Gill Tissue Research Articles

Employing molecular, chemical and physiological techniques using Crassostrea virginica to assess ecosystem health along coastal South Carolina and North Carolina, United States

Natural and anthropogenic environmental impacts can introduce contaminants into sensitive habitats, threatening ecosystems and human health. Consistent monitoring of coastal areas provides critical environmental assessment data. Sediments and Eastern Oyster (Crassostrea virginica) tissues were collected at fourteen South Carolina (SC) and four North Carolina (NC) sites as part of the National Oceanic and Atmospheric Administration's Mussel Watch environmental monitoring program. Cellular and molecular techniques were employed to measure C. virginica stress response, specifically, Lipid Peroxidation (LPx), Glutathione (GSH), and qPCR techniques. Gene specific primers targeted for detecting oxidative stress and cellular death were developed in C. virginica to gauge response to current environmental conditions using gill and hepatopancreas (HP) tissue. In order to validate gene specific markers as additional assessment tools, a 96 h zinc (Zn) laboratory exposure was performed. Cellular biomarker data revealed tissue specific responses. Hepatopancreas data showed C. virginica exhibited stress through the lipid peroxidation assay amongst sampling sites, however, response was managed through glutathione detoxification. Gill tissue data had significantly lower levels of cellular biomarker response compared to hepatopancreas. Molecular biomarkers targeting these cellular stress pathways through qPCR analysis show upregulation of Metallothionein in hepatopancreas and gill tissue with a concurrent > 2-fold upregulation in the detoxification marker Superoxide Dismutase (SOD) at three NC sites. SC sites displayed higher stress levels through LPx assays and down-regulation in GPx gene activity. Laboratory zinc exposure revealed no significance in cellular biomarker results, however, molecular data showed gills responding to zinc treatment through upregulation of Metallothionein, SOD and Cathepsin L, indicating an acute response in gills. Collectively, chemical, cellular and molecular methods clarify sentinel stress response of biological impacts and aid in evaluating environmental health in coastal ecosystems. This combined methodological approach provides a detailed analysis of environmental conditions and improves land-use management decisions.

Heritability of Immunity Traits and Resistance of Atlantic Salmon against the Sea Louse Caligus rogercresseyi.

The immune response of Atlantic salmon to sea lice has been extensively studied, but we still do not know the mechanisms by which some fish become resistant and others do not. In this study, we estimated the heritabilities of three key proteins associated with the innate immunity and resistance of Salmo salar against the sea louse Caligus rogercresseyi. In particular, we quantified the abundance of 2 pro-inflammatory cytokines, Tnfα and Il-8, and an antioxidant enzyme, Nkef, in Atlantic salmon skin and gill tissue from 21 families and 268 individuals by indirect ELISA. This covers a wide parasite load range from low or resistant (mean sea lice ± SE = 8.7 ± 0.9) to high or susceptible (mean sea lice ± SE = 43.3 ± 2.0). Our results showed that susceptible fish had higher levels of Nkef and Tnfα than resistant fish in their gills and skin, although gill Il-8 was higher in resistant fish, while no significant differences were found in the skin. Furthermore, moderate to very high heritable genetic variation was estimated for Nkef (h2 skin: 0.96 ± 0.14 and gills: 0.97 ± 0.11) and Tnfα (h2 skin: 0.53 ± 0.17 and gills: 0.32 ± 0.14), but not for Il-8 (h2 skin: 0.22 ± 0.12 ns and gills: 0.09 ± 0.08 ns). This work provides evidence that Nkef and Tnfα protein expressions are highly heritable and related to resistance against sea lice in Atlantic salmon.

