Histopathological Evaluation of Tissue Specific Responses of Subacute Clothianidin Administration in Oncorhynchus mykiss

Clothianidin, one of the latest members of neonicotinoids, is a systemic insecticide of the neonicotinoid group that affects the central nervous system by acting as a nicotinic acetylcholine receptor agonist. Although it is stated that it has no dangerous potential for aquatic organisms, accumulation in water basins is important in terms of environmental toxicity. In this study, the histopathological changes caused by clothianidin applied in subacute application (7 days) form and in environmental doses (3, 15 and 30 µg/L) in the brain, kidney, muscle and gill tissue of juvenile Oncorhynchus mykiss were determined. Parallel to the administration of increasing doses of clothianidin, an increase in the severity of pathological lesions is observed in the brain, muscle, kidney and gill tissue. In particular, it shows that as a result of the accumulation of pesticides in aquatic organisms, lesions may develop as tissue-specific responses, thus leading to tissue dysfunction.

Effects of Melissa officinalis L. Essential Oil in Comparison with Anaesthetics on Gill Tissue Damage, liver metabolism and Immune Parameters in Sea Bass (Lateolabrax maculatus) during Simulated live Transport

In the current study, Melissa officinalis L. essential oil (MOEO), a novel sedative and anaesthetic, was employed in transport water to obtain a lower stress effect and higher survival rate for live marine fish. The effect of MOEO and various types of anaesthetics, administered at a low temperature on gill morphology, liver function and immunological parameters of living sea bass (Lateolabrax maculatus) subjected to transport stress, was evaluated to optimize the anaesthetic and sedative concentrations during live sea bass transport. Light microscopy and scanning electron microscopy of sea bass, subjected to simulated live transport for 72 h, demonstrated that the changes in the morphological characteristics of gill tissue treated with 40 mg/L MOEO (A3 group) were minimal in comparison to those observed in untreated sea bass. The results of pyruvate kinase (PK), phosphofructokinase (PFK), hexokinase (HK), hepatic glycogen (Gly), superoxide dismutase (SOD), lipid peroxides (MDA) and Caspase-3 assays indicated that the glycolysis rate, energy consumption, lipid peroxidation and hepatocyte apoptosis were the lowest in the A3 group. The values of the two immune parameters, lysozyme (LZM) and fish immunoglobulin M (IgM), indicated the strongest immunity ability in the A3 group. After 12 h recovery, sea bass treated with 30 mg/L MS-222 (B group) displayed a 100% survival rate, sea bass treated with 20 mg/L (A2 group) and 40 mg/L (A3 group) MOEO displayed a 96% survival rate, sea bass treated with 20 mg/L eugenol (C group) had a 94% survival rate, and untreated sea bass (CK group) had a 50% survival rate. Therefore, the addition MOEO to the transport water had anaesthetic and sedative effects similar to MS-222 and eugenol. The results confirmed that the addition of MOEO to the transport water could reduce tissue damage, energy metabolism, and the oxidative stress response in sea bass during transport.

Gill Transcriptomic Responses to Toxin-producing Alga Prymnesium parvum in Rainbow Trout

The gill of teleost fish is a multifunctional organ involved in many physiological processes, including protection of the mucosal gill surface against pathogens and other environmental antigens by the gill-associated lymphoid tissue (GIALT). Climate change associated phenomena, such as increasing frequency and magnitude of harmful algal blooms (HABs) put extra strain on gill function, contributing to enhanced fish mortality and fish kills. However, the molecular basis of the HAB-induced gill injury remains largely unknown due to the lack of high-throughput transcriptomic studies performed on teleost fish in laboratory conditions. We used juvenile rainbow trout (Oncorhynchus mykiss) to investigate the transcriptomic responses of the gill tissue to two (high and low) sublethal densities of the toxin-producing alga Prymnesium parvum, in relation to non-exposed control fish. The exposure time to P. parvum (4–5 h) was sufficient to identify three different phenotypic responses among the exposed fish, enabling us to focus on the common gill transcriptomic responses to P. parvum that were independent of dose and phenotype. The inspection of common differentially expressed genes (DEGs), canonical pathways, upstream regulators and downstream effects pointed towards P. parvum-induced inflammatory response and gill inflammation driven by alterations of Acute Phase Response Signalling, IL-6 Signalling, IL-10 Signalling, Role of PKR in Interferon Induction and Antiviral Response, IL-8 Signalling and IL-17 Signalling pathways. While we could not determine if the inferred gill inflammation was progressing or resolving, our study clearly suggests that P. parvum blooms may contribute to the serious gill disorders in fish. By providing insights into the gill transcriptomic responses to toxin-producing P. parvum in teleost fish, our research opens new avenues for investigating how to monitor and mitigate toxicity of HABs before they become lethal.

