Gills Of Tilapia Research Articles

Immune Suppression and Rapid Invasion of Nile Tilapia Gills Following an Acute Challenge by Flavobacterium davisii

Flavobacterium davisii is one of the causative agents of columnaris disease, significantly impacting Nile tilapia aquaculture. This study examines the invasion and immune evasion mechanisms of a highly virulent F. davisii strain through transcriptomic profiling of tilapia gills following acute immersion. We identified 8192 differentially expressed genes (DEGs) at 2 h, 6 h, and 12 h post-infection. They are enriched in pathways related to oxidative stress, immune suppression, tissue necrosis, and bacterial infection. Notably, early overexpression of rhamnose-binding lectin and mucin genes facilitated bacterial adhesion. Key immune genes, including those encoding major histocompatibility complex (MHC), immunoglobulins (Ig), Toll-like receptors (TLRs), and chemokines, were downregulated, indicating immune suppression. Conversely, immune evasion genes such as Fc receptor-like (FcRL) and programmed death-ligand 1 (PDL1) were upregulated, along with genes associated with reactive oxygen species (ROS) production, leading to increased tissue damage. Additionally, the upregulation of fibroblast growth factor and collagen genes suggested active tissue repair. In conclusion, F. davisii rapidly invades its host by enhancing adhesion to gill tissues, suppressing immune function, and inducing tissue damage. These findings enhance our understanding of F. davisii infection mechanisms and support the future breeding of disease-resistant tilapia and the development of sustainable control strategies.

Alginate/CuO-gC3N4 composite: a novel, reusable, non-toxic photocatalyst for methylene blue degradation.

Increasing industrial contamination necessitates development of sustainable water treatment solutions. Photocatalysis is a green technology utilizing light-activated materials (photocatalysts), which can degrade pollutants into harmless by-products. It is an emergent need to develop a photocatalyst that presents a significant advancement for sustainable water treatment and non-toxic to the environment. This study investigates the photocatalytic activity and in vitro cytotoxicity of a novel hybrid material comprising of alginate, copper oxide (CuO) and graphitic carbon nitride (gC3N4) for methylene blue (MB) degradation. The hybrid material was synthesized by a two-step process: (i) doping of CuO on gC3N4 through co-precipitation method formed CuO-gC3N4 (CG) and (ii) incorporation of CG in the calcium alginate (A) by ionotropic gelation method that is named as ACG. The characteristic features of the synthesized A, CG and ACG were studied using Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD) and thermogravimetric analysis (TGA). The optical characteristic of A, CG and ACG was studied using UV-diffuse reflectance spectroscopy (UV-DRS). The morphology and elemental composition of ACG was evaluated by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS). To assess the environmental impact of ACG, a two-step approach was employed. First, the photocatalytic activity of ACG under UV-visible light (UV-vis) irradiation for MB degradation was evaluated. ACG exhibited photocatalytic activity by achieving 86.26% of degradation efficiency for MB within 60min. Second, the in vitro cytotoxicity of ACG, MB and MB degraded products towards tilapia gill cell lines were assessed. By comparing the toxicity of the MB and the secondary products, it is concluded that the overall process leads to a sustainable outcome.

Anti-parasitic activity of garlic (Allium sativum) and onion (Allium cepa) extracts against Dactylogyrus spp. (Monogenean) in Nile tilapia (Oreochromis niloticus): Hematology, immune response, histopathological investigation, and inflammatory cytokine genes of gills

