Gill Tissue Research Articles

Gene expression profiles of white bass (Morone chrysops) and hybrid striped bass (M. chrysops x M. saxatilis) gill tissue following Flavobacterium covae infection

Columnaris disease is a prevalent disease in freshwater environments caused by the ubiquitous aquatic pathogen Flavobacterium species. Adhesion to the external mucosal surfaces of fishes is the initial stage of infection, and the gills specifically have been identified as both a primary target and release site for this pathogen. Demonstrated here and in previous research, the hybrid striped bass (Morone chrysops x M. saxatilis), a prominent United States aquaculture product, is more susceptible to infection with F. covae than the maternal white bass (M. chrysops) parental species. To further elucidate the mechanisms underlying differences in resistance between these fish we examined gill gene expression profiles using RNA sequencing at different timepoints after F. covae infection. Patterns of differential gene expression and association with key enrichment terms indicate the effective immune response observed in white bass includes the up-regulation of multiple cytokines (IL-1β, IL-17C, TNF-α, G-CSF, IL-8, CCL16, CXCL9), hepcidins (HAMP and HAMP2), ribosomal subunit components (e.g., RPL13), and, interestingly, the down-regulation of leptin (LEPA) during initial (1 – 4 h) stages of infection. Conversely, up-regulation of the same genes was not detected in hybrid striped bass until 24 h after infection, indicating a delay in immune response mechanisms that is ultimately ineffective in protecting the host, as this was concurrent with the onset of mortality in these fish. Collectively, the presented results include several putative pathways and candidate genes for further investigation toward characterizing immune defense mechanisms underlying the resistance (white bass) and susceptibility (hybrid striped bass) for selective breeding efforts and/or biotechnological intervention.

At-sea application of the comet assay to a deep-sea fish

Given the go ahead, deep-sea mining operations are likely to continue for decades on a substantial spatial scale and the resulting sediment plumes combined, are likely to extend beyond the licenced mining areas, and could lead to the chronic exposure of deep-sea organisms to a mixture of metals, even mobile species, such as fish, that could conceivably display avoidance behaviour. The metal concentrations, often substantially below lethal doses, mean that individual mortality is too blunt a measure to allow assessment of “serious harm”. Commonly used cellular biomarkers of exposure in ecotoxicology include DNA damage using the Comet assay. True deep-sea ecotoxicological studies with fish are rare and to our knowledge, there are no published data or method optimizations for deep-sea fish. Coryphaenoides ssp. were collected during SMARTEX expedition 1 (Feb/Mar, 2023) to the Clarion Clipperton Zone (CCZ) in the Eastern Pacific Ocean using a baited trap deployed between 4580–4,732m depth for 24–48 h. Blood and gill tissue were removed and processed for the Comet assay. In order to reduce artefactual DNA damage from cryopreservation observed previously, two sets of samples were prepared: a cryopreservative (10% DMSO) was added to one set of samples and stored at −80 °C; the second set was used to perform a Comet assay within hours of collection. A custom-built gimble table enabled horizontal electrophoresis at sea after which Comet assay slides were dried and stored at room temperature until further analysis. The Comet assay was also assessed in freshly sampled and frozen rainbow trout cells as a proxy control in order to evaluate potential artefacts from the collection and sampling procedure of the deep-sea fish. The blood samples processed at sea had a significantly reduced level of DNA damage compared to the frozen samples. There was no significant difference between the fresh deep-sea and rainbow trout samples. However, the freshly prepared gill samples in Coryphaenoides ssp. showed substantial artefacts, possibly as a consequence of barotrauma. These results represent the first effort at establishing baseline DNA damage data for deep-sea fish, an essential component in understating and quantifying the impact of deep-sea mining.

