Effects of chronic exposures to the herbicides atrazine and glyphosate to larvae of the threespine stickleback (Gasterosteus aculeatus)

In vivo estrogenicity of glyphosate, its formulations, and AMPA on transgenic zebrafish (Danio rerio) embryos

In this study, the disrupting effects of glyphosate (GLY), aminomethylphosphonic acid (AMPA), and three glyphosate-based herbicides (GBHs) on vitellogenesis in a non-concentration-dependent manner are reported for the first time in 120 h of acute exposure of zebrafish at environmentally relevant concentrations. GBHs are commonly used worldwide in weed control management. Due to their extensive application, they frequently occur in aquatic ecosystems and may affect various organisms. The active substance GLY and its major by-product, AMPA, are the most thoroughly studied chemicals; however, the adverse effects of the complex formulas of GBHs with diverse and unknown content of co-formulants are still not sufficiently researched. This study focused on the embryotoxicity, sublethal malformations, and estrogenic potency of GLY, AMPA, and four commonly used GBHs on zebrafish embryos using a wild type and an estrogen-sensitive, transgenic zebrafish line (Tg(vtg1:mCherry)). After 120 h of exposition, AMPA did not cause acute toxicity, while the LC50 of GLY was 160 mg/L. The GBHs were more toxic with LC50 values ranging from 31 to 111 GLY active equivalent (a.e.) mg/L. Exposure to 0.35-2.8 mg/L GBHs led to sublethal abnormalities: typical symptoms were structural deformation of the lower jaw and anomalies in the olfactory region. Deformity rates were 10-30% in the treated groups. In vivo, fluorescently expressed vtg1 mCherry protein in embryonic liver was detected by a non-invasive microscopic method indicating estrogenic action through vitellogenin production by GLY, AMPA, and GBHs. To confirm the in vivo findings, RT-qPCR method was performed to determine the levels of the estrogenicity-related vtg1 mRNA. After 120 h of exposure to GLY, AMPA, and three GBHs at a concentration of 0.35 mg/L, the expression of vtg1 gene was significantly up-regulated. Our results highlight the risk that short-term GLY and GBH exposure can cause developmental malformations and disrupt the hormonal balance in zebrafish embryos.

Sublethal effects of the herbicides atrazine and glyphosate at environmentally relevant concentrations on South American catfish (Rhamdia quelen) embryos

The objective of this work was to evaluate the effects following exposure (96 h) of South American catfish (R. quelen) embryos to active ingredients and commercial formulations from atrazine and glyphosate, isolated and in mixtures, at environmentally relevant concentrations. While the survival rates were not affected, sublethal effects were evidenced after exposure. The most frequent deformities were fin damage and axial and thoracic damage. The mixture of active ingredients caused an increase in SOD and GST, differing from the treatment with the mixture of commercial formulations. The activity of AChE was significantly reduced following the treatment with the active ingredient atrazine and in the mixture of active ingredients. In general, herbicide mixtures were responsible for causing more toxic effects to R. quelen embryos. Therefore, these responses showed to be suitable biomarkers of herbicides' exposure, in addition to generating more environmentally relevant baseline data for re-stablishing safety levels of these substances in aquatic bodies.

The exposure in ovo of embryos belonging to Amazonian turtle species Podocnemis expansa (Testudines) to commercial glyphosate and fipronil formulations impairs their growth and changes their skeletal development

Pesticides are widely used in agricultural production; moreover, they can have direct and indirect effect on both flora and fauna. Aquatic organisms, among other animals, including reptiles, are mainly susceptible to contamination effects. Accordingly, the aim of the present study is to test the hypothesis that the incubation of Podocnemis expansa eggs in substrate added with glyphosate and fipronil formulations changes their viability, interferes with their growth and induces bone alterations. Eggs collected in natural environment were artificially incubated in sand moistened with water added with glyphosate Atar 48, at concentrations of 65 or 6500 μg/L (groups G1 and G2, respectively), and with fipronil Regent 800 WG at 4 or 400 μg/L (groups F1 and F2, respectively) or, yet, with the combination of 65 μg/L glyphosate and 4 μg/L fipronil, or with 6500 μg/L glyphosate and 400 μg/L fipronil (groups GF1 and GF2, respectively). The level of exposure to the herein assessed pesticides was quantified at the end of the incubation period; it was done by dosing its concentration in eggshells. Eggs exposed to the tested pesticides did not have their viability affected by it; however, all embryos exposed to the tested pesticides showed lowered body mass at hatch, as well as impaired development. In addition, bone malformation in the scleral ossicular ring was observed in individuals in groups F1, F2 and GF1. Pesticides accumulated in eggshells at concentrations related to exposure level. Thus, the recorded results have evidenced some remarkably relevant, and previously unknown, impacts associated with the exposure of a species listed as lower risk/conservation dependent, which spends most of its life in the water, to two widely used pesticides, at a very sensitive stage of its life, namely: egg incubation on land.

