Search Results (53)

Lactococcosis has emerged as an economically and ecologically significant disease in aquatic animals worldwide. This study employed multilocus sequence typing (MLST) to investigate the genetic diversity of Lactococcus spp. strains from Brazilian fish species and evaluate their phylogenetic relationships with global isolates to elucidate potential epidemiological connections involving multiple host species and distinct geographic regions. A total of 55 isolates from different laboratories had their DNA extracted, followed by the amplification and sequencing of the internal fragments of seven housekeeping genes (als, atpA, tuf, gapC, gyrB, rpoC and galP). Sequence types (STs) and clonal complexes (CCs) were defined. An unrooted neighbor-joining phylogenetic tree was generated using allele profiles from this study and those previously reported from other aquatic animal species. The isolates comprised 29 STs (11 previously reported, 18 novel ones), which were grouped into species-specific CCs: CC5 (L. formosensis); CC4, CC17, CC62 (L. garvieae); CC24, CC29, CC97 (L. petauri). Considerable genetic divergence was observed, with L. formosensis and L. garvieae forming heterogeneous populations, while L. petauri was more homogeneous. These findings describe the MLST structure of the sampled isolates and should be interpreted as hypothesis-generating rather than population-level estimates of genotype prevalence. Phylogenetics confirmed groupings within the CCs and revealed additional phylogenetic clustering patterns. In conclusion, the Brazilian Lactococcus spp. strains analyzed in this study constitute a genetically diverse population based on their STs. MLST and phylogenetic analysis demonstrated genetic relatedness between the L. garvieae and L. formosensis isolates from this study and those from other aquatic animal species. In contrast, all the STs identified for L. petauri in this study were unrelated to the MLST lineages responsible for outbreaks in Brazilian Nile tilapia (Oreochromis niloticus) and North American rainbow trout (Oncorhynchus mykiss). This suggests that piscine L. petauri populations in the Americas evolved from distinct ancestral origins. Full article

Diatoms are recognized as a valuable source of bioactive compounds that can stimulate the immune defense mechanisms of fish. This study aimed to assess the effects of Chaetoceros sp. in modulating the specific and non-specific immunity of red hybrid tilapia through in vitro functional assays, an in vivo feeding trial, and a bacterial challenge. The in vitro experiment (Phase One) examined the immune response of tilapia cells exposed to Chaetoceros sp. extract, while the in vivo experiment (Phase Two) evaluated the immune response following an 8-week dietary supplementation with Chaetoceros sp. powder. In Phase One, an 8 mg/mL concentration of Chaetoceros sp. extract demonstrated an overall enhancement in lysozyme activity and lymphocyte proliferation. In Phase Two, tilapia fed a diet containing 2% Chaetoceros sp. showed significantly improved lysozyme activity, while the 5% supplemented group exhibited a significant increase in lymphoproliferation activity (p < 0.05). Growth performance parameters were generally comparable among dietary groups, indicating that supplementation did not adversely affect growth. Notably, the 2% diet also enhanced fish survivability following a challenge with Streptococcus agalactiae. These findings highlight the immunomodulatory potential of the diatom Chaetoceros sp. as a functional feed additive for freshwater fish, particularly red hybrid tilapia, and suggest its positive impact on fish health management in aquaculture. Full article

Antimicrobial resistance in bacteria associated with aquaculture, such as Edwardsiella spp., represents an emerging challenge because of their relevance to fish health and their potential impact on animal, environmental, and human health. In this study, we primarily investigated the antimicrobial susceptibility profiles of Edwardsiella anguillarum isolated from farmed Nile tilapia (Oreochromis niloticus) in Brazil. Based on our findings, herein, we propose provisional local epidemiological cut-off values (pECVs) using the normalized resistance interpretation method, with data for Edwardsiella tarda included as an exploratory context. Fifty isolates (31 E. anguillarum and 19 E. tarda) collected between 2017 and 2025 were tested against 28 antibacterial agents using the disk diffusion method. Based on the pECVs, isolates were classified as wild type (WT) or non-WT (NWT), and the multiple antibiotic resistance (MAR) index was calculated. Most E. anguillarum isolates remained susceptible to several classes, although NWT and multidrug-resistant profiles were detected with a MAR index of 0.68, suggesting selective pressure in intensive tilapia farming systems. These findings support the use of local, species-specific pECVs for resistance surveillance in aquaculture, highlighting the importance of continuous antimicrobial resistance monitoring in aquaculture from a One Health perspective. Full article