Different Responses of Histology, Antioxidant, and Inflammation in Gill and Kidney of Yellow Catfish Pelteobagrus fulvidraco under Three Dietary Fat Levels

This experiment investigated the influences of different dietary fat levels on histology, oxidative status, and immune response in gill and kidney of yellow catfish (Pelteobagrus fulvidraco). Three diets with different fat levels of 63.1 g/kg (low-fat, LF), 93.3 g/kg (medium-fat, MF), and 153.2 g/kg (high-fat, HF) were prepared to feed yellow catfish. The experiment continued for 56 days, and at the end of the experiment, gill and kidney tissues were sampled. As a result, both gill and kidney showed different degrees of tissue damage in HF group in terms of histology observation. HF increased the malondialdehyde content in gill but showed no effect on kidney, indicating that gill is more susceptible to injury than kidney under high-energy intake conditions. Additionally, HF diet significantly increased the activities of total-superoxide dismutase and catalase to eliminate excess peroxides both in gill and kidney. Moreover, HF diet significantly upregulated the expressions of pro-inflammatory cytokines (il6 and tnfα) and downregulated the expression of anti-inflammatory cytokines (il10), indicating that HF-diet-induced inflammatory response both in gill and kidney. These findings reveal the potential regulatory approach for fish gill and kidney health by dietary fat level, which will help to understand the adverse impacts of dietary lipid imbalance on the health of fish.

A newly discovered trematode parasite infecting the bay scallop, Argopecten irradians

A novel parasite infecting the gill tissue of bay scallops (Argopecten irradians) was first observed in North Carolina in 2012 and has also been found infecting bay scallop populations along the Gulf Coast of Florida. Because the parasite infects a host of great fisheries interest and is extremely conspicuous to the naked eye, and yet was not observed before 2012, it is likely an introduced species. Preliminary morphological analyses indicate that this parasite is a trematode in the superfamily Hemiuroidea and that it uses the bay scallop as a first intermediate host. All other hosts are currently unknown. Phylogenetic analyses show that this novel parasite belongs to family Didymozoidae and forms a strongly supported clade with a recently described trematode from Australia, Saccularina magnacetabula. Histological analysis indicates that Saccularina sp. sporocysts inhabit and greatly expand the afferent vessels of the host's gills. Prevalence monitoring of Saccularina sp. in caged and wild bay scallop populations in North Carolina shows a strong pattern of seasonality that is consistent across sites, but no latitudinal gradient was found, suggesting that prevalence is likely driven by final host distribution in time and space. This research provides important baseline information on the basic biology of Saccularina sp. and impacts on its economically important host, the bay scallop.

Characterization of a novel immune deficiency gene of Macrobrachium rosenbergii reveals antibacterial and antiviral defenses.

We sought to identify and characterize an immune deficiency (IMD) homolog from the giant freshwater prawn (also known as the giant river prawn) Macrobrachium rosenbergii. The IMD is a death-domain-containing protein that plays a crucial role as an adaptor protein in the IMD pathway-one of the most important response mechanisms to viral and bacterial invasion of invertebrates. An IMD homolog gene from M. rosenbergii (MrIMD) was isolated using rapid amplification of complementary DNA ends. The tissue distribution and response to immune challenge of MrIMD were analyzed by real-time reverse transcription polymerase chain reaction to understand the regulatory mechanism of MrIMD messenger RNA (mRNA) expression in M. rosenbergii. The open reading frame of MrIMD comprised 555 nucleotides encoding a protein consisting of 184 amino acids, with a conserved death domain at the C-terminus. The MrIMD protein demonstrated 53-74% similarity with IMDs from other crustaceans; the highest similarity was with the IMD from the oriental river prawn M. nipponense. Gene expression analysis revealed that MrIMD mRNA levels were highest in gill tissues. After Aeromonas hydrophila stimulation, MrIMD was significantly upregulated in the muscle, gills, and intestine, whereas there was no significant difference in the hemocytes and hepatopancreas. In the case of Macrobrachium rosenbergii nodavirus stimulation, MrIMD was dramatically upregulated in the muscle and hepatopancreas, whereas downregulation was observed in the gills. These results suggest that the MrIMD gene may play different roles in response to gram-negative bacteria and viral infection and plays a crucial role in innate immunity as an important key molecule in the defense against bacterial and viral infections.

