Altered exoskeleton composition and vitellogenesis in the crustacean Gammarus sp. collected at polluted sites in the Saguenay Fjord, Quebec, Canada

Complexity of trophic relationships between Gammarus aequicauda (Amphipoda) and Eucypris mareotica (Ostracoda) in a hypersaline lake

In the hypersaline lakes of Crimea, only 5-7 species of animals are common including Gammarus aequicauda (Amphipoda) and Eucypris mareotica (Ostracoda). Two experiments were carried out to characterize the trophic interactions between these species. In one, G. aequicauda were used freshly caught from the lake, and in the other, after they were starved for 2.5 days in the laboratory. The experimental options were one male or female G. aequicauda and either 10, 20, or 30 ostracods. The gammarids actively fed on the ostracods, and significant differences were between females and males. The feeding intensity of males was higher than that of females. However, ostracods are not passive prey, they can actively attack their predator and are capable of causing them harm. Ostracods attacked a Gammarus only if it had captured one of the ostracods. Sex differences in G. aequicauda were also evident in the reaction to the group's aggressive behavior of ostracods. Interactions between Ostracoda and Gammarids cannot be considered unidirectional; they both may be prey or predators depending on the situation.

In-Vivo NMR Spectroscopy: A Powerful and Complimentary Tool for Understanding Environmental Toxicity

Part review, part perspective, this article examines the applications and potential of in-vivo Nuclear Magnetic Resonance (NMR) for understanding environmental toxicity. In-vivo NMR can be applied in high field NMR spectrometers using either magic angle spinning based approaches, or flow systems. Solution-state NMR in combination with a flow system provides a low stress approach to monitor dissolved metabolites, while magic angle spinning NMR allows the detection of all components (solutions, gels and solids), albeit with additional stress caused by the rapid sample spinning. With in-vivo NMR it is possible to use the same organisms for control and exposure studies (controls are the same organisms prior to exposure inside the NMR). As such individual variability can be reduced while continual data collection over time provides the temporal resolution required to discern complex interconnected response pathways. When multidimensional NMR is combined with isotopic labelling, a wide range of metabolites can be identified in-vivo providing a unique window into the living metabolome that is highly complementary to more traditional metabolomics studies employing extracts, tissues, or biofluids.

Prediction of a peptidome for the ecotoxicological model Hyalella azteca (Crustacea; Amphipoda) using a de novo assembled transcriptome

Due to its sensitivity to many environmental and anthropogenic stressors, including a wide range of chemical compounds, Hyalella azteca, a freshwater amphipod, has emerged as one of the most commonly used invertebrates for ecotoxicological assessment.Peptidergic signaling systems are key components in the control of organism-environment interactions, and there is a growing literature suggesting that they are targets of a number of aquatic toxicants.Interestingly, and despite its model species status in the field of ecotoxicology, little is known about the peptide hormones of H. azteca.Here, a transcriptome was produced for this species using the de novo assembler Trinity and mined for sequences encoding putative peptide precursors; the transcriptome was assembled from 460,291,636 raw reads and consists of 133,486 unique transcripts.Seventy-six sequences encoding peptide pre/preprohormones were identified from this transcriptome, allowing for the prediction of 202 distinct peptides, which included members of the allatostatin A, allatostatin B, allatostatin C, allatotropin, bursicon, CCHamide, corazonin, crustacean cardioactive peptide, crustacean hyperglycemic hormone/molt-inhibiting hormone, ecdysis-triggering hormone, eclosion hormone, elevenin, FMRFamide-like peptide, glycoprotein hormone, GSEFLamide, inotocin, leucokinin, myosuppressin, neuropeptide F, orcokinin, orcomyotropin, pigment dispersing hormone, proctolin, pyrokinin, red pigment concentrating hormone, RYamide, short neuropeptide F, SIFamide, sulfakinin, tachykinin-related peptide and trissin families.These peptides expand the known peptidome for H. azteca approximately nine-fold, forming a strong foundation for future studies of peptidergic control, including disruption by aquatic toxicants, in this important ecotoxicological model.