With increasing global demand for fishery products, saline-alkaline aquaculture has emerged as a potential solution. However, limited information exists regarding the tolerance and adaptability of red tilapia (Oreochromis spp.) to alkaline environments. This study evaluated the acute semi-lethal toxicity of alkaline water and its physiological effects on juvenile red tilapia (44.80 ± 1.09 g; 12.84 ± 1.02 cm). Fish were exposed to NaHCO₃ for 96 h at five alkalinity levels (50, 55, 60, 65, and 70 mmol/L). Survival declined significantly with increasing alkalinity, and the 96 h LC₅₀ was 60.66 mmol/L, indicating relatively high alkaline tolerance. Gill tissue and serum samples were collected at 0, 12, 24, 48, and 96 h under 50 mmol/L NaHCO₃ and freshwater (control). Under prolonged alkaline exposure, gill structure exhibited marked alterations, with SLL and ILCMT progressively decreasing over time. Serum antioxidant responses were impaired, showing a sustained decline in SOD activity and a rise in MDA content, indicating the onset of oxidative stress. TAOC, CAT, and GSH-Px displayed a biphasic response, rising initially before declining with continued stress. TP and GLU levels remained largely stable throughout. Energy metabolism indices also shifted dynamically: TC showed a transient increase followed by a decrease, whereas TG and LDH initially declined before rising later in the exposure period. Stress-related markers, including cortisol, T3, ALP, and ACP, were notably elevated during the exposure. Additionally, serum ion concentrations (K⁺, Ca²⁺, Na⁺, Cl⁻) increased gradually over the 96 h period, reflecting progressive osmoregulatory disturbance under alkaline stress. Overall, this study shows that juvenile red tilapia (Oreochromis spp.) have high alkaline tolerance (96 h LC₅₀ = 60.66 mmol/L NaHCO₃), but exposure to alkaline water causes significant physiological stress, affecting gill structure, antioxidant defense, metabolism, and ion balance. These results offer valuable insights into their adaptability to saline-alkaline aquaculture. Full article

One major bottleneck for the sustainable development of the aquaculture sector is the reliance on conventional feed ingredients, such as fishmeal and soy protein. Another challenge is nutrient loss from these systems, which contributes to environmental pollution but also represents a waste of valuable resources. To make aquaculture truly sustainable, a shift toward circular, sustainable systems is necessary. This study compared a regionally available alternative feed, based on blue mussel meal and pea protein concentrate, to a conventional fish meal and soybean control diet in Nile tilapia (Oreochromis niloticus) reared in coupled aquaponic systems. Fish performance and stress levels, water quality, plant growth, and microbial quality were investigated. Growth performance and feed intake were similar between aquaponic and control recirculating aquaculture systems (RASs) during the control feed (CF) phase. Only the feed conversion ratio (FCR) was slightly lower in the aquaponic system during the mussel-pea feed (MPF) phase. Tatsoi (Brassica rapa) growth in the aquaponic systems was comparable to, or even greater than, that of the hydroponic control systems, throughout the experiment, especially during the MPF phase. In addition, the MPF had a positive impact on phenotypic parameters and contributed to enhanced shoot growth. However, the presence of pathogens with potential biohazard impacts on human and fish health remains a concern and warrants further investigation. In our study, Salmonella spp. was detected in both systems, but levels were considerably reduced with the MPF phase. In contrast, Escherichia coli was detected only in RASs and was absent from aquaponic systems. Overall, the findings support the potential of blue mussel and pea protein as sustainable, local feed components in integrated aquaponic production, contributing to nutrient circularity and reducing dependence on limited marine stocks and imported resources. Full article

Intensive aquaculture practices heighten oxidative stress and infectious disease risk, necessitating sustainable alternatives to antibiotics. This study evaluated the integrative probiotic and postbiotic potential of Bacillus velezensis AAHM-BV2302 in red tilapia (Oreochromis spp.), focusing on growth, antioxidant defense, immune modulation, and resistance to Streptococcus agalactiae. Whole-genome sequencing confirmed its classification as B. velezensis (4.16 Mb, GC 45.9%, ANI 99.4% with NRRL B-41580). Fish were fed diets supplemented with probiotic cells (Cell), cell-free supernatant (Cfs), or their combination (Cell + Cfs) for 30 days, followed by 30 days without probiotic supplementation. Growth performance significantly improved in Cell and Cell + Cfs groups at both Day 30 and Day 60 (p < 0.05). Antioxidant enzymes (SOD, CAT, GSH) increased significantly across tissues at Day 30, while malondialdehyde (MDA) declined (p < 0.05), indicating enhanced redox homeostasis. Humoral immunity was elevated, with higher lysozyme, bactericidal activity, and total IgM persisting post-supplementation (p < 0.05). Expression of il1b, il6, and il8 was upregulated in immune-related and mucosal tissues, reflecting robust immune activation (p < 0.05). After S. agalactiae challenge, survival rates were 55% in Cfs, 60% in Cell, and 70% in Cell + Cfs, corresponding to relative percent survivals (RPS) of 43.8%, 50.0%, and 62.5%, respectively (p < 0.05). These results demonstrate that B. velezensis AAHM-BV2302 enhances growth, antioxidant capacity, and immune resilience through complementary probiotic–postbiotic mechanisms, supporting its application as a safe, multifunctional biotic for antibiotic-free tilapia aquaculture. Full article

