Molting as a mechanism of depuration of metals in the fiddler crab, Uca pugnax

The role of the carapace in the accumulation of metals from seawater in the green crab (Carcinus maenas): Studies with radio-labeled calcium, zinc, and nickel

The role of the carapace in the uptake and storage of newly accumulated metals was investigated in the green crab exposed to environmentally relevant concentrations of calcium ([Ca] = 389 mg L-1 or 9.7 mmol L-1), zinc ([Zn] = 82 μg L-1 or 1.25 μmol L-1), and nickel ([Ni] = 8.2 μg L-1 or 0.14 μmol L-1) in 12 °C seawater, using radio-tracers (45Ca, 65Zn, 63Ni). After 24-h exposure, carapace exhibited the highest concentration of newly accumulated Ca, whereas carapace and gills exhibited the highest concentrations of both newly accumulated Zn and Ni relative to other tissues. For all three metals, the carapace accounted for >85 % of the total body burden. Acute temperature changes (to 2 °C and 22 °C) revealed the highest overall temperature coefficient Q10 (2.15) for Ca uptake into the carapace, intermediate Q10 for Ni (1.87) and lowest Q10 (1.45) for Zn. New Ca uptake into the carapace continued linearly with time for 24 h, new Zn uptake gradually deviated from linearity, whereas Ni uptake reached a plateau by 6 h. Attachment of a rubber membrane to the dorsal carapace, thereby shielding about 20 % of the total crab surface area from the external water, eliminated both new Zn and Ni incorporation into the shielded carapace, whereas 36 % of new Ca incorporation persisted. When recently euthanized crabs were exposed, new Zn uptake into the carapace remained unchanged, whereas Ca and Ni uptake were reduced by 89 % and 71 %, respectively. We conclude that the carapace is a very important uptake and storage site for all three metals. All of the uptake of new Zn and new Ni, and most of the uptake of new Ca into this tissue comes directly from the external water. For Zn, the mechanism involves only physicochemical processes, whereas for Ca and Ni, life-dependent processes make the major contribution.

The impact of settleable atmospheric particulate on the energy metabolism, biochemical processes, and behavior of a sentinel mangrove crab

We use the sentinel mangrove crab, Minuca rapax, as a model to investigate the effects of metallic settleable particulate matter (SePM) on wetland. Multiple levels of energetic responses, including (i) metabolic rate and energy budget, (ii) oxidative stress, and (iii) behavioral response by righting time, were assessed as well as the metal and metalloid content in crabs exposed to 0, 0.1 and 1 g.L-1 of SePM, under emerged and submerged conditions over five days, simulating the rigors of the intertidal habitat. Al, Fe, Mn, Cr, and Y exhibited a concentration-dependent increase. Metal concentrations were higher in submerged crabs due to the continuous ingestion of SePM and direct exposure through gills. Exposure concentration up to 1 g.L-1 decreased metabolic rate and enzymatic activities, reduced assimilation efficiency and energy for maintenance, and induces a slower response to righting time, probably by metal effects on nervous system and energy deficits. In conclusion, SePM exposure affects the redox status and physiology of M. rapax depending on he submersion regime and SePM concentration. The disruption to the energy budget and the lethargic behavior in M. rapax exposed to SePM implies potential ecological alterations in the mangrove ecosystem with unknown consequences for the local population.

Metal concentrations in fish, crabs, and bivalve molluscs from marine waters adjacent to a multi-metals smelter and refinery

Metal concentrations were determined in tissues of finfish, crabs, and bivalve molluscs collected from marine waters near Port Pirie, South Australia, the site of a long-standing multi-metals smelter and refinery. A general trend of tissue metal concentrations in order of highest to lowest was observed in bivalves > crabs > finfish. A lead concentration of 158 ± 6.6 mg/kg (wet wt.) was observed in blue mussels (Mytilus galloprovincialis) sampled close to the smelter. Lead concentrations correlated positively with proximity to the smelter in all biota analysed. Similar relationships were observed for cadmium, copper, zinc and selenium in all biota except razorfish (Pinna bicolor; Bivalvia: Pinnidae), which showed no correlation with proximity to the smelter for these metals. Inorganic arsenic concentrations were below the limit of reporting in the majority of the analysed samples, however inorganic arsenic concentrations in blue swimmer crabs (Portunus armatus) and blue mussels correlated with proximity to the smelter. Mercury concentrations in the biota analysed were generally low and showed variable relationships with proximity to the smelter, with no significant correlation observed in finfish and razorfish, a significant positive correlation in blue mussels, and a significant negative correlation in blue swimmer crabs. This is the first major study of metal concentrations in recreationally-targeted marine species near Port Pirie species for more than two decades. Comparison with data from previous studies conducted shows little change in tissue metal concentrations in marine biota near Port Pirie over the past 40 years.

Opportunistic omnivory impairs the use of the Atlantic blue crab Callinectes sapidus as a trace metal biomonitor in invaded Mediterranean coastal waters

The contribution of non-indigenous species to the transfer of contaminants in invaded food webs represents an active research area. Here we measured trace metals and CN stable isotopes in five populations of the invasive Atlantic blue crab Callinectes sapidus and in baseline bivalve species from Spain, Italy and Greece. They were used to estimate trophic transfer effects and the trophic position and isotopic niche of C. sapidus. Maximum trophic transfer effects occurred where the crab showed the largest isotopic niches and highest trophic positions; furthermore, the consistency of trace metal profiles between bivalves and crabs co-varied with the trophic position of the latters. Omnivory may influence the success of an invasive species, but also limit its effectiveness for biomonitoring. However, our results indicated that stable isotopes analysis provides a clarifying background where to cast patterns of contamination of the blue crab as well as of other omnivorous biomonitor species.

Chronic Cadmium Exposure can Alter Energy Allocation to Physiological Functions in the Shrimp Penaeus vannamei

Environmental stressors in aquatic organisms can be assessed using a bioenergetic approach based on the evaluation of changes in their physiological parameters. We evaluated the chronic effects of cadmium (Cd2+) on the energy balance as well as the survival, growth, metabolism, nitrogen excretion, hepatosomatic index, oxidized energy substrate, and osmoregulation of the shrimp Penaeus vannamei with the hypothesis that the high energy demand related to the homeostatic regulation of Cd2+could disrupt the energy balance and as a consequence, their physiological functions. The shrimp exposed to Cd2+ had higher mortality (30%), directed more energy into growth (33% of energy intake), ingested 10% more energy, and defecated less than control animals. Cd2+ exposure caused a tendency to decrease metabolism and ammonia excretion but did not alter the hepatosomatic index, type of energy substrate oxidized, and the hyperosmorregulatory pattern of the species. The Cd+2 exposure may have induced a trade-off response because there was a growth rate increase accompanied by increased mortality.

Feces and molting as microplastic sinks in a mangrove crab

We exposed adult individuals of the sentinel mangrove crab Minuca rapax to waterborne microplastics (MP; 53-63 μm polyethylene spheres) in a long-term experiment (56 days). Weassessed 1) MP effects on growth, survival, and food intake. and 2) the MP tissue acumulation and its reduction of body burden through feces and molting. MP exposure did not affect growth and survival. The hepatopancreas accumulated more MP than the gills and muscle. Most of the ingested MP particles were released in the feces and molts, indicating a rapid passage through the digestive tract. MP impaired food intake of M. rapax, with unknown consequences to the local populations. These results provide insights on MP translocation mechanisms, its elimination and toxicity associated with MP.

