Evaluation of stress in farmed Atlantic salmon (Salmo salar) using different biological matrices.

Atlantic salmon were subjected to an acute crowding scenario, and their subsequent stress responses were observed under three distinct swimming speed/water flow (WF) conditions: 0.5, 1, and 1.5 body lengths per second (BL/s). Feces, dermal mucus, and plasma were collected for analysis at 1, 6, and 24 h (h) post-stress. Additionally, the head kidney and two regions of the brain (pituitary and POA) were collected for transcript expression analysis. Fish swimming at 0.5 BL/s exhibited higher pre-stress (baseline) cortisol levels. Across all groups and matrices, the highest cortisol/cortisol metabolites (CM) levels were observed at the 1 h post-stress sampling point. At 6 h (second sampling time point), a clear decline toward baseline levels were observe in all groups. Significant increases in mean plasma glucose levels were observed at 1 h post-stress for all groups. The mean plasma lactate levels varied based on WF treatments, with a significant increase observed at 1 h only for the 1.5 BL/s group. Additionally, significant decreases in mean plasma lactate were noted at 6 and 24 h post-stress for some groups. The mRNA abundances of the tested genes (star, cyp17a1, hsd11ß2, srd5a1) increased following the stress events. These changes were not uniform across all groups and were tissue dependent. In summary, the results indicate that mucus and feces can be used as potentially less invasive matrices than blood for evaluating stress and, consequently, the welfare of Atlantic salmon in captivity.

Effects of Exposure Timing on cyp1a Expression, PAH Elimination, and Lipid Utilization in Lumpfish Embryos Exposed to Produced Water.

Intentional discharges of produced water from oil production platforms to the marine environment contain a complex mixture of toxicants, including polycyclic aromatic hydrocarbons (PAHs). Early life stages of fish are highly sensitive to petrogenic exposure, and short-term exposure during critical periods of embryonic development may have detrimental effects on larvae health and survival. However, why different periods are more sensitive to exposure than others are not fully understood. Three identical exposure experiments (48 h, approx. 30 µg/L tPAH, sum 42 PAHs) on lumpfish (Cyclopterus lumpus) embryos were conducted where only exposure timing was varied: 0-48 h post fertilization (hpf, starting before chorion hardening), 36-84 hpf (starting after chorion hardening), and 240-288 hpf (during organogenesis). Total PAH (tPAH) uptake at the end of exposure was 5× higher when exposed during fertilization than when exposed late (during organogenesis). The first evidence of cyp1a induction in lumpfish during embryogenesis was observed after 84 hpf. Early exposure affected lipid droplet coagulation, indicating altered lipid utilization during embryogenesis. Although no significant impacts of exposure were observed on hatching success, hatching was delayed when exposed at the latest time point. This study shows that chorion properties, lipid content, biotransformation potential, and timing of produced water exposure during lumpfish embryogenesis affected PAH uptake and elimination.

The threat of COVID-19 to the conservation of Tanzanian national parks.

In many low-income countries, the conservation of natural resources in protected areas relies on tourism revenue. However, tourist numbers in Africa were severely reduced by the COVID-19 pandemic, thus, putting the conservation of these important protected areas at risk. We use records from gate passings at national parks across Tanzania to demonstrate the immediate and severe impact on tourist numbers and revenues resulting from the COVID-19 pandemic and associated restrictions, and whether international and local (East African) tourists were affected equally. We discuss mechanisms that may reduce future negative impacts of sudden loss of revenue from international tourism, such as increasing the revenue portfolio and thereby decrease the dependency on revenues from international tourists. More important, we encourage local governments, national park authorities, and the world community to further develop and initiate external funding options to reduce the dependency on income from international nature-based tourism to preserve national parks and biodiversity. An additional long-term goal for ensuring sustained conservation would be to increase benefits to local communities adjacent to national parks, encouraging local involvement and thereby reducing the dependence on external funding in the future.

Element concentrations, histology and serum biochemistry of arctic char (Salvelinus alpinus) and shorthorn sculpins (Myoxocephalus scorpius) in northwest Greenland.