Trace element and metal sequestration in vitellaria and sclerites, and reactive oxygen intermediates in a freshwater monogenean, Paradiplozoon ichthyoxanthon

Exposure to metals and other trace elements negatively affects infection dynamics of monogeneans, including diplozoids, but, physiological mechanisms linked to exposure have yet to be documented. In this study sequestration of trace elements and reactive oxygen intermediate production in the monogenean, Paradiplozoon ichthyoxanthon, was demonstrated. During dissection of host fish, Labeobarbus aeneus, the gills were excised and assessed for P. ichthyoxanthon, which were removed and frozen for fluorescence microscopy or fixed for transmission electron microscopy. Trace elements were sequestered in the vitellaria and sclerites in P. ichthyoxanthon, and the presence of reactive oxygen intermediates was observed predominantly in the tegument of the parasite. Trace elements and metals identified and ranked according to weight percentages (wt%) in the vitellaria were Cu > C > Au > O > Cr > Fe > Si while for the sclerites C > Cu > O > Au > Fe > Cr > Si were identified. For most element detected, readings were higher in the vitellaria than the sclerites, except for C and O which were higher in sclerites. Specifically for metals, all levels detected in the vitellaria were greater than in sclerites. Based on the proportion of trace elements present in the vitellaria and sclerites it appears that most trace elements including metals were sequestered in the vitellaria. The results of reactive oxygen intermediate production in the tegument of the parasite suggests either trace element accumulation takes place across the tegument or results from the action of the host's immune response on the parasite. The results serve as the first demonstration of trace element sequestration and reactive oxygen intermediates in a freshwater monogenean parasite.

Changes of exoskeleton surface roughness and expression of crucial participation genes for chitin formation and digestion in the mud crab (Macrophthalmus japonicus) following the antifouling biocide irgarol

Irgarol is a common antifoulant present in coastal sediment. The mud crab Macrophthalmus japonicus is one of the most abundant of the macrobenthos in the costal environment, and its exoskeleton has a protective function against various environmental threats. We evaluated the effects of irgarol toxicity on the exoskeleton of M. japonicus, which is the outer layer facing the environment. We analyzed transcriptional expression of exoskeleton, molting, and proteolysis-related genes in the gill and hepatopancreas of these exposed M. japonicus. In addition, changes in survival and exoskeleton surface characteristics were investigated. In the hepatopancreas, mRNA expression of chitinase 1 (Mj-chi1), chitinase 4 (Mj-chi4), and chitinase 5 (Mj-chi5) increased in M. japonicus exposed to all concentrations of irgarol. Mj-chi1 and Mj-chi4 expressions from 1 to 10μgL(-1) were dose- and time-dependent. Ecdysteroid receptor (Mj-EcR), trypsin (Mj-Tryp), and serine proteinase (Mj-SP) in the hepatopancreas were upregulated in response to different exposure levels of irgarol at day 1, 4, or 7. In contrast, gill Mj-chi5, Mj-Tryp, and Mj-SP exhibited late upregulated responses to 10μgL(-1) irgarol compared to the control at day 7. Mj-chi1 showed early upregulation upon exposure to 10μgL(-1) irgarol and Mj-chi4 showed no changes in transcription in the gill. Gill Mj-EcR presented generally downregulated expression patterns. In addition, decreased survival and change of exoskeleton surface roughness were observed in M. japonicus exposed to the three concentrations of irgarol. These results suggest that exposure to irgarol induces changes in the exoskeleton, molting, and proteolysis metabolism of M. japonicus.

Comprehensive multiphase NMR applied to a living organism

Comprehensive Multiphase NMR provides an overview as to all components (liquids, gels, solids) in a living organism.

Comprehensive multiphase (CMP) NMR is a novel technology that integrates all the hardware from solution-, gel- and solid-state into a single NMR probe, permitting all phases to be studied in intact samples. Here comprehensive multiphase (CMP) NMR is used to study all components in a living organism for the first time. This work describes 4 new scientific accomplishments summarized as: (1) CMP-NMR is applied to a living animal, (2) an effective method to deliver oxygen to the organisms is described which permits longer studies essential for in-depth NMR analysis in general, (3) a range of spectral editing approaches are applied to fully differentiate the various phases solutions (metabolites) through to solids (shell) (4) ¹³C isotopic labelling and multidimensional NMR are combined to provide detailed assignment of metabolites and structural components in vivo. While not explicitly studied here the multiphase capabilities of the technique offer future possibilities to study kinetic transfer between phases (e.g. nutrient assimilation, contaminant sequestration), molecular binding at interfaces (e.g. drug or contaminant binding) and bonding across and between phases (e.g. muscle to bone) in vivo. Future work will need to focus on decreasing the spinning speed to reduce organism stress during analysis.