Rare Earth Element Accumulation in Fiddler Crabs (Minuca rapax) from the Rio Doce Tropical Estuary Strongly Affected by Mine Tailings Following the Fundão Disaster

A mining tailing dam rupture in Brazil in November 2015 released millions of tons of mining waste into the Rio Doce ecosystem, leading to long-term aquatic ecosystem impacts. Although multiple lines of evidence indicate tailings associations with potentially toxic elements in estuarine sediments and biological impact and bioaccumulation pathways in fishes, the extent of contamination in base benthic species is still largely unknown. Moreover, Rare Earth Elements (REE) have not received any attention in this regard. This study assessed REE in fiddler crabs (Minuca rapax) sampled from the Rio Doce estuary in 2017, nearly 2 years after the disaster. The ΣREE in crab hepatopancreas and muscle were high (327.83 mg kg-1 w.w. and 33.84 mg kg-1 w.w., respectively, compared to other assessments in crabs, indicating a preference for REE bioaccumulation in the hepatopancreas compared to muscle. Neodimium, La, and Ce were detected at the highest concentrations. The REE from the Rio Doce Basin were, thus, transported and deposited in the estuary with the mine tailings slurry, leading to bioaccumulation in crabs. This may lead to trophic effects and other ecological impacts not readily measured by typical impact assessment studies, revealing an invisible and not typically acknowledged damage to the Rio Doce estuary.

Synergistic effects of microplastic and lead trigger physiological and biochemical impairment in a mangrove crab

Microplastics (MP) are vectors for other environmental contaminants, such as metals, being a considerable problem, especially in the aquatic ecosystem. To investigate the combined effects of MP (high density polyethylene) with lead (Pb), we exposed the mangrove fiddler crab Minuca vocator to Pb (50 mg L-1), and MP (25 mg L-1) alone and in mixture, for 5 days. We aimed to determine Pb and MP bioaccumulation, as well as physiological (oxygen consumption and hemolymph osmolality) and biochemical (superoxide dismutase, catalase, glutathione peroxidase, and lipid peroxidation) traits effects. Co-exposure of MP and Pb significantly increased the bioaccumulation of Pb, but reduced MP tissue accumulation. Regarding the physiological traits, increasing osmolality and oxygen consumption rates compared to the control were observed, particularly in the combined Pb and MP exposure. As to biochemical traits, the combination of Pb and MP induced the most significant responses in the enzymatic profile antioxidant enzyme activity. The catalase (CAT), glutathione peroxidase (GPx), and dismutase superoxide (SOD) decreased compared to individual exposure effects; the combination of MP and Pb had a synergistic effect on promoting lipid peroxidation (LPO). The co-exposure of MP and Pb acted synergistically when compared to the effects of the isolated compounds. Due to the increasing MP contamination in mangroves, more severe physiological and biochemical effects can be expected on mangrove crabs exposed to metal contamination.

Trophic transfer mechanisms of potentially toxic elements from sediment and plant leaves (Rhizophora mangle) to fiddler crabs (Minuca rapax) ()

To assess "bottom-up" to "top-down" trophic transfer, we analyze As, Cd, Co, Cr, Cu, Hg, Ni, Se, Zn, Fe, and Mn from two sediment chemical fractions (exchangeable and organic-bound), red mangrove (Rhizophora mangle) leaves, and fiddler crab (M. rapax) soft tissues from Isla del Carmen, Yucatán Peninsula. Both mechanisms were observed indictive that R. mangle and M. rapax indeed bioaccumulated the toxic elements from the different matrices with the latter being a macro-concentrator only for Cu and Zn. Although the modified Geo-accumulation factor (combined exchangeable and organic matter fractions) suggested that the studied sites are practically "uncontaminated", Hg is the only toxic element to be having a "moderately to strongly" impact. Data shows how M. rapax had progressively bioaccumulated Hg, but no biomagnification could be corroborated given that the fiddler crab behaved as a de-concentrator.

Zinc is incorporated into the exoskeleton during post-ecdysial mineralization and inhibits exoskeletal calcification in the blue crab, Callinectes sapidus

Zinc is an essential but toxic metal with both natural and anthropogenic sources. Zinc has been reported to be present in crustacean exoskeleton, but it has remained unknown as to when zinc is incorporated into the shell during the molting cycle and the effects zinc has on exoskeleton properties. This study was conducted to identify a period during the molting cycle, in which zinc is incorporated into the exoskeleton of the blue crab, Callinectes sapidus, and to identify deleterious effects of zinc incorporation on the exoskeleton. It was hypothesized that zinc would be incorporated into the shell during the mineralization phase using calcium transporters, which would inhibit exoskeletal calcification. Post-ecdysial blue crabs were given two injections of zinc in the form of zinc chloride dissolved in Pantin's crustacean saline at the arthrodial membrane at three treatment levels: 0.0, 1.0 and 5.0 µg Zn/g wet weight. Exoskeletal and hemolymph samples were then analyzed for zinc, calcium, and magnesium content. Gill, muscle, and hepatopancreas samples were analyzed for zinc only. Epidermis samples were analyzed for carbonic anhydrase activity. The results showed that the injection dose of 1.0 µg Zn/g wet weight resulted in significant accumulation of zinc in the exoskeleton. There was no significant accumulation of exoskeletal zinc following 5.0 µg Zn/g wet weight injections. A significant reduction in exoskeletal calcium content in crabs treated with 1.0 or 5.0 µg Zn/g wet weight was also observed. The hypothetical model explaining zinc's incorporation into the exoskeleton and inhibition of exoskeletal calcification is proposed. Additionally, for the soft tissues examined, significant zinc accumulation was only observed in the hepatopancreas following zinc treatment. Our data points to the existence of crustacean zinc transporter. This study is the first to present evidence that zinc is deposited to the exoskeleton during post-ecdysial mineralization and inhibits exoskeletal calcification in a crustacean.

Biomineralisation and metal sequestration in a crustacean ectoparasite infecting the gills of a freshwater fish

It has been suggested that parasites are effective bioindicators as they are sensitive to environmental changes and, in some cases, accumulate trace elements in higher concentrations than their hosts. Accumulated elements sequester in different organs. In monogenean and crustacean ectoparasites, sclerotised structures and egg yolk appear to be the preferred site for element sequestration. In this study, the sequestration of trace elements; Mg, Al, Ca, Fe, Cu, and Zn in Lamproglena clariae was studied from two rivers. Adult L. clariae were collected from the gills of Clarias gariepinus from Lake Heritage in the Crocodile River and in the Vaal River below the Vaal Dam, South Africa. Collected parasites were flash frozen in liquid nitrogen and sectioned with a cryomicrotome. Sections were treated with Phen-Green to observe fluorescent signals. Trace elements in the parasite were analysed using a scanning electron microscope with an energy-dispersive spectroscope (SEM-EDS). Results showed more intense fluorescence signals in the exoskeleton compared to tissues, and in the egg yolk. Analysis by SEM-EDS confirmed the presence of elements in the parasite from both sites. Levels of Al were higher in L. clariae from the Vaal River than those from Lake Heritage, and Fe was higher in L. clariae from Lake Heritage. Element distribution patterns in the parasite matched those in the water from the sites. Unlike other crustaceans, regulation of metals in adult females of L. clariae does not occur through moulting, but high levels occurred in the yolk.

