Determination of acute mortality in adults and sublethal embryo responses of Palaemonetes pugio to endosulfan and methoprene exposure

Larval mosquito management and risk to aquatic ecosystems: A comparative approach including current tactics and gene-drive Anopheles techniques

Genetic engineering of mosquitoes represents a promising tactic for reducing human suffering from malaria. Gene-drive techniques being developed that suppress or modify populations of Anopheles gambiae have the potential to be used with, or even possibly obviate, microbial and synthetic insecticides. However, these techniques are new and therefore there is attendant concern and uncertainty from regulators, policymakers, and the public about their environmental risks. Therefore, there is a need to assist decision-makers and public health stewards by assessing the risks associated with these newer mosquito management tactics so the risks can be compared as a basis for informed decision making. Previously, the effect of gene-drive mosquitoes on water quality in Africa was identified as a concern by stakeholders. Here, we use a comparative risk assessment approach for the effect of gene-drive mosquitoes on water quality in Africa. We compare the use of existing larvicides and the proposed genetic techniques in aquatic environments. Based on our analysis, we conclude that the tactic of gene-drive Anopheles for malaria management is unlikely to result in risks to aquatic environments that exceed current tactics for larval mosquitoes. As such, these new techniques would likely comply with currently recommended safety standards.

Effects of agricultural pesticides on the reproductive system of aquatic wildlife species, with crocodilians as sentinel species

Agricultural pesticides represent a significant class of endocrine-disrupting chemicals (EDCs) to which non-target organisms around the world are constantly exposed. Laboratory studies have found strong evidence showing the endocrine-disruptive potential of these pesticides at environmentally relevant exposure levels. Since the field of endocrine disruption continues to grow in richness and complexity, this review aims to provide an update on the effects of two agricultural pesticides that act as EDCs: atrazine and endosulfan. We will focus mainly on the effects on crocodilians due to their worldwide occurrence in tropical and sub-tropical wetland ecosystems and their ecological and physiological features, which render them vulnerable to exposure to pesticides with endocrine-disrupting action at all life stages. The results here reviewed provide important insights into the effects of hormonally active agricultural pesticides at cellular, tissue, and organ levels in the reproductive system of crocodiles. A better understanding of the effects of exposure to environmentally relevant doses of EDCs on the reproductive system of crocodilians will contribute to protect and improve the health of both wildlife species and humans.

The risk of neonicotinoid exposure to shrimp aquaculture

Widespread agricultural use of systemic neonicotinoid insecticides has resulted in the unintended contamination of aquatic environments. Water quality surveys regularly detect neonicotinoids in rivers and waterways at concentrations that could impact aquaculture stock. The toxicity of neonicotinoids to non-target aquatic insect and crustacean species has been recognised, however, there is a paucity of information on their effect on commercial shrimp aquaculture. Here, we show that commercially produced shrimp are likely to be exposed to dietary, sediment and waterborne sources of neonicotinoids; increasing the risks of disease and accidental human consumption. This review examines indicators of sublethal neonicotinoid exposure in non-target species and analyses their potential usefulness for ecotoxicology assessment in shrimp. The identification of rapid, reliable responses to neonicotinoid exposure in shrimp will result in better decision making in aquaculture management.

Environmental safety review of methoprene and bacterially-derived pesticides commonly used for sustained mosquito control

Some pesticides are applied directly to aquatic systems to reduce numbers of mosquito larvae (larvicides) and thereby reduce transmission of pathogens that mosquitoes vector to humans and wildlife. Sustained, environmentally-safe control of larval mosquitoes is particularly needed for highly productive waters (e.g., catchment basins, water treatment facilities, septic systems), but also for other habitats to maintain control and reduce inspection costs. Common biorational pesticides include the insect juvenile hormone mimic methoprene and pesticides derived from the bacteria Bacillus thuringiensis israelensis, Lysinibacillus sphaericus and Saccharopolyspora spinosa (spinosad). Health agencies, the public and environmental groups have especially debated the use of methoprene because some studies have shown toxic effects on non-target organisms. However, many studies have demonstrated its apparent environmental safety. This review critically evaluates studies pertinent to the environmental safety of using methoprene to control mosquito larvae, and provides concise assessments of the bacterial larvicides that provide sustained control of mosquitoes. The review first outlines the ecological and health effects of mosquitoes, and distinguishes between laboratory toxicity and environmental effects. The article then interprets non-target toxicity findings in light of measured environmental concentrations of methoprene (as used in mosquito control) and field studies of its non-target effects. The final section evaluates information on newer formulations of bacterially-derived pesticides for sustained mosquito control. Results show that realized environmental concentrations of methoprene were usually 2-5µg/kg (range 2-45µg/kg) and that its motility is limited. These levels were not toxic to the vast majority of vertebrates and invertebrates tested in laboratories, except for a few species of zooplankton, larval stages of some other crustaceans, and small Diptera. Studies in natural habitats have not documented population reductions except in small Diptera. Bacterial larvicides showed good results for sustained control with similarly limited environmental effects, except for spinosad, which had broader effects on insects in mesocosms and temporary pools. These findings should be useful to a variety of stakeholders in informing decisions on larvicide use to protect public and environmental health in a 'One Health' framework.