The increasing exploratory efforts in the Greenland mineral industry, and in particular, the proposed rare earth element (REE) mining projects, requires an urgent need to generate data on baseline REE concentrations and their potential environmental impacts. Herein, we have investigated REE concentrations in anadromous Arctic char (Salvelinus alpinus) and shorthorn sculpins (Myoxocephalus scorpius) from uncontaminated sites in Northwest Greenland, along with the relationships between the element concentrations in gills and liver, and gill histology and serum biochemical parameters. Concentrations of arsenic, silver, cadmium, cerium, chromium, copper, dysprosium, mercury, lanthanum, neodymium, lead, selenium, yttrium, and zinc in gills, liver and muscle are presented. No significant statistical correlations were observed between element concentrations in different organs and gill histology or serum biochemical parameters. However, we observed positive relationships between age and histopathology, emphasizing the importance of including age as a co-variable in histological studies of fish. Despite no element-induced effects were observed, this study is considered an important baseline study, which can be used as a reference for the assessment of impacts of potential future REE mine sites in Greenland.

Effects of an environmentally relevant PFAS mixture on dopamine and steroid hormone levels in exposed mice.

In the present study, we investigated the dopaminergic and steroid hormone systems of A/J mice fed environmentally relevant concentrations of a perfluoroalkyl substance (PFAS) mixture over a period of 10 weeks. The PFAS mixture was chosen based on measured PFAS concentrations in earthworms at a Norwegian skiing area (Trondheim) and consisted of eight different PFAS. Dietary exposure to PFAS led to lower total brain dopamine (DA) concentrations in male mice, as compared to control. On the transcript level, brain tyrosine hydroxylase (th) of PFAS exposed males was reduced, compared to the control group. No significant differences were observed on the transcript levels of enzymes responsible for DA metabolism, namely - monoamine oxidase (maoa and maob) and catechol-O methyltransferase (comt). We detected increased transcript level for DA receptor 2 (dr2) in PFAS exposed females, while expression of DA receptor 1 (dr1), DA transporter (dat) and vesicular monoamine transporter (vmat) were not affected by PFAS exposure. Regarding the steroid hormones, plasma and muscle testosterone (T), 11-ketotestosterone (11-KT) and 17ß-estradiol (E2) levels, as well as transcripts for estrogen receptors (esr1 and esr2), gonadotropin releasing hormone (gnrh) and aromatase (cyp19) were unaltered by the PFAS treatment. These results indicate that exposure to PFAS doses, comparable to previous observation in earthworms at a Norwegian skiing area, may alter the dopaminergic system of mice with overt consequences for health, general physiology, cognitive behavior, reproduction and metabolism.

Quality screening of the Lagos lagoon sediment by assessing the cytotoxicity and toxicological responses of rat hepatoma H4IIE and fish PLHC-1 cell-lines using different extraction approaches.

In this study, sediment samples from Makoko and Ikorodu sites of the Lagos lagoon (Nigeria) were screened for toxicological responses on mammalian and fish cell lines using different extraction methods. Rat hepatoma H4IIE and fish PLHC-1 cell-lines were exposed to serial dilutions of the elutriate, polar and non-polar extracts. We evaluated exposed cells for cytotoxicity and aryl hydrocarbon receptor (AhR)-mediated toxicity. Cells exposed to polar and water extracts from Makoko and Ikorodu showed viability percentage of >80% at 48 h. On the other hand, exposure to the non-polar extracts exhibited cell viability of 50-60% at all tested dilutions. For both cell lines, a significant concentration-dependent induction of cyp1a mRNA was observed after exposure to the different extracts from both sites. Interestingly, the extracts affected functional enzymes differently for both cell lines. For H4IIE cells, while EROD activity paralleled cyp1a mRNA expression patterns, MROD showed significant concentration-specific reduction in cells exposed to polar and water extracts. On the contrary, while the MROD activity paralleled cyp1a mRNA, EROD activity was significantly inhibited in PLHC-1 cells exposed to water-, polar and non-polar extracts from both sites. These observations paralleled sediments PAH contamination burden from the study sites as revealed by co-relation analysis. In conclusion, although the different extracts did not exert high cytotoxic effects (except the non-polar) at the tested concentrations, they significantly modulated phase I biotransformation responses, showing that the studied sediments contain complex chemical mixture in the different extracts, with potential for overt physiological and general health consequences.