Toxic effects and mechanisms of common pesticides (Roundup and chlorpyrifos) and their mixtures in a zebrafish model (Danio rerio)

Agrochemicals can adversely affect biodiversity, environment and human health, and commonly occur in mixtures with poorly characterized toxic mechanisms and health hazards. Here, we evaluated the individual and mixture toxicities of Roundup and chlorpyrifos in environmentally relevant concentrations to zebrafish using molecular and biochemical indices. Studied pesticides alone and in combination caused depletion of total antioxidant capacity and cellular thiols, overproduction of ROS, accumulation of oxidative lesions and elevated DNA damage in zebrafish liver. Notably, low concentration of Roundup induced a hormesis-like effect by stimulating the protective cellular mechanisms. Chlorpyrifos showed stronger prooxidant effects than Roundup and additionally caused nitrosative and carbonyl stress in zebrafish. At the organismal level, studied pesticides and their mixtures induced hepato- and neurotoxicity. The effects of the studied pesticides on biomarkers of apoptosis, endocrine disruption and immune disorders were generally weak and inconsistent. The multibiomarker assessment showed that chlorpyrifos is considerably more toxic than Roundup to zebrafish. The toxic effects of the pesticide mixtures were mostly driven by chlorpyrifos, with minimal or mitigating effects of Roundup addition. These findings elucidate the toxic mechanisms of common pesticides in a model vertebrate and demonstrate that health hazards of pesticide mixtures cannot be predicted from the effects of single pesticides.

Effects of environmentally relevant concentrations of atrazine and glyphosate herbicides, isolated and in mixture, on two generation of the freshwater microcrustacean Daphnia magna

The herbicides atrazine and glyphosate are used worldwide and their excessive usage results in the frequent presence of these pesticides in environmental compartments. We evaluated the effects of environmentally relevant concentrations of analytical standards and commercial formulations of atrazine (2 µg L-1) and glyphosate (65 µg L-1), isolated and in mixture (2 + 65 µg L-1) on the microcrustacean Daphnia magna. Through chronic exposure (21 days) of two generations, we observed effects on survival, reproductive capacity and responses of the antioxidant defense system (catalase) and biotransformation system (glutathione S-transferase). The survival of organisms was affected in the second generation (F1) with a mortality of 17% in the mixture of commercial formulations treatments. In the evaluation of the first generation (F0) we observed only effects on sexual maturation of organisms, while in the F1, changes were observed in all parameters evaluated. A statistical difference (p < 0.05) was also observed between the analytical standards and the commercial formulations for all parameters evaluated, indicating that other components present in the formulations can change the toxicity of products. We suggest that atrazine can modulate toxicity when mixed with glyphosate, as the standard analytical atrazine and mixture of analytical standards results were similar in most parameters. Given the difficulty in estimating effects of mixtures and considering that various stressors are found in the environment, our results support the need to carry out long-term studies and, above all, to verify what are the impacts across generations, so that the toxicity of products is not underestimated. Graphical abstract.

Acute and early life-stage toxicity of atrazine in sheepshead minnow (Cyprinodon variegatus)

Given the limited data available for estuarine/marine fish species and potential risk of being exposed to the herbicide atrazine, additional toxicity data regarding sensitive life-stages are needed. As such, this work sought to characterize: 1) the acute larval toxicity, and 2) early life-stage toxicity of technical atrazine in the model marine species sheepshead minnow (Cyprinodon variegatus). Atrazine was observed to be slightly to moderately toxic towards C. variegatus under acute conditions (as per U.S. EPA 2017 criteria). After 96 h exposure, mortality rates of 5%, 15%, 35%, and 90% were observed among fish exposed to atrazine at 4.6, 7.6, 13, and 22 mg a.i./L, respectively. Sub-lethal effects were observed among surviving fish exposed to > 3.2 mg a.i/L. The 96 h LC50 was 13 mg a.i./L and the NOEC was 3.2 mg a.i./L. In the 33 d early-life stage test, mean embryo survival rates in 0.15, 0.30, 0.57, 1.1, and 2.2 mg a.i./L treatments ranged from 71% to 79% and were not different from survival in the control (78%). Following 28 d post-hatch exposure (Day 33), mean larval survival ranged from 98% to 100% in all treatments and the control. Larval length and wet weight were the most sensitive indicators of the toxicity of atrazine to early life-stage sheepshead minnow. The NOEC for growth was 1.1 mg a.i./L and the LOEC was 2.2 mg a.i./L. Based on these, the MATC for atrazine to sheepshead minnow embryos and larvae was estimated to be 1.6 mg a.i./L. These results were consistent with previous investigations in sheepshead minnow and other marine fish species. Based on the results, atrazine would not be expected to pose unacceptable risks for sheepshead minnow early life-stages at environmentally relevant concentrations.