Health risk-benefit assessment of the commercial red mangrove crab: Implications for a cultural delicacy

Mangrove forests, provide vital food resources and are an endangered ecosystem worldwide due to pollution and habitat destruction. A risk-benefit assessment (RBA) was performed on the red mangrove crab (Ucides occidentalis) from the threatened Guayas mangroves in Ecuador. It was aimed to assess the combined potential adverse and beneficial health impact associated with crab consumption and define a recommended safe intake (SI) to improve the diet of the Ecuadoran population while ensuring safe food intake. Target hazard quotients (THQs), benefit quotients (Qs), and benefit-risk quotients (BRQs) were calculated based on the concentrations of the analyzed contaminants (121 pesticide residues, 11 metal(loid)s, antimicrobial drugs from 3 classes) and nutrients (fatty acids, amino acids, and essential nutrients). Except for inorganic arsenic (iAs), the THQ was below 100 for all investigated contaminants, suggesting that the average crab consumer is exposed to levels that do not impose negative non-carcinogenic or carcinogenic health effects in the long and/or short term. Concentrations of iAs (average AsIII: 25.64 and AsV: 6.28 μg/kg fw) were of the highest concern because of the potential to cause negative health effects on long-term consumption. Despite the thriving aquaculture in the Guayas estuary, concentrations of residues of the antimicrobial drugs oxytetracycline (OTC), florfenicol, and nitrofurans still were low. Based on the fact that different risk reference values exist, related to different safety levels, four SI values (0.002, 0.04, 4, and 18 crabs/day) were obtained. The strictest intake values indicate a concern for current consumption habits. In conclusion, the red mangrove crab contains various important nutrients and can be part of a balanced diet for the Ecuadorian population when consumed in limited portions. The present study emphasizes the importance of safeguarding the quality of the environment as a prerequisite for procuring nutritious and safe food.

Does the presence of heavy metal and catechol contaminants in organic waste challenge the physiological performance of the bioconverter Hermetia illucens?

The increased human activities and the worldwide population growth are constantly increasing the production of solid wastes. Over the years, waste management has thus become a prominent issue for several companies and municipalities, and several engineering techniques have been developed over the years in order to convert wastes into other solid materials or fuels. Yet, several techniques are important contributors to environmental pollution, and biological-based solutions have thus become progressively very popular. In particular, insect-based conversion of organic wastes represent eco-friendly tools, and the growth and development of insect species such as the black soldier fly have been tested and improved for a large diversity of organic wastes. However, organic wastes, including food wastes, may contain several pollutants such as heavy metals and catechol which could affect the bioconversion efficiency by incurring physiological costs that would be undetectable at the organismal level, i.e. have null to little effects on the life cycle of Hermetia illucens. In this context, assessments of antioxidant capacities can provide a rapid and low-cost evaluation of the capability of insects to handle exposure to heavy metals and catechol. Here, we aimed at measuring the physiological responses of the black soldier fly H. illucens grown on food wastes (kitchen, fruit or vegetable wastes) contaminated by cadmium, iron, lead or catechol. Biomarkers of oxidative stress (concentrations of hydrogen peroxide and protein carbonyls), non-enzymatic total antioxidant capacity (ascorbic acid amounts) and activity of enzymatic antioxidants (activities of superoxide dismutase and polyphenoloxidase) were measured from the gut of the larvae. We found no evidence of deleterious impacts of food waste contamination by catechol or heavy metals on H. illucens. In most experimental treatments, the array of physiological endpoints we measured for evaluating the degree of oxidative stress experienced by the larvae remained similar to controls. Possible physiological effects were reported for cadmium and catechol only, which tended to increase the oxidation of proteins and hydrogen peroxide in the larvae. Finally, our results suggested that the nature of the food waste could equally affect the physiological responses of the insect.

Ecological traits influence the bioaccumulation of microplastics in commercially important estuarine crabs from the southeastern Gulf of Mexico

We assessed microplastics (MPs) contamination in water, sediments, and tissues (gills, digestive tract, and muscle) of two intertidal crab species with different ecological traits and commercial importance (Menippe mercenaria and Callinectes sapidus), from a coastal lagoon in the southeastern Gulf of Mexico. There were significant differences between MP abundances in the abiotic matrices and between crab species. The burrower, sedentary and carnivorous M. mercenaria bioaccumulates 50 % more MPs than the free-swimming, omnivorous C. sapidus. However, no differences were observed between species' tissues. Fragments were the predominant shape in the tissues of both species, with the exception in the digestive tract of M. mercenaria. We identified polyethylene, and polyethylene terephthalate in water samples and Silopren® in sediment. In both crab species, Silopren and polyethylene predominated. Differences in ecological traits resulted in different bioaccumulation patterns in intertidal crabs.

Effects of pile driving sound playbacks and cadmium co-exposure on the early life stage development of the Norway lobster, Nephrops norvegicus

There is an urgent need to understand how organisms respond to multiple, potentially interacting drivers in today's world. The effects of the pollutants anthropogenic sound (pile driving sound playbacks) and waterborne cadmium were investigated across multiple levels of biology in larval and juvenile Norway lobster, Nephrops norvegicus under controlled laboratory conditions. The combination of pile driving playbacks (170 dB_pk-pk re 1 μPa) and cadmium combined synergistically at concentrations >9.62 μg_[Cd] L^-1 resulting in increased larval mortality, with sound playbacks otherwise being antagonistic to cadmium toxicity. Exposure to 63.52 μg_[Cd] L^-1 caused significant delays in larval development, dropping to 6.48 μg_[Cd] L^-1 in the presence of piling playbacks. Pre-exposure to the combination of piling playbacks and 6.48 μg_[Cd] L^-1 led to significant differences in the swimming behaviour of the first juvenile stage. Biomarker analysis suggested oxidative stress as the mechanism resultant deleterious effects, with cellular metallothionein (MT) being the predominant protective mechanism.

Metallic Study of the Invasive Species Cronius ruber—Assessment of Toxic Risk

Three toxic heavy metals (Cd, Pb, and Hg) were analyzed in the newly found invasive species in the Canary Islands, Cronius ruber. Its high growth rate and its widely varied diet are affecting the Canary marine ecosystem. The study was conducted using electrothermal vaporization atomic absorption spectrometry (GF-AAS) and cold-vapor atomic absorption spectrophotometry (CV-AAS). Significant differences were found in terms of the location and sex of the specimens, with the highest concentrations being found in areas with higher tourism activity and in the female specimens. On the other hand, the conclusion of the study is that human consumption of this species does not pose any toxic risk to public health, as the levels obtained in muscle tissue do not exceed the established limits for these metals. Therefore, its consumption and the fishing of this species can stop the proliferation of the same in the Canary coasts and thus not be harmful for the ecosystem.

Lead Inhibits Postecdysial Exoskeletal Calcification in the Blue Crab (Callinectes sapidus)

Postecdysial mineralization in crustaceans involves the deposition of carbonate salts, such as calcium carbonate, to the organic matrix. Because of the resemblance between Pb²⁺ and Ca²⁺ , the present study was carried out to investigate whether Pb is incorporated into the new shell during postecdysial mineralization using the blue crab (Callinectes sapidus) as the model crustacean. It was hypothesized that injected Pb would be deposited in the shell via calcium transporters in the epidermis during the mineralization process. Postecdysial blue crabs were injected with two doses of 5 µg Pb/g wet weight each in lead acetate, and then Pb, Ca, and Mg contents were analyzed in the exoskeleton, while only Pb bioaccumulation was quantified for the hepatopancreas, gills, muscles, and hemolymph. The results showed a statistically nonsignificant increase in exoskeletal Pb content in Pb-treated crabs compared to control, suggesting that exoskeletal Pb may not be a sensitive proxy for aquatic Pb pollution. There was a significant decrease in Ca content in Pb-treated crabs, suggesting that Pb hindered the deposition of Ca to crab exoskeleton, thereby obstructing calcification. A trend of a decrease in exoskeletal Mg was also observed in Pb-treated crabs. There was a significant increase in Pb content found in the gills, hepatopancreas, muscle, and hemolymph in Pb-treated crabs. The rank of the Pb level among three soft tissues in a decreasing order is hepatopancreas > gill > muscle. This is the first study to present evidence that Pb disrupts postecdysial exoskeletal calcification in a crustacean. Environ Toxicol Chem 2022;41:474-482. © 2021 SETAC.

