Reference intervals for urinary metanephrines to creatinine ratios in dogs in Japan.

The urinary normetanephrine to creatinine ratio (uNMN/Cr) and urinary metanephrine to creatinine ratio (uMN/Cr) are commonly evaluated for the diagnosis of pheochromocytomas (PCC) in dogs. This study aimed to establish reference intervals for uNMN/Cr and uMN/Cr in 56 healthy dogs in Japan and to investigate the effect of urine collection methods on these measurements in 15 non-PCC dogs. The upper limits of reference intervals for uNMN/Cr and uMN/Cr were 124.4 nmol/mmol (90% confidence interval [CI] 107.7-137.0) and 121.1 nmol/mmol (90% CI 102.8-145.1), respectively. Both uNMN/Cr and uMN/Cr were significantly higher when urine was collected in the hospital compared to at home. Several factors, including the method of urine collection, should be considered when utilizing these reference intervals.

Characterization of Neonicotinoid Metabolites by Cytochrome P450-Mediated Metabolism in Poultry.

Neonicotinoids, a neuro-effective class of insecticides, are heavily applied in agricultural activities worldwide. Poultry can be exposed to neonicotinoids by several routes, but the knowledge of neonicotinoid's metabolism in poultry and its associated interspecies differences is highly limited. Hence, this study aims to investigate the species differences in metabolite formations, as well as cytochrome P450 (CYP)-dependent metabolism of four major neonicotinoid compounds, acetamiprid, imidacloprid, clothianidin, and thiamethoxam, in poultry. In vitro biotransformation assays using hepatic microsomes of chicken, ducks, geese, quails, and rats were conducted. Metabolites of neonicotinoids were then screened by LC/Q-TOF and quantified by LC/MS/MS. The results revealed an existence of interspecies differences in the formations of N-[(6-chloro-3-pyridyl) methyl] -N-methyl acetamidine (IM-1-5) of acetamiprid and dm-clothianidin of clothianidin between chicken and other species. In addition, the greatest CYP activities in the metabolism of most neonicotinoid substrates, such as acetamiprid to dm-acetamiprid, imidacloprid to hydroxylated-imidacloprid and imidacloprid-olefin, clothianidin to dm-clothianidin, and thiamethoxam to clothianidin, were found in chicken. These results suggested that the CYPs in chicken may have a greater capacity for metabolism of neonicotinoids compared to other poultry. This study further revealed that the maximum intrinsic clearance of dn-imidacloprid and dn-clothianidin in ducks may be superintended by CYP-mediated nitro-reductions of imidacloprid and clothianidin. Further studies employing CYP recombinant enzymes may be required to elucidate the specific CYP isoforms that may be involved in neonicotinoid metabolism in avian species.

FOUR-WEEK ORAL ADMINISTRATION OF BALOXAVIR MARBOXIL AS AN ANTI-INFLUENZA VIRUS DRUG SHOWS NO TOXICITY IN CHICKENS.

High pathogenicity avian influenza is an acute zoonotic disease with high mortality in birds caused by a high pathogenicity avian influenza virus (HPAIV). Recently, HPAIV has rapidly spread worldwide and has killed many wild birds, including endangered species. Baloxavir marboxil (BXM), an anti-influenza agent used for humans, was reported to reduce mortality and virus secretion from HPAIV-infected chickens (Gallus domesticus, order Galliformes) at a dosage of ≥2.5 mg/kg when administered simultaneously with viral challenge. Application of this treatment to endangered birds requires further information on potential avian-specific toxicity caused by repeated exposure to BXM over the long term. To obtain information of potential avian-specific toxicity, a 4-wk oral repeated-dose study of BXM was conducted in chickens (n = 6 or 7 per group), which are commonly used as laboratory avian species. The study was conducted in reference to the human pharmaceutical guidelines for nonclinical repeated-dose drug toxicity studies to evaluate systemic toxicity and exposure. No adverse changes were observed in any organs examined, and dose proportional increases in systemic exposure to active pharmaceutical ingredients were noted from 12.5 to 62.5 mg/kg per day. BXM showed no toxicity to chickens at doses of up to 62.5 mg/kg per day, at which systemic exposure was approximately 71 times higher than systemic exposure at 2.5 mg/kg, the reported efficacious dosage amount, in HPAIV-infected chickens. These results also suggest that BXM could be considered safe for treating HPAIV-infected endangered birds due to its high safety margin compared with the efficacy dose. The data in this study could contribute to the preservation of endangered birds by using BXM as a means of protecting biodiversity.