Influence of heat shock protein 90 on the replication of spring viremia of carp virus

Spring viremia of the carp virus (SVCV) infection leads to a lethal acute hemorrhagic viral illness that causes substantial damage to the global aquaculture industry. Heat shock protein 90 (HSP90) is a highly conserved ATP-dependent molecular chaperone that plays important roles with intracellular proteins. Currently, little is known about the effect of HSP90 on SVCV replication. Therefore, in this study, we examined the transcription and expression levels of HSP90 in various organs of Cyprinus carpio var. Jian fish, including the brain, spleen, kidneys, liver, intestine, gills, heart, eyes, and muscles. We found that HSP90 was expressed at the highest levels in the liver, intestine, and gills and at the lowest levels in the spleen, eyes, and muscles. The SVCV-G and HSP90 levels in kidney, spleen, liver, and gill tissues peaked on day 3 following SVCV infection. We also constructed a recombinant HSP90 plasmid and demonstrated HSP90 overexpression in Epithelioma papulosum cyprinid (EPC) cells, using Pcs2 + 8CmCherry vector as a negative control. Laser confocal microscopy demonstrated that HSP90 was present in the cytoplasm of EPC cells. HSP90 expression gradually increased in EPC cells as the SVCV infection progressed. To gain insight into the influence of HSP90 on SVCV infection and its interconnectedness, we assessed apoptosis and immune gene expression by overexpressing and silencing HSP90. EPC cells infected with SVCV and overexpressing HSP90 showed considerably higher apoptosis, mortality, and IRF3 and IRF7 expression that EPC cells that were subjected to SVCV infection alone. HSP90 suppression increased the ability of cells to survive. Our initial investigation into the involvement of HSP90 in SVCV infection offers valuable insights. In addition, our findings offer novel approaches and techniques for constructing efficient systems to prevent and treat viral infections.

The Effect of Short-Term Artificial Feed Domestication on the Expression of Oxidative-Stress-Related Genes and Antioxidant Capacity in the Liver and Gill Tissues of Mandarin Fish (Siniperca chuatsi).

To investigate whether Mandarin fish developed oxidative stress after being domesticated with artificial feed, we conducted a series of experiments. Oxidative stress is an important factor leading to diseases and aging in the body. The liver integrates functions such as digestion, metabolism, detoxification, coagulation, and immune regulation, while the gills are important respiratory organs that are sensitive to changes in the water environment. Therefore, we used the liver and gills of Mandarin fish as research materials. The aim of this study was to investigate the effects of short-term artificial feed domestication on the expression of oxidative stress genes and the changes in oxidative-stress-related enzyme activity in the liver and gills of Mandarin fish. We divided the Mandarin fish into two groups for treatment. The control group was fed with live bait continuously for 14 days, while the experimental group was fed with half artificial feed and half live bait from 0 to 7 days (T-7 d), followed by solely artificial feed from 7 to 14 days (T-14 d). The experimental results showed that there was no difference in the body weight, length, and standard growth rate of the Mandarin fish between the two groups of treatments; after two treatments, there were differences in the expression of genes related to oxidative stress in the gills (keap1, kappa, gsta, gstt1, gstk1, SOD, and CAT) and in the liver (GPx, keap1, kappa, gsta, gstt1, gr, and SOD). In the liver, GPx activity and the content of MDA were significantly upregulated after 7 days of domestication, while in the gills, SOD activity was significantly upregulated after 7 days of domestication and GPx activity was significantly downregulated after 14 days of domestication. These results suggest that artificial feed domestication is associated with oxidative stress. Moreover, these results provide experimental basic data for increasing the production of aquaculture feed for Mandarin fish.

Transcriptomic WGCNA analyses reveal endoplasmic reticulum response of Patinopecten yessoensis under acute heat stress