Ecology of free-living metacercariae (Trematoda)

The presence of trematodes with a free-living metacercarial stage is a common feature of most habitats and includes important species such as Fasciola hepatica, Parorchis acanthus and Zygocotyle lunata. These trematodes encyst on the surface of an animal or plant that can act as a transport host, which form the diet of the target definitive host. Although these species are often considered individually, they display common characteristics in their free-living biology indicating a shared transmission strategy, yet in comparison to species with penetrative cercariae this aspect of their life cycles remains much overlooked. This review integrates the diverse data and presents a novel synthesis of free-living metacercariae using epibiosis as the basis of a new framework to describe the relationship between transport hosts and parasites. All aspects of their biology during the period that they are metabolically independent of a host are considered, from cercarial emergence to metacercarial excystment.

Invertebrates as indicators for chemical stress in sewage-influenced stream systems: toxic and endocrine effects in gammarids and reactions at the community level in two tributaries of Lake Constance, Schussen and Argen

The present study investigates the impact of releases from waste water treatment plants and storm water overflow basins on gammarids and other macrozoobenthos. The study relates to a recent upgrading of a waste water treatment plant (Langwiese) at the Schussen river, an important tributary to Lake Constance. Samples were taken at different sites at the Schussen river upstream and downstream of a storm water overflow basin and the waste water treatment plant Langwiese and, in parallel, at the Argen river, a less polluted reference stream. We assessed the influence of water quality on the distribution of macrozoobenthos and on the health of gammarid populations by a variety of ecotoxicological methods including biomarkers prior to the expansion of the waste water treatment plant. Through histopathological studies, the impact of parasites on host tissue health was evaluated. Analyses of heat shock protein (hsp70) levels allowed us to draw conclusions about the proteotoxicity-related stress status of the organisms. Furthermore, gammarid populations from all sites were investigated in respect to sex ratio, parasitism rate, and fecundity. Macrozoobenthos community integrity was determined by means of the saprobic index and the abundance as well as by the number of taxa. In gammarids, the sex ratio was significantly shifted towards females, fecundity was significantly decreased, and the hsp70 level was significantly increased downstream of the waste water treatment plant Langwiese, compared to the upstream sampling site. Similarly, these effects could be detected downstream of three small storm water overflow basins. In the macrozoobenthos communities, the abundance of taxa, the number of taxa, the number of ephemeroptera, plecoptera, and trichoptera taxa (EPT-taxa), and the number of sensitive taxa decreased downstream of the storm water overflow basin Mariatal as well as downstream of the waste water treatment plant Langwiese. Our study showed, that waste water treatment plants and storm water overflow basins affected macroinvertebrate communities and the health of gammarids.

The impact of gypsum mine water: a case study on morphology and DNA integrity in the freshwater invertebrate, Gammarus balcanicus

The aim of our study was to investigate how exposure to heavy metal-rich waters from gypsum mining affects the morphology and levels of primary DNA damage in Gammarus balcanicus. Chemical analysis revealed increased concentrations of metals in water and sediment collected at a site impacted by gypsum mine wastewaters. The specimens also showed elevated total tissue metal levels when compared with the organisms collected at the reference site. The most prominent increase was observed for strontium, followed by iron, nickel, vanadium, aluminium, and manganese. The major pathway of entry for these toxic substances was through the degraded exoskeleton as a consequence of excessive strontium input (unbalanced calcium/strontium ratio) and altered permeability. Disturbed exoskeleton integrity was observed only in individuals collected downstream of the gypsum mine, which was confirmed by electron microscopy. Levels of primary DNA damage were evaluated using the alkaline comet assay in the haemolymph of the specimens.

Vitellogenin-like protein measurement in caged Gammarus fossarum males as a biomarker of endocrine disruptor exposure: inconclusive experience