Role of brain monoamines in acetamiprid-induced anxiety-like behavior.

Neonicotinoid (NN) pesticides have been linked to increased brain dysfunction in mammals, such as anxiety-like behavior; this is thought to involve monoamines (MA), neurotransmitters that control behavior, memory, and learning. However, the mechanism by which NNs affect the central nervous system is not fully understood. In this study, we aimed to investigate whether MAs affect NNs-induced anxiety-like behavior. Mice were orally administered acetamiprid (ACE), an NN, at the no observed adverse effect level (NOAEL) of mouse (20 mg/kg body mass) set by the Food Safety Commission of Japan, and the elevated zero-maze (EZM) test was performed 30 min after administration. After behavioral analysis, levels of four MA (dopamine, 3-MT, serotonin, and histamine) in selected brain regions were determined by liquid chromatography mass spectrometry (LC/MS/MS). In the exposed group, a trend toward increased anxiety-like behavior was observed, and at least one MA concentration was significantly increased in each region. Further, significant correlations were found between behavioral test results and hippocampal serotonin and striatal dopamine concentrations, as well as between dopamine and serotonin concentrations, in the exposed group. As anxiety can influence activity in the behavioral tests, the activity of neurons in the raphe nuclei (RN), a brain region greatly involved in anxiety via the serotonergic system, was examined by staining with anti-serotonin antibodies, and increased serotonergic activity was observed. Taken together, these results suggest that ACE regulates MA levels, notably serotonin levels in the hippocampus and that RN plays an important role in ACE-induced anxiety-like behavior.

Current situation of lead (Pb) exposure in raptors and waterfowl in Japan and difference in sensitivity to in vitro lead exposure among avian species.

Although lead (Pb) poisoning in wild birds has been considered a serious problem in Japan for over 30 years, there is little information about Pb exposure and its sources throughout Japan except for Hokkaido. Furthermore, to identify and effectively prioritize the conservation needs of highly vulnerable species, differences in sensitivity to Pb exposure among avian species need to be determined. Therefore, we investigated the current situation of Pb exposure in raptors (13 species, N = 82), waterfowl (eight species, N = 44) and crows (one species, N = 6) using concentration and isotope analysis. We employed blood or tissue samples collected in various Japanese facilities mainly in 2022 or 2023. We also carried out a comparative study of blood δ-ALAD sensitivity to in vitro Pb exposure using blood of nine avian species. Pb concentrations in the blood or tissues displayed increased levels (>0.1 µg/g blood) in two raptors (2.4%), ten waterfowl (23%) and one crow (17%). Among them, poisoning levels (>0.6 µg/g blood) were found in one black kite and one common teal. The sources of Pb isotope ratios in ten blood samples with high Pb levels were determined as deriving from shot pellets (N = 9) or rifle bullets (N = 1). In the δ-ALAD study, red-crowned crane showed the highest sensitivity among the nine tested avian species and was followed in order by five Accipitriformes species (including white-tailed and Steller's sea eagle), Blakiston's fish owl, Muscovy duck and chicken, suggesting a genetically driven variance in susceptibility. Further studies on contamination conditions and exposure sources are urgently needed to inform strict regulations on the usage of Pb ammunition. Furthermore, detailed examinations of δ-ALAD sensitivity, interspecific differences, and other factors involved in the variability in sensitivity to Pb are required to identify and prioritize highly sensitive species.

Pesticide Contamination Levels in the Stomach Contents of Wild Raccoons (Procyon lotor) and Masked Palm Civets (Paguma larvata) in Japan.

