Toxic effects of oral 2-amino-4,6-dinitrotoluene in the Western fence lizard (Sceloporus occidentalis)

Tissue distribution and toxicity effects of myclobutanil enantiomers in lizards (Eremias argus)

In recent years, serious environmental pollution has caused a decrease in the abundance of many species worldwide. Reptiles are the most diverse group of terrestrial vertebrates. There are large amounts of toxicological data available regarding myclobutanil, but the adverse effects of myclobutanil on lizards has not been widely reported. In this study, treatment groups were orally administered a single-dose of myclobutanil (20mg/kg body weight (bw)). Subsequently, it was found that there were differences in myclobutanil levels between the different tissues and concentrations also changed with degradation time. The tissue concentrations of myclobutanil decreased in the order of: stomach > liver > lung > blood > testis > kidney > heart > brain. Based on our results, the liver and testis were considered to be the main target organs in lizards, indicating that the myclobutanil could induce potential hepatic and reproductive toxicity on lizards. Meanwhile, it was also demonstrated that the toxic effects of myclobutanil was different in different species, and the distribution of different pesticides in lizards were different.

Imidacloprid induces morphological and molecular damages on testis of lizard (Podarcis sicula)

The insecticide imidacloprid was evaluated under laboratory conditions in the adult male Italian wall lizards (Podarcis sicula) to assess its potential toxicity. By an acute oral test, LD50 was 503.76 mg/kg. Changes in spermatogenesis, plasma sex hormone levels and androgen and oestrogen receptor mRNAs were analysed by subchronic test and simulated environmental exposure. 15-days subchronic test, in which lizards were orally dosed on alternate days at 0, 10, 50, 100 mg/kg bw, showed a dose-dependent changes of testicular architecture and an increase of apoptotic processes. In a 30-days simulated environmental exposure spermatogenesis was arrested at secondary spermatocyte level and only few primary spermatocytes were TUNEL-positive. In all experimental groups imidacloprid was able to decrease both the level of sex hormones and the steroid receptor mRNAs. The results demonstrate that imidacloprid affects reproduction function of male lizards therefore precautions must be taken to minimize the harmful effects of this compound.

The characteristics and two-step reaction model of p-nitroacetophenone biodegradation mediated by Shewanella decolorationis S12 and electron shuttle in the presence/absence of goethite

The current study mainly focused on the biodegradation process of p-nitroacetophenone (NP) in the presence and absence of goethite mediated by iron-reducing microbe (Shewanella decolorationis S12) and electron shuttle. The results showed that introduction of electron shuttle could obviously lead to an accumulation of biodegradation intermediate, especially in reaction systems containing high content of electron shuttle in the absence of goethite. Goethite could enhance the degree and rate of NP biodegradation. The microbial reductively generated Fe(II) played an active role in the biodegradation process. The relationship between the concentrations of biodegradation end product and the reaction times could be fitted by a consecutive reaction model with correlation coefficients (adjusted R(2)) in the range from 0.9241 to 0.9831 during the biodegradation stage from the beginning to about 250 h of incubation. However, during the subsequent biodegradation stages, in the presence and absence of goethite, transitions from the consecutive reaction model to zero-order reaction model and from the consecutive reaction model to exponential growth reaction model were observed, respectively. The newly proposed two-step reaction model will help understand the mechanism of the biodegradation process of nitroaromatic compounds and related pollutants.

Stereoselective metabolism, distribution, and bioaccumulation brof triadimefon and triadimenol in lizards