Patinopecten yessoensis is one of the most important aquaculture shellfish worldwide. As a cold-water species, the increasing seawater temperatures due to global warming have been a great challenge for P. yessoensis. Understanding the response mechanism of P. yessoensis to high temperatures is essential to the genetic breeding of heat-tolerant varieties. In this study, histological, cytological and transcriptomic analyses were performed on the gill tissues of P. yessoensis under different acute heat stresses (temperature: 22 °C, 25 °C, 28 °C; time: 6 h, 36 h). A total of 10,601 differentially expressed genes (DEGs) were detected, among which, 141 DEGs were shared by all heat-stressed groups. Weighted gene co-expression network analysis (WGCNA) identified three modules (M1, M2 and M3) that were significantly correlated with heat stress. Functional enrichment analysis revealed that heat stress probably caused serious endoplasmic reticulum (ER) stress in gill cells, with many associated GO terms and KEGG pathways markedly enriched. Notably, the protein processing in ER pathway probably played a key role in the response to heat stress; this pathway was upregulated and was the most enriched in all heat-stressed groups, as well as in the M1 and M2 modules. DEGs from this pathway participated in different processes of the ER stress response, alleviating ER stress by upregulating the protein correct folding, ER-associated degradation (ERAD) and unfolded protein response (UPR) processes. Excessive ER stress induced apoptosis via the UPR, and excessive apoptosis resulted in tissue injury as observed by histological and TUNEL assays. Further, numerous Hsps were upregulated in all heat-stressed groups, and some members were identified as hub genes, including BiP, NEF, Hsp70 and Hsp90. These genes may perform crucial functions during heat stress as molecular chaperones. This study elucidates the key molecular components of the ER stress response to heat stress in scallops. The findings provide new insights into the adaptation mechanisms of molluscs to environmental stress.

Comprehensive analysis of histophysiology, transcriptome and metabolome tolerance mechanisms in black porgy (Acanthopagrus schlegelii) under low temperature stress

Low temperature stress has adverse effects on fish growth and reproduction, causing huge economic losses to the aquaculture industry. Especially, black porgy (Acanthopagrus schlegelii) farming industry in north of Yangtze River has been severely affected by low temperature for a long time. To explore the tolerance mechanism of black porgy to low temperature stress, the experiment was designed. The liver and gill tissues of black porgy were taken from the water temperature point of 15 °C (control group named as CG), 3.8 °C (cold sensitive group named as CS) and 2.8 °C (cold tolerant group named as CT) with a cooling rate of 3 °C/d from 15 °C for histophysiology, transcriptomics and metabolomics analysis. After cold stress, the histological results showed that the nucleus of the black porgy liver tissue appeared swelling, the cell arrangement was disordered; meanwhile the gill lamellae were twisted and broken, the epidermis was detached and aneurysm appeared. In addition, the expression of antioxidant, glucose metabolism and immune-related enzymes in the liver and gill of black porgy also changed significantly after low temperature stress. By analyzing the transcriptome and metabolome dates of black porgy liver, 3474 differentially expressed genes (DEGs) and 689 differentially expressed metabolites (DEMs) involved in low temperature stress were identified, respectively. The results of the transcriptome and metabolome combined analysis showed that individuals in the CS group mainly supplied energy to the body through lipid metabolism and amino acid metabolism, and meanwhile the apoptosis pathway was activated. While, individuals in the CT group mainly through glucose metabolism and steroid hormone biosynthesis to supply energy for the body. The validation results of qPCR on eight functional genes further demonstrated the reliability of RNA-Seq data. In summary, the results provide molecular information about adaptation to climate change and genetic selection of black porgy.

Metal nanoparticle-induced effects on green toads (Amphibia, Anura) under climate change: conservation implications.

The toxicity of aluminum oxide (Al2O3), copper oxide (CuO), iron oxide (Fe3O4), nickel oxide (NiO), zinc oxide (ZnO), and titanium dioxide (TiO2) nanoparticles (NPs) on amphibians and their interaction with high temperatures, remain unknown. In this study, we investigated the survival, developmental, behavioral, and histological reactions of Bufotes viridis embryos and larvae exposed to different NPs for a duration of 10 days, using lethal concentrations (LC25%, LC50%, and LC75% mg/L) under both ambient (AT: 18 °C) and high (HT: 21 °C) temperatures. Based on LC, NiONPs > ZnONPs > CuONPs > Al2O3NPs > TiO2NPs > Fe3O4NPs showed the highest mortality at AT. A similar pattern was observed at HT, although mortality occurred at lower concentrations and Fe3O4NPs were more toxic than TiO2NPs. The results indicated that increasing concentrations of NPs significantly reduced hatching rates, except for TiO2NPs. Survival rates decreased, abnormality rates increased, and developmental processes slowed down, particularly for NiONPs and ZnONPs, under HT conditions. However, exposure to low concentrations of Fe3O4NPs for up to 7 days, CuONPs for up to 72 h, and NiO, ZnONPs, and TiO2NPs for up to 96 h did not have a negative impact on survival compared with the control group under AT. In behavioral tests with larvae, NPs generally induced hypoactivity at AT and hyperactivity at HT. Histological findings revealed liver and internal gill tissue lesions, and an increase in the number of melanomacrophage centers at HT. These results suggest that global warming may exacerbate the toxicity of metal oxide NPs to amphibians, emphasizing the need for further research and conservation efforts in this context.