Pesticides, which are vital for agriculture, pose a significant threat to wildlife in transformed Japanese landscapes. Despite global reports of pesticide poisoning in animals, limited studies have examined current wildlife exposure in croplands or metropolitan areas in the region. Using liquid chromatography-tandem mass spectrometry (LC-MS/MS) and gas chromatography-tandem mass spectrometry (GC-MS/MS), our study aimed to assess the contamination status of 368 commonly used pesticides. The stomach contents of raccoons living in croplands contained 13 pesticides, including six herbicides and 11 fungicides. Neonicotinoid insecticides, some fungicides, and previously banned insecticides (benzene hexachloride and dichlofenthion) were most frequently detected and found at the highest concentrations, suggesting direct soil-plant transfer and direct consumption by crop-eating species. In masked palm civets living in metropolitan areas, four insecticides and six fungicides were detected, indicating urban wildlife exposure from raided dustbins, urban gardens, and lumber from houses. Although the maximum measured concentrations of all pesticides were lower than the acceptable daily intake for humans, it remains unclear whether these concentrations may have toxic or adverse health effects on the species evaluated in these transformed landscapes. Our study is the first to examine recent pesticide exposures in wild mammals in Japan. Application of the method we developed will lay the foundation for the examination of pesticides in other wildlife species to assist conservation management efforts in the region. Environ Toxicol Chem 2024;43:943-951. © 2024 SETAC.

Sensitivity assessment of diphacinone by pharmacokinetic analysis in invasive black rats in the Bonin (Ogasawara) Archipelago, Japan.

The Bonin Archipelago is a United Nations Educational, Scientific and Cultural Organization's World Natural Heritage Site in Japan with a unique ecosystem; however, the invasive rodents preying on endemic species have been a significant concern. The anticoagulant rodenticide, diphacinone, sprayed by the Ministry of the Environment, has succeeded; however, its repeated use leads to rodenticide resistance. This study evaluated the sensitivity by in vivo pharmacokinetics/pharmacodynamics (PK/PD) analysis and physiologically-based pharmacokinetic modeling to diphacinone in black rats (Rattus rattus) captured on the Bonin Archipelago in February 2022. The Bonin rats exhibited prolonged coagulation time after diphacinone administration. They recovered earlier than susceptible black rats, indicating that Bonin rats were less susceptible, though there were no genetic mutations in Vkorc1, the target enzyme of diphacinone. After the administration of diphacinone, hepatic expression levels of Fsp1, identified as the vitamin K reductase, was decreased, however, the Bonin rats exhibited the most minor suppression. The PK analysis showed that the excretion capacity of the Bonin rats was lower than that of the resistant black rats. In the PBPK modeling, the resistant black rats showed higher clearance than the Bonin and susceptible black rats due to high hepatic metabolic capacity. The Bonin rats demonstrated slow absorption and relatively low clearance. This study highlighted the reduced rodenticide-sensitive tendency of wild black rats in the Bonin Archipelago at an in vivo phenotype level. At the same time, they do not have known rodenticide resistance mechanisms, such as hepatic metabolic enhancement or Vkorc1 mutations. It is crucial to monitor the biological levels to evaluate rodenticide sensitivity accurately.

Exposure of Male Farmers and Nonfarmers to Neonicotinoid Pesticides in the South-West and Littoral Regions of Cameroon: A Comparative Study.