In this research, Chinese lizards (Eremias argus) were chosen as laboratory animal to evaluate the stereoselectivity in the processes of metabolism, distribution, and bioaccumulation of triadimefon. A validated chiral high-performance liquid chromatography coupled with triple quadruple mass spectrometry (HPLC-MS/MS) method was developed for determining enantiomers' residues of parent compound triadimefon and its metabolite triadimenol in lizard blood and tissues. Pharmacokinetic results of single-does exposure suggested that S-(+)-triadimefon was metabolized easier than R-(-)-triadimefon, and RR-(+)-triadimenol was the main metabolic product of triadimefon. During the continuous exposure of two dose (40mg/kg(bw)·d and 200mg/kg(bw)·d), enantiomers of triadimefon and triadimenol were detected in all body compartments, with the highest triadimefon concentrations in brain. However, the triadimenol concentrations were not significantly different among the compartments. The concentrations of RS-(+)-triadimenol were negative correlated with concentrations of RR-(+)-triadimenol both in blood (r=-0.775, p=0.024) and liver (r=-0.834, p=0.02) in 200mg/kg(bw)·d group, which indicates that chiral conversion between enantiomers of triadimenol might exist in the metabolic process of triadimefon. In all the processes, the enantiomer fractions (EFs) of R-(-)-triadimefon and RR-(+)-triadimenol were significantly different from their natural ratios, 0.5 and 0.1, respectively, which proved that metabolism, bioaccumulation, and distribution of triadimefon and triadimenol in lizards were enantioselective. These results help enrich and supplement the knowledge of the stereoselective behaviour of triadimefon and triadimenol in reptile.

Furthering the derivation of predictive wildlife toxicity reference values for use in soil cleanup decisions

The development of media-specific ecological values for risk assessment includes the derivation of acceptable levels of exposure for terrestrial wildlife (e.g., birds, mammals, reptiles, and amphibians). Although the derivation and subsequent application of these values can be used for screening purposes, there is a need to identify toxicological effects thresholds specifically for making remedial decisions at individual contaminated sites. A workshop was held in the fall of 2012 to evaluate existing methods and recent scientific developments for refining ecological soil screening levels (Eco-SSLs) and improving the derivation of site-specific ecological soil clean-up values for metals (Eco-SCVs). This included a focused session on the development and derivation of toxicity reference values (TRVs) for terrestrial wildlife. Topics that were examined included: methods for toxicological endpoint selection, techniques for dose-response assessment, approaches for cross-species extrapolation, and tools to incorporate environmental factors (e.g., metal bioavailability and chemistry) into a reference value. The workgroup also made recommendations to risk assessors and regulators on how to incorporate site-specific wildlife life history and toxicity information into the derivation of TRVs to be used in the further development of soil cleanup levels.

Unraveling the relative importance of oral and dermal contaminant exposure in reptiles: insights from studies using the western fence lizard (Sceloporus occidentalis)

Despite widespread recognition of significant data deficiencies, reptiles remain a relatively understudied taxon in ecotoxicology. To conduct ecological risk assessments on reptiles frequently requires using surrogate taxa such as birds, but recent research suggests that reptiles have significantly different exposure profiles and toxicant sensitivity. We exposed western fence lizards, Sceloporus occidentalis, to the same quantities of three model chemicals via oral (gavage) and dermal (ventral skin application) exposure for either 24 or 48 hours. Three phthalate esters (di-methyl phthalate [DMP], di-iso-butyl phthalate [DIBP], and di-n-octyl phthalate [DNOP]) were chosen as model chemicals because they represent a gradient of lipophilicity but are otherwise structurally similar. Overall, the more lipophilic phthalates (DIBP and DNOP) were found to have higher concentrations in tissues than the less lipophilic DMP. Significant differences in tissue concentrations between DIBP and DNOP were tissue-dependent, suggesting that delivery to a site of action following exposure is not only a simple function of lipophilicity. In dermal treatments, DMP usually had fewer detections (except in ventral skin samples), suggesting that lipophilicity (log Kow>2) is a requirement for uptake across the skin. In general, tissue residues were greater in oral treatments than dermal treatments (significant in adipose and liver tissue), but differences were driven strongly by differences in DMP which did not appear to be absorbed well across skin. When differences in tissue residue concentrations between oral and dermal exposure did occur, the difference was not drastic. Taken together these results suggest that dermal exposure should be considered in risk assessments for reptilian receptors. Dermal exposure may be an especially important route for reptiles as their ectothermic physiology translates to lower energetic demands and dietary exposure compared to birds and mammals.