Evaluation of the health of Mediterranean mussels (Mytilus galloprovincialis Lamarck, 1819) distributed in the Çanakkale strait, Turkey

The observation of mortality in Mediterranean mussels (Mytilus galloprovincialis) distributed in the Çanakkale Strait in recent years was influential in developing the research question for this study. In this study, the presence of bacteria (Vibrio spp.) and parasites (Marteilia spp. and Haplosporidium spp.) in mussels collected from Kumkale, Kepez, and Umurbey stations in the Çanakkale Strait was investigated seasonally. Microbiological findings, histopathology, oxidative stress enzymes and their gene expressions, lipid peroxidation, lysosomal membrane stability, and changes in haemolymph were examined. In summer samples, both the defence system and the extent of damage were higher in gill tissue. In winter samples, enzyme activities and lipid peroxidation were found to be predominantly higher in digestive gland tissues. Histological examinations and Hemacolor staining revealed the presence of protozoan cysts, and for bacterial examination, molecular analysis performed after culturing revealed the presence of 7 Vibrio species. While the total numbers of heterotrophic bacteria detected in all samples were at acceptable levels, the predominance of Vibrio spp. numbers among the total heterotrophic bacteria detected in almost all samples were noteworthy. The total hemocyte count was calculated as 5.810(4)±0.58 (cells/mm3) in winter and 7.210(4)±1.03 (cells/mm3) in summer. These factors are considered to be possible causes of mussel mortality.

Effects of dietary garlic (Allium sativum) oil on growth performance, haemato-biochemical and histopathology of cypermethrin-intoxicated Nile tilapia (Oreochromis niloticus).

When pesticides are introduced into wetlands by agriculture, fish quickly absorb them through their gills. Pesticides reduce hatchability, impede growth, and antioxidant response, killing fish. Therefore, it's crucial to find effective pesticide mitigation methods for fish. In this study, the effects of garlic (Allium sativum) oil on the growth, haematology, biochemistry and histopathology parameters of Nile tilapia (Oreochromis niloticus) exposed to cypermethrin toxicity were investigated. In the research, cypermethrin was added to the water of the experimental groups at a rate of 1:20 of the LC50 value, and 1.00% garlic oil was added to the fish feed. Fish with an initial weight of 30.26 ± 0.26g were fed for 45 days. At the end of feeding, the final weights were determined as 69.39 ± 0.41 (G1), 61.81 ± 0.65 (G2), 82.25 ± 0.36 (G3), and 75.04 ± 0.68 (G4) grams, respectively. Histopathological examinations revealed serious lesions in the gill, liver, brain, and muscle tissues in the cypermethrin group, whereas these lesions were minimal or absent in the garlic oil group. Garlic oil supplementation had positive effects on growth, haematology, blood biochemistry, hepatosomatic index and histopathological parameters. These findings suggest that garlic oil is a potential protective agent against cypermethrin toxicity.

The osmoregulatory mechanism in response to hypoosmotic stress and the key role of ABCC1 in osmoregulation in the mud crab, Scylla paramamosain