Quantitative transcriptomics, and lipidomics in evaluating ovarian developmental effects in Atlantic cod (Gadus morhua) caged at a capped marine waste disposal site.

In the present study, a previously capped waste disposal site at Kollevåg (Norway) was selected to study the effects of contaminant leakage on biomarkers associated with Atlantic cod (Gadus morhua) reproductive endocrinology and development. Immature cod were caged for 6 weeks at 3 locations, selected to achieve a spatial gradient of contamination, and compared to a reference station. Quantitative transcriptomic, and lipidomic analysis was used to evaluate the effects of the potential complex contaminant mixture on ovarian developmental and endocrine physiology. The number of expressed transcripts, with 0.75 log2-fold differential expression or more, varied among stations and paralleled the severity of contamination. Particularly, significant bioaccumulation of ∑PCB-7, ∑DDTs and ∑PBDEs were observed at station 1, compared to the other station, including the reference station. Respectively 1416, 698 and 719 differentially expressed genes (DEGs), were observed at stations 1, 2 and 3, compared to the reference station, with transcripts belonging to steroid hormone synthesis pathway being significantly upregulation. Transcription factors such as esr2 and ahr2 were increased at all three stations, with highest fold-change at Station 1. MetaCore pathway maps identified affected pathways that are involved in ovarian physiology, where some unique pathways were significantly affected at each station. For the lipidomics, sphingolipid metabolism was particularly affected at station 1, and these effects paralleled the high contaminant burden at this station. Overall, our findings showed a novel and direct association between contaminant burden and ovarian toxicological and endocrine physiological responses in cod caged at the capped Kollevåg waste disposal site.

Biotransformation and oxidative stress responses in rat hepatic cell-line (H4IIE) exposed to organophosphate esters (OPEs).

Organophosphate esters (OPEs) are frequently used as replacements for the banned polybrominated diphenyl ether (PBDEs). Since OPEs are structurally similar to organophosphate pesticides, exposure and toxicity of these compounds is of significant societal and scientific interest. Cytotoxicity (MTT), biotransformation (cyp1a1) and oxidative stress responses (gpx1, gr, gsta2, cat) were investigated in H4IIE cells exposed for 48 h to four different OPEs (tributyl phosphate (TBP), tris(2-butoxyethyl) phosphate (TBOEP), tris-(2-chloroethyl) phosphate (TCEP) and triphenyl phosphate (TPP)). MTT assay revealed a dose-dependent decrease of cell viability following exposure to TBP, TBOEP, TCEP and TPP. Cells treated with TBP and TBOEP exhibited significant increase of cyp1a1 at the highest tested concentration, at transcriptional and enzymatic (MROD) levels. Significant increases of oxidative stress markers were observed after exposure to TBP and TBOEP. On the other hand, cells treated with TCEP and TPP showed opposite trends between cyp1a1 mRNA and enzymatic activities. Furthermore, exposure to TCEP increased gst and cat especially at the highest concentration tested, whereas TPP produced significant changes only for gr and cat at the highest concentration. In conclusion, OPEs produced compound and concentration-specific effects on biotransformation and oxidative stress processes. Overall, our results suggest the participation of multiple mechanisms of detoxification in defense of OPEs exposure with different modes of action depending on their chemical structure.

Levels, Patterns, and Biomagnification Potential of Perfluoroalkyl Substances in a Terrestrial Food Chain in a Nordic Skiing Area.