RNA-seq and Analysis of Argyrosomus japonicus Under Different Salinities

Salinity variation affects the physiological processes of fish. This study analyzed the transcriptome of the gill tissue of Argyrosomus japonicus to determine the significantly differentially expressed genes (DEGs) of A. japonicus under salinity changes. Transcriptome analysis of nine samples yielded 55.873 Gb of clean data, 64,912 transcripts, and 29,567 unigenes, and 83.62% of the transcripts and 81.89% of the unigenes were annotated. Compared with the control group, the high- and low-salt groups showed 1,731 and 695 DEGs, respectively. Gene Ontology enrichment analysis revealed that the DEGs were significantly enriched in transportation, metabolism, and stress response. Kyoto Encyclopedia of Genes and Genomes pathway enrichment revealed that the DEGs were significantly enriched in some signaling pathways. Several key genes (KRT1, KRT2, ATP1A, LDH, PFN, ACTB_G1, TUBB, GZMB, MHC2, CCL19, EPX, ANXA5, ACBP, EHF, BHMT, COL1A, and RHOA) were related to salinity adaptation. When environmental salinity fluctuated, genes related to stress, immunity, ion transport, and metabolism became more sensitive. These results suggest that the adaptation of A. japonicus under salinity changes is a complex process that involves multiple genes acting together.

Effect of Berberine Hydrochloride Treatment on Transcriptomic Response in Gill Tissue of Charybdis japonica Infected With Aeromonas hydrophila

Berberine hydrochloride is the main active ingredient of Coptis chinensis, which has demonstrated significant antibacterial activity against bacteria. However, the molecular mechanism underlying its effects is unclear in crabs. In this study, we used transcriptome sequencing to investigate the molecules involved in the therapeutic and defensive responses of Charybdis japonica infected with 105 colony-forming units (CFU)/L of Aeromonas hydrophila following treatment with berberine hydrochloride. A total of 5,409 differentially expressed genes were observed after exposure of C. japonicus for 72 h to 100 mg/L berberine hydrochloride, 100 mg/L berberine hydrochloride plus injection of 105 CFU/L A. hydrophila, and a control group injected with equal amount of physiological saline solution. Enrichment analysis revealed that these genes were involved in metabolism, cellular processes, signal transduction, and immune function. The transcriptomic results indicated that exposure to berberine hydrochloride activated glutathione metabolism, oxidative phosphorylation, fatty acid degradation, retinol metabolism, pyruvate metabolism, and the hypoxia-inducible factor 1 signaling pathway. Transcriptomic analysis and relative mRNA level analysis also identified acid hydrolase genes and phagosomal genes as key factors regulating the adaptation of acid berberine-infused C. japonicus to infection with A. hydrophila, Based on the ability of berberine hydrochloride to induce acid hydrolase and phagosomal gene expression, which can in turn remove bacteria, immersion in berberine hydrochloride may remove A. hydrophila and thus improve the survival of C. japonica. The results of this study provided a new scientific basis for the potential role of berberine hydrochloride in the immune mechanisms of crabs.