Scylla paramamosain is an important mariculture animal. In the present study, we examined the physiological and biochemical characteristics of juvenile S. paramamosain under hypoosmotic stress and further verified the function of ABCC1, a key transport protein in gill tissue. The results showed that Na+/K+-ATPase, Ca2+-ATPase, and Na+/K+/2Cl- cotransporter in gill tissues increased first and then decreased. In addition, SOD and CAT activities also began to gradually increase, protecting gill tissues from oxidative damage. The hemolymph osmolarity decreased rapidly from 792 mOsm/kg to 560 mOsm/kg within 6 h, and then rose to 626.25 mOsm/kg at 48 h, and then remained stable. At the same time, Na+, Cl-, K+, and Ca2+ concentrations were decreased to varying degrees. There were significant changes in free amino acids such as aspartic acid, glutamic acid, and asparagine in hemolymph in response to acute salt depletion. By injection of ABCC1 inhibitor/activator, it was found that while ABCC1 transporter activity in the MK-571 group showed a decreasing trend at 9 h, Na+/K+ -ATPase activity began to increase and reached a peak at 48 h. Compared with the control group, the levels of aspartic acid, glutamic acid, asparagine, glycine, arginine, alanine, lysine, and proline in the MK-571 group showed significant differences at 6 h; Significant differences in glutamate, asparagine, arginine, alanine, lysine, and proline appeared at 12 h in the Thiethylperazine group. These results suggested that the dynamic changes of gill ion transport enzymes, antioxidant enzymes, inorganic ions, and free amino acids in hemolymph occurred in S. paramamosain under hypoosmotic stress, and the ABCC1 transporter played an important role in this regulatory process.

Assessing the negative impact of chlorantraniliprole, isoxaflutole, and simazine pesticides on phospholipid membrane models and tilapia gill tissues

The indiscriminate and, very often, incorrect use of pesticides in Brazil, as well as in other countries, results in severe levels of environmental pollution and intoxication of human life. Herein, we studied plasma membrane models (monolayer and bilayer) of the phospholipid Dioleoyl-sn-glycerol-3-phosphocholine (DOPC) using Langmuir films, and large (LUVs) and giant (GUVs) unilamellar vesicles, to determine the effect of the pesticides chlorantraniliprole (CLTP), isoxaflutole (ISF), and simazine (SMZ), used in sugarcane. CLTP affects the lipid organization of the bioinspired models of DOPC π-A isotherms, while ISF and SMZ pesticides significantly affect the LUVs and GUVs. Furthermore, the in vivo study of the gill tissue in fish in the presence of pesticides (2.0 × 10−10 mol/L for CLTP, 8.3 × 10−9 mol/L for ISF, and SMZ at 9.9 × 10−9 mol/L) was performed using optical and fluorescence images. This investigation was motivated by the gill lipid membranes, which are vital for regulating transporter activity through transmembrane proteins, crucial for maintaining ionic balance in fish gills. In this way, the presence of phospholipids in gills offers a model for understanding their effects on fish health. Histological results show that exposure to CLTP, ISF, and SMZ may interfere with vital gill functions, leading to respiratory disorders and osmoregulation dysfunction. The results indicate that exposure to pesticides caused severe morphological alterations in fish, which could be correlated with their impact on the bioinspired membrane models. Moreover, the effect does not depend on the exposure period (24h and 96h), showing that animals exposed to pesticides for a short period suffer irreparable damage to gill tissue. In summary, we can conclude that the harm caused by pesticides, both in membrane models and in fish gills, occurs due to contamination of the aquatic system with pesticides. Therefore, water quality is vital for the preservation of ecosystems.

Effect of Rutin on the Behavioural, Biochemical and Liver Morphological Changes in Danio Rerio Exposed to Reduced Graphene Oxide (Rgo) Nanoparticles

ABSTRACT: Reduced graphene oxide (rGO) is a carbon nanomaterial with unique characteristics that permit application in numerous fields. Rutin is a flavonoid with a variety of biological functions and pharmaceutical applications. In topical years, a handful of research has stated on the environmental impacts of carbon nanoparticles (NPs) and the consequences of reduced graphene oxide on the species that live in water bodies. However, the capacity to recuperate after exposure is still mostly unfamiliar. This study analyzed the protective effect of rutin against rGO NPs in zebrafish and the optimal dose required to inverse the impairment caused by rGO NPs exposure in zebrafish. In this study, fish were treated for 14 days and 8 study groups were examined: control, rGO exposure alone (10 mg/L), rutin exposure alone (50, 100 and 200 mg/L) and rGO combined with 3 distinct rutin doses (10 mg/L of rGO + rutin 50, 100, and 200 mg/L). In the zebrafish gill tissues, rGO impairs cells by increasing LPO levels and inducing oxidative stress by suppressing antioxidants (SOD, CAT, GPx, GSH, GR, GST, and vitamin C). Multiple alterations, including sinusoidal and venous congestion, vacuole formation or cytoplasmic vacuolation of hepatocytes, an enlarged hepatic plate gap, and necrosis, were revealed on the structural examination of liver tissues. Based on our results, we conclude that sub-lethal doses of rGO (10 mg/L) could be harmful to zebrafish. Rutin supplementation between 100 and 200 mg/L can protect against the toxic effects of rGO, even though rGO is detrimental to the exposed fish population.