Acute toxicity, biochemical and histopathological responses of endosulfan in Chanos chanos

This study investigated 96h median lethal concentration of endosulfan (99%, pure α: β ratio of 7:3) by conducting static non-renewable acute toxicity bio-assay in Chanos chanos juvenile with average weight (110±5.65g). Further, the effect of different definitive doses (18.5, 19.5, 20.5, 21.5 and 22.5µg/L) of endosulfan on metabolic, heamato-immunoligcal and histopathological response were probed. Anti-oxidative enzymes CAT, SOD and GST showed significant (p<0.01) increase of activity in the liver, gill and brain during exposure to endosulfan in a dose and time dependent manner. The brain AChE activity showed significant (p<0.01) inhibition from 18.5 to 22.5µg/L exposure of endosulfan than the control group. LDH and MDH activity gradually increased with consequent increasing dose of endosulfan exposure in the liver, gill and brain. Similarly, ALT, AST and G6PDH activities in both liver and gill increased with consequent increases in the dose of endosulfan exposure. Immunological profile such as blood glucose and serum cortisol level significantly enhanced while respiratory burst activity declined with consequent increasing doses of endosulfan exposure. Histopathological alteration in the gill demonstrated curling of secondary lamellae, thickening of primary epithelium, shorting of secondary lamellae, epithelial hyperplasia, fusion of secondary lamellae, aneurism, and collapsed secondary lamellae due to dose dependent exposure of endosulfan. Liver histology illustrated cloudy swelling and necrosis with pyknotic nuclei to the moderate dose of endosulfan, whereas higher dose of endosulfan (21.5µg/L) displayed severe necrosis of hepatic cells. Overall results clearly indicate that acute exposure of endosulfan led to pronounced deleterious alterations on biochemical, heamato-immunological, and histopathological responses of C. chanos juvenile.

Endosulfan isomers and sulfate metabolite induced reproductive toxicity in Caenorhabditis elegans involves genotoxic response genes

Endosulfan is enlisted as one of the persistent organic pollutants (POPs) and exists in the form of its α and β isomers in the environment as well as in the form of endosulfan sulfate, a toxic metabolite. General endosulfan toxicity has been investigated in various organisms, but the effect of the isomers and sulfate metabolites on reproductive function is unclear. This study was aimed at studying the reproductive dysfunction induced by endosulfan isomers and its sulfate metabolite in Caenorhabditis elegans (C. elegans). We also determined a role for the DNA-damage-checkpoint gene hus-1. Compared to β-endosulfan and its sulfate metabolite, α-endosulfan caused a dramatically higher level of germ cell apoptosis, which was regulated by DNA damage signal pathway. Both endosulfan isomers and the sulfate metabolite induced germ cell cycle arrest. Loss-of-function studies using hus-1, egl-1, and cep-1 mutants revealed that hus-1 specifically influenced the fecundity, hatchability, and sexual ratio after endosulfan exposure. Our data provide clear evidence that the DNA-checkpoint gene hus-1 has an essential role in endosulfan-induced reproductive dysfunction and that α-endosulfan exhibited the highest reproductive toxicity among the different forms of endosulfan.