Lethal toxicity LC50 of permethrin insecticide and its physiological and histopathological effect on common carp and nile tilapia

Permethrin insecticide is commonly used in the worldwide due to the best effectivity in pest control and easier to degrade in the field. However, the implementation in the field of this insecticide is high will cause environmental pollution. It has been reported that aquatic environment at Singkarak lake containing permethrin. The aims of this experiment is to determine of lethal toxicity (LC50) of permethrin insecticide and its physiological effect on common carp and nile tilapia fish. The test fish was common carp and nile tilapia. Insecticide formula with permethrin active agent as a material test was used. Static toxicity method in the laboratorium was performed. Parameters in this experiment observed such as LC50, blood glucose, and histopathological of gill and liver tissues. The result showed that the permethrin insecticide had a high toxic to common carp and nile tilapia with the LC50-96h values were 0.49 dan 0.52 mg/L, respectively. The blood glucose of common carps was ranging from 29.7±0.6–118.3±0.7 mg/DL where the nile tilapia was ranging from 27.7±0.9 – 58.7±1.5 mg/DL. The blood glucose would be increased with increasing the permethrin concentration. The histopathological of gills and liver tissues both of common carp and nile tilapia were hyperplasia and necrosis.

First transcriptome profiling in gill and hepatopancrease tissues of Metapenaeus ensis in response to acute ammonia-N stress.

The greasyback shrimp, Metapenaeus ensis, suffers from ammonia-N stress during intensive factory aquaculture. Optimizing ammonia-N stress tolerance has become an important issue in M. ensis breeding. The metabolic and adaptive mechanisms of ammonia-N toxicity in M. ensis have not been comprehensively understood yet. In this study, a large number of potential simple sequence repeats (SSRs) in the transcriptome of M. ensis were identified. Differentially expressed genes (DEGs) in the gill and hepatopancreas at 24h post-challenges under high concentrations of ammonia-N treatment were detected. We obtained 20,108,851-27,681,918 clean reads from the control and high groups, assembled and clustered a total of 103,174 unigenes with an average of 876 bp and an N50 of 1189 bp. Comparative transcriptome analyses identified 2000 different expressed genes in the gill and 2010 different expressed genes in the hepatopancreas, a large number of which were related to immune function, oxidative stress, metabolic regulation, and apoptosis. The results suggest that M. ensis may counteract ammonia-N toxicity at the transcriptome level by increasing the expression of genes related to immune stress and detoxification metabolism, and that selected genes may serve as molecular indicators of ammonia-N. By exploring the genetic basis of M. ensis' ammonia-N stress adaptation, we constructed the genetic networks for ammonia-N adaptation. These findings will accelerate the understanding of M. ensis' ammonia-N adaptation, contribute to the research of future breeding, and promote the level of factory aquaculture of M. ensis.

Integrated transcriptome and miRNA sequencing analyses reveal that hypoxia stress induces immune and metabolic disorders in gill of genetically improved farmed tilapia (GIFT, Oreochromis niloticus).

The survival and growth of fish are significantly impacted by a hypoxic environment (low dissolved oxygen). In this study, we compared tissue structure, physiological changes, and mRNA/miRNA transcriptome, in gills of genetically improved farmed tilapia (GIFT, Oreochromis niloticus) between the hypoxic group (DO: 0.55mg/L, HG) and the control group (DO: 5mg/L, CG). The results showed that the gill filaments in the hypoxic group showed curling, engorgement, and apoptotic cells increased, and that exposure for 96h resulted in a reduction in the antioxidant capacity. We constructed and sequenced miRNA and mRNA libraries from gill tissues of GIFT at 96h of hypoxia stress. Between the HG and CG, a total of 14 differentially expressed (DE) miRNAs and 1557 DE genes were obtained. GO and KEGG enrichment showed that DE genes were mainly enriched in immune and metabolic pathways such as natural killer cell mediated cytotoxicity, steroid biosynthesis, primary immunodeficiency, and synthesis and degradation of ketone bodies. Based on the results of mRNA sequencing and screening for miRNA-mRNA pairs, we selected and verified six DE miRNAs and their probable target genes. The sequencing results were consistent with the qRT-PCR validation results. The result showed that under hypoxia stress, the innate immune response was up-regulated, and the adaptive immune response was down-regulated in the gill of GIFT. The synthesis of cholesterol in gill cells is reduced, which is conducive to the absorption of solvent oxygen. These findings offer fresh information about the processes of fish adaptation to hypoxic stress.