Thiophilicity is a determinant of bioaccumulation in benthic fauna

Aquatic contamination can settle into sediments, where it complexes with organic matter and becomes bioavailable. The resulting bioaccumulation of these contaminants by benthic fauna poses a serious threat due to the potential for trophic transfer. This paper offers an insight into the heterogenous accumulation behavior of different elements, and the consequences for ecological risk. In this study, we present field quantification of sediment-associated bioaccumulation factors (BAF_S) in freshwater benthic macroinvertebrates. 17 elements were quantified using ICP-MS in sediment and Asellus aquaticus and Gammarus sp. samples. Previously published reports of contaminant concentrations in freshwater and marine sediments and benthic fauna were likewise analyzed to provide a complementary picture of bioaccumulation across contaminants and taxa. We demonstrate that the BAF_S correlates strongly with the thiophilicity of the elemental contaminants, as defined by (Kepp, 2016), for all strata examined. These findings support the hypothesis that thiol-mediated processes, such as that of metallothionein, play a larger role in bioaccumulation than typically afforded. In conclusion, we demonstrate the potential for the thiophilic scale to act as a predictor of accumulation potential.

Ecdysis as an auxiliary route for the removal of heavy metals in crustaceans: an experimental analysis with fiddler crabs (Minuca burgersi)

We assessed fiddler crabs' (Minuca burgersi) ability to secrete metallic contaminants through ecdysis under controlled conditions. We fed them with contaminated food with different copper (Cu) and lead (Pb) amounts and measured their concentration in the released and renewed exuviae. We found a significant reduction in the average concentrations of Cu and Pb in the released and renewed exuviae-eliminating the exoskeleton in the ecdysis process helps in the metal detoxification mechanism of these animals. A portion of the concentration of metals is retained in the crustaceans' exuvia, and thus, they can be used to analyze bioaccumulation in ecosystems. Our results also reinforce the need for attention to the contamination characterization in crustaceans before and after ecdysis to avoid underestimation effects.

Short communication: Effects of acute copper exposure on ionic regulation of the freshwater crab Aegla castro

Aeglids are unique freshwater decapods whose habitats are being impacted by metallic compounds, such as copper (Cu). Thus, we investigated the effects of acute Cu exposure on ionic regulation of Aegla castro. For this, male specimens in intermolt were collected from a reference stream and acclimated for 5 days in laboratory. After which, crabs were exposed to 11 μg L^-1 Cu (Cu11) or only to water (CTR) for 24 h. Hemolymph samples were withdrawn for the determination of Na⁺, K⁺, Ca²⁺, and Mg²⁺ concentrations and the posterior gills removed for the analysis of Na⁺/K⁺-ATPase, Ca²⁺-ATPase, H⁺-ATPase, and carbonic anhydrase (CA) activities. Increased Ca²⁺ and Mg²⁺ hemolymph concentrations were observed in animals from Cu11, when compared with CTR group. In addition, decreased activity of CA was observed in animals exposed to Cu. In the current study, alterations in Ca²⁺ and Mg²⁺concentrations probably indicate that animals activated exoskeleton reabsorption mechanisms, characteristic of the premolt. Therefore, increased Ca²⁺ and Mg²⁺ concentrations in hemolymph may indicate that a biochemical signal associated with the molting cycle was triggered by Cu exposure. Despite the known harmful effects of Cu on osmoregulatory enzymes, here we observed decreased activity only in CA. However, decreased activity of CA could trigger both acid-base imbalance and ionic disruption, since CA provides H⁺ and HCO₃^- for intracellular pH maintenance, and underpins Na⁺ and Cl^- for ionic regulation. Therefore, understanding how aeglids respond to metal contamination in laboratory conditions is crucial to assess their potential as an alternative biological model for aquatic ecotoxicology.

From Mangrove to Fork: Metal Presence in the Guayas Estuary (Ecuador) and Commercial Mangrove Crabs

Mangrove wetlands provide essential ecosystem services such as coastal protection and fisheries. Metal pollution due to industrial and agricultural activities represents an issue of growing concern for the Guayas River Basin and related mangroves in Ecuador. Fisheries and the related human consumption of mangrove crabs are in need of scientific support. In order to protect human health and aid river management, we analyzed several elements in the Guayas Estuary. Zn, Cu, Ni, Cr, As, Pb, Cd, and Hg accumulation were assessed in different compartments of the commercial red mangrove crab Ucides occidentalis (hepatopancreas, carapax, and white meat) and the environment (sediment, leaves, and water), sampled at fifteen sites over five stations. Consistent spatial distribution of metals in the Guayas estuary was found. Nickel levels in the sediment warn for ecological caution. The presence of As in the crabs generated potential concerns on the consumers' health, and a maximum intake of eight crabs per month for adults is advised. The research outcomes are of global importance for at least nine Sustainable Development Goals (SDGs). The results presented can support raising awareness about the ongoing contamination of food and their related ecosystems and the corresponding consequences for environmental and human health worldwide.

Survival recovery rates by six clonal lineages of Daphnia longispina after intermittent exposures to copper

Natural populations are commonly exposed to sequential pulses of contaminants. Accordingly, this study aimed at testing the existence of an association between the tolerance to lethal levels of copper (Cu) and the survival recovery ability from pulsed partially lethal copper exposures in six clonal lineages of Daphnia longispina. It was hypothesized that the most tolerant genotypes would be the ones exhibiting a faster survival recovery from a pulsed contaminant exposure. For each clonal lineage, the intensity of pulses corresponded to the respective concentration of Cu causing 30% of mortality after 24h of exposure (LC_30,24h). The initial hypothesis was not corroborated: obtained results showed no association between survival recovery and lethal tolerance to Cu. Nevertheless, some patterns could be detected. Firstly, the most sensitive lineages to lethal levels of copper revealed a faster survival recovery from a first Cu pulse comparatively to the most tolerant ones, though they were the most sensitive to a second pulse exposure. Secondly, the most tolerant lineages, though being more tolerant to a second exposure, exhibited the lowest survival recovery capacity after exposure to a first pulse of Cu. However, differences in the survival recovery capacity of the six clonal lineages after the exposure to the two pulses of Cu were not observed. Increasing the duration of the recovery period from 24h to 72h did not significantly alter mortality rates, except for the most sensitive and most tolerant clonal lineages. The results here obtained suggests that standard lethality assays may sub-estimate the toxicity of chemicals under realistic exposure scenarios, since sequential pulses are not infrequent in natural conditions.

Behavioural and biochemical alterations in gammarids as induced by chronic metallic exposures (Cd, Cu and Pb): Implications for freshwater biomonitoring

In freshwater species, metal toxicity is usually assessed through short-term exposures, hence limiting the practical usefulness of biomarkers for monitoring long-term impacts on wildlife populations. This study investigates the biological alterations elicited by chronic metallic exposures in Gammarus fossarum using multi-level biomarkers. In aquaria, gammarids were exposed for 10 weeks to field-realistic concentrations of Cd, Cu or Pb (0.25, 1.5 or 5.0 μg/L). At the individual level, behavioural traits (respiration, locomotion and feeding) were compared between naive and chronically-exposed gammarids. At the cellular level, enzymatic activities involved in digestion, moult and cell stress were monitored after 2, 6 and 10 weeks of exposure in males and females to consider the temporal feature of their responses. Results showed that the inhibitory effects of Cd and Pb on respiration and locomotion disappeared in chronically-exposed gammarids, reflecting acclimation to maintain these processes, unlike Cu. Chronic Cu- and Pb-elicited feeding inhibition was associated with the inhibitions of digestion enzymes. Chitobiase was inhibited by Cu in males and, by Cd and Pb in females, suggesting gender-dependent disturbances in moulting. In both genders, Cd generated cellular stress by stimulating acidic phosphatase and peroxidase activities. To conclude, such cellular impairments and alterations in individual performances are likely to disturb individual growth, population dynamics and litter decomposition in the long-term. Besides, obtaining biological responses, common to metals or specific to a metal or a gender, supports the development of biomarkers highlighting long-term impacts of metals on the health of organisms and their associated ecological functions in natural environments.

