Oreochromis Mossambicus Research Articles

Enzymological Effects of Lead Acetate Exposure in Various Organs of Oreochromis mossambicus (Peters 1852)

The various enzymological effects of heavy metal Lead acetate (Pb(C2H3O2)2) exposed to fingerlings of Oreochromis mossambicus was analyzed in this study. The 30 days old fingerlings of O. mossambicus were exposed to sub lethal dose 3.80ppm of 96 hrs. LC50 of Pb(C2H3O2)2 for 21 and 28 days, various organs (liver, gill, kidney and muscle tissue) were removed from control and treated fishes and were used for various enzymological effect: Succinate dehydrogenase (SDH), Lactate dehydrogenase (LDH), Aspartate aminotransferase (AST), Alanine aminotransferase (ALT), Acid phosphatase (ACP) and Alkaline phosphatase ALP). The observed data were subjected into various statistical analysis by using IBM-SPSS version 26. Among the two different exposure periods 21 and 28 days which compared with control fingerlings organs, the various enzymological effects were drastically suffered (Treated fish enzymological levels were inversely proportionate towards the control groups of fish species) by 28 days of exposure periods. Pb(C2H3O2)2 exposed to fingerlings which tested on various organs at 28 days interval periods for assessing of SDH, LDH, AST, ALT, ACP and ALP of various organs of treated fish: Liver: 12.02, 55.75, 58.24, 125.27,12.26, 11.82 µ moles of phenol liberated/ mg of protein; Gill: 10.80, 33.75, 28.73, 28.11, 7.80, 8.63 µ moles of phenol liberated/ mg of protein; Kidney: 12.18, 46.33, 44.78, 75.40, 6.27, 10.38 µ moles of phenol liberated/ mg of protein and Muscle: 11.72, 32.44, 32.76, 44.20, 3.72, 7.20 µ moles of phenol liberated/ mg of protein were recorded on tissue of treated fish. The enzymological effect of Pb(C2H3O2)2 exposed towards O. mossambicus which observed various health defects on organism exposed to a particular toxicant. It may give sufficient information about heavy metal contamination on aquatic organism and would help us to propose policies to protect the ecosystem.

Salt tolerance candidate genes identified by QTL mapping, RNA-seq, and functional analysis in tilapia

Salt tolerance in fish is crucial for aquaculture as it enhances survival and productivity in varying salinity conditions, thus expanding the range of viable farming environments and improving economic sustainability. Through QTL mapping and GWAS in a hybrid F2 family of Mozambique and Nile tilapia, two large-effect QTL on chromosomes 11 and 18 were identified respectively. These two QTL explained a total of 39.9 % of the phenotypic variance. The identification of a QTL on LG11 suggests the presence of a previously unrecognized genetic factor contributing to salt tolerance. Comparative transcriptomic analysis of gill and kidney tissues between susceptible and tolerant tilapias highlights the importance of osmotic balance in regulation of salt tolerance in tilapia. Integration of QTL and RNA-seq data identified two candidate genes: acyl-coenzyme A thioesterase 5 (acot5) and sodium- and chloride-dependent taurine transporter (slc6a6) likely playing critical roles in such process. Functional analysis showed that over-expressing acot5 or slc6a6 in grouper kidney cells increased viability under salt stress by 4.46 % and 17.53 %, respectively. Subcellular localization revealed nuclear presence of ACOT5 and stress-induced nuclear translocation of SLC6A6. These findings highlight acot5 and slc6a6 as candidates for genetic manipulation and selection to enhance salt tolerance in tilapia, guiding genetic improvement efforts and promoting sustainable practices.