Stereoselective degradation and toxic effects of benalaxyl on blood and liver of the Chinese lizard Eremias argus

Benalaxyl as a xylem-systemic fungicide is usually direct sprayed on the soil surface, which is potential harm to the animals lived in the soil. However, the stereoselectivity of benalaxyl in reptiles have rarely been studied. In this study, Chinese lizards (Eremias argus) were firstly used to evaluate the stereoselectivity in biodegradation and toxicity of racemate and individual enantiomers of benalaxyl. A method for determining residues of the two enantiomers of benalaxyl in lizard blood and liver by high-performance liquid chromatography coupled with triple quadrupole mass spectrometry (HPLC-MS/MS) was developed. The degradation followed pseudo first-order kinetics and the degradation of the (S)-(+)-benalaxyl was faster than its antipode in blood and liver (Half-time t1/2 of (R)-(-)-benalaxyl and (S)-(+)-benalaxyl were 5.08 h and 3.75 h in blood, 6.21 h and 4.45 h in liver, separately). Moreover, antioxidant defenses consisting of activities of superoxide dismutase (SOD), catalase (CAT), glutathione S-transferase (GST) and lipid peroxide malondialdehyde (MDA) were determined in 24h acute exposure. Enantioselectivity of acute toxicity depended on the concentration and form of benalaxyl. In addition, cellular degeneration, decrease of cell number, clustering phenomena of cell nuclei and preliminary liver fibrosis were observed in pathological detection at the termination of 21-d subchronic exposure (20 mg/kg(-bw) of racemate and individual enantiomers of benalaxyl). The enantiomer fractions (EFs) in racemate and individual enantiomer groups were approached both in blood and liver caused by the chiral conversion. The chiral conversion from (R)-(-)-benalaxyl to (S)-(+)-benalaxyl and (S)-(+)-benalaxyl to (R)-(-)-benalaxyl were the primary cause for no remarkable differences in toxicity between the enantiomers of benalaxyl.

Carbaryl-induced histopathologic alterations on testes of levantine frog, Pelophylax bedriagae (Anura: Ranidae)

The aim of the study was to investigate for the first time histopathologic effects of carbaryl on the testes of adult frog, Pelophylax bedriagae. Frogs were exposed to carbaryl once by oral gavage in concentrations of 0.05, 0.1 and 0.2 mg/g. After 96 h, frogs were euthanized and dissected. Histopathological changes were more prominent in medium- (0.1 mg/g) and high-dose (0.2 mg/g) groups than in the low-dose (0.05 mg/g) group. In the low-dose group, shrinkage of some seminiferous tubules was observed. In the medium-dose group, an enlargement of interstitial spaces and germ cell necrosis were detected. In the high-dose group, prominent tubule deformation was determined. Germ cell necrosis in seminiferous tubules was frequently seen. In addition, congestion, hemorrhage, cellular infiltration and fibrosis were detected. According to these findings, it is clear that carbaryl affects male fertility in P. bedriagae.

Pollution biomarkers in the spiny lizard (Sceloporus spp.) from two suburban populations of Monterrey, Mexico

Environmental pollution may severely impact reptile species in urbanized areas. The magnitude of the impact is analyzed in the present study using lizard tail tips for the quantitative evaluation of enzymatic biomarkers of pollution. Spiny lizards (Sceloporus serrifer and S. torquatus) were collected from two suburban localities in the Monterrey metropolitan area, Mexico: Chipinque Ecological Park, a natural protected area, and El Carmen Industrial Park (IP), a highly polluted site. Different enzymes were used as biomarkers including: acetylcholinesterase (AChE), butyrylcholinesterase (BChE), carboxylesterase (CaE), alkaline phosphatase (ALP), acid phosphatase (ACP), superoxide dismutase (SOD) and glutathione S-transferase (GST). The levels of AChE, BChE and ACP activity were not significantly different between localities. AChE and BChE, commonly used as biomarkers of neurotoxic polluting agents (e.g. organophosphate pesticides) do not appear to be affecting the populations from the study locations. In contrast, the levels of CaE, GST, ALP and SOD were significantly different between the localities. These biomarkers are regularly associated with oxidative stress and processes of detoxification, and generally indicate pollution caused by heavy metals or hydrocarbons, which are common in industrial sites. The data resulting from the analysis of these biomarkers indicate that these polluting agents are affecting the populations of Sceloporus in IP. The present work validates the possibility of conducting additional ecotoxicological studies using biomarkers in combination with a nondestructive sampling technique in species of spiny lizards that are abundant in many North America areas.