Beyond the surface: Consequences of methyl tert-butyl ether (MTBE) exposure on oxidative stress, haematology, genotoxicity, and histopathology in rainbow trout

Concerns have been raised about the possible environmental effects of methyl tert-butyl ether (MTBE), which is widely used as a gasoline additive. This research aimed to look at the consequences of MTBE contamination on rainbow trout (Oncorhynchus mykiss), emphasizing oxidative stress, genotoxicity, and histopathological damage. After determining the LC50-96 h value, the effects of sub-lethal doses of MTBE (0 (control), 90, 180, and 450 ppm) on rainbow trout were investigated. In fish tissues, the levels of oxidative stress indicators such as malondialdehyde (MDA) and superoxide dismutase (SOD) were measured. The comet assay, which measures DNA damage in erythrocytes, was used to determine genotoxicity. Histopathological examinations were done on liver and gill tissues to examine potential structural anomalies. The results of this study show that MTBE exposure caused considerable alterations in rainbow trout. Increased oxidative stress was demonstrated by elevated MDA levels and decreased SOD activity, while the comet assay revealed dose-dependent DNA damage, implying genotoxic effects. Histopathological study revealed liver and gill tissue abnormalities, including cell degeneration, necrosis, and inflammation. Overall, this research highlights the possible sub-lethal effects of MTBE contamination on rainbow trout, stressing the need of resolving this issue. Future research should look at the impacts of chronic MTBE exposure and the possibility of bioaccumulation in fish populations.

Effect of anti‐fouling organotin compound (TBTCl) and the ameliorative role of spirulina on Lamellidens marginalis

AbstractOrganotin compounds (OTs) belong to persistent organic pollutants (POPs) group and are capable of persisting up to 40 years due to their chemical nature. Tributyltin (TBT) is an anti‐fouling agent and can easily leach out into water threatening the aquatic life. Molluscs are sensitive towards the presence of toxins in their surrounding environment and respond accordingly to overcome stress conditions. Lamellidens marginalis, a freshwater bivalve is popular for its food value and pink pearls. The present study focuses on the effect of Tributyltin chloride (TBTCl), a form of TBT, on Lamellidens marginalis under laboratory conditions. The 96 h median lethal concentration (LC50) was calculated to be 1 mg L−1. Bivalves were segregated into three sub‐groups that is, group I; control, group II; experimental (treated with 0.2 mg L−1 TBTCl that is, 1/5th of LC50 value), group III; experimental (treated with 0.2 mg L−1 TBTCl + 0.003% w/v spirulina). A static non‐renewal toxicity assay was performed for 96 h. Estimation of total protein, acid phosphatase (ACP), alkaline phosphatase (ALP), aspartate aminotransferase (AST), alanine aminotransferase (ALT) and glycogen was carried out. An overall decrease in the total protein, ACP, ALP, glycogen, and ALT was observed in both the experimental groups (Groups II and III) in comparison to the control group whereas, the concentration of AST was found to increase in hepatopancreas. Integrated biomarker response index (IBR) value was calculated to be 12.60 for control and 10.56 and 11.29 for groups II and III, respectively in hepatopancreas. Similarly, in gill tissue the values were 3.69, 1.37, and 3.43, respectively. After treatment with nutritional supplement spirulina, a higher BRI (biomarker response index) value of 3.3 for group III was observed, suggesting the therapeutic role of spirulina in test organisms. BRI value derived for group II was 2.7 indicating more severity of TBTCl compared to group III in the absence of spirulina.

Cooperative adaptation strategies of different tissues in blunt snout bream (Megalobrama amblycephala) juvenile to acute ammonia nitrogen stress.

Ammonia-nitrogen is a common stress factor for aquatic organisms in their habitation environment, which is enriched in water due to high-density farming and environmental pollution. Ammonia nitrogen can enter fish body through gill, epidermis, digestive tract, and other tissues, causing fish ammonia poisoning. In the present study, juvenile blunt snout bream (average weight, 45 ± 5g) were exposed to high concentrations of ammonia-nitrogen stress (25.0 ± 0.5mg/L) for six different treatment times (0, 3, 6, 12, 24, 48, and 72h); the tissue ultrastructure, mRNA levels of antioxidation system, and apoptosis patterns were studied. The antioxidant systems of malondialdehyde (MDA), catalase (CAT), acid phosphatase (ACP), and reduced glutathione (GSH) in various tissues were highly transcripted at 6 or 12h (hpt) after treatment under high ammonia-nitrogen, which may play a role in preventing cells from being attacked by highly toxic reactive oxygen species (ROS). After 24 hpt, the antioxidant capacity threshold is breached, followed by the decline of antioxidant enzyme activity. Thus, with the prolonging of high ammonia-nitrogen processing time, ammonia-nitrogen stress caused irreversible damage of organs (gill, liver, and kidney). Furthermore, the expression of caspase-3 apoptotic pathway was highly induced in different tissues, implying the apoptotic system is activated, which causes extensive cell apoptosis in different tissues as shown using TUNEL analysis. In conclusion, we observed that, in response to acute ammonia-nitrogen stress, blunt snout bream enhances antioxidant capacity and cell apoptosis.