A vitellogenin (Vg) mass spectrometry-based assay was recently developed to actively biomonitor and assess the exposure of the amphipod Gammarus fossarum to endocrine-disrupting chemicals in freshwater hydrosystems. This paper focuses on the appropriate use of this biomarker, which requires good knowledge of its basal level in males and its natural variability related to intrinsic biotic and environmental abiotic factors. To obtain the lowest biomarker variability, we first studied some of these confounding factors. We observed that the spermatogenesis stage did not have an impact on the Vg level, allowing flexibility in the choice of transplanted gammarids. In the second part of the study, males were transplanted in two clean stations for 21 days, with results indicating a spatial and temporal variability of Vg levels. These Vg changes could not be correlated to environmental factors (e.g., temperature, pH and hardness of waters). Vg induction was then assessed in 21 stations having various levels of contamination. Inductions were observed for only two of the impacted stations studied. Under reference and contaminated conditions, a high interindividual variability of Vg levels was observed in caged organisms, severely limiting the sensitivity of the biomarker and its ability to detect a significant endocrine-disruptor effect. This may be explained by unidentified environmental factors that should later be determined to improved the use of Vg as a biomarker in male G. fossarum. Moreover, as discussed in this paper, recent advancements regarding the pleiotropic functions of the Vg gene in some species may complicate the application of this biomarker in males of invertebrate species.

Vitellogenin-like proteins in the freshwater amphipod Gammarus fossarum (Koch, 1835): functional characterization throughout reproductive process, potential for use as an indicator of oocyte quality and endocrine disruption biomarker in males

This work focused on the validation of biological specificity of the quantitative LC-MS/MS assay by checking the natural variability of Vg levels during the reproductive cycle in Gammarus fossarum (i.e., including oogenesis and embryogenesis). Laboratory tests were performed for 21 days under controlled conditions to assess Vg changes in male and female gammarids after exposure to chemical stress. Females were exposed to two crustacean hormones, 20-hydroxyecdysone (0.01, 1 and 100 μg L⁻¹) and methyl-farnesoate (0.01, 1 and 100 μg L⁻¹). No effect was recorded for 20-hydroxyecdysone, whereas in females exposed to methyl-farnesoate a deleterious impact on Vg production was observed. Males were exposed to crustacean hormones 20-hydroxyecdysone (0.01, 1 and 100 μg L⁻¹) and methyl-farnesoate (0.01, 1 and 100 μg L⁻¹), the insecticide methoxyfenozide (0.001, 0.1 and 10 μg L⁻¹), the fungicide propiconazole (0.001, 0.1, 10 and 1000 μg L⁻¹), and the pharmaceutical products benzophenone, carbamazepine, cyproterone, and R-propranolol (0.001, 0.1, 10 and 1000 μg L⁻¹). Induction of Vg synthesis was recorded in males exposed to cyproterone, methoxyfenozide, methyl-farnesoate, and propiconazole. Finally, we validated the function of the ILIPGVGK peptide used to track vitellogenin in G. fossarum across reproductive processes (vitellogenesis and embryogenesis), and results confirmed the energy reserve role of Vg during embryo development. We show that oocyte surface measurement is directly related to Vg levels in the oocyte, constituting a reliable indicator of egg quality in G. fossarum. Consequently, it could be used as a reliable tool for biomonitoring programs. We recorded induction of Vg in male G. fossarum; however, the possible use of this tool as a specific biomarker of exposure to endocrine disruption should be confirmed in further studies.

Review of the reproductive biology of amphipods and their endocrine regulation: identification of mechanistic pathways for reproductive toxicants

The reproductive biology of amphipods is reviewed to update the knowledge of the male and female reproductive processes of oogenesis and spermatogenesis as well as the endocrine systems of amphipods with the aim of advancing studies of reproductive toxicology. The ovarian and reproduction cycles of female gammaridean amphipods are closely correlated with the molt cycle, which is under direct control by the steroid hormone 20-hydroxyecdysone. The ability of males to copulate and subsequently for females to ovulate is restricted to the early postmolt period of the females. New developments in our understanding of the molt cycle and the endocrine regulatory pathways for reproduction using genomics techniques on other crustacean species are also discussed. The arthropod sterol ponasterone A or xenobiotics such as the fungicide fenarimol have been shown to elicit endocrine disruption in some crustaceans by acting as an agonist for 20-hydroxyecdysone at the ecdysone receptor or by inhibiting the synthesis of 20-hydroxyecdysone, respectively, resulting in disruption of molting and reproduction. Recent studies suggest that cadmium can inhibit secondary vitellogenesis in amphipods. Experimental approaches for examining the metabolic pathways associated with ecdysteroid hormonal signaling or metabolism, exoskeleton maintenance and molting, and the regulation of vitellogenin in amphipods are discussed. This information should aid in the identification of useful biomarkers for reproductive toxicity.

