of the pollution of water by fertilizers. Cause serious changes in the blood of fishes as they bioaccumulate in various tissues of fishes and, by doing so, cause serious changes in the blood tissue of fishes and also in their behavioral reactions (Cyprinus Carpio). In the research, the impact of the phosphoric fertilizers Ammophos and Kristalon in lethal concentrations of 97.2 mg/l and 265.2 mg/l on the behavioral reactions of Cyprinus Carpio and blood indicators was studied. It is necessary to notice that these fertilizers are widely used in the cultivation of agricultural crops, but these preparations were not investigated on fish, and it is written in their passport data. It is necessary to notice that these fertilizers influence the behavioral reactions of Cyprinus Carpio and indicators of the blood of fish.

A Review and Analysis of Heavy Metals in Freshwater Reservoirs of Pakistan: their Bioaccumulation, Biological Magnification and Biotic Transmission

Problems associated with pollution are becoming more severe as industrialization advances rapidly. Inorganic and organic wastes, both water-soluble and insoluble, are discharged into the aquatic environment, contributing to one of the most critical problems: water pollution. The discharge of waste in water channels allows heavy metal ions, which are toxic to all kinds of life, to enter the food chain. Lead, nickel, sodium, potassium, zinc, copper, iron lithium, cadmium, and chromium (VI) are among the most hazardous metal ions. Because they don't break down, metal ions build up in the environment and move up the food chain. Therefore, higher trophic level animals are more susceptible to their toxicityHeavy metals found in freshwater and sediments have been found to bioaccumulate in fish tissues. Rawal Dam, Mangla Dam, and Zabi Dam were identified as highly contaminated areas of freshwater that had detrimental effects on fish and human health. The Rawal Dam, which received a lot of industrial and sewage drainage from Punjab's metropolitan areas and industry, was significantly contaminated compared to other Pakistani Dams. Changhoz and Ghol Dams, with their massive water flows and relatively few accompanying industrial facilities, have the healthiest ecosystems of all Pakistan's dams. Changhoz Dam's freshwater fish are considered to be safe for human consumption. Heavy metals are accumulated by migratory birds at Rawal Dam from eating fish from freshwater reservoirs. Heavy metal pollution has been linked to a variety of social, ecological, and economic issues. The detrimental effects of heavy metals on aquatic organisms and human well-being can be reduced if wastewater is purified before being released into freshwater.

Uncovering water quality and evaluating vulnerabilities of small-scale fisheries in Chilika Lagoon, India

Small-scale fisheries (SSFs) play a strong role in sustaining millions of livelihoods, food security, nutrition, and income globally but the fishers engaged in this sector simultaneously experience high levels of vulnerability and processes of marginalisation. Several factors are attributed to the multidimensional vulnerabilities the small-scale fishers experience, spanning both natural (e.g., natural disasters, ecosystem change) and anthropogenic (e.g., policy change, hydrological interventions, aquaculture) pressures. While there is much literature on various natural and human drivers of vulnerability in small-scale fishery communities, an absence of research connecting vulnerability with water quality is evident. Fisher communities often talk about fish in relation to the health of their aquatic habitats wherein water quality is seen as a key parameter. The link between healthy fish and good quality water has significant implications for strong and viable fishing communities. This paper examines these links further by focusing on the nature of vulnerabilities caused by water quality changes in the small-scale fishery system of Chilika Lagoon in India. We undertake detailed analysis of the invasive shrimp aquaculture activities and hydrological interventions for opening of a lagoon inlet with the Bay of Bengal as two dominant drivers adversely impacting water quality and increasing vulnerabilities of the entire small-scale fisheries social-ecological system. Our analysis suggests that there are strong interconnections between changes in water quality and the levels of vulnerabilities in the SSFs of Chilika Lagoon. Pollutants such as pesticides, and organic compounds accumulate in fish tissues and affect their growth, reproduction, and overall health. This led to declines in fish populations, making it more difficult for fishers to make a living. In addition to direct impacts on fish populations, poor water quality also has indirect effects on the social and economic vulnerability of SSFs. For example, contamination of water sources led to the reduced number of fish species reducing the amount of time fishers can spend on fishing activities. This also affected the marketability of fish products, reduced income and increased poverty. To fully understand the interconnections between water quality and vulnerability in SSFs in Chilika Lagoon, it is important to consider both environmental and social factors, as well as the complex feedback loops between these factors. The study helps in bridging a crucial gap in our understanding of the role of water quality in vulnerability analysis within resource dependent communities. We conclude with key insights on possible coping responses and adaptive capacity necessary for the small-scale fisheries communities to transition toward viability.