Sampling the fish gill microbiome: a comparison of tissue biopsies and swabs

Background Understanding the influence of methodology on results is an essential consideration in experimental design. In the expanding field of fish microbiology, many best practices and targeted techniques remain to be refined. This study aimed to compare microbial assemblages obtained from Atlantic salmon (Salmo salar) gills by swabbing versus biopsy excision. Results demonstrate the variation introduced by altered sampling strategies and enhance the available knowledge of the fish gill microbiome. Results The microbiome was sampled using swabs and biopsies from fish gills, with identical treatment of samples for 16S next generation Illumina sequencing. Results show a clear divergence in microbial communities obtained through the different sampling strategies, with swabbing consistently isolating a more diverse microbial consortia, and suffering less from the technical issue of host DNA contamination associated with biopsy use. Sequencing results from biopsy-derived extractions, however, hint at the potential for more cryptic localisation of some community members. Conclusions Overall, results demonstrate a divergence in the obtained microbial community when different sampling methodology is used. Swabbing appears a superior method for sampling the microbiota of mucosal surfaces for broad ecological research in fish, whilst biopsies might be best applied in exploration of communities beyond the reach of swabs, such as sub-surface and intracellular microbes, as well as in pathogen diagnosis. Most studies on the external microbial communities of aquatic organisms utilise swabbing for sample collection, likely due to convenience. Much of the ultrastructure of gill tissue in live fish is, however, potentially inaccessible to swabbing, meaning swabbing might fail to capture the full diversity of gill microbiota. This work therefore also provides valuable insight into partitioning of the gill microbiota, informing varied applications of different sampling methods in experimental design for future research.

Toxicity and Functional Tissue Responses of Two Freshwater Fish after Exposure to Polystyrene Microplastics

Microplastics (MPs)’ ingestion has been demonstrated in several aquatic organisms. This process may facilitate the hydrophobic waterborne pollutants or chemical additives transfer to biota. In the present study the suitability of a battery of biomarkers on oxidative stress, physiology, tissue function and metabolic profile was investigated for the early detection of adverse effects of 21-day exposure to polystyrene microplastics (PS-MPs, sized 5–12 μm) in the liver and gills of zebrafish Danio rerio and perch, Perca fluviatilis, both of which are freshwater fish species. An optical volume map representation of the zebrafish gill by Raman spectroscopy depicted 5 μm diameter PS-MP dispersed in the gill tissue. Concentrations of PS-MPs close to the EC50 of each fish affected fish physiology in all tissues studied. Increased levels of biomarkers of oxidative damage in exposed fish in relation to controls were observed, as well as activation of apoptosis and autophagy processes. Malondialdehyde (MDA), protein carbonyls and DNA damage responses differed with regard to the sensitivity of each tissue of each fish. In the toxicity cascade gills seemed to be more liable to respond to PS-MPs than liver for the majority of the parameters measured. DNA damage was the most susceptible biomarker exhibiting greater response in the liver of both species. The interaction between MPs and cellular components provoked metabolic alterations in the tissues studied, affecting mainly amino acids, nitrogen and energy metabolism. Toxicity was species and tissue specific, with specific biomarkers responding differently in gills and in liver. The fish species that seemed to be more susceptible to MPs at the conditions studied, was P. fluviatilis compared to D. rerio. The current findings add to a holistic approach for the identification of small sized PS-MPs’ biological effects in fish, thus aiming to provide evidence regarding PS-MPs’ environmental impact on wild fish populations and food safety and adequacy.

Molecular Expressions : Scanning Electron Microscope (SEM) in Gills of Cyprinus carpio Infected Myxobolus sp.

Highlight Research:It has been found that many fish died with wounds from farmers in Blitar, Indonesia.The mucosal smear test from mucosal gills of C. carpio infected with Myxobolus.In the blood smear test of C. carpio, there was no myxobolus found in the blood.In gill organ testing using SEM that Myxobolus is found in gills (C. carpio).The shape of Myxobolus resembles an imperfect ball with a hollow in the middle. AbstractThe biggest problem that is often considered to be an obstacle to Common carp culture is the emergence of disease attacks. One type of disease that often attacks the seeds of Cyprinus carpio is Myxobolus (a systemic parasite that can cause harm to fish farming). The aim of this study was to determine the molecular expression through the smear test on C. carpio gills, to determine the image of the gill organs of C. carpio using the SEM test, and to determine the description of the spores of Myxobolus sp. Data were analyzed using descriptive methods. Descriptive method used was comparative descriptive comparing molecular expression in the test of gill mucosal smear of fish using a light microscope and gill organ testing using Scanning Electron Microscope (SEM) on C. carpio infected by Myxobolus sp. In this study, the results showed that in C. carpio infected with true Myxobolus found the presence of Myxobolus in the mucosal smear test and SEM test on gill tissue, but not found in the blood smear test.