Development of ecotoxicoproteomics on the freshwater amphipod Gammarus pulex: identification of PCB biomarkers in glycolysis and glutamate pathways

PCBs are persistent organic pollutants largely distributed in the biosphere. Although their effects on vertebrates are well described, little is known about their action on freshwater invertebrate's metabolism. Gammarus pulex (Linné) was selected as an indicator model to develop a proteomic approach in order to characterize the effects of PCBs on the protein profile of this freshwater crustacean. Sublethal coplanar PCBs exposition and related 2D gel were performed. More than 560 spots were detected and a total of 21 proteins exhibiting significant expression differences in PCB exposed to G. pulex were identified by mass spectrometry. Database searches were conducted to relate the results to well-known metabolic pathways (pentose phosphate, cytoskeleton, energy, etc.). In particular, glyceraldehyde 3-phosphate dehydrogenase and arginine kinase were found to be sensitive to the PCB exposition of G. pulex. The aim of the present study was to assess the biochemical responses and the metabolic changes in G. pulex following intoxication to coplanar PCB congeners CB77 and CB169 by a proteomic approach. This approach allowed us, by the identification of key proteins, to highlight important biochemical mechanisms disturbed by the presence of these contaminants in G. pulex.

Gammarus spp. in aquatic ecotoxicology and water quality assessment: toward integrated multilevel tests

The amphipod genus Gammarus is widespread and is structurally and functionally important in epigean freshwaters of the Northern Hemisphere. Its presence is crucial, because macroinvertebrate feeding is a major rate-limiting step in the processing of stream detrius. In addition, Gammarus interacts with multiple trophic levels bu functioning as prey, predator, herbivore, detritivore, and shredder. Such a broad span of ecosystem participation underlines the importance of Gammarus to pollutants and other disturbances may render it a valuable indicator for ecosystem health. This review summarizes the vast number of studies conducted with Gammarus spp. for evaluating aquatic ecotoxicology endpoints and examines the suitability of this native invertabrate species for the assessment of stream ecosystem health in the Northern Hemisphere. Numerous papers have been published on how pollutants affect gammarind behavior (i.e., mating, predator avoidance), reproduction, development, feeding activity, population structure, as well as the consequences of pollution on host-parasite, predator-prey, or native-invasive species interactions. Some biochemical and molecular biomarkers have already been established, such as the measurement of vitellogenin-like proteins, metallothioneins, alkali-labile phosphates (in proteins), and lipogenic enzyme activities for assessing endocrine distribution and detoxification mechanisms.

Is the freshwater gammarid, Dikerogammarus villosus, a suitable sentinel species for the implementation of histochemical biomarkers?

In order to enlarge the range of potential sentinel species for the implementation of a multiple biomarker approach, spatial and monthly morphological variations of four cellular compartments and contents were assessed during two years in the hepatopancreatic caeca of the freshwater gammarid, Dikerogammarus villosus (Crustacea, Amphipoda), using histochemistry coupled to image analysis. Among the three study sites, the second one, located in a reservoir receiving the overheated and copper-contaminated waters of a nuclear power plant, was the most anthropised. During this passive biomonitoring survey, unsaturated neutral lipids were more abundant, the surface densities of the lysosomal and peroxisomal systems were, respectively less and more important, and lipofuscin granules tended to accumulate in the amphipods from the second site compared to both others. Nonetheless, in this context, the present cellular biomarker suite, analysed through an integrative approach, was not powerful enough to highlight spatial heterogeneity significantly. This may partly result from particularities in the patterns of metal accumulation and copper physiological requirements of amphipods (haemocyanin synthesis). Nevertheless, we think that the use of this Ponto-Caspian non-indigenous species in biomonitoring surveys deserves further investigation, owing to its current position in freshwater and brackish European ecosystems, considering both biomass and functioning. Cellular responses could be studied in parallel with endpoints at other levels of the biological organization to compose a more powerful biomarker suite. Furthermore, comparing biological responses to environmental stress in this invasive species and less competitive autochthonous gammarids could be of great interest.