Macroelements and Trace Elements in Invasive Signal Crayfish (Pacifastacus leniusculus) from the Wieprza River (Southern Baltic): Human Health Implications

Signal crayfish (Pacifastacus leniusculus) is an invasive species displacing native European crayfish from their natural habitats. The elemental composition of the population from the southern Baltic coastal river and the potential health hazards are not known. The aim of the conducted research was to assess the quantitative content of Al, As, Ca, Cd, Cu, Fe, K, Mg, Na, Ni, Pb, Se, and Zn in meat, hepatopancreas, and exoskeleton in a population from Wieprza River (Poland) and compare the results with the recommendations of daily human consumption. Analysis also involved the composition of water and sediments. The concentrations of elements were analyzed using an Atomic Absorption Spectrometer. The bioconcentration factor (BCF) of elements in the signal crayfish was much higher from water than from sediments. Bioaccumulation of elements differed between the particular parts of the body of crayfish, e.g., Ca showed extreme predominance in the exoskeleton, while in meat exhibited a predominance of K, Na, Ca, and Mg. Among trace elements, crayfish meat was the richest in Zn, Cu, and Fe. The concentrations of non-essential Cd, Pb, and As were low compared to other determined elements. The highest concentrations of As, Cd, Cu, Fe, Ni, and Se were found in the hepatopancreas, while the highest levels of Al and Pb were found in the exoskeleton. Generally, it was found that the meat of P. leniusculus can be a perfect supplement to the human diet, and the consumption of 100 g of meat per day did not exceed the dietary reference values for essential elements and also for Al, As, Cd, Ni, and Pb.

Uptake and detoxification of trace metals in estuarine crabs: insights into the role of metallothioneins

The detoxification process of trace metals in the estuarine burrowing crab Neohelice granulata, after previously being exposed to anthropogenic pressures in the field, is described for the first time. The objectives of this study were (a) to assess the metal content (Cd, Cu, Pb, Zn, Mn, Ni, Cr, Fe) in the sediments and the uptake of these elements in the hepatopancreas of N. granulata; (b) to quantify trace metal concentrations in the hepatopancreas before and after the detoxification experiment; and (c) to relate this information to metallothionein (MT) induction or reversibility. The detoxification assay was performed for 25 days with artificial seawater under controlled conditions in a culture chamber. The results showed higher uptake and bioaccumulation of Zn and Cu from the sediments, and the hepatopancreas exhibited increased levels of Zn and lower concentrations of the rest of the metals and MTs after the assay, mainly Fe and Mn that were significantly lower. We conclude that trace metals could be translocated to and accumulated in the hepatopancreas, the main metabolic organ, and then eliminated under controlled conditions with corresponding reversibility of MTs. Graphical abstract.

Comparative analysis of trace metal levels in the crab Dotilla fenestrata, sediments and water in Durban Bay harbour, Richards Bay harbour and Mlalazi estuary, Kwazulu-Natal, South Africa

Durban Bay and Richards Bay Harbours are the largest and most economically active shipping harbours in South Africa supporting a diversity of ecosystems and biota of ecological importance. This study assessed and compared levels of metals in selected tissues of the sand bubbler crab (Dotilla fenestrata), water and sediments from anthropogenically impacted Durban and Richards Bay Harbours with those of Mlalazi estuary, a considered pristine site due to its sheltered catchments. Metal concentrations (Cd, Cu, Pb and Zn) were investigated using Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES). Metals concentrations in crab tissues were as follows; exoskeleton > gill > digestive gland, metal concentrations in tissues followed the order Cu > Zn > Pb > Cd. Metal levels in crabs from Durban Harbour (Cd 0.42, Cu 83.8, Pb 2.43and Zn 6.4 μg/g) were significantly higher than Richards Bay (Cd 0.22, Cu 27.7, Pb 1.23 and Zn 9.54 μg/g) and Mlalazi estuary (Cd 0.17, Cu 18.7, Pb 3.53 and Zn 6.91 μg/g). Metal levels in sediments followed the order Zn > Cu > Pb > Cd. Mlalazi had significantly elevated metal levels in sediment (Cd 6.83, Cu 35.63, Pb 33.43 and Zn 56.27 μg/g) compared to Durban Harbour (Cd 2.73, Cu 16.07, Pb 12.20 and Zn 38.70 μg/g) and Richards Bay (Cd 3.10, Cu 16.00, Pb 11.43 and Zn 26.07 μg/g). Metal concentrations in water were Cu > Zn > Pb > Cd save Mlalazi estuary with significantly higher Zn levels. Mlalazi estuary, the considered pristine site had significantly elevated metal levels in the sediments and water compared with the impacted sites; however, had significantly lower metal levels in the crabs’ tissues due to lower metal bioavailability. Factors such as high natural metal concentrations, metal speciation, sediment grain and organic matter content could possibly account for high metal concentrations without corresponding bioaccumulation and magnification in crabs from Mlalazi estuary.

Mercury concentrations in store-bought shrimp

Most mercury exposure to humans comes from consumption of fish and shellfish; however, mercury concentrations are not known for all available seafood, particularly shrimp. Our objective was to estimate the concentration of mercury in a variety of store-bought shrimp and then to compare total mercury concentrations to other information such as brand, harvest type, and total fat. We sampled a total of n = 159 shrimp from 10 different brands. Across 10 brands of shrimp, there was a significant effect of brand, with mean mercury concentrations among brands varying by up to an order of magnitude. We found no significant differences comparing shrimp between two capture types (wild-caught and farm-raised), which was perfectly collinear to whether shrimp were domestic or foreign. We did detect significant differences in mercury levels among different amounts of total fat in shrimp, with the lowest fat shrimp (1 g) having significantly more mercury than the highest fat shrimp (2 g). Although our results confirm that shrimp contains relatively low levels of mercury and is generally considered a good choice for consumers, this study is the first to report significant differences in mercury among both brands of shrimp and total fat content in shrimp.

Lead toxicity on a sentinel species subpopulation inhabiting mangroves with different status conservation

Lead is a priority pollutant introduced in the aquatic environment by different sources commonly located in estuarine regions, such as ports, marinas and industries. Environmental agencies around the world set the maximum allowable concentration of lead in effluents, surface water and sediment, but few studies reported its accumulation and chronic toxicity in mangrove benthic invertebrates using concentrations believed to be safe. In the case of Brazilian mangrove environments, Ucides cordatus is a crab species of choice to be used in bioaccumulation studies. We have assessed biomarkers' responses (DNA strand breaks, micronucleated cells, metallothioneins, enzymatic activity of aminolevulinic acid dehydratase and neutral red retention time) and the total bioaccumulation in six tissues of U. cordatus crabs resident to mangrove areas under different conservation status during a 28-day period bioassay. We also investigated Pb subcellular partition and biomarkers' responses using a supposedly safe concentration (10 μg L^-1). During the Pb exposure, the highest concentration of Pb was observed in crab gills. Crabs also showed a high ability to allocate Pb in detoxified forms. Multivariate analysis pointed out that bioaccumulation (total, active and detoxified) is linked to biomarkers. Even in supposedly safe dosage, U. cordatus triggered its defense mechanisms expressing more metallothioneins and presented relevant cyto-genotoxic damage. Our data suggest the development of biological tolerance to Pb in crabs from polluted areas. Our results provided a new insight about lead toxicity even at concentrations considered environmentally safe, which could support new strategies to manage estuarine areas considering their respective conservation status.