Individual and mixture effects of caffeine and sulfamethoxazole on the daggerblade grass shrimp Palaemonetes pugio following maternal exposure

Pharmaceuticals and personal care products (PPCPs) such as caffeine and sulfamethoxazole have been detected in the estuarine environment. The present study characterized effects of a maternal exposure of these compounds on the development of the daggerblade grass shrimp Palaemonetes pugio from embryo to juvenile life stage. Ovigerous females were exposed to either caffeine (20 mg/L), sulfamethoxazole (60 mg/L), or a mixture of both (20 mg/L caffeine and 60 mg/L sulfamethoxazole). Embryos were then removed from the females and the effects of the PPCPs on hatching, metamorphosis, juvenile growth, and overall mortality were determined. No significant effect was observed on gravid female survival after 5 d of exposure to caffeine, sulfamethoxazole, or the mixture; however, development of the embryos on the female shrimp was delayed in the mixture. Caffeine and sulfamethoxazole in the mixture significantly reduced embryo survival. There was a significant effect of caffeine, sulfamethoxazole, and the mixture on embryo hatching time. Exposure to sulfamethoxazole alone significantly delayed larval metamorphosis. Exposure to caffeine and sulfamethoxazole separately led to significantly smaller length of juvenile shrimp. Maternal exposure to caffeine and sulfamethoxazole, individually and in mixture, resulted in negative effects on P. pugio offspring survival and development; however, the concentrations tested in the present study were well above maximum detected field concentrations. These results may be incorporated into PPCP risk assessments to protect sensitive estuarine ecosystems more effectively.

Effects of chlorpyrifos and endosulfan on different life stages of the freshwater burrowing crab Zilchiopsis collastinensis P.: protective role of chorion

The lethality (LC50) of endosulfan and chlorpyrifos is higher in adults (1990 and 156.78 μg/L respectively) than in embryos (95380 and 1242.54 μg/L respectively) of the crab Zilchiopsis collastinensis. The thickened embryonic coat of the freshwater species might isolate the embryo inside the egg, reducing the toxicity. Sublethal concentrations of chlorpyrifos and endosulfan caused an increase in hatching time and a decrease in effective hatching (p < 0.05), and only the control crabs survived until the first molt cycle. The effects of long-term exposure should be evaluated in the offspring in addition to the acute toxicity.

Cost of reproduction. Changes in metabolism and endosulfan lethality caused by reproductive behavior in Hyalella curvispina (Crustacea: Amphipoda)

Biocides are periodically applied in agricultural activities, reaching aquatic systems and acting upon the biota. Amphipods are widely used in toxicity tests because of their sensitivity to a wide range of pollutants. In this work, we report the differential lethality of a widely used pesticide, endosulfan, on the amphipod Hyalella curvispina at two life stages and in three different adult groups, males and females separated by sex and both sexes grouped together. In addition, oxygen consumption of adult groups was determined as a way to estimate the role of behavioral activities and exposure to endosulfan in metabolism shifts. There were no differences between the LC(50) of juveniles and the adults when they were separated by sex (p>0.05). Nevertheless, the LC(50) of adults without sexual differentiation was significantly lower than the LC(50) of juveniles and adults separated by sex (p<0.05). The oxygen consumption rate was higher when adults were grouped without sexual differentiation in the control group. The exposure to low concentrations of endosulfan causes an increase in oxygen consumption in all the treatments. The sexual behavior increased the metabolism and the sensitivity to endosulfan. In future evaluations, adults grouped without sexual differentiation, which were the most sensitive group, should be included in order to mimic the environmental conditions. Using only juveniles or adults separated by sex in toxicity tests may inaccurately estimate the lethality of biocides, especially in species with constant reproductive activities.

Bioaccumulation in freshwater crabs. Endosulfan accumulation in different tissues of Zilchiopsis collastinensis P. (Decapoda: Trichodactylidae)

We examined the bioaccumulation of α- and β-endosulfan and endosulfan sulfate in tissues from the crab Zilchiopsis collastinensis. There was more endosulfan accumulated in the hepatopancreas (from <2 to 467.8 ng g(-1)) than in the gonads (from <2 to 52.1 ng g(-1)) or muscles (<2 ng g(-1)). The endosulfan concentrations in the hepatopancreas decreased over time and with the endosulfan dilution (p < 0.05). In the gonads there was little bioaccumulation, which did not vary over time (p > 0.05). The hepatopancreas is a dynamic organ that is able to depurate itself, whereas the gonads act as a sink for pesticides.