Perfluoroalkyl substances (PFASs) are used in a wide range of consumer products, including ski products, such as ski waxes. However, there is limited knowledge on the release of PFASs from such products into the environment and the resultant uptake in biota and transport in food webs. We investigated levels, patterns, and biomagnification of PFASs in soil, earthworms (Eisenia fetida), and Bank voles (Myodes glareolus) from a skiing area in Trondheim, Norway. In general, there was higher PFAS levels in the skiing area compared to the reference area with no skiing activities. The skiing area was dominated by long-chained perfluorocarboxylic acids (PFCAs, ≥70%), while the reference area was dominated by short-chained PFCAs (>60%). The soil PFAS pattern in the skiing area was comparable to analyzed ski waxes, indicating that ski products are important sources of PFASs in the skiing area. A biomagnification factor (BMF) > 1 was detected for Bank volewhole/earthwormwhole for perfluorooctansulfonate in the skiing area. All other PFASs showed a BMF < 1. However, it should be noted that these organisms represent the base of the terrestrial food web, and PFASs originating from ski wax may result to higher exposure in organisms at the top of the food chain.

Modulation of Neuro-Dopamine Homeostasis in Juvenile Female Atlantic Cod ( Gadus morhua) Exposed to Polycyclic Aromatic Hydrocarbons and Perfluoroalkyl Substances.

The dopaminergic effect of PAH and PFAS mixtures, prepared according to environmentally relevant concentrations, has been studied in juvenile female Atlantic cod ( Gadus morhua). Benzo[a]pyrene, dibenzothiophene, fluorene, naphthalene, phenanthrene, and pyrene were used to prepare a PAH mixture, while PFNA, PFOA, PFOS, and PFTrA were used to prepare a PFAS mixture. Cod were injected intraperitoneally twice, with either a low (1×) or high (20×) dose of each compound mixture or their combinations. After 2 weeks of exposure, levels of plasma 17ß-estradiol (E2) were significantly elevated in high PAH/high PFAS treated group. Brain dopamine/metabolite ratios (DOPAC/dopamine and HVA+DOPAC/dopamine) changed with E2 plasma levels, except for high PAH/low PFAS and low PAH/high PFAS treated groups. On the transcript levels, th mRNA inversely correlated with dopamine/metabolite ratios and gnrh2 mRNA levels. Respective decreases and increases of drd1 and drd2a after exposure to the high PAH dose were observed. Specifically, high PFAS exposure decreased both drds, leading to high plasma E2 concentrations. Other studied end points suggest that these compounds, at different doses and combinations, have different toxicity threshold and modes of action. These effects indicate potential alterations in the feedback signaling processes within the dopaminergic pathway by these contaminant mixtures.

Xenobiotic biotransformation, oxidative stress and obesogenic molecular biomarker responses in Tilapia guineensis from Eleyele Lake, Nigeria.

Despite the important ecosystem and hydrological roles of coastal and inland waters, there are no established biomonitoring protocols for evaluating environmental, wildlife and human health for these coastlines in Nigeria. In the present study, contaminants tissue burden and effects at molecular and physiological levels, were investigated in Tilapia guineensis from a man-made lake (Eleyele Lake) that is used for municipal domestic water supply and compared to a reference site (Igboho Lake). Gene expression of phase I and II biotransformation systems, oxidative stress and obesogen responses were analyzed using real-time PCR, and these results were related to general health index (condition factor: CF) and muscle burden of trace metals, aliphatic and polycyclic aromatic hydrocarbons (PAHs). We observed a significant increase in phase I and II biotransformation systems, oxidative stress and obesogen responses in male and female fish from Eleyele lake compared with the reference site. Overall, our data showed significant relationships between biological responses and tissue concentrations of metals and PAHs for the Eleyele lake compared with the reference site. Given that a positive influence on genes and pathways associated with metabolic status has been previously associated with peroxisome proliferator activated receptors (PPARs), xenobiotic compounds that activate PPARs may produce changes in energy and metabolic processes, leading to obesity. The high CF (>1 = good health condition) observed, coupled with the high muscle burden of inorganic and organic contaminants in fish from Eleyele lake, suggest a potential obesogenic effect in these fishes. These findings represent co-relational evidence that the Eleyele lake is contaminated and consequently affecting biological and physiological integrity of organisms inhabiting the lake. These findings also suggest potential health risks for humans, since the lake is extensively used for domestic water supply and fisheries.