Marine macroalgae Chaetomorpha aerea as a dietary supplement: Optimizing immunity and resistance to Edwardsiella tarda in tilapia (Oreochromis mossambicus)

The intensification of aquaculture has led to a rise in fish infections, necessitating the search for alternative antibiotics. In this context, our study investigated the effects of dietary supplementation with Chaetomorpha aerea, a filamentous green algae, on the immune health and resistance to infections in tilapia (Oreochromis mossambicus). Diets containing varying concentrations of C. aerea (0, 1, 2, 5, and 10 g/kg) were prepared and administered to the fish for 30 days, followed by a challenge with Edwardsiella tarda to evaluate survival rates. The results were significant. The diet containing 5 g/kg of C. aerea (group T3) brought about substantial improvements in hematological parameters, including increases in red blood cell count (RBC), hematocrit (Hct), and hemoglobin (Hb). The T3 group exhibited a robust immune response, with higher lysozyme and ceruloplasmin activity in immunological assays. LBP gene expression was significantly elevated in the spleen and thymus of fish in the T3 group, which correlated with higher survival after bacterial challenge compared to the control group. Principal Component Analysis (PCA) and cluster analysis confirmed that the 5 g/kg concentration stood out for maximizing immunological benefits without compromising the overall health of the fish. These findings highlight the robust immune response in the T3 group, a key finding of our study. We conclude that supplementation with C. aerea represents a promising and sustainable alternative in the formulation of diets for tilapia, contributing to improved health and resistance to diseases. Future studies are recommended to explore its application in other species and development stages, in addition to evaluating other health biomarkers.

Palatability of organic acids and their derivatives for cichlid fishes (Cichlidae)

Taste attractivity of 15 organic acids and their derivatives (ascorbic, citric, sorbic, malic, oxalic, acetic, glycolic, α- and γ-aminobutyric acids, their Na+- and K+-salts; 0,1 M) was compared for 5 species of cichlid fishes (Cichlidae) – Nile Oreochromis niloticus and Mozambique O. mossambicus tilapias, golden mbuna Melanochromis auratus, lemon cichlid Neolamprologus leleupi and tailbar cichlid Vieja hartwegi. Citric and oxalic acids, Na+-ascorbate, K+-sorbate and K+-citrate, ammonium oxalate have an attractive or indifferent taste for fish, ascorbic and sorbic acids, Na+-citrate and Na+-malate have an aversive or indifferent taste. Malic acid has an attractive taste for tailbar cichlid, an aversive taste for Mozambique tilapia and an indifferent taste for other cichlids. Acetic acid and isomers of aminobutyric acid have indifferent taste for all fishes. The taste attractivity of organic acids may be different compared to salts formed on their basis. The attractiveness of salts is higher than that of the corresponding acids in 10 out of 28 cases, lower in 4 cases, and the same in 14 cases. The conversion of ascorbic and sorbic acids into Na+ and K+ salts is accompanied by an increase in taste attractivity in most cichlids, malic acid to malate Na+ – in half of the species. For most fish, citric acid and its Na+- and K+-salts have similar attractiveness. Oxalic acid, compared with ammonium oxalate, has a higher attractiveness for lemon cichlid, a lower one for Mozambique tilapia and the same taste quality for the other three fish species. There are no differences between the consumption of agar pellets with isomers of aminobutyric acid and pellets with acetic and glycolic (hydroxy acetic) acids in all cichlids. The feeding behavior shown by cichlids during the orosensory testing of pellets is similar – fish perform a small number of rejections and repeated grasps of pellets, the duration of pellet retention time in the oral cavity is similar.

Accumulation of Heavy Metals in Tissues of Oreochromis Mossambicus from the uMgeni River and Human Health Risk Assessment

Metal enrichment in aquatic ecosystems has compromised the potential of fish to enhance food security. The uMgeni River drains urban and industrialized catchment and flows through economically disadvantaged rural communities that opt for fish to supplement their protein needs. However, there are uncertainties on the safety of consuming fish from the uMgeni River. The present study aims to explore metal distribution between the water, sediment, and tissues of the preferred Oreochromis mossambicus, and evaluate whether concentrations in the muscle are safe for human consumption. The water, sediment, and fish samples were collected from Inanda and Nagle dams, and metal concentrations were analysed using inductively coupled plasma mass spectrometry. Alkaline pH was observed at both dams and metals were below detectable level in the water column. Even though metal concentrations in the water column were below detectable levels, significant concentrations were found in the sediment. No consistent trend in metal concentrations was observed across tissues, but higher levels were generally found in the liver, followed by the gill, and then the muscle. Nickel (Ni) and lead (Pb) exhibited concentrations exceeding the permissible limit for human consumption. Similarly, the target hazard quotient exceeded the threshold of 1 for Pb, chromium (Cr), and antimony (Sb) at both dams with Inanda Dam showing higher indices for Sb and Pb. The carcinogenic risk for the three metals was also found to be higher than 10–6. These findings suggest that consumption of O. mossambicus from the uMgeni River should be limited to no more than 150 g per week.