Effects of endosulfan exposure and Taura Syndrome Virus infection on the survival and molting of the marine penaeid shrimp, Litopenaeus vannamei

Molting in crustaceans is an important endocrine-controlled biological process that plays a critical role in growth and reproduction. Many factors can affect this physiological cycle in crustaceans including environmental stressors and disease agents. For example the pathology of Taura Syndrome Virus (TSV) of shrimp is closely related to molting cycle. Similarly, endosulfan, a commonly used pesticide is a potential endocrine disruptor. This study explores interrelationships between pesticide exposure, virus infection and their interactions with physiology and susceptibility of the shrimp. Litopenaeus vannamei (Pacific white shrimp) were challenged with increasing doses of endosulfan and TSV (TSV-C, a Belize reference strain) to determine the respective median lethal concentrations (LC(50)s). The 96-h endosulfan LC(50) was 5.32 μg L(-1), while the 7-d TSV LC(50) was 54.74 mg L(-1). Subsequently, based on their respective LC(50) values, a 20-d interaction experiment with sublethal concentrations of endosulfan (2 μg L(-1)) and TSV (30 mg L(-1)) confirmed a significant interaction (p<0.05, χ(2)=5.29), and thereby the susceptibility of the shrimp. Concurrently, molt-stage of animals, both at the time of exposure and death, was compared with mortality. For animals challenged with TSV, no strong correlation between molt-stage and mortality was observed (p>0.05). For animals exposed to endosulfan, animals in the postmolt stage were shown to be more susceptible to acute toxicity (p<0.05). For animals exposed to both TSV and endosulfan, interference of endosulfan-associated stress lead to increasingly higher susceptibility at postmolt (p<0.05) during the acute phase of the TSV disease cycle.

Teratogenicity and embryotoxicity in aquatic organisms after pesticide exposure and the role of oxidative stress

Many pesticides have been documented to induce embryotoxicity and teratogenicity in non-target aquatic biota such a fish, amphibians and invertebrates. Our review of the existing literature shows that a broad range of pesticides, representing several different chemical classes, induce variable toxic effects in aquatic species. The effects observed include diverse morphological malformations as well as physiological and behavioral effects. When development malformations occur, the myoskeletal system is among the most highly sensitive of targets. Myoskeletal effects that have been documented to result from pesticides were also known to interfere with the development of organ systems including the eyes or the heart and are also known to often cause lethal or sublethal edema in exposed organisms. The Physiological, behavioral, and population endpoints affected by pesticides include low or delayed hatching, growth suppression, as well as embryonal or larval mortality. The risks associated with pesticide exposure increase particularly during the spring. This is the period of time in which major pepticide applications take place, and this period unfortunately also coincides with many sensitive reproductive events such as spawning, egg laying, and early development of many aquatic organisms. Only few experimental studies with pesticides have directly linked developmental toxicity with key oxidative stress endpoints, such as lipid peroxidation, oxidative DNA damage, or modulation of antioxidant mechanisms. On the other hand, it has been documented in many reports that pesticide-related oxidative damage occurs in exposed adult fish, amphibians, and invertebrates. Moreover, the contribution of oxidative stress to the toxicity of pesticides has been emphasized in several recent review papers that have treated this topic. In conclusion, the available experimental data, augmented by several indirect lines of evidence, provide support to the concept that oxidative stress is a highly important mechanism in pesticide-induce reproductive or developmental toxicity. Other stressors may also act by oxidative mechanisms. This notwithstanding, there is much yet to learn about the details of this phenomenon and further research is needed to more fully elucidate the effects that pesticides have and the environmental risks they pose in the early development of aquatic organisms.

Characterization of two vitellogenin cDNAs from a Pandalus shrimp (Pandalopsis japonica): expression in hepatopancreas is down-regulated by endosulfan exposure

Endosulfan is a neurotoxic organochlorine insecticide of the cyclodiene family of pesticides that inhibits molting and reproduction in aquatic crustaceans. In order to determine the molecular mechanism of endosulfan as an endocrine disrupting chemical (EDC), differential display RT-PCR (DDRT-PCR) was used to isolate genes in the shrimp, Pandalopsis japonica, affected by endosulfan exposure. PCR screening of cDNA from the hepatopancreas from control and endosulfan-exposed animals, using 120 sets of random primers, yielded partial cDNAs encoding two vitellogenin-like proteins (Pj-Vg1 and -Vg2). Complete sequences were obtained using a combination of RT-PCR and RACE-PCR. Pj-Vg1 (7883bp) encoded a protein composed of 2533 amino acid residues (283.27 kDa estimated mass), whereas Pj-Vg2 (7792 bp) encoded a protein composed of 2537 amino acids residues (284.87 kDa estimated mass). Alignment of the Pj-Vgs with those of other vitellogenins identified a conserved subtilisin cleavage site (RQKR) and the lipoprotein N-terminal (vitellin), DUF1081, and von Willebrand factor type D domains, indicating both genes encoded functional proteins. Phylogenetic analysis showed that Pj-Vg1 and -Vg2 were most similar to Pandalus hypsinotus Vg. Both Pj-Vg1 and -Vg2 were expressed primarily in the hepatopancreas, although the Pj-Vg2 transcript was also detected in the ovary. The effects of the 3-day endosulfan exposure (2.5 microg/L and 25 microg/L) on Vg expression in the hepatopancreas were determined by quantitative RT-PCR. Expression of both transcripts was significantly inhibited at 25 microg/L suggesting that Pj-Vgs can be used as indicator for endosulfan exposure.