Review and analysis of the potential for glyphosate to interact with the estrogen, androgen and thyroid pathways

Glyphosate was recently evaluated for its potential to interact with the estrogen, androgen and thyroid (EAT) hormone pathways, including steroidogenesis, under the United States Environmental Protection Agency's (USEPA) Endocrine Disruptor Screening Program (EDSP), then by Germany, the rapporteur Member State who led the European Annex 1 renewal for glyphosate, and then by the European Food Protection Agency (EFSA) also as part of the Annex 1 renewal for glyphosate. Under the EDSP, 11 Tier 1 assays were run following the USEPA's validated 890-series test guidelines and included five in vitro and six in vivo assays to evaluate the EAT pathways. Steroidogenesis was evaluated as part of the estrogen and androgen pathways. An up-to-date critical review has been conducted that considered results from the EDSP Tier 1 battery, guideline regulatory studies and an in-depth analysis of the literature studies that informed an endocrine assessment. A strength of this evaluation was that it included data across multiple levels of biological organization, and mammalian and nonmammalian test systems. There was strong agreement across the in vitro and in vivo Tier 1 battery, guideline studies and relevant literature studies, demonstrating that glyphosate does not interact with EAT pathways including steroidogenesis. Based on an analysis of the comprehensive toxicology database for glyphosate and the literature, this review has concluded that glyphosate does not have endocrine-disrupting properties through estrogen, androgen, thyroid and steroidogenic modes of action. © 2020 Society of Chemical Industry.

Molecular and biochemical responses of vitellogenin in the mussel Mytilus galloprovincialis exposed to the glyphosate-based herbicide Roundup® Power 2.0

Glyphosate-based herbicides (GBHs) occur in aquatic ecosystems at concentrations of hundreds of micrograms per liter. As formulation adjuvants are suspected to be endocrine-disrupting chemicals, we assessed the effects of the recent GBH formulation Roundup® Power 2.0 on vitellogenin (VTG) in Mytilus galloprovincialis. Mussels were exposed for 7, 14, and 21 days to two concentrations of the commercial formulation, corresponding to 100 and 1000 μg/L of glyphosate. The expression of the vtg gene in gonads of females and males, as well as the levels of alkali labile phosphates (ALP) in gonads and non-gonadal tissues from the two sexes were measured. No significant alterations were observed in vtg expression values during the exposure. Conversely, a significant reduction in gonadal ALP levels was observed in females exposed for 21 days and in males exposed for 7 days. In addition, ALP levels increased significantly in gonads from males exposed for 21 days to the two concentrations of Roundup®. As for non-gonadal tissues, ALP levels did not change significantly in females, whereas ALP levels decreased significantly in non-gonadal tissues from males exposed for 21 days to the lowest concentration tested. An overall statistically significant difference in ALP levels was found between females and males. Although preliminary, our study suggests that GBH can affect reproduction-related parameters in mussels.

Effects of sublethal and realistic concentrations of the commercial herbicide atrazine in Pacu (Piaractus mesopotamicus): Long-term exposure and recovery assays

Background and Aim:

The commercial formulations of the herbicide atrazine (cATZ) are widely employed in Brazilian agriculture, and, as a consequence, ATZ has been found at levels above that established by law in the river basins in Brazil. Although the toxicity of ATZ in fish is well documented, there are few studies on the recovery capacity after cATZ exposure. This work aimed to evaluate, using several biomarkers, the toxic effects of long-term exposure to the sublethal (3.57 mg/L) and nonlethal realistic (3.00 µg/L) cATZ concentrations followed by a recovery assay, in fingerlings of a Brazilian teleost, the Piaractus mesopotamicus (pacu).

Materials and Methods:

Pacu fingerlings were housed in glass tanks and divided into the following experimental groups (two tanks/group): Exposure control = EC, recovery control = RC, the sublethal groups exposed to 3.57 mg/L of cATZ, (sublethal exposure group = SLE and sublethal recovery group = SLR) and the nonlethal groups treated with 3.00 µg/L of cATZ (nonlethal exposure group = NLE and nonlethal recovery group = NLR). The exposure assay was semi-static with a duration of 30 days and the recovery assay (after cATZ withdrawal) lasted 14 days. Several biomarkers were evaluated in fingerlings from all groups: The swimming behavior, the body weight gain, the micronucleus formation and nuclear alterations in erythrocytes, and the hepatic and renal histopathology analyzed by qualitative and semi-quantitative morphological methods (using light and electron microscopy).

Results:

No significant difference in weight gain was observed among the groups after the exposure and recovery assays. The sublethal exposure induced impaired swimming movements, significant histopathological alterations, including necrosis in the liver and kidney, and a significant increase in the frequency of micronuclei in erythrocytes. The nonlethal exposure induced only subtle histopathological changes in the liver and kidney. After recovery assay, no genotoxic alteration was noted in pacu exposed to sublethal concentration, while the cATZ-induced kidney damage was partially reversed but not the hepatic injury.

Conclusion:

cATZ exhibits long-term toxic effects on pacu, even at relatively low concentrations, affecting mainly the liver and the kidney, and the effects of sublethal concentration are only partially reversed after cATZ withdrawal.