Acute and long-term manganese exposure and subsequent accumulation in relation to idiopathic blindness in the American lobster, Homarus americanus

Manganese (Mn) is a hypoxic reactive metal commonly found in marine sediments. Under hypoxic conditions the metal becomes fully reduced to Mn²⁺ and is biologically available to the benthic community for uptake. Mn is also a potent neurotoxin and it may play a role in the etiology of idiopathic blindness that has been observed in American lobsters. An acute exposure study was designed to expose American lobster, Homarus americanus, to 0, 20, 80, 150, and 300 mg L^-1 (ppm) for 96 hs to explore disparities in Mn accumulation among several tissues: optic nerve, brain, hepatopancreas, muscle, hemolymph, gill, and exoskeleton. These concentrations were based on realistic pore-water concentrations (20 mg L^-1), high sediment concentrations (80 mg L^-1), and unrealistically high concentrations to determine lethality (150 and 300 mg L^-1). A positive correlation between Mn accumulation and exposure concentration was observed in all tissues examined. In the internal tissues, manganese concentrations showed a high affinity towards brain, optic nerve, and hemolymph. In the exoskeleton and gills, Mn concentrations were also high, possibly because of internal uptake as well as external adsorption. Concentrations of Mn in tissues from the acute exposure study followed the accumulation pattern: hemolymph > gill > exoskeleton > optic nerve > brain > hepatopancreas = muscle. A long-term exposure study lasting seven weeks was designed to investigate the potential link between high Mn exposure and idiopathic blindness, a condition that affects an estimated 50 % of the adult American lobster population off Southern New England (SNE), USA. A comparison of these exposure studies showed evidence of time-dependent Mn accumulation in brain, muscle, exoskeleton, and gill tissue. Although the relationship between Mn exposure and blindness was not apparent, there was a modest trend in the development of blindness (Chi-square, p = 0.102) in animals exposed to a high concentration (150 mg L^-1) of the metal. With no mortalities occurring in the acute study and only one mortality in the long-term study, it is highly unlikely that Mn is acutely toxic to American lobsters at environmentally relevant concentrations. Its potential role in idiopathic blindness remains to be determined.

Environmental-friendly Contamination Assessment of Habitats Based on the Trace Element Content of Dragonfly Exuviae

We tested the usefulness of exuviae as an environmentally friendly method for exploring the variability of the trace element contents of protected insect populations without killing specimens. It is a notable characteristic of dragonflies that they are good ecological indicators for both aquatic and terrestrial habitat quality. Thus, we investigated the trace element accumulation in different stages of dragonflies: larva, exuvia, and adult. Using microwave plasma atomic emission spectrometry (MP-AES), we analysed the concentrations of Al, Ba, Cr, Cu, Fe, Mn, Pb, Sr and Zn. We found that the trace element contents of exuviae are a good proxy of the trace element contents of both the larvae and the adults. We conclude that exuvia is useful for assessing the environmental health of aquatic ecosystems. It is an environmentally friendly method and it can be used even in the case of protected dragonfly species.

Assessing Human Health Risks Associated with Consumption of Metal Content in Shrimp from NW Mexico

Shrimp of Farfantepenaeus californiensis (78 groups) and Litopenaeus stylirostris (14 groups) were caught in the northwestern fishing zones in Mexico during the 2014-2015 fishing season (September-February); both shrimp species have high commercial value. Muscle, hepatopancreas and exoskeleton were analyzed to determine their metal contents. For F. californiensis, the highest Cd, Pb and Zn contents were determined in specimens caught off the State of Baja California Sur (BCS) with 22.4 ± 8.9 (hepatopancreas), 2.83 ± 4.63 (muscle), and 748.5 ± 1567 (muscle) µg/g, in the regions off Mulegé, Los Cabos and Los Cabos, respectively. For L. stylirostris, the fishing zone of Comundú (BCS) showed higher Cd (12.3 ± 11.5 µg/g), Cu (569.1 ± 646.5 µg/g) and Zn (549.7 ± 400.7 µg/g) contents; all values were determined in the hepatopancreas. Regarding the hazard quotient and total hazard quotient calculated in this study, the consumption of marine shrimp caught off NW Mexico does not represent a risk to human health (both < 1).

Seasonal environmental parameters influence biochemical responses of the fiddler crab Minuca rapax to contamination in situ

The mudflat fiddler crab Minuca rapax, typical of mangroves and intertidal zones in the Western Atlantic Ocean, responds to fluctuations in environmental parameters by biochemical and physiological adjustments. Such biochemical effects are commonly employed in environmental studies as biomarkers of estuarine contamination. This study evaluates biochemical responses in the gills and hepatopancreas of M. rapax in situ from localities exhibiting different types and levels of contamination, against a backdrop of fluctuations in environmental parameters like salinity and temperature common to estuarine regions. The biochemical biomarkers metallothionein (MT)-like protein titers and glutathione S-transferase (GST), glutathione peroxidase (GPx) and acetylcholinesterase (AChE) activities were used to evaluate responses to environmental contamination and seasonal changes in environmental parameters. Crabs were collected during two seasons, the austral winter and summer, at three sites along the coast of the state of São Paulo, Brazil that present decreasing degrees of environmental contamination: Ilha Diana, Santos (ID) > Rio Itapanhaú, Bertioga (RI) > Picinguaba, Ubatuba (P), a pristine control site. Our findings show that MT were induced in crabs from the contaminated sites (ID and RI) mainly during winter, revealing the activation of detoxification mechanisms; however MT were also induced in P crabs during the summer rainy season. GPX, GST and AChE activities were altered in P crabs during summer and in ID and RI crabs in winter. While enzyme activities in summer crabs may reflect seasonal changes in precipitation and salinity, in winter these altered activities appear to reflect contamination, although an effect of environmental parameters cannot be excluded. These findings reveal a strong seasonal influence on biochemical biomarker responses in Minuca rapax, a relevant factor to consider when interpreting the impact of environmental contamination in estuaries.

Heavy metal bioconcentration factors in the burrowing crab Neohelice granulata of a temperate ecosystem in South America: Bahía Blanca estuary, Argentina

An extensive population of the burrowing crab, Neohelice granulata, inhabits the intertidal areas of the Bahía Blanca estuary, a moderately polluted temperate ecosystem located to the southwest of the province of Buenos Aires, Argentina. In order to determine the metal-accumulating ability of this species, concentrations of Cd, Cu, Pb, Ni, Zn, Mn, Cr, and Fe in soft tissues of adult specimens were measured. Subsequently, the bioconcentration factors (BCFs) of all heavy metals were determined using levels of concentrations previously obtained in intertidal sediments. The results showed concentrations above the detection limit in soft tissues of male and female crabs for all metals except Pb and Cr. BCF > 1 were obtained for Cd, Cu, and Zn, indicating that these metals are accumulated and biomagnified. However, BCF values < 1 were found for the rest of the metals (Mn, Ni, and Fe). The findings of metal accumulation in soft tissues of N. granulata is of great importance taking into account that this is a key species within this temperate ecosystem, playing a major role in the transference of pollutants to higher trophic levels.