BackgroundGills monogenean infestation causes significant mortalities in cultured fishes as a result of respiratory manifestation. Medicinal plants are currently being heavily emphasized in aquaculture due to their great nutritional, therapeutic, antimicrobial activities, and financial value.MethodsThe current study is designed to assess the effect of garlic (Allium sativum) and onion (Allium cepa) extracts as a water treatment on the hematological profile, innate immunity, and immune cytokines expression besides histopathological features of gills of Nile tilapia (Oreochromis niloticus L.) infected with gills monogenetic trematodes (Dactylogyrus sp.). Firstly, the 96-hour lethal concentration 50 (96 h-LC50) of garlic extract (GE) and onion extract (OE) were estimated to be 0.4 g/ L and 3.54 g/ L for GE and OE, respectively. Moreover, the in-vitro anti-parasitic potential for (GE) was found between 0.02 and 0.18 mg/mL and 0.4 to 1.8 mg/mL for OE. For the therapeutic trial, fish (n = 120; body weight: 40–60 g) were randomly distributed into four groups in triplicates (30 fish/group, 10 fish/replicate) for 3 days. Group1 (G1) was not infected or treated and served as control. G2 was infected with Dactylogyrus spp. and not exposed to any treatment. G3, G4 were infected with Dactylogyrus sp. and treated with 1/10 and 1/5 of 96 h LC50 of OE, respectively. G5, G6 were infected with Dactylogyrus sp. and treated with 1/10 and 1/5 of 96 h LC50 of GE, respectively.ResultsNo apparent signs or behaviors were noted in the control group. Dactylogyrus spp. infected group suffered from clinical signs as Pale color and damaged tissue. Dactylogyrus spp. infection induced lowering of the hematological (HB, MCH, MCHC and WBCs), and immunological variables (lysozyme, nitric oxide, serum Anti- protease activities, and complement 3). the expression of cytokine genes IL-ß and TNF-α were modulated and improved by treatment with A. sativum and A. cepa extracts. The obtained histopathological alterations of the gills of fish infected with (Dactylogyrus spp.) were hyperplasia leading to fusion of the gill filament, lifting of epithelial tissue, aneurism and edema. The results indecated that G4 and G5 is more regenarated epithelium in compare with the control group.ConclusionA. sativum and A. cepa extracts enhance the blood profile and nonspecific immune parameters, and down-regulated the expression level of (IL-1β and TNF-α).

Metal distribution in three organs and edibility assessment on Coptodon rendalli from the Umgeni River impacted by metallurgic industrial activities

Fish is among the most affordable and readily available protein sources for communities residing near water bodies. However, the recent pollution status of aquatic ecosystems has rendered fish consumption risky for human health. The study evaluated metal levels in the liver, gill, and muscle tissues of Redbreast tilapia (Coptodon rendalli) from Inanda and Nagle dams in the uMgeni River system. Metals, Al, Sb, Cd, Cr, Fe, Mn, Mo, Pb, and Zn were analysed using ICP-OES. Fish size showed no significant difference between the two dams (p > 0.05) whereas a descending trend liver > gill > muscle was observed for most metal levels at both dams. Moreover, there was a clear separation for metal levels in the liver, gill, and muscle between the two dams (p < 0.001) and a similar trend was observed for organs in each dam (p < 0.001). No relationship was observed between fish length and metal levels and no definite trend was observed for inter-metal relationships. Antimony, Cr, and Pb showed THQs greater than 1 at both dams which suggests health risks for consumers. Molybdenum has also shown a concerning THQs with some individuals exhibiting values ranging from 0.5 – 0.9. These findings suggest that consuming C. rendalli from the Inanda and Nagle dams could result in adverse health effects from Sb, Cr and Pb.

Heterogeneous bacterial communities in gills and intestine of Nile tilapia (Oreochromis niloticus) and in water and sediments of aquaculture ponds in Bangladesh

Tilapia aquaculture contributes significantly to the nutritional requirements of humans. Because microbes play a pivotal role in maintaining the host's physiology and biochemistry, research on the microbiomes associated with tilapia and in the rearing pond water and sediment can contribute to increased production. We applied 16S rRNA gene amplicon sequencing to elucidate the bacterial community structures in the gills and intestine of Nile tilapia as well as in the water and sediment of their rearing ponds. We identified a total of 9770 bacterial Operational Taxonomic Units (OTUs) in all the samples. The sediment samples, which generated 3884 unique OTUs, had the highest level of alpha-diversity (Shannon index, P < 0.01) among all the samples. Fusobacteria (59%) predominated and constituted the indicator phylum in tilapia gills, while Proteobacteria was prevailed in water (52%), sediment (28%), and intestine (33%). The bacterial community structures of the gills and intestine were not much similar to those of the surrounding water and sediment, probably due to host-specific microbial selection. More than 70% of the bacterial flora were beneficial, whereas nearly 10% were pathogenic in gills and intestine of tilapia. This study aims to explore the microbiome of tilapia aquaculture in Bangladesh, and the results suggest that the microbial communities in tilapia gills and intestine are in a eubiotic state, which indicates a healthy state for better growth and production of Nile tilapia aquaculture.

Bacterial community diversity, abundance, and composition of rearing water and red tilapia gills from open river cages and earthen ponds in Central Thailand

Bacterial community diversity, abundance, and composition of rearing water and red tilapia gills from open river cages and earthen ponds in Central Thailand

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.