Differentially expressed genes involved in immune pathways following Vibro parahaemolyticus challenge: A study on red swamp crayfish Procambarus clarkii

This study conducted a comprehensive analysis of the damage mechanism of Vibrio parahaemolyticus (V. parahaemolyticus) on crayfish, utilizing pathological section observations, biochemical indicator detection, and transcriptomics analysis. Histopathological examination showed fragmentation of the gill lamellae, spotted pigment deposition on the branchial membrane, degeneration of epithelial cells, and disruption of the normal structure of gill tissues. Biochemical tests indicated a significant decrease in the activity of antioxidant-related enzymes in crayfish injected with V. parahaemolyticus compared with the phosphate-buffered saline group. Transcriptomics analysis identified 2307 upregulated and 1721 downregulated differentially expressed genes (DEGs). Gene ontology enrichment analysis highlighted that DEGs were primarily involved in the regulation of lipid metabolic processes, cellular nitrogen compound biosynthesis and metabolic processes, and the negative regulation of neuron death. Kyoto Encyclopedia of Genes and Genomes pathway analysis revealed significant enrichment in N-glycan biosynthesis, fatty acid metabolism, and the mTOR signaling pathway. Gene set enrichment analysis indicated pathways related to immunity and oxidative stress, including oxidative phosphorylation and tyrosine metabolism. Quantitative reverse transcription–polymerase chain reaction results for selected genes involved in the oxidative phosphorylation pathway and immune-related genes corroborated the RNA-Seq trends, confirming the transcriptomics data's reliability. The findings suggest that infection with V. parahaemolyticus leads to excessive oxidative stress due to bacterial proliferation, overwhelming the crayfish's antioxidative defense. This causes a continuous increase in reactive oxygen species levels, leading to irreversible damage to the oxidative phosphorylation and innate immune systems. This study elucidated the mechanism of oxidative stress damage in crayfish following V. parahaemolyticus infection, providing valuable insights for reducing bacterial and viral diseases in aquaculture. A deeper understanding of pathogen affects the physiology and immune systems of aquatic organisms can help develop more effective prevention and control strategies, thereby improving the efficiency and sustainability of aquaculture.

Effects of different temperatures on Leiocassis longirostris gill structure and intestinal microbial composition

Fish are poikilothermic vertebrates and their physiological activities are affected by water temperature. In recent years, extreme weather has occurred frequently, and temperature changes have adversely affected the growth of farmed fish. To explore the changes in gill tissue structure caused by changing the water temperature and the relationship between the intestinal microbiota and the Leiocassis longirostris host adaptation mechanism, gill tissue sections and intestinal microbial 16S rRNA amplicon sequencing were conducted under different temperature stress (low temperature 4 °C, normal temperature 26 °C and high temperature 32 °C). The results showed that heat stress and cold stress caused injury and swelling, terminal congestion, cell vacuolation, and necrosis of the gill tissue of L. longirostris. For intestinal microbiota, the abundances of Pseudomonadota and Bacillota increased at the cold stress, while the abundances of Fusobacteriota and Bacteroidota increased at the heat stress. The number of opportunistic bacteria, mainly Aeromonas and Acinetobacter, was the highest under cold stress. In addition, the richness of the intestinal microbiota decreased significantly at heat and cold stresses, while evenness increased. Prediction of intestinal microbiota function showed that most common functions, such as metabolism of cofactors and vitamins, energy metabolism and replication and repair, were decreased significantly at heat stress and cold stress, and phylogenetic relationship analysis revealed significant differences among the groups. In conclusion, the change of temperature altered the gill tissue structure, and affected the structure and homeostasis of the intestinal microbiota, thus affecting the survival time of L. longirostris, and cold stress had a greater effect than heat stress.