Effects of egg exposure to atrazine and/or glyphosate on bone development in Podocnemis unifilis (Testudines, Podocnemididae)

This study was designed to investigate skeletal changes in Podocnemis unifilis embryos derived from artificially incubated eggs exposed to different concentrations of atrazine, glyphosate or atrazine and glyphosate mixture. Forty-two eggs were randomly allocated to one of seven trays containing vermiculite treated distilled water (control group) or the following solutions: 2 or 200 μg L-1 of atrazine (groups A1 and A2 respectively); 65 or 6500 μg L-1 of glyphosate (groups G1 and G2 respectively); 2 μg L-1 and 65 μg L-1 or 200 μg L-1 and 6500 μg L-1 of atrazine and glyphosate mixture (groups AG1 and AG2 respectively). Three eggs per tray were randomly collected on days 30 and 50 of the incubation period. Embryos were submitted to soft tissue diaphanization and stained with Alizarin red S or Alcian blue for morphological analysis of bone and cartilage tissues; histological analysis was performed to confirm ossification changes. Findings were compared between groups. Morphological changes were limited to sclerotic ring features and number of ribs. Malformations rates differed significantly (p < 0.05) between embryos in the control and treated groups A2, AG1 and AG2. Concurrent exposure to atrazine and glyphosate did not affect the presence or severity of embryonic malformations and was not associated with appendicular skeleton changes in P. unifilis embryos. However, further studies focusing on the axial skeleton with particular emphasis on rib abnormalities are warranted.

Extended fish short term reproduction assays with the fathead minnow and Japanese medaka: No evidence of impaired fecundity from exposure to atrazine

Short-term reproduction assays were conducted with fathead minnow (Pimephales promelas) and Japanese medaka (Oryzias latipes) to evaluate responses from atrazine exposure at environmentally relevant concentrations and above. Breeding groups of fish with multiple males and females were exposed to atrazine under flow-through conditions. Fathead minnows were exposed to mean measured concentrations of 1.0, 10, 26, 52, and 105 μg atrazine/L for 28 days. Medaka were exposed to mean measured concentrations of 9.4, 48, 74, 97, and 244 μg atrazine/L for 28 or 29 days. Fish were evaluated for survival, fecundity, fertility, total length, wet weight, secondary sex characteristics, gonadosomatic index (GSI) (P. promelas only), plasma or hepatic vitellogenin (VTG), and histopathology of gonads. General observations of health and behaviour were also conducted. There were no statistically significant effects (i.e., p < 0.05) of atrazine on survival, size, reproduction, behaviour, GSI, VTG, or secondary sex characteristics in either species at any exposure level. In fathead minnows, there were no histopathological findings associated with atrazine exposure in male fish, but there was an increased proportion of Stage 4.0 ovaries accompanied by an increase in proportion of Grade 3 post-ovulatory follicles in females of the 105 μg/L treatment group. Without a concomitant increase in oocyte atresia, neither of these findings are considered adverse for the health of the fish. In medaka, there were no significant effects of atrazine exposure on histopathology in either sex. These data support current weight-of-evidence assessments that atrazine does not cause direct adverse effects on fish reproduction at environmentally realistic concentrations.

Toxicity of atrazine- and glyphosate-based formulations on Caenorhabditis elegans

Atrazine and Glyphosate are herbicides massively used in agriculture for crop protection. Upon application, they are available to the biota in different ecosystems. The aim of this research was to evaluate the toxicity of Glyphosate and Atrazine based formulations (GBF and ABF, respectively). Caenorhabditis elegans was exposed to different concentrations of each single formulation, and to the mixture. Lethality, locomotion, growth, and fertility were measured as endpoints. Effects on gene expression were monitored utilizing green fluorescence protein transgenic strains. ABF caused lethality of 12%, 15%, and 18% for 6, 60, and 600 μM, respectively, displaying a dose dependence trend. GBF produced lethality of 20%, 50%, and 100% at 0.01, 10, and 100 μM, respectively. Locomotion inhibition ranged from 21% to 89% at the lowest and maximum tested concentrations for Atrazine; whereas for Glyphosate, exposure to 10 μM inhibited 87%. Brood size was decreased by 67% and 93% after treatment to 0.06 and 6 μM Atrazine, respectively; and by 23% and 93% after exposure to 0.01 and 10 μM Glyphosate, respectively. There were no significant differences in growth. Changes in gene expression occurred in all genes, highlighting the expression of sod-1, sod-4, and gpx-4 that increased more than two-fold after exposure to 600 μM ABF and 10 μM GBF. The effects observed for the mixture of these formulations were additive for lethality, locomotion and fertility. In short, GBF, ABF, and their mixture induced several toxic responses related to oxidative stress on C. elegans.