Multiple environmental stressors elicit complex interactive effects in the western fence lizard (Sceloporus occidentalis)

Evaluation of multiple-stressor effects stemming from habitat degradation, climate change, and exposure to chemical contaminants is crucial for addressing challenges to ecological and environmental health. To assess the effects of multiple stressors in an understudied taxon, the western fence lizard (Sceloporus occidentalis) was used to characterize the individual and combined effects of food limitation, exposure to the munitions constituent 2,4,6-trinitrotoluene (TNT), and Plasmodium mexicanum (lizard malaria) infection. Three experimental assays were conducted including: Experiment I--TNT × Food Limitation, Experiment II--Food Limitation × Malaria Infection, and Experiment III--TNT × Malaria Infection. All experiments had a 30 day duration, the malaria treatment included infected and non infected control lizards, food limitation treatments included an ad libitum control and at least one reduced food ration and TNT exposures consisting of daily oral doses of corn oil control or a corn oil-TNT suspension at 5, 10, 20, 40 mg/kg/day. The individual stressors caused a variety of effects including: reduced feeding, reduced testes mass, anemia, increased white blood cell (WBC) concentrations and increased mass of liver, kidney and spleen in TNT exposures; reduced cholesterol, WBC concentrations and whole body, testes and inguinal fat weights given food limitation; and increased WBC concentrations and spleen weights as well as decreased cholesterol and testes mass in malaria infected lizards. Additive and interactive effects were found among certain stressor combinations including elimination of TNT-induced hormesis for growth under food limitation. Ultimately, our study indicates the potential for effects modulation when environmental stressors are combined.

Histopathological effects of carbaryl on testes of snake-eyed lizard, Ophisops elegans

BACKGROUND, AIM AND SCOPE

Due to their ecological niche and insectivore nature, lizards are of increased risk of exposure to pesticides in agricultural areas. In addition to their potential direct effects on non-target species, insecticides can also result in indirect impacts on lizard population by reducing their food source. Carbaryl is a common insecticide that is widely used in areas of Turkey that are home to a variety of reptiles. However, to date, little is known about the potential effects of the exposure of reptiles such as lizards or snakes to this pesticide. The aim of the study was to investigate toxic effects of carbaryl on the testes of snake-eyed lizard, Ophisops elegans that is common to regions in Turkey where Carbaryl is applied and that it can be easily cultured in the laboratory.

MATERIAL AND METHODS

Adult male lizards were exposed to carbaryl once by oral gavage in concentrations of 2.5, 25 and 250 μg/g. After 96 h, lizards were euthanized and dissected. Histopathological changes were detected by randomly counting 100 tubules in each lizard. Seminiferous tubules were categorized as normal, sloughing and disorganized tubules. Diameters of tubules were also measured. The differences in histopathological changes and tubule diameters were compared for statistical significance by one-way ANOVA, using SPSS 16.0.

RESULTS AND DISCUSSION

Histopathological changes were more prominent in medium- (25 μg/g) and high-dose (250 μg/g) groups than in the low-dose (2.5 μg/g) group. In the medium-dose group, the hexagonal appearance of most tubules disappeared, and they took on an oval shape. Sloughing was the characteristic tubule appearance of the medium group. In the high-dose group, significant increases in the number of disorganized tubules and prominence of haemorrhages was observed.

CONCLUSION

Carbaryl caused histopathological defects on the testes of O. elegans, so it is clear that carbaryl affects male fertility in O. elegans.