Modulation of immune genes in the mucosal-associated lymphoid tissues of cobia by Sarcodia suae extract.

Rachycentron canadum (cobia) is a marine fish species of high economic value in aquaculture due to its fast growth rate and good feed conversion efficacy. Regrettably, the industry has been affected by significant setbacks from high mortality due to diseases. Consequently, an improved perception of innate immunity correlated to each mucosal-associated lymphoid tissue (MALT) in teleost fish is necessary to understand hosts' response towards infections better. The utilization of polysaccharides in seaweed to stimulate the immune system has gathered unprecedented attention. The present study examined the immunostimulatory effects of Sarcodia suae water extracts (SSWE) on in vivo gill-, gut- and skin-associated lymphoid tissues (GIALT, GALT, and SALT) via immersion and oral ingestions. The GIALT genes (TNF-α, Cox2, IL-1β, IL-6, IL-8, IL-17A/F1-3, IL-11, IL-12, IL-15, IL-18, MHCIa, IgM, and IgT) except IL-10 recorded positive upregulations in a dose-dependent manner post 24h immersion in SSWE, indicating the algae extract contained bioactive compounds that could stimulate the immune genes. The upregulation of IL-12, IL-15, and IL-18 in the gills and hindgut post-SSWE immersion indicated that the extract could promote Th1-related responses in the MALTs. The modulation of immune gene expressions in the feeding trial was less potent than in the SSWE immersion. These findings indicated that the SSWE stimulated robust immune responses in both the GIALT and GALT of cobia. This suggests that the SSWE could be further explored as an effective immersive stimulant for fish, enhancing their immune system against pathogens.

Discovery, characterization, and adipocyte differentiation regulation in perirenal adipose tissue of large yellow croaker (Larimichthys crocea).

Adipose tissue is an essential tissue for lipid deposition in fish and is associated with excess lipid accumulation in aquaculture. However, the knowledge of the distribution and characterization of adipose tissue in fish still needs further investigation. This study for the first time discovered perirenal adipose tissue (PAT) in large yellow croaker by MRI and CT technologies. Then, the morphological and cytological characteristics of PAT were observed, showing a typical characteristic of white adipose tissue. Meanwhile, the mRNA expression of marker genes of white adipose tissue was highly expressed in PAT compared with the liver and muscle in large yellow croaker. Moreover, based on the discovery of PAT, preadipocytes from PAT were isolated, and the differentiation system of preadipocytes was established. The lipid droplet and TG content of cell were gradually increased during adipocyte differentiation. In addition, mRNA expressions of lipoprotein lipase, adipose triglyceride lipase, and transcription factors related to adipogenesis (cebpα, srebp1, pparα, and pparγ) were quantified to explain the regulation mechanism during the differentiation process. In summary, the present study first discovered perirenal adipose tissue in fish, then explored the characterization of PAT, and revealed the regulation of adipocyte differentiation. These results could advance the understanding of adipose tissue in fish and provide a novel idea for the study of the mechanism of lipid accumulation.