Per-recruit analysis and proposed sustainable harvest strategy for rednose labeo Labeo rosae and Mosambique tilapia Oreochromis mossambicus in Flag Boshielo Dam, Olifants River, South Africa

Inland fisheries development in South Africa has been proposed to improve rural livelihoods and food security. However, inland fisheries are susceptible to collapse through overfishing. Therefore, establishing biological reference points for these fisheries is essential for long-term sustainability. Here, spawner-biomass-per-recruit (SBR) analysis was used to set biological reference points for a gillnet fishery targeting the rednose labeo Labeo rosae and Mozambique tilapia Oreochromis mossambicus at Flag Boshielo Dam on the Oliphants River in Limpopo Province, South Africa. Both species are currently exploited at the impoundment by subsistence fishers that keep their entire catch. The current yields are estimated at 59 and 172 g yr−1 for L. rosae and O. mossambicus, respectively. The per-recruit analysis showed that age-at-first-capture for both species should be 4 years, at minimum lengths of 280 mm TL and 250 mm TL for L. rosae and O. mossambicus, respectively, with fishers using a minimum mesh size of 100 mm to reduce the risk of stock collapse. To maintain a SBR value greater than 25% of a pristine population, the L. rosae yield could be increased to 98 g yr−1, while the O. mossambicus yield could be increased to 176 g yr−1, following implementation of the recommended mesh size and size limits. A per-recruit analysis for O. mossambicus that includes recruitment variability and error to accurately calculate the biological reference points is recommended.

Analysis of the pharyngeal structure of the genus Oreochromis for species identification through geometric morphometrics in the Aguamilpa reservoir, Nayarit, Mexico

Tilapia is an important fishing resource in economic terms for continental ecosystems such as dam reservoirs and lagoons. In Nayarit, the Aguamilpa Dam reservoir contributes around 50 % of the tilapia production in the state. However, despite the social and economic importance of the resource, there are few studies on it in this reservoir, and it is still unknown with certainty which species are found in the reservoir. This work is the first report for the Aguamilpa reservoir, where geometric morphometrics was used as a tool for the identification of tilapia species. The pharyngeal plate of 230 organisms was used for the geometric morphometrics analysis. According to this study, the existence of three species of the genus Oreochromis (O. aureus, O. niloticus and Oreochromis mossambicus) is confirmed; according to the analysis of canonical variables, the three species were correctly discriminated. This allows us to conclude that the use of geometric morphometrics in the pharyngeal plate is a useful structure for the identification of species in the reservoir.

Effects of feeding regime on growth, production, and economics of Oreochromine cichlids (Oreochromis mossambicus) in earthen ponds of Bangladesh

The experiment was carried out to evaluate the effects of feeding frequency on the growth, production, and economic aspects of Oreochromine cichlids (Oreochromis mossambicus) in nine earthen ponds for 120 days. Three different feeding regimes (T1, T2, and T3) with three replications each were used. The stocking density was uniform across all treatments at 25,000 fish per hectare. The fish were fed a commercially available pelleted feed with the same feeding rate in all treatments, but the feeding frequency varied. The feeding rate was 10%, 8%, 7%, 6 %, 5%, and 4% which was consecutively adjusted after each fortnightly sampling and 3% for the last 4 weeks of the study period. Feeding frequencies were once a day for T1, twice a day for T2, and three times a day for T3. The average weight gain of Oreochromine cichlids in T3 (295±5 gm) was significantly higher (P<0.05) than those of T2 (240.67±6.66 gm) and T1 (217.17±7.64 gm). The survival rates were 95.20%, 96.99%, and 97.33% for T1, T2, and T3, respectively. The net production of fish in T3 (2882.00±62.00 kg/ha) was significantly higher (P<0.05) than in T2 (2413.00± kg/ha) and T1 (2223±30.55). Furthermore, the highest net return (USD 1163/ha with a cost-benefit ratio of 1.42) was achieved from T3, followed by T2 (USD 527/ha with a cost-benefit ratio of 1.19) and T1 (USD 270/ha with a cost-benefit ratio of 1.09). The results demonstrated that increasing the feeding frequency has positive effects on the growth and production of Oreochromine cichlids.