Hazardous properties and toxicological update of mercury: From fish food to human health safety perspective.

The mercury (Hg) poisoning of Minamata Bay of Japan widely activated a global attention to Hg toxicity and its potential consequences to the aquatic ecosystem and human health. This has resulted to an increased need for a dynamic assembly, contextualization, and quantification of both the current state-of-the-art and approaches for understanding the cause-and-effect relationships of Hg exposure. Thus, the objective of this present review is to provide both hazardous toxic properties and toxicological update of Hg, focusing on how it ultimately affects the aquatic biota to potentially produce human health effects. Primarily, we discussed processes that relate to Hg exposure, including immunological aspects and risk assessment, vulnerability, toxicokinetics, and toxicodynamics, using edible fish, swordfish (Xiphias gladius), as a model. In addition, we summarized available information about Hg concentration limits set by different governmental agencies, as recognized by national and international standardization authorities.

Biphasic modulation of neuro- and interrenal steroidogenesis in juvenile African sharptooth catfish (Clarias gariepinus) exposed to waterborne di-(2-ethylhexyl) phthalate.

Receptor (i.e. genomic) and non-receptor (or non-genomic) effects of endocrine toxicology have received limited or almost non-existent attention for tropical species and regions. In the present study, we have evaluated the effects of di-(2-ethylhexyl) phthalate (DEHP) on neuro- and interrenal steroidogenesis of the African catfish (Clarias gariepinus) using molecular, immunochemical and physiological approaches. Juvenile fish (mean weight and length: 5.6±0.6g and 8.2±1.2cm, respectively), were randomly distributed into ten 120L rectangular glass tanks containing 60L of dechlorinated tap water, at 50 fish per exposure group. The fish were exposed to environmentally relevant concentrations of DEHP, consisting of 0 (ethanol solvent control), 10, 100, 200, and 400µg DEHP/L water and performed in two replicates. Brain, liver and head kidney samples were collected at day 3, 7 and 14 after exposure, and analysed for star, p450scc, cyp19a1, cyp17, cyp11ß-, 3ß-, 17ß- and 20ß-hsd, and 17ß-ohase mRNA expression using real-time PCR. The StAR, P450scc and CYP19 proteins were measured using immunoblotting method, while estradiol-17ß (E2) and testosterone (T) were measured in liver homogenate using enzyme immunoassay (EIA). Our data showed a consistent and unique pattern of biphasic effect on star and steroidogenic enzyme genes with increases at low concentration (10µg/L) and thereafter, a concentration-dependent decrease in both the brain and head kidney, that paralleled the expression of StAR, P450scc and CYP19 proteins. Cellular E2 and T levels showed an apparent DEHP concentration-dependent increase at day 14 of exposure. The observed consistency in the current findings and in view of previous reports on contaminants-induced alterations in neuro- and interrenal steroidogenesis, the broader toxicological and endocrine disruptor implication of our data indicate potentials for overt reproductive, metabolic, physiological and general health consequences for the exposed organisms.

Differential modulation of neuro- and interrenal steroidogenesis of juvenile salmon by the organophosphates - tris(2-butoxyethyl)- and tris(2-cloroethyl) phosphate.