Результаты воздействия комплекса β-циклодекстрина с левофлоксацином на убойные качества гибрида русского и сибирского осетра в регулируемых условиях

When producing aquaculture products in conditions of increased planting densities of aquatic organisms, it is not always possible to avoid various diseases and injuries. The use of therapeutic baths and feeds often does not al-low to achieve a positive effect. Therefore, the use of cyclodextrin nanosponge with therapeutic and prophylactic agents included in their cavity will allow a targeted effect on the bioavailability of substances and the formation of productive indicators of hydrobionts already since early postnatal ontogenesis. All this will contribute to the improvement of industrial technology for growing table and valuable fish species, characterized by higher survival and productivity. The antibiotic levofloxacin, a broad-spectrum antimicrobial bactericidal agent of the fluoroquinolone group, was chosen as a therapeutic EDN agent. There is presented information on the effect of the complex of β-cyclodextrin with levofloxacin on the lethal qualities of a Russian and Siberian sturgeon hybrid of different live weight. The influence of this complex on the pre-slaughter mass, the mass of individual internal organs, the fatness coefficient, the indices of the internal organs of hybrid individuals was studied according to two stages of the experiment performed in the laboratory “Progressive Biotechnologies in Aquaculture” of Vavilov University. The results of the control slaughter demonstrate the highest values for the indicators in individuals of the 2nd experimental group treated with the main diet at the first stage of the complex chitosan-β-cyclodextrin in various dosages of levofloxacin. Its results exceeded the control in the muscle mass, fatness coefficient, muscle tissue index, respectively. Thus, there was no negative effect of the β-cyclodextrin complex with an antibiotic on the functional state of internal organs and tissues of fish. The results obtained expand the information about the cultivation of sturgeon fish in industrial conditions using cyclodextrin nanosponge.

The Effect of Sodium Bicarbonate Injection on the Physico-Chemical Quality of Post-Harvest Trout.

The muscle hardness of fish is an important parameter associated with meat quality, and the post-mortem decrease in the pH of fish tissue pH affects its physical properties. We hypothesized that maintaining a high pH in fish tissue after death would prevent protein denaturation and consequent textural deterioration. This study aimed to determine the effectiveness of sodium bicarbonate (SBC) injections in preventing tissue softening caused by low pH after death in trout. We injected varying molar concentrations of SBC in rainbow trout (Oncorhynchus mykiss; 0 M, 0.5 M, 0.75 M, and 1 M) after harvest, and the product quality was assessed at 0, 24, 48, 72, and 96 h of ice storage. Quality was evaluated using proximate analyses for color, pH, water holding capacity (WHC), texture profile, and rigor index. The 0 M group had the lowest pH, and the 0.75 M group had the highest pH at all time points during storage. We observed improved tissue texture during storage in fish treated with 0.75 and 1 M SBC. The texture profile analysis showed higher hardness, frangibility, and stickiness in the tail than in the other regions. These varying results can be explained by significant differences between parts of the fish and sampling point selection. We also observed the highest pH and WHC values in the groups injected with 0.75 and 1 M SBC during storage.

Parasite Diversity and Histopathological Changes Due to Infection on Three Croakers (Pennahia Anea, Panna Microdon and Johnius Argentatus) of Saint Martin’s Island, Bay of Bengal

This study investigated the parasites of three species of croakers (Pennahia anea, Panna microdon, and Johnius argentatus) and their effect on host’s tissues. Fish samples were collected directly from the local fishermen and the fish landing station of Saint Martin’s Island, Bay of Bengal on a regular monthly basis. A total of 448 individuals of parasites were collected of which nine species of parasites were identified including three crustaceans, four nematodes, one pentastomida, and one acanthocephala. The nematode Procamallanus longus had the highest prevalence (50%) and intensity (10.33) compared with the other parasites. The prevalence and intensity of parasites were slightly higher in female fish (55%, 35) than in male fish (50%, 20). The stomach and liver were the most favorable infection sites (53.33%). Furthermore, parasites with the largest length and weight showed the highest prevalence and intensity (66.66% and 38.4 as well as 80% and 72.5, respectively). In histopathological investigations, the most important alterations in various tissues of fish were hemorrhage, necrosis, fatty droplets, edema, vacuolar degenerations, missing villi, haemosiderotic nodules, ovarian follicle disruption, and parasitic cell distribution.
 Bioresearch Commu. 9(2): 1297-1304, 2023 (July)