Subcellular localization of Na+/K+-ATPase isoforms resolved by in situ hybridization chain reaction in the gill of chum salmon at freshwater and seawater

The Na+/K+-ATPase (NKA) α1-isoforms were examined by in situ hybridization chain reaction (ISHCR) using short hairpin DNAs, and we showed triple staining of NKA α1a, α1b, and α1c transcripts in the gill of chum salmon acclimated to freshwater (FW) and seawater (SW). The NKA α1-isoforms have closely resembled nucleotide sequences, which could not be differentiated by conventional in situ hybridization. The ISHCR uses a split probe strategy to allow specific hybridization using regular oligo DNA, resulting in high specificity at low cost. The results showed that NKA α1c was expressed ubiquitously in gill tissue and no salinity effects were observed. FW lamellar ionocytes (type-I ionocytes) expressed cytoplasmic NKA α1a and nuclear NKA α1b transcripts. However, both transcripts of NKA α1a and α1b were present in the cytoplasm of immature type-I ionocytes. The developing type-I ionocytes increased the cytoplasmic volume and migrated to the distal region of the lamellae. SW filament ionocytes (type-II ionocytes) expressed cytoplasmic NKA α1b transcripts as the major isoform. Results from morphometric analysis and nonmetric multidimensional scaling indicated that a large portion of FW ionocytes was NKA α1b-rich, suggesting that isoform identity alone cannot mark the ionocyte types. Both immature or residual type-II ionocytes and type-I ionocytes were found on the FW and SW gills, suggesting that the chum salmon retains the potential to switch the ionocyte population to fit the ion-transporting demands, which contributes to their salinity tolerance and osmoregulatory plasticity.

Adaptation strategies of juvenile grass carp (Ctenopharyngodon idella) facing different dissolved oxygen concentrations in a recirculating aquaculture system

Fishes exposed to different dissolved oxygen concentrations over prolonged time periods have different susceptibility and adaptation mechanisms. In this study, healthy grass carp with an average weight of 214.6 ​± ​18.7 ​g were selected for long-term culture in recirculating aquaculture systems at three different dissolved oxygen concentrations, i.e., 3.00 ​mg/L [(2.57 ​± ​0.33) mg/L, DO2.57), 5.00 ​mg/L [(4.61 ​± ​0.11) mg/L, DO4.61], which was the control group, and 7.00 ​mg/L [(6.50 ​± ​0.48) mg/L, DO6.50]. Blood, gill, muscle, and liver samples were collected after 60 ​days. Using hematoxylin-eosin (HE), alcian blue periodic acid Schiff (AB-PAS) staining, determination of respiratory metabolism enzyme activity, and fluorescent quantitative PCR, the adaptability of juvenile grass carp facing different dissolved oxygen levels were explored. The results showed that the respiration rate increased, and hemoconcentration and hemoglobin (Hb), electrolyte and pH changed at DO2.57. Furthermore, gill lamellae became thinner and longer, the distance between them increased, the mucus on them decreased and the interstitial cell mass decreased. In addition, the relative expression of apoptosis-related genes bcl-2 and bcl-xl in gill tissue decreased, while caspase-3 and bax increased. In muscles and liver tissues, lactate dehydrogenase (LDH) activity and lactic acid content (LA) increased, pyruvate dehydrogenase (PDH) activity decreased, and genes related to the respiratory metabolic enzymes PDH-A4 and PDH-E1α also changed accordingly. The oxygen consumption rate decreased significantly (P ​< ​0.05). At DO6.50, the distance between gill lamellae, numbers of red blood cells (RBC) and the content of hemoglobin decreased wheras the mucus on gill lamellae increased. The activity of PDH, the expression of PDH-E1a in liver and oxygen consumption rate increased. Different dissolved oxygen concentrations affected the respiratory behavior, gill tissue structure, blood transport capacity and tissue enzyme activity of juvenile grass carp. In summary, juvenile grass carp showed different adaptation strategies when facing different dissolved oxygen concentrations over prolonged periods in recirculating aquaculture systems.