Vitellogenin as a biomarker of exposure to estrogenic compounds in aquatic invertebrates: a review

Vitellogenins (Vg) are the major precursor of the egg-yolk proteins, vitellins (Vn), which provide energy reserves for embryonic development in oviparous organisms. In mature females, Vg are generally synthesised in response to endogenous estrogens, such as 17beta-estradiol (E2), released into the bloodstream and then stored in developing oocytes. In males, the Vg gene, although present, is normally silent. However, it may be activated by (xeno)-estrogens. These substances belong to a large and heterogeneous group of environmental contaminants capable of altering endocrine functions in organisms. For this reason, they are named endocrine disrupting chemicals (EDCs). Natural steroidal estrogens [E2, estrone (E1), estriol (E3)] and synthetic chemicals, such as pesticides, polychlorinated biphenyls (PCBs) and household products (surfactants) are estrogenic compounds widespread in aquatic ecosystems. The main sources of contamination mostly stem (or originate) from municipal and industrial effluents, agricultural practices, livestock wastes and sewage treatment plants (STP). Recently, Vg induction, mainly in males and immature females, has been proposed as a useful biomarker to assess estrogenic contamination in aquatic environments. Indeed, estrogenicity of individual chemicals and mixtures has extensively been evaluated, in both laboratory and field studies, albeit mostly in fish. In contrast, limited attention has centred on evaluating xenoestrogen effects in aquatic invertebrates, probably owing to limited knowledge of their endocrinology. This review focuses on a brief description of xenoestrogens and their occurrence in aquatic environments, and on Vg induction in aquatic invertebrates in response to both experimental and environmental exposure to estrogenic compounds. Results of recent field and laboratory studies are presented. In addition, new perspectives about the use of Vg induction as a biomarker of exposure to estrogenic compounds are also discussed.

Limb regeneration and molting processes under chronic methoprene exposure in the mud fiddler crab, Uca pugnax

Insect growth regulator application for wetland mosquito control remains controversial due to the potential for disruption of normal development and growth processes in non-target crustaceans and beneficial arthropods, e.g. Apis mellifera. Concerns include slow-release methoprene formulations and its environmental breakdown products which mimic an endogenous crustacean hormone and retinoids, respectively. Our primary objective was to evaluate the effect that a chronic methoprene exposure would have on male and female Uca pugnax limb regeneration and molting. After single limb autonomy, limb growth and molt stage were monitored every two days while eyestalk ablation was used to induce proecdysis. Dorsal carapace was collected 6 days post-molt to determine protein and chitin content. In post-molt crabs, methoprene-exposed individuals displayed lower percent gain in body weight. Male crabs lost more weight per body volume than females, took significantly longer to proceed through proecdysis than females exposed to 0.1 microg/L methoprene and exhibited significantly elevated frequency for abnormal limb formation at 1.0 microg/L while females displayed no such trend. Methoprene did not significantly alter extractable exoskeleton protein or chitin content. However, variable water-soluble protein expression increased with exposure at 1.0 microg/L (1 ppb) which contributed to overall variability in total protein content. Our findings suggest that adult male U. pugnax possess greater sensitivity to chronic methoprene exposure during limb regeneration and molting, potentially affecting their post-molt fitness. Furthermore, methoprene has the potential to impact post-molt biomass and exocuticle quality.

Crustacean endocrine toxicology: a review

Crustaceans are major constituents to aquatic ecosystems that provide a variety of ecological and economic services. Individual crustacean species are adept at occupying diverse niches and their success, in part, stems from neuro-endocrine signaling cascades that regulate physiology in response to environmental and internal cues. Peptide hormones are major signal transducers in crustaceans. The crustacean hyperglycemic hormone family of peptides regulates various aspects of growth, reproduction, and metabolism. These peptides may function as the terminal hormone to regulate some physiological activities or may function as intermediates in a signaling cascade. Ecdysteroids and terpenoids are two major classes of terminal signaling molecules in these cascades. Hormones from these two classes function independently or in concert to regulate various processes. Ecdysteroid signaling is subject to toxicological disruption through disturbances in ecdysteroid synthesis or binding of toxicants to the ecdysteroid receptor. Methyl farnesoate is the major terpenoid hormone of crustaceans and also is susceptible to disruption by environmental chemicals. However, the methyl farnesoate signaling pathway is poorly understood and only limited mechanistic confirmation for disruption of this endocrine signaling pathway exists. Disruption of the ecdysteroid/terpenoid signaling pathways in crustaceans has been associated with aberrations in growth, metamorphosis, reproductive maturation, sex determination, and sex differentiation. Population studies have revealed disruptions in crustacean growth, molting, sexual development, and recruitment that are indicative of environmental endocrine disruption. However, environmental factors other that pollution (i.e., temperature, parasitism) also can elicit these effects and definitive causal relationships between endocrine disruption in field populations of crustaceans and chemical pollution is generally lacking.