МОНИТОРИНГ ФОНОВОГО СОДЕРЖАНИЯ РТУТИ В БИОСИСТЕМЕ И ОРГАНИЗМЕ ДЕТСКОГО НАСЕЛЕНИЯ НИЖНЕГО ТЕЧЕНИЯ РЕКИ АМУР

Study Objective: to determine the mercury content in the body of children as well as in soil and river fish to assess the level of risk of adverse effects on a human body. Study Design: analytical observational, cross-sectional study. Materials and Methods. A quantitative analysis of mercury in hair of conditionally healthy children (n=62), the upper layer of soil (n=15) taken on the territory of the former cellulose and cardboard manufacturing plant (CCMP) located in one of the cities of the Khabarovsk region and in fish (n=27) living in the Amur river downstream was performed using inductively coupled plasma mass spectrometry. The relationship between the level of mercury and cognitive abilities of adolescents was studied. Study Results. An average content of mercury in the upper layer of the soil was 0.85 mg/kg; with the maximum value of the mass fraction of mercury 1.25 mg/kg, the mercury concentration was 8.5-12.5 times higher than the Russian background value. When determining the concentration of mercury in the fish muscle tissue – the main source of organic mercury for children, it was revealed that the content of mercury in the tissues of predatory fish ranged from 0.47-0.52 mg/kg, while the mercury level in non-predatory fish was 0.24 mg/kg. The average mercury content in hair of adolescence was 0.47±0.05 mg/kg and 0.19±0.02 mg/kg in 6-7-year-old children, and it did not exceed the critical level. Conclusion. It was found out that the content of mercury in the soil had significantly decreased compared to 2009, but the level remains above the Russian background value. Mercury content in part of the fish muscle living in the Amur River downstream was higher in predatory species. The concentration of mercury in the children organism permanently living on the territory of anthropogenic pollution did not exceed the threshold level, but the detected background values may have contributed to concentration decrease.

Bioaccumulation, tissue distribution, and maternal transfer of novel PFOS alternatives (6:2 Cl-PFESA and OBS) in wild freshwater fish from Poyang Lake, China

As emerging alternatives to perfluorooctane sulfonate (PFOS), 6:2 chlorinated polyfluoroalkyl ether sulfonic acid (6:2 Cl-PFESA) and sodium p-perfluorous nonenox-benzenesulfonate (OBS) were frequently detected in the four freshwater fish species collected from Poyang Lake. Median concentrations of 6:2 Cl-PFESA and OBS in fish tissues were 0.046–6.0 and 0.46–5.1 ng/g wet weight, respectively. The highest concentrations of 6:2 Cl-PFESA was found in fish livers, whereas OBS was found in the pancreas, brain, gonads, and skin. The tissue distribution pattern of 6:2 Cl-PFESA is similar to that of PFOS. The tissue/liver ratios of OBS were higher than those of PFOS, suggesting that OBS has a greater tendency to transfer from the liver to other tissues. The logarithmic bioaccumulation factors (log BAFs) of 6:2 Cl-PFESA in three carnivorous fish species were greater than 3.7, whereas those of OBS were less than 3.7, indicating that 6:2 Cl-PFESA had a strong bioaccumulation potential. Notably, sex- and tissue-specific bioaccumulation of OBS has also been observed in catfish. Most tissues (except the gonads) exhibited higher OBS concentrations in males than in females. However, no differences were found for 6:2 Cl-PFESA and PFOS. Maternal transfer efficiency of OBS was higher than that of 6:2 Cl-PFESA and PFOS in catfish (p < 0.05), indicating that OBS presents a higher risk of exposure to males and offspring through maternal offloading.

An effect assessment of microplastics and nanoplastics interacting with androstenedione on mosquitofish (Gambusia affinis)