Nile tilapia (Oreochromis niloticus) is an indispensable source of high-quality protein worldwide. Along with the exponential expansion of tilapia aquaculture, several novel pathogenic viruses have emerged, and some cause significant economic losses. Unfortunately, there is scarce information on the biology and epidemiology of these viruses. This exploratory metagenomic study used Oxford Nanopore Technology (ONT) sequencing to profile the virome compositions of both wild and farmed Nile tilapia across five regions in Egypt. The Nile tilapia virome was dominated by two double-stranded DNA bacteriophages, Muvirus mu and M. sfmu, which constituted 79.8% of the detected sequences. Eukaryotic viruses, including members of the families Amnoonviridae, Peribunyaviridae, and Baculoviridae, were also identified. Two giant DNA viruses known to infect Acanthamoeba spp., Mollivirus sp., and Pandoravirus sp. were identified in the spleen virome of tilapia from a single sampling site. The diversity analysis showed no significant differences among tissue types or sampling sites. Phylogenetic analyses were performed on a single virus detected of potential pathogenicity, an amnoonvirus. The analyses demonstrated that the detected virus is a member of the family Amnoonviridae and placed it alongside members of the Tilapinevirus genus. The virus, however, was distinct from the other two members in the genus: T. tilapae and T. poikilos. This study underscores the usefulness of ONT in providing a foundational understanding of the Nile tilapia virome. Full article

The utilization of saline–alkali water resources presents a promising approach for freshwater aquaculture. Red tilapia (Oreochromis spp.) exhibits moderate salinity tolerance, but its adaptation mechanism to alkaline conditions remains poorly understood. In the current study, five alkaline carbonate concentrations in a 60-day chronic stress experiment on red tilapia were evaluated. The experimental design included a control group (CA0, 0 mmol/L) and three treatment groups (CA10, 20 mmol/L; CA30, 30 mmol/L; and CA40 40 mmol/L). The results indicated that at alkaline carbonate concentrations exceeding 20 mmol/L, the gill filaments exhibited curling and deformation, the hepatocytes displayed migration, and tissue damage increased significantly. The gill’s antioxidant capacity initially decreased and then increased, with severe gill injury in the CA40 group, leading to significantly reduced levels of SOD, CAT, and GSH-PX compared to the CA40 group (p < 0.05). Conversely, the enzymatic activities related to energy metabolism showed an opposite trend under alkaline carbonate stress. The transcriptome analyses of gill tissues across five groups identified significant alterations in key pathways, including the metabolic process (endocytosis, focal adhesion, PI3K−Akt signaling pathway, MAPK signaling pathway, and Citrate cycle (TCA cycle)), and immune responses (mTOR signaling and NOD−like receptor signaling pathways). Additionally, we screened 13 differentially expressed genes (DEGs) as potential regulators of alkaline stress and validated their expression levels using quantitative real-time PCR (qPCR). This study preliminarily elucidated the molecular mechanism of red tilapia in the physiological regulation process under chronic alkaline stress, and offers a theoretical foundation for breeding programs aimed at developing alkali-tolerant strains for aquaculture in alkaline water environments. Full article