Oxidative stress, protein carbonylation and heat shock proteins in the black tiger shrimp, Penaeus monodon, following exposure to endosulfan and deltamethrin

The impact of commonly used pesticides, endosulfan and deltamethrin, on the molecular stress level in black tiger shrimp Penaeus monodon, was assessed using classical oxidative stress biomarkers, protein carbonylation profiles, and levels of heat shock proteins. Results showed that 4 days exposure to 0.1 μg L(-1) deltamethrin significantly (p<0.05) increased lipid peroxidation (LPO) level in gills (64.3 ± 3.2 compared to 34.2 ± 5.3 nmol MDA equiv.g(-1) tissue at day 0). However, no pesticide treatment had significant effect on the activities of antioxidant enzymes catalase (CAT), glutathione peroxidase (GPx) and glutathione S-transferase (GST). Carbonylated protein profiles were determined on gills following 2,4-dinitrophenylhydrazine derivatization and 2D-PAGE along with Western blotting. Immunoblotting with dinitrophenol-specific antibody revealed 17 protein spots carbonylated in response to 4 days exposure to 0.1 μg L(-1) deltamethrin while 24 protein spots specifically oxidized at day 0 were no longer detected after deltamethrin treatment. On the other hand, endosulfan exposure at 0.1 and 1 μg L(-1) induced up to 2.1-fold increase of HSP90 level in muscle. This approach is providing new insights into the molecular impacts of deltamethrin and endosulfan on an economically important crustacean. While deltamethrin has shown a pro-oxidant effect in gills, endosulfan exposure rather induced proteotoxic effects in muscles. This argues that LPO level, protein carbonylation specificities, and HSP90 levels may be potential discriminating biomarkers to assess the chemical stress level in farm shrimp.

Effects of endosulfan and ethanol on the reproduction of the snail Biomphalaria tenagophila: a multigeneration study

Endosulfan (END) is an insecticide used in agriculture and as a wood preservative. Since END is practically insoluble in water, ethanol (ETOH) is often employed as a carrier solvent to spike it in the test medium in aquatic toxicity assays. In this study were investigated the effects of END and ETOH on the reproduction of the freshwater snail Biomphalaria tenagophila exposed over three successive generations. END (0, 0.001, 0.01, 0.1 mg L(-1)) was dissolved in the medium water using ETOH (up to 19.8 mg L(-1)) as carrier solvent. ETOH (19.8, 198, 1980 mg L(-1)) alone was tested as well. Adult snails (F(0)-generation) were exposed to END and ETOH for 8 weeks. The F(1)-generation continued to be exposed from embryo to reproductive maturity, while their descendants (F(2)) were exposed until day 10 after spawning. Effects on the fecundity (8-week production of eggs and egg-masses) of mature F(0) and F(1) snails were evaluated. Developmental toxicity was investigated in F(1) and F(2) embryos. END at the highest level tested (0.1 mg L(-1)) inhibited egg production by F(0) and F(1) snails. ETOH at levels 198 mg L(-1) also reduced fecundity of F(0) and F(1) an effect that was apparently aggravated by exposure over successive generations. END 0.1 mg L(-1) increased mortality and malformations and decreased hatching among F(1) embryos. ETOH drastically reduced the proportion of hatchings among F(2) embryos. The study-derived NOECs (no-observed-effect-concentrations) for END was 0.01 mg L(-1) (reduction in fecundity), and for ETOH were 19.8 mg L(-1) for reduction in fecundity and <19.8 mg L(-1) for developmental toxicity (hatching retardation).