Assessing the potential for trace organic contaminants commonly found in Australian rivers to induce vitellogenin in the native rainbowfish (Melanotaenia fluviatilis) and the introduced mosquitofish (Gambusia holbrooki)

In Australia, trace organic contaminants (TrOCs) and endocrine active compounds (EACs) have been detected in rivers impacted by sewage effluent, urban stormwater, agricultural and industrial inputs. It is unclear whether these chemicals are at concentrations that can elicit endocrine disruption in Australian fish species. In this study, native rainbowfish (Melanotaenia fluviatilis) and introduced invasive (but prevalent) mosquitofish (Gambusia holbrooki) were exposed to the individual compounds atrazine, estrone, bisphenol A, propylparaben and pyrimethanil, and mixtures of compounds including hormones and personal care products, industrial compounds, and pesticides at environmentally relevant concentrations. Vitellogenin (Vtg) protein and liver Vtg mRNA induction were used to assess the estrogenic potential of these compounds. Vtg expression was significantly affected in both species exposed to estrone at concentrations that leave little margin for safety (p<0.001). Propylparaben caused a small but statistically significant 3× increase in Vtg protein levels (p=0.035) in rainbowfish but at a concentration 40× higher than that measured in the environment, therefore propylparaben poses a low risk of inducing endocrine disruption in fish. Mixtures of pesticides and a mixture of hormones, pharmaceuticals, industrial compounds and pesticides induced a small but statistically significant increase in plasma Vtg in rainbowfish, but did not affect mosquitofish Vtg protein or mRNA expression. These results suggest that estrogenic activity represents a low risk to fish in most Australian rivers monitored to-date except for some species of fish at the most polluted sites.

Does anti-androgen, flutamide cancel out the in vivo effects of the androgen, dihydrotestosterone on sexual development in juvenile Murray rainbowfish (Melanotaenia fluviatilis)?

The aim of the present study was to investigate if the effects of the androgen, dihydrotestosterone (DHT) on the sexual development in juvenile Murray rainbowfish (Melanotaenia fluviatilis) are canceled out by the anti-androgen, flutamide. Fish (60 days post hatch) were exposed to 250ng/L of DHT, 25μg/L of flutamide (Flu-low), 250μg/L of flutamide (Flu-high), DHT+Flu low and DHT+Flu high. After 35 days of exposure, lengths and weights of the fish were measured and the condition factor (CF) calculated; vitellogenin (VTG) concentrations were measured in tail tissue; sex steroid hormones (17β-estradiol [E2] and 11-keto testosterone [11-KT]) were measured in the head tissue and abdominal regions were used in histological investigation of the gonads. Treatment with DHT reduced the body-length of both male and female fish, an effect which was canceled out by low and high concentrations of flutamide. However, flutamide (low or high) could not nullify the DHT-induced reduction in the CF in either sex. The E2 levels were reduced only in female fish after exposure to DHT but returned to normal after treatment with Flu-high. DHT increased the levels of 11-KT and decreased the E2/11-KT ratio in both sexes. Flu-high, but not Flu-low, could nullify these effects. Both DHT and flutamide (low or high) induced VTG production and this effect persisted when both chemicals were co-administered. Treatment with DHT did not affect gonadal cell development in the testes. However, the female fish treated with DHT contained ovaries in early-vitellogenic stage in comparison to the pre-vitellogenic ovaries in control fish. Co-treatment with flutamide (low or high) resulted in oocyte atresia. The results from the present study suggest that treatment with Flu-high could cancel out DHT-induced effects only on the hormonal profile and body-length in both male and female fish. Juvenile fish co-treated with DHT and flutamide (low or high) had high VTG levels and low CF. In addition, the ovaries in female fish were atretic. These data represent potential adverse effects on the ability of the fish to reproduce successfully.

Effects of atrazine in fish, amphibians, and reptiles: an analysis based on quantitative weight of evidence

A quantitative weight of evidence (WoE) approach was developed to evaluate studies used for regulatory purposes, as well as those in the open literature, that report the effects of the herbicide atrazine on fish, amphibians, and reptiles. The methodology for WoE analysis incorporated a detailed assessment of the relevance of the responses observed to apical endpoints directly related to survival, growth, development, and reproduction, as well as the strength and appropriateness of the experimental methods employed. Numerical scores were assigned for strength and relevance. The means of the scores for relevance and strength were then used to summarize and weigh the evidence for atrazine contributing to ecologically significant responses in the organisms of interest. The summary was presented graphically in a two-dimensional graph which showed the distributions of all the reports for a response. Over 1290 individual responses from studies in 31 species of fish, 32 amphibians, and 8 reptiles were evaluated. Overall, the WoE showed that atrazine might affect biomarker-type responses, such as expression of genes and/or associated proteins, concentrations of hormones, and biochemical processes (e.g. induction of detoxification responses), at concentrations sometimes found in the environment. However, these effects were not translated to adverse outcomes in terms of apical endpoints. The WoE approach provided a quantitative, transparent, reproducible, and robust framework that can be used to assist the decision-making process when assessing environmental chemicals. In addition, the process allowed easy identification of uncertainty and inconsistency in observations, and thus clearly identified areas where future investigations can be best directed.