Following the ban of polybrominated diphenyl ether (PBDEs) flame retardants under well-documented toxicity issues, organophosphate such as tris(2-butoxyethyl) phosphate (TBOEP) and tris(2-cloroethyl) phosphate (TCEP) were considered as potential substitutes. Although TBOEP and TCEP are consistently detected in the aquatic environment, there are few data about the possible toxicological effects of these compounds on aquatic organisms, including fish. In the present study, we have investigated the influence of TBOEP and TCEP on neuro- and interrenal steroidogenesis of juvenile Atlantic salmon (Salmo salar), after a seven-day exposure to four different concentrations (0 (control), 0.04, 0.2 and 1mg/L) of each compound. TBOEP and TCEP were diluted in Milli-Q water. The expression of genes involved in steroidogenesis (StAR, cyp19a, cyp19b, cholesterol side-chain cleavage enzyme (P450scc), 3ß-hydroxysteroid dehydrogenase (3ß-hsd), and 11ß-hydroxylase (cyp11ß)), were analyzed in the brain and head kidney using real-time PCR. Plasma 11-ketotestosterone (11-KT) analysis was performed using enzyme immunoassay (EIA). Our results showed that TBOEP accumulated more rapidly than TCEP in fish muscle tissue. Surprisingly, TBOEP produced less pronounced effects than TCEP on neural and interrenal steroidogenic responses, despite the observed rapid uptake and bioaccumulation pattern. Specifically, TBOEP produced significant and consistent concentration-specific alterations on neural- and interrenal steroidogenesis. Plasma levels of 11-KT were not significantly altered by any of the exposures. The increased expression of steroidogenic genes demonstrated in the present study could produce time-specific alterations in the production of glucocorticoids and steroid hormones that play integral roles in fish metabolism, stress responses and adaptation, sexual maturation, reproduction and migration with overt consequences on reproductive success and survival.

Lipid peroxidation and oxidative stress responses in juvenile salmon exposed to waterborne levels of the organophosphate compounds tris(2-butoxyethyl)- and tris(2-chloroethyl) phosphates.

There is limited knowledge on the toxicological, physiological, and molecular effects attributed to organophosphate (OP) compounds currently used as flame retardants or additives in consumer products. This study investigated the effects on oxidative stress and lipid peroxidation in juvenile Atlantic salmon liver and brain samples after exposure to two OP compounds, tris(2-butoxyethyl) phosphate (TBOEP) and tris(2-chloroethyl) phosphate (TCEP). In this study, groups of juvenile Atlantic salmon were exposed using a semistatic experimental protocol over a 7-d period to 3 different concentrations (0.04, 0.2, or 1 mg/L) of TBOEP and TCEP. When toxicological factors such as bioaccumulation and bioconcentration, and chemical structural characteristics and behavior, including absorption to solid materials, are considered, these concentrations represent environmentally relevant concentrations. The concentrations of the contaminants were derived from levels of their environmental occurrence. The expression of genes related to oxidative stress-glutathione peroxidase (GPx), glutathione reductase (GR), glutathione S-transferase (GST)-and to lipid peroxidation-peroxisome proliferator-activated receptors (PPAR)-were determined using quantitative (real-time) polymerase chain reaction (PCR). The presence of PPAR proteins was also investigated using immunochemical methods. Levels of thiobarbituric acid-reactive substances (TBARS) in liver were used as a measure of lipid peroxidation. Overall, our data show an increase in lipid peroxidation, and this was associated with an augmented expression of genes from the glutathione family of responses. Interestingly, PPAR expression in liver after exposure to TBOEP and TCEP was consistently decreased compared to controls, while expression in brain did not show a similar trend. The results suggest that OP contaminants may induce oxidative stress and thus production of reactive oxygen substances (ROS), and modulate lipid peroxidation processes in organisms.

Concentration of polychlorinated biphenyl (PCB) congeners in the muscle of Clarias gariepinus and sediment from inland rivers of southwestern Nigeria and estimated potential human health consequences.

The distributions of polychlorinated biphenyl (PCB) congeners were determined in sediment and muscle of the African sharptooth catfish (Clarias gariepinus) from the Ogun and Ona rivers, southwest Nigeria. In addition, the effect of PCB congeners on condition factor (CF) and associated human health risk was assessed using muscle levels for a noncarcinogenic hazard quotient (HQ) calculation. Elevated concentrations of high-molecular-weight (HMW) PCB congeners were detected in sediment and fish downstream of discharge points of both rivers. A significant reduction in fish body weight and CF was observed to correlate with high PCB congener concentrations in the Ona River. A principal component (PC) biplot revealed significant site-related PCB congener distribution patterns for HMW PCB in samples from the Ogun River (71.3%), while the Ona River (42.6%) showed significant PCB congener patterns for low-molecular-weight (LMW) congeners. Biota-sediment accumulation factor (BSAF) was higher downstream for both rivers, presenting PCB congener-specific accumulation patterns in the Ona River. Significant decreases in fish body weight, length and CF were observed downstream compared to upstream in the Ona River. The non-carcinogenic HQ of dioxin-like congener 189 downstream in both rivers exceeded the HQ = 1 threshold for children and adults for both the Ogun and Ona rivers. Overall, our results suggest that industrial discharges contribute significantly to PCB inputs into these rivers, with potential for significant health implications for neighboring communities that utilize these rivers for fishing and other domestic purposes.