Endosulfan sulphate interferes with reproduction, embryonic development and sex differentiation in Daphnia magna

Endosulfan sulphate is the transformation product of endosulfan and it is the most frequent form of surface water contamination with endosulfan. The aim of this study was to evaluate the possible effects promoted by endosulfan sulphate in changes on the life cycle, embryo development and sex differentiation of Daphnia magna. The endpoints used were moulting frequency, fecundity, growth, developmentally abnormalities and sexual differentiation. The nominal concentrations of endosulfan sulphate tested ranged from 9.2 to 458.7 microg L(-1). Endosulfan sulphate promoted a significant decrease of the offspring number in all concentrations. Results showed a reduction of the size of females, together with a decrease in moulting frequency. Furthermore, an increase in embryo deformities was observed at all concentrations tested. Above a concentration of 91.7 microg L(-1) there was an increased production of males. The results suggest that endosulfan sulphate interferes with the life cycle and sex determination of the crustacean D. magna.

Aquatic risk assessment of pesticides in surface waters in and adjacent to the Everglades and Biscayne National Parks: I. Hazard assessment and problem formulation

An aquatic risk assessment under the U.S. Environment Protection Agency (EPA) ecological risk framework was conducted for atrazine, metolachlor, malathion, chlorpyrifos, and endosulfan in the C-111 freshwater basin (eastern boundary of the Everglades National Park), northeast Florida Bay, and south Biscayne Bay in South Florida. Based on the use of the hazard quotient approach, measured concentrations of chlorpyrifos and endosulfan in surface waters suggest potential hazards to aquatic organisms and were, therefore, considered as chemicals of potential ecological concern (COPECs). The problem formulation included an overview of the physical/chemical and environmental fate characteristics and aquatic toxicology of the COPECs. Background surface water exposure concentrations of endosulfan and toxicity data from laboratory and field studies indicate that fish and invertebrate mortality may be a concern when endosulfan is applied in agricultural areas near aquatic ecosystems.

Survival and growth of Palaemonetes argentinus (Decapoda; Caridea) exposed to insecticides with chlorpyrifos and endosulfan as active element

Pesticides with chlorpyrifos and endosulfan as active element are used for pest control on agricultural lands and are high-risk inputs in aquatic systems. The acute toxicity of these insecticides in the freshwater prawn Palaemonetes argentinus was evaluated. The results were used to determine the lowest observed-effect and no observed-effect concentrations. Individual growth of prawns in relation to chlorpyrifos and endosulfan exposure was analyzed. LC(50) values to chlorpyrifos and endosulfan exposure were 2.98 microg L(-1) and 14.10 at 24 hours and 0.49 microg L(-1) and 6.28 microg L(-1) at 96 hours of exposure, respectively. The size increment of prawns was the same in all treatments; cephalothorax length increased linearly per molt. The intermolt period was influenced by the toxic effect of pesticides during rearing time, and this decreased with the molt cycles compared with the normal growth pattern. The results suggest that juveniles of P. argentinus are sensitive to chlorpyrifos and endosulfan pollution.

Marsupial development in the mysid Neomysis integer (Crustacea: Mysidacea) to evaluate the effects of endocrine-disrupting chemicals

Embryonic development is a crucial time window within an organism's life history. Relatively few studies have focused on understanding the potential effects of endocrine disruptors on embryogenesis in invertebrates. Mysids (Crustacea: Mysidacea) have been used extensively in regulatory toxicity testing and they are the only invertebrate model currently included in the U.S. EPA's Endocrine Disruptor Screening and Testing Program. We developed a method for studying mysid embryonic development in multiwell plates until the release of free-swimming juveniles. This method was used to evaluate the potential effects of the insecticide methoprene, a juvenile hormone analog, on mysid embryogenesis. Embryos were exposed to nominal concentrations 0.01, 1, and 100 microg methoprene/L. Average percentage survival, hatching success, total development time and duration of each developmental stage were analyzed. Embryos exposed to 1 and 100 microg methoprene/L had a significantly lower hatching success and lower survival rates. Our study indicates that in vitro embryogenesis can be used as a valuable tool to study the impact of endocrine disruptors in mysids.

Cathepsin B and glutathione peroxidase show differing transcriptional responses in the grass shrimp, Palaemonetes pugio following exposure to three xenobiotics

The common molecular biology techniques, suppressive-subtractive hybridization (SSH) and semi-quantitative real-time PCR (SQRT-PCR), were used to identify differentially expressed genes in the grass shrimp, Palaemonetes pugio following exposure to three different xenobiotics. Lab-acclimated adult male grass shrimp were exposed to empirically derived 96-hr male-specific LC50 concentrations of fipronil (FP, a phenylpyrazole GABA disrupting pesticide), endosulfan (ES, a cyclodiene GABA disrupting pesticide), or cadmium (Cd), as well as a control (CC). An SSH gene expression library was constructed from surviving shrimp from the fipronil and control exposures. Clones obtained by SSH were identified by searching against the NCBI website. A total of 42 genes were identified that were up-regulated by FP exposure, and 47 that were down-regulated. A subset of the affected genes was tested with SQRT-PCR to verify responsiveness to fipronil, as well as to endosulfan and cadmium. Two genes showed strong and significant responses to the exposures: glutathione peroxidase was significantly up-regulated by all three exposures, while Cathepsin B was strongly responsive to the two pesticides, but not to cadmium.