Pesticides, especially the newly developed neonicotinoids, are increasingly used in many countries around the world, including Cameroon, to control pests involved in crop destruction or disease transmission. Unfortunately, the pesticides also pose tremendous environmental problems because a predominant amount of their residues enter environmental matrices to affect other nontargeted species including humans. This therefore calls for continuous biomonitoring of these insecticides in human populations. The present study sought to assess the neonicotinoid insecticide exposures in two agrarian regions of Cameroon, the South-West region and Littoral region. The study involved 188 men, including 125 farmers and 63 nonfarmers. Spot urine samples were obtained from these subjects and subjected to liquid chromatographic-tandem mass spectrometric analysis for concentrations of neonicotinoid compounds, including acetamiprid, clothianidin, dinotefuran, imidacloprid, thiacloprid, nitenpyram, thiamethoxam, and N-dm-acetamiprid. Neonicotinoid compounds were detected in all study participants, and residues of all the screened pesticides were detected among participants. N-dm-Acetamiprid and imidacloprid were the most prevalent among the subjects (100.0% and 93.1%, respectively), whereas nitenpyram was less common (3.2%). The median values of imidacloprid and total urinary neonicotinoid concentrations were elevated among farmers (0.258 vs. 0.126 µg/L and 0.829 vs. 0.312 µg/L, respectively). Altogether the findings showed that both the farmer and nonfarmer study populations of Cameroon were exposed to multiple residues of neonicotinoids, with relatively higher levels of pesticides generally recorded among farmers. Although exposure levels of the neonicotinoids were generally lower than their respective reference doses, these results warrant further research on the health risk evaluation of multiple residues of the pesticides and reinforcement of control measures to minimize the exposure risks, especially among farmers. Environ Toxicol Chem 2024;43:952-964. © 2024 SETAC.

No-observed-adverse-effect-level (NOAEL) clothianidin, a neonicotinoid pesticide, impairs hippocampal memory and motor learning associated with alteration of gene expression in cerebellum.

Neonicotinoid pesticides (NNs) have been associated with numerous neurobehavioral effects in rodents, raising concerns about their impact on cognitive function. Clothianidin (CLO), a type of NN, was orally administered to male mice (10 weeks old, C57BL/6N) at the no-observed-adverse-effect level (NOAEL) of 50 mg/kg/day as indicated in the pesticide risk assessment report. Behavioral tests (novel location recognition and rotarod tests) evaluated hippocampal memory and cerebellar motor learning. After each test, plasma monoamines (3-methoxytyramine, histamine, serotonin, tryptamine) were measured by LC-ESI/MS/MS (Liquid chromatography-electrospray ionization/tandem mass spectrometry), and cerebellar mRNA expression was quantified by microarray and qRT-PCR analyses. The NOAEL of CLO was found to impair hippocampal memory, leading to decreased spontaneous locomotor activity and motor function. We reported, for the first time, multiple alterations of gene expression in the cerebellum associated with motor dysfunction.

Effect of clothianidin exposure at the no-observed-adverse-effect level (NOAEL) in a mouse model of atopic dermatitis.

The effects of exposure to clothianidin (CLO), a neonicotinoid pesticide (NN), on the thymus and intestinal microbiota were recently revealed. Immune cells express nicotinic acetylcholine receptors (nAChRs), an NN target, suggesting CLO may disrupt the immune system. However, the relationship between CLO and atopic dermatitis (AD) is unknown. We administered a no-adverse-effect-level (NOAEL) dose of CLO to male NC/Nga mice with induced AD and measured, at three time points, key AD symptom indicators: epidermal thickening, mast cell number, total plasma IgE, and histamine levels. CLO increased total plasma IgE levels but reduced epidermal thickening, mast cell number, and plasma histamine levels in the early stages of AD. This demonstrates for the first time that CLO exposure inhibits AD's early symptoms.

Quantification of the tissue distribution and accumulation of the neonicotinoid pesticide clothianidin and its metabolites in maternal and fetal mice.

Neonicotinoids (NNs) are commonly used pesticides that have a selective agonistic action on insect nicotinic acetylcholine receptors. Recent evidence has shown that NNs have adverse effects in the next generation of mammals, but it remains unclear how NNs transferred from dams to fetuses are distributed and accumulated in fetal tissues. Here, we aimed to clarify the tissue distribution and accumulation properties of the NN clothianidin (CLO) and its 6 metabolites in 7 tissues and blood in both dams and fetuses of mice administered CLO for a single day or for 9 consecutive days. The results showed that the total concentrations of CLO-related compounds in the brain and kidney were higher in fetuses than in dams, whereas in the liver, heart, and blood they were lower in fetuses. The multi-day administration increased the total levels in heart and blood only in the fetuses of the single administration group. In addition, dimethyl metabolites of CLO showed fetus/dam ratios >1 in some tissues, suggesting that fetuses have higher accumulation property and are thus at higher risks of exposure to CLO-related compounds than dams. These findings revealed differences in the tissue-specific distribution patterns of CLO and its metabolites between dams and fetuses, providing new insights into the assessment of the developmental toxicity of NNs.