Nanopore sequencing for identification and characterization of antimicrobial-resistant Escherichia coli and Salmonella spp. from tilapia and shrimp sold at wet markets in Dhaka, Bangladesh.

Wet markets in low-and middle-income countries are often reported to have inadequate sanitation resulting in fecal contamination of sold produce. Consumption of contaminated wet market-sourced foods has been linked to individual illness and disease outbreaks. This pilot study, conducted in two major wet markets in Dhaka city, Bangladesh during a 4-month period in 2021 aimed to assess the occurrence and characteristics of Escherichia coli and non-typhoidal Salmonella spp. (NTS) from tilapia (Oreochromis niloticus) and shrimp (Penaeus monodon). Fifty-four individuals of each species were collected. The identity of the bacterial isolates was confirmed by PCR and their susceptibility toward 15 antimicrobials was tested by disk diffusion. The whole genome of 15 E. coli and nine Salmonella spp. were sequenced using Oxford Nanopore Technology. E. coli was present in 60-74% of tilapia muscle tissue and 41-44% of shrimp muscle tissue. Salmonella spp. was found in skin (29%) and gills (26%) of tilapia, and occasionally in muscle and intestinal samples of shrimp. The E. coli had several Multilocus sequence typing and serotypes and limited antimicrobial resistance (AMR) determinants, such as point mutations on glpT and pmrB. One E. coli (BD17) from tilapia carried resistance genes for beta-lactams, quinolones, and tetracycline. All the E. coli belonged to commensal phylogroups B1 and A and showed no Shiga-toxin and other virulence genes, confirming their commensal non-pathogenic status. Among the Salmonella isolates, five belonged to Kentucky serovar and had similar AMR genes and phenotypic resistance patterns. Three strains of this serovar were ST198, often associated with human disease, carried the same resistance genes, and were genetically related to strains from the region. The two undetermined sequence types of S. Kentucky were distantly related and positioned in a separate phylogenetic clade. Two Brunei serovar isolates, one Augustenborg isolate, and one Hartford isolate showed different resistance profiles. This study revealed high fecal contamination levels in tilapia and shrimp sold at two main wet markets in Dhaka. Together with the occurrence of Salmonella spp., including S. Kentucky ST198, a well-known human pathogen, these results stress the need to improve hygienic practices and sanitation standards at markets to improve food safety and protect consumer health.

Uptake, tissue distribution, and biotransformation pattern of triclosan in tilapia exposed to environmentally-relevant concentrations

Although triclosan has been ubiquitously detected in aquatic environment and is known to have various adverse effects to fish, details on its uptake, bioconcentration, and elimination in fish tissues are still limited. This study investigated the uptake and elimination toxicokinetics, bioconcentration, and biotransformation potential of triclosan in Nile tilapia (Oreochromis niloticus) exposed to environmentally-relevant concentrations under semi-static regimes for 7 days. For toxicokinetics, triclosan reached a plateau concentration within 5-days of exposure, and decreased to stable concentration within 5 days of elimination. Approximately 50 % of triclosan was excreted by fish through feces, and up to 29 % of triclosan was excreted through the biliary excretion. For fish exposed to 200 ng·L−1, 2000 ng·L−1, and 20,000 ng·L−1, the bioconcentration factors (log BCFs) of triclosan in fish tissues obeyed similar order: bile ≈ intestine > gonad ≈ stomach > liver > kidney ≈ gill > skin ≈ plasma > brain > muscle. The log BCFs of triclosan in fish tissues are approximately maintained constants, no matter what triclosan concentrations in exposure water. Seven biotransformation products of triclosan, involved in both phase I and phase II metabolism, were identified in this study, which were produced through hydroxylation, bond cleavages, dichlorination, and sulfation pathways. Metabolite of triclosan-O-sulfate was detected in all tissues of tilapia, and more toxic product of 2,4-dichlorophenol was also found in intestine, gonad, and bile of tilapia. Meanwhile, two metabolites of 2,4-dichlorophenol-O-sulfate and monohydroxy-triclosan-O-sulfate were firstly discovered in the skin, liver, gill, intestine, gonad, and bile of tilapia in this study. These findings highlight the importance of considering triclosan biotransformation products in ecological assessment. They also provide a scientific basis for health risk evaluation of triclosan to humans, who are associated with dietary exposure through ingesting fish.