Assessment of the health status of wild fish inhabiting a cotton basin heavily impacted by pesticides in Benin (West Africa)

To determine the impact of agricultural pesticides used in cotton cultivation on the health status of fish living in a Beninese cotton basin, we compared the reproductive and hepatic systems of fish sampled from rivers located in both contaminated and pristine conditions. Different types of biomarkers, including biometric indices (a condition factor K, a gonadosomatic index GSI, and a hepatosomatic index HSI), plasma levels of sex steroids (11-ketotestosterone 11-KT, testosterone T and estradiol-17β E2) and the histopathology of the gonads and liver, were investigated for two different trophic levels of the following two fish species: the Guinean tilapia Tilapia guineensis and the African catfish Clarias gariepinus. The fish were captured during both the rainy season (when there is heavy use of pesticides on cotton fields) and the dry season from one site, in Pendjari River (reference site), which is located outside the cotton-producing basin, and from three other sites on the Alibori River within the cotton-producing basin. Comparing fish that were sampled from contaminated (high levels of endosulfan, heptachlor and DDT and metabolites) and reference sites, the results clearly indicated that agricultural pesticides significantly decreased K and GSI while they increased HSI, regardless of the season, species and sex of the fish. These pesticides also induced a decrease in the plasma levels of 11-KT and T and increased those of E2. The histopathology of the testes revealed, in both species, a high rate of testicular oocytes, up to 50% in the African catfish, downstream of the Alibori River, which indicated estrogenic effects from the pesticides. The disruption of male spermatogenesis primarily included necrosis, fibrosis and the presence of foam cells in the lobular lumen. The histopathology of the ovaries revealed high levels of pre-ovulatory follicular atresia, impaired oogenesis, a decrease in the oocyte vitellogenic diameter and other lesions, such as fibrosis, vacuolation and melano-macrophagic centers. The histopathology of the liver revealed the presence of necrosis, hypertrophic hepatocytes, foci of vacuolation, glycogen depletion and hemosiderin. An assessment of the general health of the fish indicated that all of the sampled fish from the polluted sites were in poorer health compared with those from the reference site but that the African catfish appeared much more affected than the Guinean tilapia, regardless of the sex and season. In conclusion, the overall results indicated that agricultural pesticides significantly impair the endocrine regulation of fish living in the Beninese cotton basin and that this would most likely be one of the causes of the severe damage observed in the liver and gonads and the reduced health condition.

Detection of immunotoxic effects of estrogenic and androgenic endocrine disrupting compounds using splenic immune cells of the female three-spined stickleback, Gasterosteus aculeatus (L.)

Today, the list of endocrine disrupting compounds (EDCs) in freshwater and marine environments that mimic or block endogenous hormones is expanding at an alarming rate. As immune and reproductive systems may interact in a bidirectional way, some authors proposed the immune capacities as attractive markers to evaluate the hormonal potential of environmental samples. Thus, the present work proposed to gain more knowledge on direct biological effects of natural and EDCs on female fish splenic leucocyte non-specific immune activities by using ex vivo assays. After determining the optimal required conditions to analyze splenic immune responses, seven different EDCs were tested ex vivo at 0.01, 1 and 100nM over 12h on the leucocyte functions of female three-spined stickleback, Gasterosteus aculeatus. In summary, we found that natural hormones acted as immunostimulants, whilst EDCs were immunosuppressive.

Reprint of "Current perspectives on the androgen 5 alpha-dihydrotestosterone (DHT) and 5 alpha-reductases in teleost fishes and amphibians"

The androgen 5 alpha-dihydrotestosterone (DHT) is a steroidogenic metabolite that has received little attention in non-mammalian species. DHT is produced by the reduction of the double-bond of testosterone by a group of enzymes called 5 alpha-reductases of which there can be multiple isoforms (i.e., srd5a1, srd5a2, and srd5a3). Data from amphibians suggest that the expression of the srd5a genes occurs in early development, and continues until adulthood; however insufficient data exist in fish species, where DHT is thought to be relatively biologically inactive. Here, we demonstrate that fathead minnow (FHM; Pimephales promelas) developing embryos and adults express srd5a enzyme isoforms. During FHM embryogenesis, both srd5a1 and srd5a3 mRNA levels were significantly correlated in expression levels while srd5a2 showed a more unique pattern of expression. In adult FHMs, males had significantly higher levels of srd5a2 in the liver and gonad compared to females. In the male and female liver, transcript levels for srd5a2 were more abundant compared to srd5a1 and srd5a3, suggesting a prominent role for srd5a2 in this tissue. Interestingly, the ovary expressed higher mRNA levels of srd5a3 than the testis. Thus, data suggest that srd5a isoforms can show sexually dimorphic expression patterns in fish. We also conducted a literature review of the biological effects observed in embryonic and adult fish and amphibians after treatments with DHT and DHT-related compounds. Treatments with DHT in teleost fishes and amphibians have resulted in unexpected biological responses that are characteristic of both androgens and anti-androgens. For example, in fish DHT can induce vitellogenin in vitro from male and female hepatocytes and can increase 17β-estradiol production from the teleost ovary. We propose, that to generate further understanding of the roles of DHT in non-mammals, studies are needed that (1) address how DHT is synthesized within tissues of fish and amphibians; (2) examine the full range of biological responses to endogenous DHT, and its interactions with other signaling pathways; and (3) investigate how DHT production varies with reproductive stage. Lastly, we suggest that the Srd5a enzymes can be targets of endocrine disruptors in fish and frogs, which may result in disruptions in the estrogen:androgen balance in aquatic organisms.