Bioaccumulation of metal(loid)s in Cardisoma crassum and pollution assessment in a mangrove protected area in Mexico

The bioaccumulation of several elements in "mouthless crabs" (Cardisoma crassum) and their concentrations in environmental samples were assessed in a mangrove forest within a natural protected area located in the middle of Puerto Vallarta, Mexico. The concentrations of Al, As, Ba, Cd, Cr, Cu, Fe, Ni, Pb, Sr, Si, V, and Zn in sediments, mangrove litterfall, and pore water and their bioaccumulations in the muscle and shell tissue of C. crassum were determined during rainy and dry seasons. Two different sampling sites were compared, selected according to the influence of the tide. The samples were analyzed by ICP-OES. In pore water, half of the elements of interest were below the limits of detection. Pb and Cd concentrations were only detected in the sedimentary phase. Al and Fe presented the highest concentrations at both sampling sites in the sediments and mangrove litterfall. There were no significant differences between sampling seasons in water samples (P > 0.05). Only Cu presented significant differences between sampling seasons in the mangrove litterfall samples and V in the sediment samples (P < 0.05). The sediment quality guidelines indicated that only Cd was above the threshold effect limit. As, Cd, Cr, Ni, and Pb remained below the limits of detection in muscle tissue and shell samples. The biota-sediment accumulation factors (BSAFs) determined for Cu and Zn were above 1.0, indicating the accumulation of these elements in the muscle tissue of C. crassum, while the BSAF values in the shell were above the threshold for Ba, Si, and Sr.

Mercury fractionation in marine macrofauna using thermodesorption technique: Method and its application

Mercury (Hg) is one of the most dangerous elements, and its toxicity and ability to accumulate in organisms depend on its chemical form. There are numerous methods of Hg speciation analysis, out of which the least expensive and the least time-consuming one is thermodesorption. The method has been successfully used for the analysis of abiotic samples - soils and sediments. The aim of this study was to verify whether the simplified thermodesorption method can be used in the analysis of the tissues of animal organisms from different trophic levels. Hg fractionation analyses were performed on a DMA-80 analyser (Milestone, Italy). The results presented in this paper are the first published data on Hg fractionation by thermodesorption method in animal tissues. The study showed that the 5-step thermodesorption method can be applied to various types of environmental matrices, which makes it universal. This method is of great importance in terms of estimating the Hg uptake and transfer in the trophic chain, and also enables the assessment of global Hg circulation in the environment. The presented method does not require previous digestion of samples or the use of expensive reagents. It can also be used for the preliminary selection of samples for MeHg analysis. The results obtained by this 5-step fractionation could be comparable with different research, conducted using other Hg analysers.

Trace element biomineralisation in the carapace in male and female Argulus japonicus

Parasites of fishes have been shown to be effective bioindicators of the aquatic environment. Few investigations have been conducted on ectoparasite models and therefore little is known about the fate of trace elements and metals which they accumulate. In this study trace element sequestration was observed in the carapace of the fish louse, Argulus japonicus and found to relate to the sex of the parasite, as well as, the degree of sclerotization of the carapace. Adults of A. japonicus were collected from cyprinid hosts in the Vaal Dam, South Africa. Parasites were removed and flash frozen in liquid nitrogen before being sectioned with a cryomicrotome. Sections and whole mounts of parasites were prepared and treated with Phen–Green ^TM FL cell–permeant diacetate. Cryosections were assessed for trace elements and metals using a scanning electron microscope equipped with energy dispersive spectroscopy. Results indicated that in both male and female parasites, trace elements become bound to the carapace and produce more intense fluorescence than in soft tissues. Sexual dimorphic differences were further observed between male and female parasites. The intensity of the fluorescence signals was greater in the carapace of male parasites than in females, particularly when comparing the carapace of the ventral side of the thorax. In females, an amorphous layer of material surrounding the eggs was observed and produced an intense fluorescent signal. Levels of trace elements and metals detected were not significantly different between male and female parasites. Results observed serve as a demonstration for the first time of trace element sequestration in a freshwater crustacean parasite and possible mechanisms employed to reduce body burdens of trace elements and metals.

Cadmium in the shore crab Carcinus maenas along the Norwegian coast: geographical and seasonal variation and correlation to physiological parameters

Previously, high concentrations of cadmium have been found in the hepatopancreas of the edible or brown crab (Cancer pagurus) sampled from positions north of about 67° N, compared to regions further south along the Norwegian coast, with no clear understanding why. In order to study a similar organism in the same ecosystem, the present study analyzed 210 shore crabs (Carcinus maenas) from four different locations along the Norwegian coast, two in the North and two in the South. The physiological variables size, sex, molting stage, hepatosomatic index, carapace color, and gonad maturation were registered, in attempt to explain the high inter-individual variation in cadmium levels in hepatopancreas. In contrast to the brown crabs, the shore crabs showed no clear geographical differences in cadmium concentrations. This indicates physiological differences between the two crab species. No clear and consistent correlations were found between cadmium levels and physiological parameters, except for sex, where cadmium concentration in hepatopancreas was twice as high in males compared to females. The cadmium levels also varied with season, with approximately 40 and 60% lower cadmium concentration in April than August for male and female shore crabs, respectively. None of the analyzed cadmium concentrations in muscle meat from claws exceeded EUs food safety limit, and low cadmium levels in soup prepared from shore crabs clearly indicated that this dish is not problematic regarding food safety.

Mercury content of blue crabs (Callinectes sapidus) from southern New England coastal habitats: Contamination in an emergent fishery and risks to human consumers

Total mercury (Hg; ppm dry weight) was measured in blue crabs, Callinectes sapidus, collected from Narraganset Bay and adjacent coastal lagoons and tidal rivers (Rhode Island/Massachusetts, USA) from May to August 2006-2016. For juvenile crabs (21-79mm carapace width, CW), total Hg was significantly greater in chelae muscle tissue (mean±1 SD=0.32±0.21ppm; n=65) relative to whole bodies (0.21±0.16ppm; n=19), and irrespective of tissue-type, crab Hg was positively related to CW indicating bioaccumulation of the toxicant. Across a broader range of crab sizes (43-185mm CW; n=465), muscle Hg concentrations were significantly higher in crabs from the Taunton River relative to other locations (0.71±0.35ppm and 0.20±0.10ppm, respectively). Spatial variations in crab Hg dynamics were attributed to habitat-specific Hg burdens of their prey, including bivalves, gastropods, polychaetes, and shrimp. Prey Hg, in turn, was directly related to localized sediment Hg and methylmercury conditions. Biota-sediment accumulation factors for crabs and prey were negatively correlated with sediment organic content, verifying that organically-enriched substrates reduce Hg bioavailability. From a human health perspective, frequent consumption of crabs from the Taunton River may pose a human health risk (23% of legal-size crabs exceeded US EPA threshold level); thus justifying spatially-explicit Hg advisories for this species.

Heavy Metals Bioaccumulation in Tissues of Spiny-Cheek Crayfish (Orconectes limosus) from Lake Gopło: Effect of Age and Sex

The aim of the present work was to assess the concentrations of metals in the abdominal muscle and exoskeleton of 3-year-old males and 4-year-old females and males of spiny-cheek crayfish (Orconectes limosus) collected from Lake Gopło. A total of 93 males and 35 females were collected in autumn (October 2014). The analyzes of heavy metals were conducted by means of atomic absorption spectroscopy with a PU9100X spectrometer. The content of mercury was determined using AMA 254 mercury analyser. As analyses indicated heavy metals accumulated in the muscle and exoskeleton in the following sequence: Zn > Cu > Pb > Mn > Ni > Hg and Mn > Pb > Zn > Ni > Cu > Hg, respectively. Statistically significant differences between 3- and 4-year-old males were found for all analyzed metals. Gender dependent differences were calculated only for Ni in the muscle tissue and for Mn and Hg in the exoskeleton. In comparison with the study carried out 2 years ago notably higher concentrations of Pb were found in the muscle and a higher content of Zn, Pb, Mn and Ni was determined in the exoskeleton.