The characteristic of myxosporean infection in several organs of nile tilapia cultivation

The myxosporean is a parasite that frequently infects several fish organs, therefore it can be identified by histopathologically assessing the character of the infection in the infected organs. The present study was carried out to assess the infection of myxosporean (Myxobolus sp.) in nile tilapia cultivation by observing the histomorphological characteristic of several organs. Live Nile tilapia sample from Gresik cultivations immediately was done necropsy and observation on gill, intestine and liver. Histological preparation was made for the gills, liver and intestines and observed with HE staining. In the gills of nile tilapia, variable numbers of active spore of Myxobolus sp. can displace the gill lamellae, inflammatory and incite hyperplastic responses, lamellar fusion, and gill distortion in several infections. The spore infiltrates the surface of the liver of the host causing serious damage to the liver tissue. Fish infected with the parasite exhibit necrosis and cysts in the gut. Parasites were detected within multiple segments of the intestine. While occurrences within the intestinal lumen were infrequent, conspicuous clinical indications were notably absent upon inspection of the fish’s external body surface. The findings unequivocally establish that Myxobolus sp. infection in tilapia induces substantial damage to the crucial organs of the fish.

Hook Types Influence The Catch Effectiveness, Injuries, and Survival Rates of Fishes in Recreational Fishing

The physical damage inflicted on captured fish in recreational fishing activities tends to be influenced by hook type. Therefore, the present study aims to investigate the suitability of hook type for catching fish as well as the evaluation of injuries and survival rates after catch-and-release. The sampling was conducted at a recreational fish pond situated at Universiti Putra Malaysia Bintulu Sarawak Campus from July until November 2022. Three sets of fishing rods with two types of hooks (circle hook &amp; octopus hook) were used in this study. The catch efficiency, injury level, and survival rates of both types of hooks were assessed. A total of 41 and 22 fish were successfully caught using circle hooks and octopus hooks, respectively. Of the total fish caught, 39 out of 41 and nine out of 22 of the fishes caught were tilapia. The hooking location (non-critical area) of octopus hooks and circle hooks on the tilapia was approximately 100% and 81.8%, respectively. A total of 15.38% of hooks are located within the critical area (gills) of tilapia when using the circle hook and none for octopus hooks. There was 100% mortality in fish hooked in the critical area, for instance, hooks pinned inside gills. This occurrence may relate to the shape of the circle hook whereby the length of the gape is shorter in comparison to the octopus hook. Now when fish ingested the bait, the hook easily entered deeper areas of the fish’s mouth, which led to severe damage. Thus the present study recommends the use of octopus hooks in recreational fishing to reduce fish mortality rate for catch and release excursions. The results obtained from this study will be useful baseline input for recreational anglers to improve C&amp;R practices in Malaysia.

Effect of microplastic particles on the gills structure of freshwater fish supplemented with probiotics and vitamin C

This study aims to determine the effectiveness of commercial feed with probioticand vitamin C supplements in repairing damage to the gill structure of freshwater fish, tilapia (Oreochromis niloticus). Tilapia in this study were divided into control group (commercial feed), probiotic group (commercial feed with probiotic 200 mg/kg of feed), and vitamin C group (commercial feed with vitamin C 100 mg/kg of feed). Each group was givenmicroplastic particles exposure treatment in aqueous media (0, 0.1, 1, 10 mg/L volume of aquarium water) which was carried out twice a day for 14 days. The results showed that the administration of vitamin C as fish feed supplement reduced the damage that occurred in the tilapia gills in the form of edema (22 ± 3.57%), necrosis (33 ± 4.07%), hyperplasia (38 ± 5.91%), epithelial lifting (28 ± 3.43%), and fusion (17 ± 3.49%) of the secondary lamellae. Meanwhile, the administration of probiotics only reduced the histopathological conditions of necrosis (34 ± 4.57%) and fusion (18 ± 3.07%) of secondary lamellae. From all treatments, it was shown that feeding with vitamin C was the most effective in improving the histopathological condition that occurred in the histological structure of tilapia gills.