Effects of Diisodecyl Phthalate on PPAR:RXR-Dependent Gene Expression Pathways in Sea Bream Hepatocytes.

Evidence that endocrine-disrupting chemicals (EDCs) may target metabolic disturbances, beyond interference with the functions of the endocrine systems has recently accumulated. Among EDCs, phthalate plasticizers like the diisodecyl phthalate (DiDP) are commonly found contaminants of aquatic environments and have been suggested to function as obesogens by activating peroxisome proliferator activated receptors (PPARs), a subset of nuclear receptors (NRs) that act as metabolic sensors, playing pivotal roles in lipid homeostasis. However, little is known about the modulation of PPAR signaling pathways by DiDP in fish. In this study, we have first investigated the ligand binding efficiency of DiDP to the ligand binding domains of PPARs and retinoid-X-receptor-α (RXRα) proteins in fish using a molecular docking approach. Furthermore, in silico predictions were integrated by in vitro experiments to show possible dose-relationship effects of DiDP on PPAR:RXR-dependent gene expression pathways using sea bream hepatocytes. We observed that DiDP shows high binding efficiency with piscine PPARs demonstrating a greater preference for RXRα. Our studies also demonstrated the coordinate increased expression of PPARs and RXRα, as well as their downstream target genes in vitro. Principal component analysis (PCA) showed the strength of relationship between transcription of most genes involved in fatty acid metabolism and PPAR mRNA levels. In particular, fatty acid binding protein (FABP) was highly correlated to all PPARs. The results of this study suggest that DiDP can be considered an environmental stressor that activates PPAR:RXR signaling to promote long-term changes in lipid homeostasis leading to potential deleterious physiological consequences in teleost fish.

Occurrence, Species, and Organ Differences in Bioaccumulation Patterns of Phthalate Esters in Municipal Domestic Water Supply Lakes in Ibadan, Nigeria.

The occurrence of phthalate esters (PE) was examined in biota, ambient water, and sediments of two man-made lakes (Asejire and Eleyele) in southwestern Nigeria. Five fish species (Tilapia zillii, Hepsetus odoe, Parachanna obscura, Chrysichthys nigrodigitatus, and Mormyrus rume) were analyzed for PE levels and used for calculating bioconcentration factors (BCF) and biota-sediment accumulation factors (BSAF). In addition, measured PE levels were thereafter used to calculate the phthalate pollution index (PPI) in biota and the environment. At both lakes, all sampled species had k-factor > 1, showing apparently normal growth and health condition. Higher PE levels were found in sediments compared with water at both lakes, with a pattern showing that di(2-ethylhexyl) phthalate (DEHP) was predominant PE. While there were no unique patterns of PE concentrations in both lakes, differences were observed in organ concentration patterns that were evident at both lakes. For T. zillii, the BSAF was higher for dibutyl phthalate (DBP) compared to diethyl phthalate (DEP) and lowest for DEHP. The concentration pattern demonstrated that DBP concentrated more in gills (BCF: 6.7), while DEHP concentrated more in liver (BCF: 15.2) of T. zillii at Asejire. At Eleyele, T. zillii liver and gills concentrated less DEP and DEHP. The PPI value was significantly higher in sediment with respective values of 0.27 and 0.44 at Asejire and Eleyele lakes compared with water with respective values of 0.1 and 0.18 at Asejire and Eleyele lakes. Overall, our findings suggest a broader environmental and human health implication of high PE levels in these lakes, since they provide vast water volumes that are used for municipal domestic water supply. Further, these lakes support intense artisanal fisheries, representing significant sources of aquatic food resources for neighboring communities.