Effects of exposure to the neonicotinoid pesticide clothianidin on α-defensin secretion and gut microbiota in mice.

The mechanism by which the neonicotinoid pesticide clothianidin (CLO) disrupts the intestinal microbiota of experimental animals is unknown. We focused on α-defensins, which are regulators of the intestinal microbiota. Subchronic exposure to CLO induced dysbiosis and reduced short-chain fatty acid-producing bacteria in the intestinal microbiota of mice. Levels of cryptdin-1 (Crp1, a major α-defensin in mice) in feces and cecal contents were lower in the CLO-exposed groups than in control. In Crp1 immunostaining, Paneth cells in the jejunum and ileum of the no-observed-adverse-effect-level CLO-exposed group showed a stronger positive signal than control, likely due to the suppression of Crp1 release. Our results showed that CLO exposure suppresses α-defensin secretion from Paneth cells as part of the mechanism underlying CLO-induced dysbiosis.

Metals and arsenic distribution in stray dogs' tissues around a lead-zinc mine in Kabwe, Zambia.

Metal contamination poses a threat to human, animal, and environmental health. The purpose of the current study was to assess the accumulation of toxic and trace metal concentrations in tissues of stray dogs in Kabwe, a town known for lead pollution due to a long history of lead and zinc mining. Brain, spleen, heart, stomach, stomach content, small intestine, kidney, liver, and bone samples were collected from 29 stray dogs (14 from locations within 3 km of the mine and 15 from sites 7 km away from the mine) after necropsy. Inductively coupled plasma mass spectrometry was used to analyze toxic metals, arsenic (As), cadmium (Cd), and lead (Pb), and trace elements, copper (Cu) and zinc (Zn). The lungs (0.117 ± 0.114 mg/kg dry weight), kidney (7.515 ± 8.830 mg/kg dry weight), and bone (41.68 ± 66.83 mg/kg dry weight) were found to have the highest concentrations of As, Cd, and Pb, respectively. In contrast, higher Cu and Zn concentrations were measured in the liver than in other tissues. In all tissues analyzed, tissues sampled from dogs near the mine had significantly higher mean concentrations of Cd and Pb than dogs far away. Neither sex nor age-related differences were observed in the distribution of metals in most tissues. There were significant associations among toxic (Pb and Cd) and trace metals (Cu and Zn). In the kidney, Cd positively correlated with Pb (ρ = 0.534) and Zn (ρ = 0.600), whereas in the liver, Cu correlated with Zn (ρ = 0.565). The current study's findings suggest that environmental pollution is still a problem in Kabwe, and environmental remediation is needed to address the pollution.

Evaluation of anticoagulant rodenticide sensitivity by examining in vivo and in vitro responses in avian species, focusing on raptors.

Anticoagulant rodenticides (ARs) are used to control pest rodent species but can result in secondary poisoning of non-target animals, especially raptors. In the present study, differences in AR sensitivity among avian species were evaluated by comparing in vivo warfarin pharmacokinetics and effects, measuring cytochrome P450s (CYPs) expression involved in AR metabolism, and conducting in vitro inhibition assays of the AR target enzyme Vitamin K 2,3-epoxide reductase (VKOR). Oral administration of warfarin at 4 mg/kg body weight did not prolong prothrombin time in chickens (Gallus gallus), rock pigeons (Columba livia), or Eastern buzzards (Buteo japonicus). Rock pigeons and buzzards exhibited shorter plasma half-life of warfarin compared to chickens. For the metabolite analysis, 4'-hydroxywarfarin was predominantly detected in all birds, while 10-hydroxywarfarin was only found in pigeons and raptors, indicating interspecific differences in AR metabolism among birds likely due to differential expression of CYP enzymes involved in the metabolism of ARs and variation of VKOR activities among these avian species. The present findings, and results of our earlier investigations, demonstrate pronounced differences in AR sensitivity and pharmacokinetics among bird species, and in particular raptors. While ecological risk assessment and mitigation efforts for ARs have been extensive, AR exposure and adverse effects in predatory and scavenging wildlife continues. Toxicokinetic and toxicodynamic data will assist in such risk assessments and mitigation efforts.