Assessment of Infection Prevalence and Intensity of Disease-Causing Parasitic Protozoans Perkinsus marinus and Haplosporidium nelsoni in Georgia Oysters.

Eastern oysters, Crassostrea virginica, are ecologically and economically important coastal species which provide a commercially valuable food product while also improving water quality through filtration, protecting shorelines, and providing habitat. The protozoan parasites Perkinsus marinus and Haplosporidium nesloni commonly infect oysters along the United States Atlantic and Gulf coasts and have been linked to poor oyster health and mass mortality events. In this study, wild oysters were collected from multiple reefs within four tidal creeks along the coast of Georgia to investigate P. marinus and H. nelsoni prevalence and intensity, their potential impact on oyster health, and identify possible drivers of the parasites. A second study occurred on four sites on Sapelo Island, Georgia, with continuous water quality monitoring data to further elucidate potential drivers. Oyster density and condition index, a proxy for health, were measured, and parasites were quantified using a TaqMan probe based quantitative real-time PCR within gill tissue. Real-time PCR showed that 86% of oysters tested were infected by one or both parasites in the coast-wide survey, and 93% of oysters from Sapelo Island were also infected by one or both parasites. Prevalence and infection intensity for both P. marinus and H. nelsoni varied across sites. Overall impacts on oysters were complex-intensity was not linked to oyster metrics in the coastwide study, but oyster condition was negatively correlated with P. marinus prevalence in the Sapelo Island study. Several relationships between both parasites and water quality parameters were identified, providing valuable information about potential drivers that should be investigated further.

Immune responses in carp strains with different susceptibility to carp edema virus disease.

Carp edema virus disease (CEVD), also known as koi sleepy disease (KSD), represents a serious threat to the carp industry. The expression of immune-related genes to CEV infections could lead to the selection of crucial biomarkers of the development of the disease. The expression of a total of eleven immune-related genes encoding cytokines (IL-1β, IL-10, IL-6a, and TNF-α2), antiviral response (Mx2), cellular receptors (CD4, CD8b1, and GzmA), immunoglobulin (IgM), and genes encoding-mucins was monitored in gills of four differently KSD-susceptible strains of carp (Amur wild carp, Amur Sasan, AS; Ropsha scaly carp, Rop; Prerov scaly carp, PS; and koi) on days 6 and 11 post-infection. Carp strains were infected through two cohabitation infection trials with CEV genogroups I or IIa. The results showed that during the infection with both CEV genogroups, KSD-susceptible koi induced an innate immune response with significant up-regulation (p<0.05) of IL-1β, IL-10, IL-6a, and TNF-α2 genes on both 6 and 11 days post-infection (dpi) compared to the fish sampled on day 0. Compared to koi, AS and Rop strains showed up-regulation of IL-6a and TNF-α2 but no other cytokine genes. During the infection with CEV genogroup IIa, Mx2 was significantly up-regulated in all strains and peaked on 6 dpi in AS, PS, and Rop. In koi, it remained high until 11 dpi. With genogroup I infection, Mx2 was up-expressed in koi on 6 dpi and in PS on both 6 and 11 dpi. No significant differences were noticed in selected mucin genes expression measured in gills of any carp strains exposed to both CEV genogroups. During both CEV genogroups infections, the expression levels of most of the genes for T cell response, including CD4, CD8b1, and GzmA were down-regulated in AS and koi at all time points compared to day 0 control. The expression data for the above experimental trials suggest that both CEV genogroups infections in common carp strains lead to activation of the same expression pattern regardless of the fish's susceptibility towards the virus. The expression of the same genes in AS and koi responding to CEV genogroup IIa infection in mucosal tissues such as gill, gut, and skin showed the significant up-regulation of all the cytokine genes in gill and gut tissues from koi carp at 5 dpi. Significant down-regulation of CD4 and GzmA levels were only detected in koi gill on 5 dpi but not in other tissues. AS carp displayed significant up-expression of Mx2 gene in all mucosal tissues on 5 dpi, whereas in koi, it was up-regulated in gill and gut only. In both carp strains, gill harbored a higher virus load on 5 dpi compared to the other tissues. The results showed that resistance to CEV could not be linked with the selected immune responses measured. The up-regulation of mRNA expression of most of the selected immune-related genes in koi gill and gut suggests that CEV induces a more systemic mucosal immune response not restricted to the target tissue of gills.