Effects on development, growth responses and thyroid-hormone systems in eyed-eggs and yolk-sac larvae of Atlantic salmon (Salmo salar) continuously exposed to 3,3',4,4'-tetrachlorobiphenyl (PCB-77).

Thyroid hormones (triiodothyronine, T3; and thyroxine, T4) play significant roles in development, metamorphosis, metabolism, homeostasis, cellular proliferation, and differentiation, for which the effects are mediated through thyroid hormone receptors (TRα and TRß). Similarly, the insulin-like growth factor (IGF) is involved in growth and development through regulation of somatic growth. This study was designed to examine the effects of the dioxin-like 3,3',4,4'-tetrachlorobiphenyl (PCB-77) on responses related to growth and thyroid hormone system in eyed eggs and yolk-sac larvae of Atlantic salmon. Salmon eggs were continuously exposed to two waterborne concentrations of PCB-77 (1 or 10 ng/L) over a period of 50 d covering hatching and through yolk-sac absorption stages. Sampling was performed regularly throughout the exposure period and at different time intervals. Gene expression patterns were performed on whole-body homogenate at age 500, 548, 632, 674, and 716 dd (dd: day degrees) using quantitative polymerase chain reaction (PCR). Total T3 (TT3) and total T4 (TT4) were measured using radioimmunoassay (RIA). Data showed that 10 ng PCB-77 increased dioiodinase 2 (Dio2) at 500 dd and both PCB-77 concentrations decreased dio2 expression at 548 dd. PCB-77 elevated cellular TT3 at 500 dd and was lowered at 548 dd only at 10 ng. Otherwise, time-related reduction was not affected by PCB-77 exposure as observed for the rest of the exposure period. For TT4, 1 ng PCB-77 produced a rise at 500 dd, and an apparent concentration decrease at 548 dd, before a total inhibition at 632 dd. The IGF-1 and IGF-1R were variably affected by PCB-77. For IGF-2, PCB-77 produced a concentration-dependent increase at 548 dd, and thereafter an elevation (1 ng) and fall (10 ng) at 632 dd. TRß mRNA demonstrated PCB-77 related increases during the exposure period, and this effect returned to control levels at 716 dd. For TRα, a rise was noted only after exposure to 10 ng PCB-77 at 500 dd. Overall, the present study demonstrates some possible growth and developmental consequences following exposure to PCB-77 during early life stages of Atlantic salmon.

Role of niche and micro-habitat preferences in per- and polyfluoroalkyl substances occurrence in the gills of tropical lake fish species.

The present study has investigated per- and poly-fluoroalkyl substances (PFAS) in the gill tissues of various fish species inhabiting different trophic levels within Eleyele Lake, a tropical freshwater lake in Nigeria. The mean concentrations of PFAS congeners were determined, and their trends and patterns were analyzed across different trophic species. The results revealed variations in congener abundance and species-specific patterns that was influenced by habitat and niche preferences. Multivariate associations using canonical-correlation analysis (CCA) revealed distinct trends in the relationships between gill concentrations of specific PFAS congeners and different trophic groups. The strongest congener relationships were observed in the pelagic omnivore (Oreochromic niloticus: ON) with positive associations for 4:2 FTS, 9CL-PF3ONS, PFTDA, MeFOSA and PFHxS. The differences in congener profiles for the two herbivorous fish (Sarotherodon melanotheron (SM) and Coptodon galilaeus (CG)) reflect possible divergence in microhabitat and niche preferences. Furthermore, the congener overlaps between the herbivore (CG), and benthic omnivore (Clarias gariepinus: ClG) indicate a possible niche and microhabitat overlap. Our study provides valuable insights into the congener dynamics of PFAS at Eleyele Lake. However, the dissimilarity and overlapping PFAS congener profile in fish gills reflects the interplay of species niche preference and microhabitat associations. The present study highlights the need for further research to assess ecological risks and develop effective PFAS management strategies.