Effects of exposure to the neonicotinoid pesticide clothianidin on mouse intestinal microbiota under unpredictable environmental stress.

Recent research has demonstrated the toxicity of neonicotinoid pesticides (NNs) in mammals through their interaction with nicotinic acetylcholine receptors (nAChRs). These effects are reported to extend to the intestinal microbiota as well. In addition, environmental stress affects the expression of nAChRs, which may alter sensitivity to NNs. In this study, we analyzed the intestinal microbiota of mice exposed to clothianidin (CLO), a type of NN, under environmental stress, and aimed to clarify the effects of such combined exposure on the intestinal microbiota. C57BL/6N male mice (9 weeks old) were subchronically administered a no-observed-adverse-effect-level (NOAEL) CLO-mixed rehydration gel for 29 days and simultaneously subjected to chronic unpredictable mild stress (CUMS). After the administration period, cecum contents were collected and analyzed by 16S rRNA sequencing for intestinal microbiota. CLO exposure alone resulted in alterations in the relative abundance of Alistipes and ASF356, which produce short-chain fatty acids. The addition of CUMS amplified these changes. On the other hand, CLO alone did not affect the relative abundance of Lactobacillus, but the abundance decreased when CUMS was added. This study revealed that the combined exposure to CLO and stress not only amplifies their individual effects on intestinal microbiota but also demonstrates combined and multifaceted toxicities.

An adverse outcome pathway-based approach to assess the neurotoxicity by combined exposure to current-use pesticides.

Exposure to multiple pesticides in daily life has become an important public health concern. However, the combined effects of pesticide mixtures have not been fully elucidated by the conventional toxicological testing used for individual chemicals. Grouping of chemicals by mode of action using common key events (KEs) in the adverse outcome pathway (AOP) as endpoints could be applied for efficient risk assessment of combined exposure to multiple chemicals. The purpose of this study was to investigate whether exposure to multiple pesticides has synergistic neurotoxic effects on mammalian nervous systems. According to the AOP-based approach, we evaluated the effects of 10 current-use pesticides (4 neonicotinoids, 4 pyrethroids and 2 phenylpyrazoles) on the common KEs in AOPs for neurotoxicity, such as KEs involving mitochondrial and proteolytic functions, in a mammalian neuronal cell model. Our data showed that several pyrethroids and phenylpyrazoles partly shared the effects on several common KEs, including decreases in mitochondrial membrane potential and proteasome activity and increases in autophagy activity. Furthermore, we also found that combined exposure to a type-I pyrethroid permethrin or a type-II pyrethroid deltamethrin and the phenylpyrazole fipronil decreased the cell viability and the benchmark doses much more than either single exposure, indicating that the pair exhibited synergistic effects, since the combination indexes were less than 1. These findings revealed that novel pairs of different classes of pesticides with similar effects on common KEs exhibited synergistic neurotoxicity and provide new insights into the risk assessment of combined exposure to multiple chemicals.

Surveys of eleven species of wild and zoo birds and feeding experiments in white-tailed eagles reveal differences in the composition of the avian gut microbiome based on dietary habits between and within species.

The composition of the gut microbiome varies due to dietary habits. We investigated influences of diet on the composition of the gut microbiome using the feces of 11 avian species, which consumed grain-, fish- and meat-based diets. We analyzed gut microbiome diversity and composition by next-generation sequencing (NGS) of 16S ribosomal RNA. The grain-diet group had higher gut microbiome diversity than the meat- and fish-diet group. The ratio of Bacteroidetes and Firmicutes phyla was higher in the grain-diet group than in the meat- and fish-diet groups. The grain-diet group had a higher ratio of Veillonellaceae than the meat-diet group and a higher ratio of Eubacteriaceae than the fish-diet habit group. To clarify the influence of diet within the same species, white-tailed eagles (Haliaeetus albicilla, n=6) were divided into two groups, and given only deer meat or fish for approximately one month. The composition of the gut microbiome of individuals in both groups were analyzed by NGS. There were indications of fluctuation in the levels of some bacteria (Lactobacillus, Coriobacteriales, etc.) in each diet group. Moreover, one individual for each group which switched each diet in last week changed to each feature of composition of bacterial flora. The above results show that the composition of the gut microbiome differ depending on diet, even within the same species.