Cu(II)-tyrosinase enzyme catalyst mediated synthesis of mosquito larvicidal active pyrazolidine-3,5-dione derivatives with molecular docking studies and their ichthyotoxicity analysis

The objective of this study was to develop pyrazolidine-3,5-dione derivatives with potential as environmentally friendly pesticides for pest control, specifically focusing on their efficacy as larvicidal agents. A novel one-pot synthesis of multicomponent pyrazolidine-3,5-dione derivatives (1a-m) was accomplished via the grindstone method using Cu(II)tyrosinase enzyme as a catalyst under mild reaction conditions, yielding 84%–96%. The synthesised derivatives (1a-m) were characterized using various spectroscopic methods (mass spectrometry, elemental analysis, FT-IR, and 1H and 13C NMR). NMR characterisation using DMSO-d6 as a solvent. The larvicidal and antifeedant activities of the synthesised compounds were screened and in silico computational studies were performed. The larvicidal activity against Culex quinquefasciatus and antifeedant activity against Oreochromis mossambicus were evaluated. Among the synthesised compounds, compound 1c demonstrated superior efficacy (LD50: 9.7 μg/mL) against C. quinquefasciatus compared to permethrin (LD50: 17.1 μg/mL). Regarding antifeedant activity, compounds 1a, 1e, 1f, 1j, and 1k exhibited 100% mortality at 100 μg/mL. Molecular docking analysis was performed to assess the binding capacity of a mosquito odorant-binding protein (3OGN) from Culex quinquefasciatus to compound 1c. The results revealed that compound 1c had a docking score of -10.4 kcal/mol, surpassing that of standard permethrin (-9.5 kcal/mol). Furthermore, DFT calculations were conducted to acquire theoretical data aligned with the experimental FT-IR results. According to experimental research, compound 1c demonstrates promising larvicidal activity against mosquito larvae of C. quinquefasciatus.

When less is more for dietary Lactobacillus rhamnosus IMC 501: The complex role gut microbiota play in energy budgets and allostasis of early juvenile Mozambique Tilapia (Oreochromis mossambicus)

In aquaculture, exposure to stressors results in heightened neuroendocrine responses, increasing metabolic activities and reducing growth to offset additional stressor-related energetic costs for allostasis. Supplementation with probiotics increases metabolic expenditures from elevated fish digestion and upregulated immune systems, but effects of the probiotics concentrations on energy budgets remains unknown. This study used respirometry to determine the effects of five different probiotic concentrations: T0 control (0 × 1011 CFU/g), T1 (5 × 1011 CFU/g), T2 (10 × 1011 CFU/g), T3 (15 × 1011 CFU/g), and T4 (20 × 1011 CFU/g) of a dietary single-strain probiotic (Lactobacillus rhamnosus IMC 501) on feed consumption, and the proportion of feed intake energy (C) allocated to growth (G), and routine metabolic rates (Rr), in the energy budgets of early juvenile (1-3 g wet weight) Mozambique tilapia (Oreochromis mossambicus), weekly over a 28-day experimental period. Two-factor ANOVA analyses revealed that the amount of feed intake energy (C) increased in probiotic treatments over controls. Allocation of feed energy for growth (G) differed among treatments, but not with time, but for routine metabolic activities (Rr), allocation of feed energy differed among treatments and over time. Increases of somatic tissue (TTW) was highest in the T2 treatment (intermediate concentration), while Rr was highest in the T3 and T4 (highest concentration) treatments, but only after 14–21 days of supplementation. Within energy budgets, the highest proportion of feed energy was allocated to growth in all treatments (G; mean ± SE, 43.0 ± 3.1 %), followed by routine metabolic activities (Rr; mean ± SE, 26.12 ± 2.1 %). Overall, the mean net mass-specific cost of growth (cr) (mgO2l−1 g−1) was highest, and the net growth efficiency (% KN) was lowest, in the T3 and T4 treatments indicating that higher probiotic concentrations were related to higher allostatic loads (AL) compared to lower probiotic treatments (T1, T2). Overall, our results revealed that the proportion of C allocated to G and Rr varied differently with probiotic concentration, was tightly related to gut bacteria metabolic expenditures, and highlighted the importance of carefully evaluating the probiotic concentrations for optimization of growth performance in Mozambique tilapia aquaculture.