Protective effects of allozyme genotype during chemical exposure in the grass shrimp, Palaemonetes pugio

The primary objective of this research was to determine if the genotype of the enzymes glucose phosphate isomerase (Gpi), phosphoglucomutase (Pgm), or mannose phosphate isomerase (Mpi) are factors affecting survival during acute endosulfan, fluoranthene, and chromium(VI) exposures. Palaemonetes pugio were exposed in the laboratory to 6.3 microg/L endosulfan, 100 mg/L chromium(VI), or 0.6 mg/L fluoranthene. Dead shrimp were removed at approximately 15-30 min intervals and the individual's genotypes for the Gpi, Mpi, and Pgm enzymes were determined. These data were used to establish whether allozyme genotype was related to tolerance as analyzed with non-parametric methods (i.e. development of survival curves using the Kaplan-Meier method of estimation) and parametric methods (i.e. proportional hazards models). Since the sex and/or size of the organism was expected to affect tolerance, these variables were accounted for in the proportional hazards models. Results indicated individuals that were heterozygous (MF) for the Gpi allozyme survived longer and had less overall mortality than the homozygous MM genotype when exposed to chromium(VI) and to fluoranthene. No allozyme genotypes were related to tolerance during the endosulfan exposure when sex was included as a covariate in the analysis. These results support the hypothesis that there is a genetic basis for tolerance in P. pugio during acute exposures to chromium(VI) and to fluoranthene. Although a relationship between Gpi genotype and contaminant tolerance has been identified in previous studies, no such relationship has been documented in P. pugio or with chromium(VI) as the contaminant.

Use and Role of Invertebrate Models in Endocrine Disruptor Research and Testing

Historically, invertebrates have been excellent models for studying endocrine systems and for testing toxic chemicals. Some invertebrate endocrine systems are well suited for testing chemicals and environmental media because of the ease of using certain species, their sensitivity to toxic chemicals, and the broad choice of models from which to choose. Such assays will be useful in identifying endocrine disruptors to protect invertebrate populations and as screening systems for vertebrates. Hormone systems are found in all animal phyla, although the most simple animals may have only rudimentary endocrine systems. Invertebrate endocrine systems use a variety of types of hormones, including steroids, peptides, simple amides, and terpenes. The most well-studied hormone systems are the molting and juvenile hormones in insects, the molting hormones in crustaceans, and several of the neurohormones in molluscs and arthropods. These groups offer several options for assays that may be useful for predicting endocrine disruption in invertebrates. A few invertebrate phyla offer predictive capabilities for understanding vertebrate endocrine-disrupting chemicals. The echinoderms, and to a lesser extent molluscs, have closer evolutionary relationships with the vertebrates than the arthropods and these phyla. The recently identified estrogen receptor structure within the genome of the marine gastropod, Aplysia, indicates that the estrogens, and probably the basic steroid receptor, are quite old evolutionarily. This review of the recent literature confirms the effects of some endocrine-disrupting chemicals on invertebrates--tributyltin on snails, pesticides on insects and crustaceans, and industrial compounds on marine animals.

Stereoselective degradation of aqueous endosulfan in modular estuarine mesocosms: formation of endosulfan gamma-hydroxycarboxylate

Solutions of alpha-endosulfan, beta-endosulfan, and technical grade endosulfan (70alpha:30beta) were added to modular estuarine mesocosms; the kinetics and degradation products from each mesocosm are reported. The persistent product endosulfan sulfate was generated in all cases; however, its yield was approximately a factor of three higher from alpha-endosulfan relative to beta-endosulfan. Beta-endosulfan hydrolyzed faster than alpha-endosulfan to endosulfan diol, which then rapidly degraded to endosulfan ether, endosulfan alpha-hydroxyether (major product), and endosulfan lactone. The ring-opened form of the lactone, endosulfan gamma-hydroxycarboxylate, is reported for the first time; it appears to be a terminal product, at least over the timescale of the experiment. The equilibrium between endosulfan gamma-hydroxycarboxylate and endosulfan lactone is dependent on pH, as only the protonated form of the gamma-hydroxy acid undergoes ring-closure. The pKa of the gamma-hydroxy acid was determined to be 5.7, implying that the lactone will quickly open and deprontonate under environmentally relevant conditions.