Study of the Level of Lead and Zinc in Five Species of Fish in Tigris River

The research was carried out in the Tigris River, specifically in two distinct areas, namely Tikrit and Samarra within the Salah al-Din province, during the period of May 1, 2022, to January 9, 2021. The selection of these two stations was made with the intention of collecting fish samples for the purpose of assessing the presence of heavy element contamination in the fish population. This study was conducted at the laboratories of the Department of Food Sciences in the College of Agriculture, and the Department of Chemical Engineering in the College of Engineering at the University of Tikrit. The objective of the study was to assess the extent of heavy metal contamination, specifically lead and zinc, in various parts of fish including meat, liver, gills, and intestines. The study focused on five species of fish commonly found in the Tigris River, namely Zori, Nile tilapia, Aspius vorax, Silurus triostegus, and Carrasobarbus luteus. Additionally, the study encompassed two regions, Tikrit and Samarra, located in Salah al-Din province. The bi-interaction recorded a significant difference in the lead element, the highest value of which was (5.14 PPM) in the Nile tilapia muscles, and the lowest value (0.001 PPM) in the Nile tilapia gills, where the bi-interaction between the type of fish and the location was not recorded in the zinc element in the Samarra location, it reached the highest level The zinc element in the average of the sample type was (37.17 PPM) in the liver of the studied fish, and the lowest value was (8.82 PPM) in the intestines of the studied fish.

Oreoch-1: A Peptide from Oreochromis niloticus as a Potential Tool against Staphylococci.

Staphylococci, including Staphylococcus aureus and Staphylococcus epidermidis, are important human pathogens associated with potentially life-threatening infections. Their great biofilm-producing ability and the development of resistance mechanisms often account for therapeutic failure. Hence, the scientific community has devoted intensive efforts to the development of antimicrobial compounds active against both planktonic and sessile bacterial populations. Contextually, antimicrobial peptides (AMPs) are natural peptides produced by the innate immunity of every organism, representing a potential new therapeutic solution against human microbial pathogens. Our work focused on the in vitro activity of Oreoch-1, an AMP from the gills of Nile tilapia (Oreochromis niloticus), against standard and clinical S. aureus and S. epidermidis strains. Firstly, the cytotoxicity profile of Oreoch-1 was determined in human colon carcinoma cells. Secondly, its antibacterial spectrum was explored against staphylococcal strains to set up the minimum inhibitory concentration (MIC) and the minimum bactericidal concentration (MBC). Our results highlighted an antibacterial activity in the range 6.25-25 μM, with a general bacteriostatic effect. Therefore, the biofilm-inhibitory property was assessed against S. aureus ATCC 25923 and S. epidermidis ATCC 35984, indicating a significant reduction in S. aureus biomass at sub-MIC concentrations. Overall, our study indicates Oreoch-1 as a promising new therapeutic weapon against staphylococcal infections.

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.

PENGUJIAN PENYAKIT KOMODITAS IKAN AIR TAWAR PADA LALU LINTAS DOMESTIK DI STASIUN KARANTINA IKAN JAMBI

Increased trade flows of international and domestic fishery coomodities in the opportunity to enter and spread Hama penyakit Ikan Karantina (HPIK) caused by pathogenic organism, namely bacteria, parasites, fungi, and viruses. This study aims to identify whether freshwater fish commodities in domestic traffic are infected with parasites, the bacteria Edwardsiella ictaluri, TiLV (Tilapia lake Virus) and the fungus Aphanomyces invadans at the Fish Quarantine Stasion, Quality Control and Safety of Fishery Products Jambi. Fish samples consist of 15 fish samples to be tranported. Based on results of the examinatoin of fish diseases, Parasite Examination there were 4 parasites with 3 types of parasites, namely 2 parasites of Dactylogyrus sp. On the gills of Tilapia and catfish. One (1) parasite Gyrodactylus sp. On fish slime Stripe 3, and 1 parasite Camallanus sp.in the intestines of betta fish; on bacterial examination of the 4 samples of fish examined, Edwardsiella ictaluri bacteria were nof found; on virus examination the result were negative for TiLV (Tilapia lake Virus); on examination of the fungus with the PCR method, negatif result were obtained for the fungus Aphanomyces invadans which is the cause of EUS (Epizootic Ulcerative Syndrome).

Glucocorticoid Receptor Mediates Cortisol Regulation of Glycogen Metabolism in Gills of the Euryhaline Tilapia (Oreochromis mossambicus)