Rapid altitude displacement induce zebrafish appearing acute high altitude illness symptoms

Rapid ascent to high-altitude areas above 2500 m often leads to acute high altitude illness (AHAI), posing significant health risks. Current models for AHAI research are limited in their ability to accurately simulate the high-altitude environment for drug screening. Addressing this gap, a novel static self-assembled water vacuum transparent chamber was developed to induce AHAI in zebrafish. This study identified 6000 m for 2 h as the optimal condition for AHAI induction in zebrafish. Under these conditions, notable behavioral changes including slow movement, abnormal exploration behavior and static behavior in the Novel tank test. Furthermore, this model demonstrated changes in oxidative stress-related markers included increased levels of malondialdehyde, decreased levels of glutathione, decreased activities of superoxide dismutase and catalase, and increased levels of inflammatory markers IL-6, IL-1β and TNF-α, and inflammatory cell infiltration and mild edema in the gill tissue, mirroring the clinical pathophysiology observed in AHAI patients. This innovative zebrafish model not only offers a more accurate representation of the high-altitude environment but also provides a high-throughput platform for AHAI drug discovery and pathogenesis research.

The Influence of Triphenyltin Exposure on the Osmoregulatory Capacity of Marine Medaka (Oryzias melastigma) at Different Salinities

Triphenyltin (TPT) is an organotin pollutant widely found in the aquatic environment. It has endocrine-disrupting and osmotic pressure toxicity. In this study, the physiological and biochemical effects of TPT and various salinities were investigated in different tissues (gut, gill, and brain) of marine medaka. The exposure experiments were conducted for 42 days in different salinities (0, 15, and 30 ppt) without TPT exposure and in different salinity groups with TPT exposure concentrations of 100 ng/L, respectively. The results showed that the Na+-K+-ATPase (NKA) and Ca2+ATPase activity had significant tissue-specific differences, with the highest activity observed in the gills, indicating their major contribution to osmoregulation. Changes in salinity also resulted in significant alterations in the ion concentrations of the gut and gill tissues in the 0-C and 15-C groups. While the changes in Na+ and Cl− were relatively stable, the presence of TPT disrupted the regulation of Ca2+ and K+. In conclusion, substantial variations were observed in the osmoregulatory capacity of marine medaka tissues. Environmental concentrations of TPT had little effect on osmotic enzyme activity but interfered with the regulation of Ca2+ and K+ concentrations in the tissues. This study provides valuable insights into the osmotic toxicity of TPT in aquatic environments with different salinities.

Effects of Microplastic Exposure against White Spot Syndrome Virus Infection in Pacific White Shrimp (Penaeus vannamei).

Plastic waste has emerged as a major environmental concern in recent years. As plastic waste discharged into the marine environment, it undergoes a breakdown process, eventually accumulating in aquatic organisms in the form of microplastics (MPs). To date, reduced food intake, nutritional absorption, and impaired immune system are known adverse effects of MPs-exposed aquatic organisms. This study aims to investigate whether MP exposure accelerated white spot syndrome virus (WSSV) infection in Pacific white shrimp (Penaeus vannamei) via laboratory tests. Briefly, experimental shrimp were divided into four groups; WSSV (group 1); MP (group 2); WSSV + MP (group 3); and Control (group 4). No mortality was observed in group 2, group 4, and even in group 1. However, group 3 showed a cumulative mortality of 50% during the experimental period. The PCR assay results showed no WSSV in the other three groups (groups 1, 2, and 4), but the dead and alive shrimp collected from group 3 were confirmed to be infected with the virus. Histopathological examination revealed normal structures in the hepatopancreas, gill, and muscle tissues of group 4, whereas numerous abnormally shaped nuclei were detected in the gill tissue of group 2. Moreover, group 1 showed minor WSSV-related lesions with few basophilic inclusion bodies in the gills, interestingly, group 3 exhibited severe lesions with numerous basophilic inclusion bodies in the gills. In conclusion, this study confirmed the correlation between the viral disease of shrimp and MPs, which can cause significant economic losses to the shrimp aquaculture industry.