Surface-catalyzed transformations of aqueous endosulfan

We report the effect of suspended solids on the oxidation and hydrolysis of the insecticide endosulfan (alpha and beta isomers) and its degradation products: endosulfan diol, endosulfan sulfate, endosulfan ether, and endosulfan lactone in 0.001 M NaHCO3 buffer (pH 8.15). Suspensions of sea sand, TiO2, alpha-Fe2O3, alpha-FeOOH, Laponite, and SiO2 all catalyzed the hydrolysis of endosulfan to the less toxic endosulfan diol. Suspended creek sediment (Bread and Butter Creek SC, 4% OC) inhibited endosulfan hydrolysis. Heterogeneous and homogeneous rate constants of endosulfan hydrolysis were measured and indicate that beta-endosulfan hydrolyzes faster than alpha-endosulfan. This observation was explained by a more stable transition state for beta-endosulfan that was confirmed with ab initio molecular orbital calculations (STO-6G) on the anionic intermediates of endosulfan hydrolysis. Rates of endosulfan hydrolysis over the different surfaces corresponded to their tritium-exchange site-density and suggest a mechanism involving surface coordination prior to nucleophilic attack. The oxidation of alpha-endosulfan and beta-endosulfan to the persistent pollutant endosulfan sulfate was not observed in this study.

Endocrine-mediated effects of UV-A irradiation on grass shrimp (Palaemonetes pugio) reproduction

Although much is known regarding photoperiodic effects on crustacean egg production, the effects of ultraviolet (UV) light on reproduction has not been investigated. Likewise, little is known concerning the interaction between UV and xenobiotic exposure on crustacean reproductive cycles. In this study, male and female grass shrimp, Palaemonetes pugio, were exposed to sublethal concentrations of endosulfan (200 ng/l and 400 ng/l ES) under both white fluorescent (WF) and UV-A (315-400 nm) light conditions for 50 days in laboratory bioassays. Female endocrine (vitellogenin, ecdysteroids, and cholesterol), reproductive (percent gravid, clutch size), and embryo (days to hatch, hatching success, and hatching survival) responses were assessed. UV-exposure alone caused a significant (>4-fold) increase in total Palaemonetes pugio female egg production over the course of 50 days. Exposure to ES and UV significantly lowered the percentage of gravid females relative to UV controls, whereas ES-exposed shrimp under WF lighting did not exhibit these trends. Although higher vitellogenin concentrations and lower ecdysteroid titers were correlated with increased female egg production, cholesterol titers only exhibited a dose-dependent change when exposed to ES. Embryos from females exposed to UV had significantly lower ecdysteroid titers and shorter hatching times but there were no differences in embryo vitellogenin concentrations, hatching success, or hatching survival. These results indicate that UV-A exposure has a pronounced effect on grass shrimp (Palaemonetes pugio) reproduction and is likely mediated through 5-hydroxytrptamine (5-HT)-related neuroendocrine pathways. The implications for decapod aquaculture and evaluating chronic contaminant effects are discussed.

Reproductive alterations in adult grass shrimp, Palaemonetes pugio, following sublethal, chronic endosulfan exposure

Grass shrimp (Palaemonetes pugio) populations exposed to anthropogenic contaminant sources in South Carolina (SC) have reduced densities when compared with populations at SC-reference sites. This laboratory study examined the effects of a commonly used agricultural insecticide, endosulfan, on grass shrimp reproduction. Reproductively active grass shrimp were chronically exposed to sublethal concentrations of endosulfan (200 or 400 ng/l) for 43 days. The cumulative number of females that became gravid and the rate at which they became gravid were measured. Endosulfan exposure reduced the cumulative number of gravid females by 31% in the 200 ng/l exposure and 39% in the 400 ng/l exposure. The first appearance of gravid females in the population was significantly delayed in treated populations compared with the control treatment in a dose dependent manner. Clutch size in these gravid females was not significantly different among the treatments. Additionally, there was no difference in the onset of reproduction in the treated populations. These results implicate a population reduction due to a decrease in the overall number of females becoming gravid in a population over time, not a reduction in clutch size per individual. While the mechanisms of action have yet to be defined, these results indicate that sublethal endosulfan concentrations may have a negative effect on grass shrimp reproductive biology.