In this study, we investigated the effects of cortisol on the regulation of the glycogen metabolism biomarkers glycogen synthase (GS) and glycogen phosphorylase (GP) in the glycogen-rich cells of the gills of tilapia (Oreochromis mossambicus). In the gills of tilapia, GP, GS, and glycogen were immunocytochemically colocalized in a specific group of glycogen-rich cells adjacent to the gills’ main ionocytes and mitochondria-rich cells. Cortisol plays a vital role in the regulation of physiological functions in animals, including energy metabolism, respiration, immune response, and ion regulation. However, no studies have elucidated the mechanisms regulating cortisol and glycogen-rich cells in the gills. Therefore, we treated tilapia larvae with exogenous cortisol and a glucocorticoid receptor (GR) antagonist to investigate the regulatory mechanisms between cortisol and glycogen-rich cells in the gills. Our results showed that cortisol promoted the expression of gill glycogen phosphorylase isoform (GPGG) mRNA via GR, whereas the GS gene expression remained unaffected. We also found that GR mRNA was colocalized with some glycogen-rich cells in the gills, further confirming our hypothesis that cortisol directly acts on glycogen-rich cells in the gills of tilapia and regulates glycogen metabolism by promoting GPGG mRNA expression.

Chromatin accessibility in gill tissue identifies candidate genes and loci associated with aquaculture relevant traits in tilapia

The Nile tilapia (Oreochromis niloticus) accounts for ∼9% of global freshwater finfish production however, extreme cold weather and decreasing freshwater resources has created the need to develop resilient strains. By determining the genetic bases of aquaculture relevant traits, we can genotype and breed desirable traits into farmed strains. We generated ATAC-seq and gene expression data from O. niloticus gill tissues, and through the integration of SNPs from 27 tilapia species, identified 1168 highly expressed genes (4% of all Nile tilapia genes) with highly accessible promoter regions with functional variation at transcription factor binding sites (TFBSs). Regulatory variation at these TFBSs is likely driving gene expression differences associated with tilapia gill adaptations, and differentially segregate in freshwater and euryhaline tilapia species. The generation of novel integrative data revealed candidate genes e.g., prolactin receptor 1 and claudin-h, genetic relationships, and loci associated with aquaculture relevant traits like salinity and osmotic stress acclimation.

The myxozoan parasite Myxobolus bejeranoi (Cnidaria: Myxozoa) infection dynamics and host specificity in hybrid tilapia aquaculture.

Nile × blue tilapia hybrid (Oreochromis niloticus × O. aureus) has become an important food fish in intensive freshwater aquaculture. Recently, the parasite Myxobolus bejeranoi (Cnidaria: Myxozoa) was found to infect hybrid tilapia gills at high prevalence, causing immune suppression and high mortality. Here, we explored additional characteristics of M. bejeranoi–tilapia interaction, which enable efficient proliferation of this parasite inside its specific host. Highly sensitive quantitative polymerase chain reaction (qPCR) and in situ hybridization analyses of fry collected from fertilization ponds provided evidence to an early-life infection of fish by a myxozoan parasite, occurring less than 3 weeks post-fertilization. Because Myxobolus species are highly host-specific, we next compared infection rates in hybrid tilapia and in both its parental species following a 1-week exposure to infectious pond water. Analysis by qPCR and histological sections showed that while blue tilapia was as susceptible to M. bejeranoi as the hybrid, Nile tilapia appeared to be resistant. This is the first report of differential susceptibility of a hybrid fish vs its parental purebreds to a myxozoan parasite. These findings advance our understanding of the relationship between M. bejeranoi and tilapia fish and raise important questions regarding the mechanisms that allow the parasite to distinguish between very closely related species and to infect a specific organ at very early-life stages.

Size-Dependent Uptake and Depuration of Nanoplastics in Tilapia (Oreochromis niloticus) and Distinct Intestinal Impacts.

Nanoplastics (NPs, <1 μm) are of great concern worldwide because of their high potential risk toward organisms in aquatic systems, while very little work has been focused on their tissue-specific toxicokinetics due to the limitations of NP quantification for such a purpose. In this study, NPs with two different sizes (86 and 185 nm) were doped with palladium (Pd) to accurately determine the uptake and depuration kinetics in various tissues (intestine, stomach, liver, gill, and muscle) of tilapia (Oreochromis niloticus) in water, and subsequently, the corresponding toxic effects in the intestine were explored. Our results revealed uptake and depuration constants of 2.70-378 L kg-1 day-1 and 0.138-0.407 day-1 for NPs in tilapia for the first time, and the NPs in tissues were found to be highly dependent on the particle size. The intestine exhibited the greatest relative accumulation of both sizes of NPs; the smaller NPs caused more severe damage than the larger NPs to the intestinal mucosal layer, while the larger NPs induced a greater impact on microbiota composition. The findings of this work explicitly indicate the size-dependent toxicokinetics and intestinal toxicity pathways of NPs, providing new insights into the ecological effects of NPs on aquatic organisms.