Effects of atrazine on endocrinology and physiology in juvenile barramundi, Lates calcarifer (Bloch)

Exposure to certain environmental contaminants such as agricultural pesticides can alter normal endocrine and reproductive parameters in wild fish populations. Recent studies have found widespread pesticide contamination across the rivers that discharge into the Great Barrier Reef lagoon. Potential impacts on native fish species exposed to known endocrine disrupting chemicals such as atrazine, simazine, and diuron have not been assessed. In the present study, the authors examined the endocrine and physiological effects of short-term, acute exposure of environmentally relevant concentrations of analytical grade atrazine in juvenile barramundi (Lates calcarifer) in a controlled laboratory experiment. Expression of hepatic vitellogenin was not affected, supporting results of previous studies that showed that atrazine does not have a direct estrogenic effect via mediation of estrogen receptors. The lack of effect on brain cytochrome P19B (CYP19B) expression levels, combined with increases in testosterone (T) and 17β estradiol and a stable T:17β estradiol ratio, does not support the hypothesis that atrazine has an indirect estrogenic effect via modulation of aromatase expression. Gill ventilation rate, a measure of oxidative stress, did not change in contrast to other studies finding enhanced osmoregulatory disturbance and gill histopathology after atrazine exposure. To more closely reflect field conditions, the authors recommend that laboratory studies should focus more on examining the effects of commercial pesticide formulations that contain additional ingredients that have been found to be disruptive to endocrine function.

Transcriptomics profiling and steroid production in mummichog (Fundulus heteroclitus) testes after treatment with 5α-dihydrotestosterone

5α-Dihydrotestosterone (DHT) is a potent androgen in mammals with multiple roles; however the physiological actions of DHT in male fishes are not well known. To address this knowledge gap, male mummichog (Fundulus heteroclitus) were continuously exposed to 0, 5, and 50 μg/L DHT for 21 days. Following exposure, testes were separated for histology, ex vivo incubation to measure steroidogenic capacity, and gene expression analyses (real-time PCR and microarray). DHT significantly decreased ex vivo 11-ketotestosterone (11KT) production in males exposed to 50 μg/L DHT but not 5 μg/L DHT, and DHT exposure did not affect ex vivo testosterone production. Histological examination revealed that the amount of interlobular and connective tissue present in the testes was increased in the 50 μg/L DHT treatment. Despite reductions in the production of 11KT, DHT did not affect the expression of targeted genes in the steroidogenic pathway such as steroidogenic acute regulatory protein (star), P450 side chain cleavage (cyp11a1) and 11β-hydroxysteroid dehydrogenase (hsd11b3). Microarray analysis in the testes of individuals from control and 50 μg/L DHT revealed that males exposed to 50 μg/L DHT showed regulated transcriptional sub-networks that were related to immunity, regulation of blood flow, lipids and xenobiotic clearance, suggesting that DHT may be involved in the physiological regulation of these processes in the fish testes. A second objective of this study was to determine the feasibility of measuring mRNA levels in tissues used for ex vivo steroid production by comparing RNA integrity and transcript levels in testes of both immediately flash frozen tissue and incubated tissue. There was no significant difference in RNA quality between the two time points, indicating RNA integrity can remain intact for at least 18 h in ex vivo assays, thereby providing a viable option for researchers assessing multi-level biological reproductive endpoints when limited tissue is available. While the gene expression levels of actb, efla, rps12, rps18, star, and hsd11b3 remained unchanged, esr2a (esrba), esr2b (esrbb) and cyp11a1 were significantly lower in incubated tissue compared to flash frozen tissue. Therefore caution must be used as the steady-state levels of select genes may change over time. This study improves our understanding of DHT action in the teleostean testis and generates new hypotheses regarding cell processes that are regulated by this underexplored and potent androgen.

Impact of glyphosate and glyphosate-based herbicides on the freshwater environment

Glyphosate [N-(phosphonomethyl) glycine] is a broad spectrum, post emergent herbicide and is among the most widely used agricultural chemicals globally. Initially developed to control the growth of weed species in agriculture, this herbicide also plays an important role in both modern silviculture and domestic weed control. The creation of glyphosate tolerant crop species has significantly increased the demand and use of this herbicide and has also increased the risk of exposure to non-target species. Commercially available glyphosate-based herbicides are comprised of multiple, often proprietary, constituents, each with a unique level of toxicity. Surfactants used to increase herbicide efficacy have been identified in some studies as the chemicals responsible for toxicity of glyphosate-based herbicides to non-target species, yet they are often difficult to chemically identify. Most glyphosate-based herbicides are not approved for use in the aquatic environment; however, measurable quantities of the active ingredient and surfactants are detected in surface waters, giving them the potential to alter the physiology of aquatic organisms. Acute toxicity is highly species dependant across all taxa, with toxicity depending on the timing, magnitude, and route of exposure. The toxicity of glyphosate to amphibians has been a major focus of recent research, which has suggested increased sensitivity compared with other vertebrates due to their life history traits and reliance on both the aquatic and terrestrial environments. This review is designed to update previous reviews of glyphosate-based herbicide toxicity, with a focus on recent studies of the aquatic toxicity of this class of chemicals.