Carp edema virus, a great threat for carp and koi farming in Henan, China

A carp disease with clinical signs of acute gill rot (AGR) has frequently occurred in Henan province of China since 2013, leading to substantial economic losses. However, the causative agent of virus-related carp AGR (CAGR) disease has been controversial. Our study showed that carp edema virus (CEV), specifically the sub-genogroup IIa, might be the primary agent causing virus-related CAGR that is endemic to Henan, China. This conclusion is based on a cohabitation experiment using isolates from an outbreak in 2019 and a retrospective analysis of CAGR samples collected between 2013 and 2015 in Henan, China. In the cohabitation experiment, the clinical development and pathological changes of CEV disease were observed. The pathological alterations in the fish brain were first noticed to be strongly associated with clinical signs of being sleepy, suggesting that pathological alterations in the fish brain may be a critical differential characteristic of CEV. Another important finding in our study was that the mortality in common carp and koi carp was strongly associated by a temperature change and less correlated to the viral loads in organs. Considering the frequent outbreaks of virus-related CAGR disease in Henan (China), effective prevention, good environmental stress management, and efficient diagnosis are needed. Based on comparing the qPCR and the nested PCR designed at the CEFAS Weymouth Laboratory, we recommend using the qPCR method on gills to identify this pathogen because of the assay's sensitivity and the viral load in gill tissues.

Phthalate induced hormetic effect reveals susceptibility of gill compared to muscle tissue after depuration in commercially important fish (Etroplus suratensis)

Effect of Bis-2ethylhexyl phthalate (DEHP) on commercially important tropical fish pearl spot has not been demonstrated at environmental concentrations along with depuration. The species is estuarine, juvenile and difficult to maintain but widely consumed and well distributed in tropical estuaries. Antioxidant activity of SOD, CAT and GPx was enhanced on all exposure days for gill and muscle suggesting high oxidative stress, except on day 5. Detoxifying enzyme-GST behaved differentially in gill and muscle tissue after depuration, depicting inhibited activity of GST in gill leading to lipid peroxidation. However, the muscle tissue was able to recover from stress after 7 days of depuration with the help of detoxifying enzymes. Overcompensation of antioxidant activity was observed over disruption of homeostasis defining hormesis effect. Integrated biomarker (IBR) index depicted high toxicity during entire exposure time, but after depuration, gill could not mediate LPO at lowest concentration (10 μg/l) while muscle tissue recovered, suggesting persistence of stress in gill.

Biochemical changes in the gill, liver, and muscle tissue of Anabas testudineus on exposure to varying concentration of Lead acetate

AbstractHeavy metal pollution in aquatic systems is a global concern because of its toxicity, persistent nature, and its bioaccumulation. The present study was carried out to understand the sub‐lethal effects of lead acetate on Anabas testudineus despite its ability to tolerate stress. Fish were exposed to various concentrations of lead acetate (1.291, 1.936, 3.873 mg/L) for a period of 96 h for assessment of acute toxicity. Various biochemical (protein and glycogen) and enzymatic parameters (acid phosphatase, alkaline phosphatase, aspartate aminotransferase, and alanine aminotransferase) were investigated to have an insight on lead acetate toxicity. Protein content increased in all tissues in comparison to the control group. Glycogen increased in gill and muscle tissue whereas it decreased in liver tissues. Increase in the activity of phosphatase enzyme was observed in all tissues of the experimental group in comparison with the control group. All the studied parameters in different tissues were normalized to score values for calculation of integrated biomarker index (IBR) for better interpretation of data. Biomarker response index (BRI) was also calculated for a simple indication of the health status of control and experimental fish. Higher BRI value indicates less toxic effect on liver cells due to detoxification process, whereas lead acetate was found to be toxic for both gill and muscle tissue due to low BRI value. Lead acetate induced changes in the physiology of the experimental fish A. testudineus and the parameters taken into account can serve as biomarkers of lead acetate toxicity.