Assessing the risk of consuming fish from Kanyakumari (Tamil Nadu), India: An evaluative study on bioaccumulated heavy metals in different fish species using inductively coupled plasma mass spectrometry

Environmental pollutants which are developing an alarming situation in the contemporary world captured attention in the present research. When it comes to food safety and security concerns it becomes an important field to be studied rigorously as food contributes majorly to human and animal health. The pollution of aquatic ecosystems by heavy metals (HMs) ultimately results in adverse effect on the food chain, which is covered in the current study. Fish is considered to be one of the main components of a balanced diet plate due to its high-quality protein, which sets it apart from other dietary sources. On the other hand, it is also susceptible to the absorption and bioaccumulation of HMs at toxic levels. In our study, we have considered three different species (Nemipterus japonicus, Oreochromis mossambicus, and Lates calcarifer) of fish collected from Kanyakumari, Tamil Nadu (India). Three organs namely liver, gill, and muscle were taken into consideration for the HM profiling using Inductively Coupled Plasma Mass Spectrometry (ICP-MS). The Arsenic (As), Cadmium (Cd), Chromium (Cr), Mercury (Hg) and Lead (Pb) were found to be in varied concentrations ranging from 0.1 to 1.13, 0.89–1.45, 9.95–30.66, 0.14–1.62, and 24.69–189.5 µg/kg respectively, in the studied organs of fish. Carcinogenic and noncarcinogenic risk assessments were also done indicating a notable level of Pb and Cr in selected fish species. The Hazard Index (HI) for Oreochromis mossambicus was >1 for adults and children, indicating future possibility of probable health hazards on daily consumption of these fish. In Oreochromis mossambicus, the cancer risk (CR) values for Cr and As were significantly high, particularly for children, indicating a possible occurrence of acute health risk as it exceeded the threshold of 1 × 10−3 and suggesting a significant concern. Though consumption of fish on daily basis in such significant quantity is practically impossible both for adult and children, rendering these species safe.

A Study on Total Mercury Content in Surface Water and Backwater Fishes of Periyar

Aquatic systems are extensively contaminated with heavy metals released due to anthropogenic activities. Mercury is one of toxic elements and its toxicity to humans has been established. The concern about mercuric pollution in the environments started with the incident of ‘Minamata’ in Japan in 1950’s. During the study period, flowing mercury electrode was used for the preparation of caustic at Travancore Cochin Chemicals Ltd (TCC), Eloor and effluents of small industries at Edayar were the sources of mercuric pollution. Surface water samples were collected from 1Km apart from TCC, near to Indian Rare Earth Ltd (IRE), Muttinakam and Mannamthuruth and fishes (male and female) were collected from this region with the help of local fishermen. This study implies the amount of mercury in aquatic system and its influence in different body components of three fishes. Total mercury content in both the samples analysed using cold vapour atomic absorption using Mercury Analyser MA-5840 and loss on mercury on heating processes (fishes) was decreased by the use of Bethge Apparatus. Fishes were Oreochromis mossambicus (Thilapia), Mugil cephalus (Mullet) and Arius arius (Cat fish) which were living in surface to near shore, middle of the river and bottom. The proximate composition (AOAC, 2000) of fishes showed that they were low fat (0.57-4.24%) with high protein content (18.4-21.96%). The total mercury content in surface water varied from 1.667- 3.334ng/ml and it was above tolerance level (1ng/ml) while in fishes followed the order A. arius> M. cephalus> O. mossambicus. Relatively higher concentrations of mercury were noticed in gut and liver than muscle, and also male fishes predominated over female. This study shows that mercury cycle in the habitat water did not influence to any hazardous level in these three fishes.