The intensive farming of aquaculture species such as red tilapia (Oreochromis spp.) across diverse production systems can lead to changes in genetic parameters and responses of economically important traits in this species. This study represents the first attempt to understand these changes in growth traits (body weight, total length), quality attributes (body colour), and survival rate in red tilapia. Data for these traits were collected from 75,950 individual fish, progeny of 970 full-sib families (comprising 970 dams and 486 sires); they were selected for high body weight and evaluated in two distinct culture environments: fresh- and saltwater ponds. A multi-trait mixed model was employed to estimate genetic parameters and selection responses. Genetic variance estimates for the quality and survival traits varied across the two environments. However, genetic correlations among the traits studied were similar between fresh and saline water. Furthermore, significant G × E interactions, particularly for the quality and survival traits, were evidenced by divergent genetic correlations (r_g = 0.57–0.83) between homologous traits across different environments. The findings emphasise the importance of incorporating G × E interactions into the selection program for red tilapia, particularly when the breeding objectives extend to include quality and survival traits. Selection strategies should consider the prevailing culture system—for instance, favouring genotypes suited to the freshwater pond environment over those adapted to the saltwater environment. Continual assessment of full-sib groups across these environments is recommended to refine our understanding of G × E interactions and optimise future breeding programs for red tilapia. This may involve selecting genotypes capable of consistent performance across environments or developing environment-specific breeding programs. Full article

Growth traits are the most important economic traits in red tilapia (Oreochromis spp.) production, and are the main targets for its genetic improvement. Increasing salinity levels in the environment are affecting the growth, development, and molecular processes of aquatic animals. Red tilapia tolerates saline water to some degree. However, few credible genetic markers or potential genes are available for choosing fast-growth traits in salt-tolerant red tilapia. This work used genome-wide association study (GWAS) and RNA-sequencing (RNA-seq) to discover genes related to four growth traits in red tilapia cultured in saline water. Through genotyping, it was determined that 22 chromosomes have 12,776,921 high-quality single-nucleotide polymorphisms (SNPs). One significant SNP and eight suggestive SNPs were obtained, explaining 0.0019% to 0.3873% of phenotypic variance. A significant SNP peak associated with red tilapia growth traits was located on chr7 (chr7-47464467), and plxnb2 was identified as the candidate gene in this region. A total of 501 differentially expressed genes (DEGs) were found in the muscle of fast-growing individuals compared to those of slow-growing ones, according to a transcriptome analysis. Combining the findings of the GWAS and RNA-seq analysis, 11 candidate genes were identified, namely galnt9, esrrg, map7, mtfr2, kcnj8, fhit, dnm1, cald1, plxnb2, nuak1, and bpgm. These genes were involved in ‘other types of O-glycan biosynthesis’, ‘glycine, serine and threonine metabolism’, ‘glycolysis/gluconeogenesis’, ‘mucin-type O-glycan biosynthesis’ and ‘purine metabolism signaling’ pathways. We have developed molecular markers to genetically breed red tilapia that grow quickly in salty water. Our study lays the foundation for the future marker-assisted selection of growth traits in salt-tolerant red tilapia. Full article

Overexploitation has led to a rise in pathogenic bacteria within aquaculture, increasing reliance on antibiotics, and developing microorganism resistance. This situation underscores the need to explore alternatives with a reduced ecological impact. Metabolites derived from essential oils have demonstrated antimicrobial properties that can inhibit or diminish the activity of various microorganisms. In this study, the antimicrobial efficacy of cinnamon (Cinnamomum zeylanicum), tea tree (Melaleuca alternifolia), and thyme (Thymus vulgaris) essential oils against pathogenic bacteria (Aeromonas, Pseudomonas, Shewanella, Comamonas, Vibrio, Acinetobacter, and Empedobacter) isolated from tilapia (Oreochromis spp.) brooded in Hidalgo State, Mexico, were investigated. Diffusion tests were conducted using discs infused with 12 different antibiotics and discs infused with essential oils at concentrations of 15, 10, and 5 μL each. Minimal inhibitory concentration tests were performed using a 96-well microplate format. All bacterial strains exhibited multi-resistance to various antibiotics; however, thyme and cinnamon effectively inhibited the tested bacteria at the lowest concentrations, while tea tree oil was the least effective. The findings suggest the potential incorporation of thyme and cinnamon as an alternative prevention to decrease the use of antibiotic treatment. Full article

The increase in the human population has created pressure, due to the high consumption of natural resources, to meet basic needs. Poor waste management resulting from human activities has caused plastics to become pollutants that are present around the planet, including aquatic environments. The degradation of plastics through physicochemical processes has resulted in the presence of microplastics (particles < 5 mm), which have been found in species for human consumption and economic importance, including tilapia. In the last decade, research has shown the presence of microplastics in tilapia collected from different water bodies and aquaculture ponds, as well as in fish markets. In addition to this, there are studies that demonstrate that exposure to microplastics can have negative effects on the health of tilapia. The aim of this review is to compile and analyze the available information on microplastic contamination in Oreochromis spp., as well as in their environment, due to their importance as a species for human consumption. Full article