Biological responses to imazapic and methyl parathion pesticides in bioinspired lipid membranes and Tilapia fish

Pesticide misuse has well-documented detrimental effects on ecosystems, with Nile tilapia (Oreochromis niloticus) being particularly vulnerable. The current study focuses on the impact of widely used sugarcane crop pesticides, Imazapic (IMZ) and Methyl Parathion (MP), on tilapia gill tissues and their lipid membranes. This investigation was motivated by the specific role of the lipid membrane in transport regulation. Bioinspired cell membrane models, including Langmuir monolayers and liposomes (LUVs and GUVs), were utilized to explore the interaction of IMZ and MP. The results revealed electrostatic interactions between IMZ and MP and the polar head groups of lipids, inducing morphological alterations in the lipid bilayer. Tilapia gill tissue exposed to the pesticides exhibited hypertrophic increases in primary and secondary lamellae, total lamellar fusion, vasodilation, and lifting of the secondary lamellar epithelium. These alterations can lead to compromised oxygen absorption by fish and subsequent mortality. This study not only highlights the harmful effects of the pesticides IMZ and MP, but also emphasizes the crucial role of water quality in ecosystem well-being, even at minimal pesticide concentrations. Understanding these impacts can better inform management practices to safeguard aquatic organisms and preserve ecosystem health in pesticide-affected environments.

Major histocompatibility complex class IIα and IIβ of pufferfish (Takifugu obscurus): Identification and functional characterization in response to bacterial challenge.

Classical major histocompatibility complex (MHC) class II molecules play an essential role in immune system. In this study, MHC IIα (Pf-MHC IIα) and MHC IIβ (Pf-MHC IIβ) homology genes from pufferfish (Takifugu obscurus) were cloned and their functional characterization in response to bacterial challenge was identified. The nucleotide sequences of the open reading frames (ORFs) of pufferfish Pf-MHC IIα and Pf-MHC IIβ were 708 bp and 750 bp, encoding 235 aa and 249 aa, respectively. The structure of Pf-MHC IIα or Pf-MHC IIβ contained a signal peptide, an α1/β1 domain, an α2/β2 domain, a transmembrane region and a cytoplasmic region. Multiple sequence alignment and phylogenetic analysis showed that Pf-MHC IIα and Pf-MHC IIβ molecules had the highest similarity with Fugu rubripes (Takifugu rubripes). Cellular localization analysis indicated that the distribution of Pf-MHC IIα and Pf-MHC IIβ was in the lymphocyte membrane and cytoplasm. qRT-PCR results showed that Pf-MHC IIα and Pf-MHC IIβ expressed relatively high in skin, gills and gut. In addition, after stimulation challenge in vitro (lipopolysaccharide, or polyinosinic: polycytidylic acid) and in vivo (A. hydrophila), the mRNA expressions of Pf-MHC IIα and Pf-MHC IIβ were significantly up-regulated in lymphocytes and in tissues of skin, gills, gut and head kidney. Moreover, Pf-MHC IIα or Pf-MHC IIβ neutralization reduced the ability of A. hydrophila to induce the expressions of lymphocyte cytokines (TNF-α, IL-1β and IL-10). Overall, it is speculated that Pf-MHC IIα and Pf-MHC IIβ may play an important role in the host response against A. hydrophila in pufferfish.