Copper and Temperature Interaction Induced Gill and Liver Lesions and Behaviour Alterations in Mozambique Tilapia (Oreochromis mossambicus)

Climate changes linked to extreme events pose a threat to freshwater biodiversity, impacting organs, behaviour, and reproduction. Moreover, these changes can be amplified by pollution. Copper sulphate (CuSO4) is used in agriculture and aquaculture, so the copper can reach streams, rivers, and lakes impacting fish. This study evaluated the combined effects of temperature and copper on gills and liver histology biomarkers and in the behaviour of Mozambique tilapia over 28 days. Tilapias were exposed to different water temperatures (25 °C and 32 °C) and CuSO4 concentrations (1.1 and 3.6 mg/L). Fish from the control group were exposed to water without copper sulphate and at 25 °C (within their optimum range). Histopathological analysis revealed significant tissue lesions, namely aneurysms and bending of gill lamellae, and hyalinization and vacuolization in the liver at the higher temperature and CuSO4 level. Moreover, behavioural observations revealed increased stress changes under the same conditions. These findings highlight the effects of fast climate change, and rising temperatures on copper toxicity, underlining the necessity for strict monitoring and regulation of copper use due to future climate change scenarios to protect aquatic ecosystems, ichthyofauna population and trophic web dynamics. This data also alerts for similar problems with other toxic metals or chemicals, at short term, in streams and rivers, under rapid climate changes and more frequent extreme events.

Environmental conditions elicit a slow but enduring response of histone post-translational modifications in Mozambique tilapia.

This study sheds new light on the timescale through which histone post-translational modifications (PTMs) respond to environmental stimuli, demonstrating that the histone PTM response does not necessarily precede the proteomic response or acclimation. After a variety of salinity treatments were administered to Mozambique tilapia (Oreochromis mossambicus) throughout their lifetimes, we quantified 343 histone PTMs in the gills of each fish. We show here that histone PTMs differ dramatically between fish exposed to distinct environmental conditions for 18 months, and that the majority of these histone PTM alterations persist for at least 4 weeks, irrespective of further salinity changes. However, histone PTMs respond minimally to 4-week-long periods of salinity acclimation during adulthood. The results of this study altogether signify that patterns of histone PTMs in individuals reflect their prolonged exposure to environmental conditions.

Effect of temperature fluctuations during frozen storage on ice crystal distribution and quality of tilapia (Oreochromis mossambicus)

The study constructed a model of temperature fluctuation (TF, −20 °C ∼ -10 °C) during frozen status to build a link between the tilapia fillets muscle of ice crystal morphology, moisture distribution, protein oxidation index and the edible quality. When TF treatment more than 3 times, the brightness, color and hardness of frozen tilapia fillets decreased significantly, and the cooking loss and thawing loss increased significantly. The free and unconjugated water in frozen fish fillets exceeded 97 % and did not change much after 9 times TF. The K and TVB-N values were within the safety standards (K < 60 %, TVB-N < 30 mg N/100 g). The ice crystals in the tissues were significantly increased. Protein carbonyls and Ca2+-ATPase were significantly reduced, and secondary structures were irregular. Network correlation analysis showed that ice crystal morphology was significantly correlated with the color, texture and protein oxidation index of frozen tilapia fillets. The results would provide theoretical approach for the transportation and sales of tilapia industrial enterprises.

Assessing biological invasion predatory impacts through interaction strengths and morphological trophic profiling