Effect of a glyphosate-based herbicide on gene expressions of the cytokines interleukin-1β and interleukin-10 and of heme oxygenase-1 in European sea bass, Dicentrarchus labrax L

Glyphosate-based herbicides are the most frequently used herbicides in the world. We evaluated the effect of Roundup 360 SL on the expression of interleukin-1β (il-1β), interleukin-10 (il-10) and heme-oxygenase-1 (ho-1) in the gills, intestines and spleen of young European sea bass (Dicentrachus labrax L.), aged 8 mo. A group of fish was exposed to 647 mg/L of Roundup for 96 h. This treatment did not alter gene expression levels of il-1β and il-10 cytokine in the intestines, but significantly lowered both levels in the gills (p = 0.02 and p = 0.04 respectively). Expression levels of ho-1 were increased significantly in the three organs of fish from the treated group (the gills p = 0.04, the intestines p = 0.004 and the spleen p < 0.001). These changes may in turn negatively impact the immune system of European sea bass exposed to Roundup.

Effects of glyphosate and its formulation, roundup, on reproduction in zebrafish (Danio rerio)

Roundup and its active ingredient glyphosate are among the most widely used herbicides worldwide and may contaminate surface waters. Research suggests both Roundup and glyphosate induce oxidative stress in fish and may also cause reproductive toxicity in mammalian systems. We aimed to investigate the reproductive effects of Roundup and glyphosate in fish and the potential associated mechanisms of toxicity. To do this, we conducted a 21-day exposure of breeding zebrafish (Danio rerio) to 0.01, 0.5, and 10 mg/L (glyphosate acid equivalent) Roundup and 10 mg/L glyphosate. 10 mg/L glyphosate reduced egg production but not fertilization rate in breeding colonies. Both 10 mg/L Roundup and glyphosate increased early stage embryo mortalities and premature hatching. However, exposure during embryogenesis alone did not increase embryo mortality, suggesting that this effect was caused primarily by exposure during gametogenesis. Transcript profiling of the gonads revealed 10 mg/L Roundup and glyphosate induced changes in the expression of cyp19a1 and esr1 in the ovary and hsd3b2, cat, and sod1 in the testis. Our results demonstrate that these chemicals cause reproductive toxicity in zebrafish, although only at high concentrations unlikely to occur in the environment, and likely mechanisms of toxicity include disruption of the steroidogenic biosynthesis pathway and oxidative stress.

Current perspectives on the androgen 5 alpha-dihydrotestosterone (DHT) and 5 alpha-reductases in teleost fishes and amphibians

The androgen 5 alpha-dihydrotestosterone (DHT) is a steroidogenic metabolite that has received little attention in non-mammalian species. DHT is produced by the reduction of the double-bond of testosterone by a group of enzymes called 5 alpha-reductases of which there can be multiple isoforms (i.e., srd5a1, srd5a2, and srd5a3). Data from amphibians suggest that the expression of the srd5a genes occurs in early development, and continues until adulthood; however insufficient data exist in fish species, where DHT is thought to be relatively biologically inactive. Here, we demonstrate that fathead minnow (FHM; Pimephales promelas) developing embryos and adults express srd5a enzyme isoforms. During FHM embryogenesis, both srd5a1 and srd5a3 mRNA levels were significantly correlated in expression levels while srd5a2 showed a more unique pattern of expression. In adult FHMs, males had significantly higher levels of srd5a2 in the liver and gonad compared to females. In the male and female liver, transcript levels for srd5a2 were more abundant compared to srd5a1 and srd5a3, suggesting a prominent role for srd5a2 in this tissue. Interestingly, the ovary expressed higher mRNA levels of srd5a3 than the testis. Thus, data suggest that srd5a isoforms can show sexually dimorphic expression patterns in fish. We also conducted a literature review of the biological effects observed in embryonic and adult fish and amphibians after treatments with DHT and DHT-related compounds. Treatments with DHT in teleost fishes and amphibians have resulted in unexpected biological responses that are characteristic of both androgens and anti-androgens. For example, in fish DHT can induce vitellogenin in vitro from male and female hepatocytes and can increase 17β-estradiol production from the teleost ovary. We propose, that to generate further understanding of the roles of DHT in non-mammals, studies are needed that (1) address how DHT is synthesized within tissues of fish and amphibians; (2) examine the full range of biological responses to endogenous DHT, and its interactions with other signaling pathways; and (3) investigate how DHT production varies with reproductive stage. Lastly, we suggest that the Srd5a enzymes can be targets of endocrine disruptors in fish and frogs, which may result in disruptions in the estrogen:androgen balance in aquatic organisms.