Effect of mercury on histological alterations in gill, liver and stomach tissues of Indian catfish, Clarias batrachus

Heavy metal pollution poses a great threat to aquatic ecosystem, ultimately threatening the survival of safe and healthy life on earth. Contaminated water persuades pathological alterations and behavioural changes in fish. Mercury is highly toxic and seriously affects aquatic organisms, ultimately affecting humans.The present study aimed to assess the histological alterations in tissues like gill, liver and stomach of Indian catfish Clarias batrachus. The fish were divided in to four groups i.e. one control (Group I) and three groups of different concentration of mercury chloride treated groups, i.e.0.0002mg/l (Group II), 0.002mg/l(Group III), and 0.02mg/l (Group IV) for 14 days. Each group contained 25 number of fish.The results indicated degenerative changes in gill, liver and stomach tissues of exposed fish. Level of changes were higher with respect to higher in concentration. Rupture of epithelial layer, club shaped gill filament, broken gill lamellae, hyperplasia of interlamellar epithelium, deletion of secondary lamellae, formation of vacuoles, blood conjugation and necrosis in gill filaments were observed in gill tissues of exposed fish. Liver damage included hepatocellular dissociation, inflamed hepatocytes, cloudy swelling, vacuole formation and hydropic degeneration. Besides, stomach tissues showed alterations such as thinner serosa, vacuolization, muscle damage, and necrosis at several points. The study confirmed that mercury is life hazardous even at very low concentration.

Host–pathogen interaction unveiled by immune, oxidative stress, and cytokine expression analysis to experimental Saprolegnia parasitica infection in Nile tilapia

The present study evaluated the pathogenicity, immunological, and oxidant/antioxidant responses against Saprolegnia parasitica (S. parasitica) infection in Nile tilapia (Oreochromis niloticus). Three groups of Nile tilapia were assigned as the control group (no zoospores exposure). The other two groups were challenged by Saprolegnia zoospores; one was used for sampling, and the other for mortality monitoring. The study lasted 3 weeks and was sampled at three point times at 1, 2, and 3 weeks. Results showed that S. parasitica zoospores were pathogenic to Nile tilapia, causing a cumulative mortality rate of 86.6%. Immunoglobulin M and C- reactive protein (IgM and CRP) levels showed a similar trend being significantly (P < 0.05, P < 0.001) higher in the infected group at weeks 1, 2, and 3, respectively, compared to the control group. Oxidant and antioxidant parameters in gills revealed that Malondialdehyde (MDA) level was significantly higher in the infected group compared to the control group. While catalase, glutathione peroxidase, and superoxide dismutase (CAT, GSH, and SOD) levels were significantly decreased in the infected group compared to the control group. Compared to the control, the tumor necrosis factor-α (TNF-α) gene was firmly upregulated in gill tissue at all-time points, particularly at day 14 post-infection. Meanwhile, Interleukin 1-β (IL-1 β) gene was significantly upregulated only at days 7 and 14 post-infection compared to control. Histopathological examination revealed destructive and degenerative changes in both skin and gills of experimentally infected Nile tilapia. Our findings suggest that Nile tilapia-S. parasitica infection model was successful in better understanding of pathogenicity and host (fish)-pathogen (oomycete) interactions, where the induced oxidative stress and upregulation of particular immune biomarkers in response to S. parasitica infection may play a crucial role in fish defense against oomycetes in fish.

Effect of Malathion (An Organophospahte) on Electrophoretic Banding Patterns of Esterase Isozymes in Gill, Liver, Brain Tissue of Fresh Water Fish Channa Punctatus (Bloch)

This investigation was conducted to compare the electrophoretetic banding patterns of esterase isozyme in the gill, liver, and brain tissues of the freshwater fish Channa punctatus (Bloch) at 24 hours, 48 hours, 72 hours, and 96 hours after exposure to Malathion (an Organophosphate) to those at the control group. Quantitative analysis of the esterase isozymes was performed using 7.5 native polyacrylamide gel electrophoresis (PAGE) stained with -naphthyl acetate as substrate. The relative mobilities of three esterase Isozyme bands in gill, liver, and brain tissue were determined to be 0.60.05, 0.40.05, and 0.30.05, respectively; these bands were designated Est-1, Est-2, and Est-3, respectively. Control samples from the gill, liver, and brain all had all three esterase bands. Both Est 2 and Est-3 Esterase Isozyme bands in gill and liver tissue were eliminated when fish were subjected to Malathion (an Organophosphate) for 72 and 96 hours, respectively. Malathion induced greater damage in Est-1 and Est-3 brain tissue than in Est-2.