AbstractBiological invasions are a major stressor on ecosystems worldwide, but tools to predict their predatory impact remain limited. Here, we quantified invader impacts using two complementary approaches: functional responses (to reveal per capita and multiple predator interaction strengths) and ecomorphology (to reveal trophic profiles and competitive overlap). We compared Mozambique tilapia Oreochromis mossambicus, a native southern African cichlid, and a near-trophically analogous invasive congener, the Nile tilapia Oreochromis niloticus. Both Nile tilapia and Mozambique tilapia exhibited a potentially prey population destabilizing Type II functional response. In both single and multiple predator pairings, invasive Nile tilapia had significantly greater prey consumption rates than native Mozambique tilapia, and thereby a greater predatory impact than its native congeneric. Attack rates were greater for Nile tilapia than Mozambique tilapia, with both species showing more similar handling times and maximum feeding rates. No evidence for multiple predator effects was detected within or between these species, and therefore impacts of both species increased additively in the presence of conspecific or heterospecific competitors. Morphological trait analyses found general differences between these two species, with the invasive Nile tilapia having distinctively larger lower jaw closing force, gill resistance and gill raker length, which facilitated greater feeding capacities over the native species. Trophic profiles predicted using morphological trait differences showed high dietary overlap and served as evidence for potential exploitative competition between the two species. These results reveal superior interaction strengths and ecomorphological trait profiles of an invasive over native species which could influence impact and native species replacement dynamics. Novel applications of functional response and ecomorphology provide complementary insights into predatory and competitive impacts from invasive species, aiding impact prediction across environmental contexts.

Benzalkonium chloride induced acute toxicity and its multifaceted implications on growth, hematological metrics, biochemical profiles, and stress-responsive biomarkers in tilapia (Oreochromis mossambicus).

This study aimed to investigate the toxic effects of benzalkonium chloride (BAC) on Oreochromis mossambicus, a freshwater fish species. Probit analysis was used to determine the lethal concentration (LC50) of BAC for different exposure periods (24, 48, 72, and 96h). The viability of fish exposed to BAC was assessed using the general threshold survival models (GUTS) and confirmed with relevant datasets to evaluate model accuracy. Experimental groups of fish were exposed to BAC concentrations equivalent to 10% and 20% of the 96-h LC50 for 45days. The study revealed significant alterations in various parameters during sublethal BAC exposure. These effects included decreased specific growth rate (SGR), red blood cell count (RBC), hemoglobin (Hb) concentration, hematocrit (Ht) value, plasma protein, and albumin levels, as well as acetylcholinesterase (AChE) activities in both gills and liver. Additionally, an increase in gastrosomatic index (GSI), feed conversion ratio (FCR), plasma glucose and creatinine concentrations, alanine aminotransferase (ALT), aspartate aminotransferase (AST) enzymatic activities, catalase (CAT), superoxide dismutase (SOD), and malondialdehyde (MDA) levels were observed in the exposed fish's gills and liver. Furthermore, the study found that glutathione S-transferase (GST) and glutathione peroxidase (GPx) levels initially increased and then decreased in both gills and liver after exposure to BAC. Correlation matrix analysis, multivariate multiple regression (MMR), canonical correspondence analysis (CCA), integrated biomarker response (IBR), and biomarker response index (BRI) were utilized to assess the impact of BAC on fish, highlighting significant effects on multiple biomarkers in O. mossambicus following surfactant exposure. Thus, the study provides valuable insights into the toxic effects of BAC on this fish species, emphasizing the importance of monitoring such pollutants in aquatic environments.

Evaluation of Heavy Metal Levels in Fish and Their Potential Health Risks to Humans

Fish is a major component of the daily diet all over the world and is a fantastic source of minerals, omega-3 fatty acids, vitamins and protein crucial to human wellness. Surprisingly, not all fish are as healthy as they appear to be, especially environmental contaminants additionally exert a detrimental effect, especially heavy metals which have the potential to bioaccumulate and biomagnify and thus it has grown to be a major public health issue throughout the world, including Bangladesh. In this investigation distribution and concentration of Pb, Cr, Cd and Mn in 36 samples of 3 fish species (Mozambique tilapia, Labeo bata, Putinussarana) were collected from four locations around Rajshahi City Corporation and have been investigated. The samples were digested with an HNO3-HClO4-HCl combination for the metal analysis. All samples were analyzed in duplicate using an atomic absorption spectrophotometer and the results reported here were averages of these duplicates. According to this research, it is observed that the concentration of Cd, Pb, Cr, and Mn in fish samples ranged from 0.0104 mg/kg to 1.2399 mg/kg, 0.6711 mg/kg to 6.051 mg/kg, 0.0799 mg/kg to 3.9084 mg/kg and 0.1622 mg/kg to 2.4685 mg/kg respectively. According to the result, several samples have heavy metal concentrations that are beyond the standard permissible range. Hazard index of those fish species in the order of Labeo bata &gt; Mozambique tilapia &gt; Putinussarana. Heavy metal concentration in those fish species and their health risk assessment (EDI, THQ, CR, HI) are recorded and discussed critically and systematically in this monograph.