Tilapia (Oreochromis spp.) is a globally important farmed fish. Analyses of genetic variation across different types of tilapia are essential for the development of superior breeding populations. We investigated the genetic structures of breeding populations of blue tilapia (Oreochromis aureus) (OA), Nile tilapia (Oreochromis niloticus) (ON), and red tilapia (Oreochromis spp.) (OS) by whole-genome resequencing. The results showed that the OS population had maintained high genetic diversity but significant genetic differentiation from the OA population. Principal component analysis, phylogenetic analysis, and genetic clustering analysis revealed a clear pattern of genetic differentiation among the three populations. The genetic structure of the ON population differed from that of the OA population but was similar to that of the OS population. Population kinship analysis revealed a close relationship between the ON and OS populations. Selective scanning analyses of three comparison groups (OA vs. ON, OA vs. OS, and ON vs. OS) revealed population-selected regions related to metabolism, endocrine, and immune systems, harboring key genes (qrsl1, pde4d, hras, ikbkb, prkag1, prkaa2, prkacb, irs2, and eif4e2). These key genes were related to growth, reproduction, and disease resistance, indicating that breeding programs have selected for these traits. Due to the lack of stable morphological characteristics of juvenile fish and the changes in external environmental conditions that lead to changes in individual morphological characteristics, SNP fingerprints were successfully constructed for the identification of the three populations based on the differences in SNPs. Based on the five core SNP markers, two combinations of SNP markers were developed to accurately identify the three populations of tilapia at the genomic level. These results provide new information about tilapia genetic resources and reference data for identification and breeding purposes. Full article

Red tilapia is highly valued as a premium variety in Asia due to its vibrant red skin coloration. However, during aquaculture production, irregular black pigmentation (melanotic spots) frequently appears on the skin of some individuals, significantly reducing their economic value. Although epigenetic regulation is suspected to play a role, its involvement remains poorly understood. To uncover the molecular mechanisms underlying black spot formation, we employed Cleavage Under Targets and Tagmentation (CUT&Tag) to compare four key histone modifications (H3K4me3, H3K4me1, H3K27me3, and H3K27ac) between red and black pigmented skin regions. Integrated with transcriptomic analysis, our data indicated that red skin regions exhibited high expression of genes suppressing melanin synthesis, whereas melanotic spots likely resulted from localized derepression, allowing upregulation of melanin biosynthetic genes. Furthermore, by combining epigenomic chromatin state analysis and transcriptome data, we identified critical genes consistently active in melanotic spots and their corresponding potential cis-regulatory elements. Motif analysis of transcription factor binding sites upstream of these regulatory elements revealed that Ehf, Klf9, and Egr1 might facilitate melanin production in black regions, while Prdm1 and Sp5 could inhibit melanogenesis in red regions by repressing the Wnt signaling pathway. These findings provide valuable epigenetic insights into the mechanisms driving melanotic spot formation in red tilapia. Full article

Integrated aquaculture–agriculture systems (IAASs) offer a sustainable approach to mitigating soil salinity by utilizing aquaculture effluents for irrigation. This study evaluates the growth performance of Nile tilapia (Oreochromis niloticus) and red tilapia (Oreochromis spp.) under varying salinity conditions and investigates their effluents on intercropped wheat and sugar beet. A field experiment was conducted using a randomized block design with seven treatments: control (chemical fertilizers dissolved in freshwater) and brackish water effluents from Nile tilapia and red tilapia at salinities of 5 ppt and 10 ppt as monocultures or mixed polycultures. Fish growth parameters were assessed, while wheat and sugar beet morphological and yield traits were monitored. Statistical analyses, including correlation and principal component analysis, were performed. Red tilapia outperformed Nile tilapia at 10 ppt salinity, achieving the highest final weight (174.52 ± 0.01 g/fish) and weight gain (165.78 ± 0.01 g/fish), while the mixed polyculture at 10 ppt exhibited optimal feed conversion (FCR: 1.32 ± 0.01). Wheat growth and yield traits (plant height, stalk diameter, and panicle weight) declined significantly under salinity stress, with 10 ppt treatments reducing plant height by ~57% compared to the control. Conversely, sugar beet demonstrated resilience, with total soluble solids (TSS) increasing by 20–30% under salinity. The mixed effluent partially mitigated salinity effects on wheat at 5 ppt but not at 10 ppt. This study highlights the potential of IAAS in saline environments, demonstrating red tilapia’s adaptability and sugar beet’s resilience to salinity stress. In contrast, wheat suffered significant reductions in growth and yield. Full article