An increasing number of microplastics have been detected in aquatic environments, causing various damage to organisms. The size of microplastics affects the toxicity once they enter the organisms. Meanwhile, there is an increasing variety of Endocrine-disrupting chemicals (EDCs) present in aquatic environments. Androstenedione (AED) is a typical EDC. In this study, we used polystyrene microspheres of 80 nm (NPs) and 8 μm (MPs) as materials to simulate environmental contaminants in the aquatic environment with AED. We used female mosquitofish (Gambusia affinis) as the research object to investigate the effects of microplastics on fish in waters containing AED. We compared different sizes of particles accumulation in some tissues of fish and variation of enzyme activities (SOD, LDH, CAT), and the content of MDA in the gut. MPs, NPs, and AED combined exposure test investigated mRNA profiles of immune-related genes (IL-1β, IL-6, IL-8, IL-10) and hormone receptor genes (ARα, ARβ, ERα, ERβ) in the liver of fish. Our results indicated that MPs emerged in various tissues (gill, gut, and liver) of mosquitofish. Besides, NPs and MPs caused enteric abnormal enzyme activity after 48 h of exposure, which was particularly pronounced in the MPs-AED group. MPs induced significant upregulation of inflammatory factors and gonadal factor genes after 96 h of exposure, which was more pronounced when co-exposed with AED. In conclusion, NPs and MPs caused mechanisms of immune damage and inflammatory response. MPs were found to be more likely to cause adverse reactions than NPs, and these responses were enhanced by the combined effects of AED. This study demonstrated that AED can exacerbate the negative effects of MPs and NPs on mosquitofish. It provided an important basis for the effective assessment of MPs and NPs on bioaccumulation and biochemical status of mosquitofish. Additionally, it serves as a foundation to investigate the interactive effects of microplastics and EDCs in living organisms.

Characterization, Expression, and Ligand Binding of LGP2 and MDA5 in Largemouth Black Bass Micropterus salmoides (Lacepède, 1802)

Melanoma differentiation-associated gene 5 (MDA5) and the laboratory of genetics and physiology 2 (LGP2) are family members of retinoic acid-inducible gene I (RIG-I)-like receptors (RLRs), which play important roles in the immune response against pathogens invasion. In the present study, MDA5 and LGP2 genes were identified in largemouth bass (Micropterus salmoides), a fish species with a great economic value. The two proteins contained similar conserved domains and motifs as their counterparts of other vertebrates, including the DExDc domain (the DEAD/DEAH box helicases domain), HELICc domain (helicases superfamily domain), and regulatory domain (RD). Real-time qPCR revealed that the two genes were constitutively expressed in tissues of healthy fish and could be induced in the spleen by polyinosinic and polycytidylic acid (polyI:C) challenge in vivo. Also, selective pressure analysis revealed that the negative selection had roles in the evolutions of the two genes. Furthermore, the dsRNA binding mechanism of msLGP2 and msMDA5 were analyzed by the molecular docking strategy. The amino acids of msLGP2 involved in dsRNA binding were V604, N663, L682, and L684, which were located in the regulatory domain (RD) of msLGP2. The amino acids of msMDA5 involved in dsRNA binding were G429, H434, L842, and L845, which were located in the DExDc domain and the RD domain of msMDA5. These results indicated that fish LGP2 and MDA5 might share similar functions and ligand binding mechanism as their mammalian counterparts.

Assessment of Metal Contamination in Oreochromis niloticus from Ekiti State’s Major Dams, Southwest, Nigeria and its Human Health Implications

Agricultural and domestic activities around dams in Nigeria involve the use of agrochemicals and insecticides to boost production and combat insect pests respectively. The study aimed to ascertain metals contents and assess the hazards associated with heavy metals in Oreochromis niloticus in three major dams in Ekiti State. Fish samples were collected for 24 months. Metal concentrations in fish samples were determined using spectrometry. The metals concentrations in the tissues were at lower concentrations compared to the maximum acceptable limits in food by Food and Agricultural Organization (FAO) and World Health Organization (WHO). Metals accumulation pattern revealed that the accumulation of the essential metals were higher than those of the non-essential metals in the fish tissues. There were significant seasonal variations in the concentrations of metal in fish tissues within the dam and among the dams. Significant relationships existed at P &lt; 0.05 or P &lt; 0.01 between some of the metals and the fish body weight and body length in the different dams while in others the relationships were not significant. Human health risk assessment showed no significant non-carcinogenic adverse health risk. Carcinogenic health assessment indicates that the utilization of the species as a protein source does not currently pose public health risk to consumers. However, the discovery of cadmium and lead in fish muscle is of great concern because of their toxic effects on human. Therefore, there is a need for close monitoring of these toxic metals contamination to prevent their excessive accumulation in the human food chain.