Identifying Universal Fish Biomarker Genes in Response to PCB126 Exposure by Comparative Transcriptomic Analyses.

Water pollution remains a major environmental concern, with increased toxic by-products being released into water bodies. Many of these chemical contaminants persist in the environment and bio-accumulate in aquatic organisms. At present, toxicological tests are mostly based on laboratory tests, and effective methods for monitoring wild aquatic environments remain lacking. In the present study, we used a well-characterized toxic chemical, 3,3',4,4',5-polychlorinated biphenyl (PCB126), as an example to try to identify common biomarker genes to be used for predictive toxicity of this toxic substance. First, we used two laboratory fish models, the zebrafish (Danio rerio) and medaka (Oryzias latipes), to expose PCB126 to obtain liver transcriptomic data by RNA-seq. Comparative transcriptomic analyses indicated generally conserved and concerted changes from the two species, thus validating the transcriptomic data for biomarker gene selection. Based on the common up- and downregulated genes in the two species, we selected nine biomarker genes to further test in other fish species. The first validation experiment was carried out using the third fish species, Mozambique tilapia (Oreochromis mossambicus), and essentially, all these biomarker genes were validated for consistent responses with the two laboratory fish models. Finally, to develop universal PCR primers suitable for potentially all teleost fish species, we designed degenerate primers and tested them in the three fish species as well as in another fish species without a genomic sequence available: guppy (Poecilia reticulata). We found all the biomarker genes showed consistent response to PCB126 exposure in at least 50% of the species. Thus, our study provides a promising strategy to identify common biomarker genes to be used for teleost fish analyses. By using degenerate PCR primers and analyzing multiple biomarker genes, it is possible to develop diagnostic PCR arrays to predict water contamination from any wild fish species sampled in different water bodies.

Effect of Dietary Supplementation with Organic Silicon on the Growth Performance, Blood Biochemistry, Digestive Enzymes, Morphohistology, Intestinal Microbiota and Stress Resistance in Juvenile Hybrid Tilapia (Oreochromis mossambicus × Oreochromis niloticus).

In recent decades, interest has been aroused worldwide in the use of silicon in nutrition; however, information on its effect on nutrition and metabolism of fish is limited. The objective of the research was to evaluate the effect of dietary supplementation with organic silicon on the growth performance, blood biochemistry, digestive enzymes, morphohistology and intestinal microbiota and stress resistance in hybrid Tilapia (Oreochromis mossambicus × Oreochromis niloticus). Methodologically, six levels of organic silicon (DOS) [control (0), 10, 20, 30, 40 and 50 mg·kg-1] were used to feed juvenile fish (initial weight 7.51 ± 0.25 g) grown for eight weeks in 18 aquariums (15 fish/aquarium). The results indicated that growth performance showed differences (p < 0.05) for specific growth rate, feed conversion and survival. Triglycerides, cholesterol and glucose, transaminases and digestive enzymes were significantly influenced by DOS levels. The histological study confirmed that the administered diets did not cause damage and induced significant morphological changes in the proximal intestine. The 16S rRNA gene sequencing analysis of the gut microbiota showed a high diversity and richness of OTU/Chao-1, with Fusobacteria, Proteobacteria, Bacteroidetes and Acidobacteria predominating in the DOS treatments compared to the control (p < 0.05). Induction of hypoxia stress after the feeding period showed a significant relative survival rate of 83.33% in fish fed 50 mg·kg-1. It is concluded that the DOS treatments performed better than the control treatment in most of the variables analysed. DOS had no negative effects on the fish. The results showed that up to 50 mg·kg-1 DOS improved digestive, metabolic and growth performance in hybrid Tilapia.