Transgenerational effects of developmental neurotoxicity induced by exposure to a no-observed-adverse-effect level (NOAEL) of neonicotinoid pesticide clothianidin.

Neonicotinoid pesticides (NNs) transfer rapidly from mother to offspring, which exhibit neurobehavioral effects. However, no studies have investigated NNs' transgenerational effects. We exposed F0 generation mice (mothers) to a no-observed-adverse-effect level (NOAEL) of clothianidin (CLO) during gestation and lactation, and examined the adult neurobehavioral effects of three generations of offspring (F1, F2, F3). F1 had lower birth weight, decreased locomotor activity, and increased anxiety-like behavior. In F2, body weight was affected, and there was a decreasing trend in locomotor activity and an increasing trend in anxiety-like behavior. In F3, locomotor activity tended to increase. Thus, even when only the mothers were exposed, the effects of CLOs were still observed in F1, F2, and F3 but the effects became smaller.

A stable isotope analysis of the dietary patterns of the aquatic apex predator, the African tigerfish (Hydrocynus vittatus).

Stable isotope analyses, specifically δ13 C and δ15 N, are useful tools increasingly used to understand ecosystem function, food web structures, and consumer diets. Although the iconic tigerfish Hydrocynus vittatus is regarded as an apex predator in southern African freshwater systems, little information is available regarding their feeding behavior and how this may change with growth or differ between ecosystems, with most information stemming from stomach content analyses (SCA). The aim of the present study was to address this lack of information through a baseline study of the diet of large and small tigerfish in various lentic and lotic ecosystems in South Africa using stable isotope methods. Fish and various food web components and food sources were collected from two river and two lake ecosystems in South Africa. The δ13 C and δ15 N values for all samples were determined and multivariate analyses and Bayesian analytical techniques applied to determine the feeding ecology of H. vittatus and how this may differ with size and habitat type. Analyses revealed a substantial difference in the type and abundance of food sources contributing to the diet of H. vittatus between ecosystems, most prominently between the lotic systems, where less dietary specialization was observed, and lentic systems where more specialization was observed. Furthermore, there was a distinct difference in diet between small and large tigerfish, especially in the lotic system, indicating an ontogenetic diet shift as tigerfish grow and further supporting previous SCA studies. This is the first study of its kind on the African continent for H. vittatus and the findings illustrate the value of stable isotope analysis in providing in-depth information into the feeding ecology of consumers and how this may differ between size classes and habitat types.

A Comparative Genomic and Phylogenetic Investigation of the Xenobiotic Metabolism Enzymes of Cytochrome P450 in Elephants Shows Loss in CYP2E and CYP4A.

Cytochrome P450 is an important enzyme that metabolizes a variety of chemicals, including exogenous substances, such as drugs and environmental chemicals, and endogenous substances, such as steroids, fatty acids, and cholesterol. Some CYPs show interspecific differences in terms of genetic variation. As little is known about the mechanisms of elephant metabolism, we carried out a comparative genomic and phylogenetic analysis of CYP in elephants. Our results suggest that elephant CYP genes have undergone independent duplication, particularly in the CYP2A, CYP2C, and CYP3A genes, a unique cluster specific to elephant species. However, while CYP2E and CYP4A were conserved in other Afrotheria taxa, their decay in elephants resulted in genetic dysfunction (pseudogene). These findings outline several remarkable characteristics of elephant CYP1-4 genes and provide new insights into elephant xenobiotic metabolism. Further functional investigations are necessary to characterize elephant CYP, including expression patterns and interactions with drugs and sensitivities to other chemicals.