Nutrient intake determines post-maturity molting in the golden orb-web spider Nephila pilipes (Araneae: Araneidae)

While molting occurs in the development of many animals, especially arthropods, post-maturity molting (PMM, organisms continue to molt after sexual maturity) has received little attention. The mechanism of molting has been studied intensively; however, the mechanism of PMM remains unknown although it is suggested to be crucial for the development of body size. In this study, we investigated factors that potentially induce PMM in the golden orb-web spider Nephila pilipes, which has the greatest degree of sexual dimorphism among terrestrial animals. We manipulated the mating history and the nutrient consumption of the females to examine whether they affect PMM. The results showed that female spiders under low nutrition were more likely to molt as adults, and mating had no significant influence on the occurrence of PMM. Moreover, spiders that underwent PMM lived longer than those that did not and their body sizes were significantly increased. Therefore, we concluded that nutritional condition rather than mating history affect PMM.

Subcellular distribution and trophic transfer of Pb from bivalves to the common prawn Palaemon serratus

The edible clam Dosinia exoleta has been reported to accumulate high contents of lead (Pb) in soft tissues disregarding the levels of Pb in the environment. This is due to the retention of Pb in the form of metal rich granules (MRG) in their kidneys throughout the mollusc lifespan. The potential for trophic transfer of Pb in this form to predators is expected to be low, since metals in the form of MRG are generally supposed to be trophically unavailable, but this assumption is based on studies with other metals (Ag, Cd, Cu or Zn) and has not been demonstrated with Pb until now. This study was designed to test if the Pb present in D. exoleta in the form of MRG is available to a decapod consumer, the common prawn Palaemon serratus, in comparison with a mussel diet showing a different subcellular distribution of Pb. As hypothesised, despite the high Pb concentrations (15µgg^-1ww) offered to the prawns as D. exoleta tissues, Pb was almost completely unavailable for trophic transfer, and the prawns fed with this diet during 28 days showed the same Pb accumulation as prawns fed with a control diet with a much lower Pb concentration. On the contrary, individuals fed with mussel tissues containing the same Pb concentrations as the diet based on D. exoleta tissues showed 10 times higher Pb bioaccumulation, corresponding to a trophic transfer factor of 1.1%. Subcellular fractionation experiments revealed that the fraction of Pb in the form of MRG was much lower for the mussel, confirming, as observed for other metals, that MRG-associated Pb is not available for trophic transfer to decapod crustaceans.

Fractionation of rare earth and other trace elements in crabs, Ucides cordatus, from a subtropical mangrove affected by fertilizer industry

Fractionation of rare earth elements (REE) and other trace metal concentrations (Th, U, Cd, Cr, Cu, Ni, Pb, and Zn) between mangrove sediments and claw muscles and shells of male crabs (Ucides cordatus) from a subtropical estuary highly impacted by fertilizer industry activities was investigated. This is the first record of REE distribution in these organisms, and the results showed higher accumulations of these metals, U and Th in shells, probably related to the replacement of Ca during molting. Contents of Cd, Cr and Ni were similar in both tissues, but Cu, Zn and Pb were mostly accumulated in the claw muscle with concentrations above those considered safe for human consumption according to the Brazilian legislation. REE fractionation was different in the analyzed tissues being softer in the shells. The results provided evidences that the water absorbed during molting controls the chemistry of REE in shells. In contrast, the chemistry of REE in the claw muscle, in which was observed preferential absorption of light REE, is controlled by diet. REE fractionation obtained for the claw muscles was closely correlated to the observed in the contaminated substrate and in materials related to the production of phosphate fertilizers (contamination source), which supports their transference to this Ucides cordatus tissue without fractionation by the ingestion of sediments. Our results showed the potential use of crab tissues for monitoring REE and trace element sources in mangrove areas, with claw muscle exhibiting the contaminant source fingerprint.

A Nutritional Profile of the Trap-Nesting Wasp Trypoxylon lactitarse (Hymenoptera: Crabronidae): Comparison of Sexes and Overwintering and Non-Overwintering Generations

The wasp Trypoxylon lactitarse Saussure is a bivoltine trap-nesting species that possesses a non-overwintering generation (G1) and a generation that overwinters as a prepupa (G2). Thus, the nutritional needs of the G1 individuals were predicted to be different than the G2 because the latter generation needs to store energy prior to diapause. Trap-nesting Trypoxylon are also of interest because, unlike most Hymenoptera, the males guard the nest while females forage. Thus, males may lose nutrients as they stay and guard the nest. In this study, a nutritional profile was created for T. lactitarse to compare the macronutrient (protein, carbohydrates, and lipids) and micronutrient (Ca, Cu, Fe, K, Mg, Mn, Na, and Zn) levels of the different life stages of the wasp and compare individuals of the G1 and G2 generations. There were distinct changes in the nutrient levels relative to the original food source as individuals metamorphosed into larvae, pupae, and adults. G1 larvae had higher levels of carbohydrates than G2 larvae. G2 larvae had higher levels of lipids and K than G1 larvae, indicating possible differences in energy storage. In adults, there was an increase in levels of carbohydrates and Mn. Parental males, which stay and guard the nest, were found to have higher levels of carbohydrates at the end of the nesting period than females and emerging adults. One possible implication is that females may feed males during the nesting period, as the females are the only individuals to forage.

Effects of metal contamination in situ on osmoregulation and oxygen consumption in the mudflat fiddler crab Uca rapax (Ocypodidae, Brachyura)

The contamination of estuaries by metals can impose additional stresses on estuarine species, which may exhibit a limited capability to adjust their regulatory processes and maintain physiological homeostasis. The mudflat fiddler crab Uca rapax is a typical estuarine crab, abundant in both pristine and contaminated areas along the Atlantic coast of Brazil. This study evaluates osmotic and ionic regulatory ability and gill Na(+)/K(+)-ATPase activity in different salinities (<0.5, 25 and 60‰ S) and oxygen consumption rates at different temperatures (15, 25 and 35°C) in U. rapax collected from localities along the coast of São Paulo State showing different histories of metal contamination (most contaminated Ilha Diana, Santos>Rio Itapanhaú, Bertioga>Picinguaba, Ubatuba [pristine reference site]). Our findings show that the contamination of U. rapax by metals in situ leads to bioaccumulation and induces biochemical and physiological changes compared to crabs from the pristine locality. U. rapax from the contaminated sites exhibit stronger hyper- and hypo-osmotic regulatory abilities and show greater gill Na(+)/K(+)-ATPase activities than crabs from the pristine site, revealing that the underlying biochemical machinery can maintain systemic physiological processes functioning well. However, oxygen consumption, particularly at elevated temperatures, decreases in crabs showing high bioaccumulation titers but increases in crabs with low/moderate bioaccumulation levels. These data show that U. rapax chronically contaminated in situ exhibits compensatory biochemical and physiological adjustments, and reveal the importance of studies on organisms exposed to metals in situ, particularly estuarine invertebrates subject to frequent changes in natural environmental parameters like salinity and temperature.

Micro x-ray absorption spectroscopic analysis of arsenic localization and biotransformation in Chironomus riparius Meigen (Diptera: Chironomidae) and Culex tarsalis Coquillett (Culicidae)

The distribution and speciation of arsenic (As) were analyzed in individuals of various life stages of a midge, Chironomus riparius, and the mosquito Culex tarsalis exposed to 1000 μg/l arsenate. X-ray absorption spectroscopy (XAS) revealed that C. riparius larvae accumulate As in their midgut, with inorganic arsenate [As(V)] being the predominant form, followed by arsenite [As(III)] and an As-thiol. Reduced concentrations of As in pupal and adult stages of C. riparius indicate excretion of As between the larval and pupal stages. In adults, As was limited to the thorax, and the predominant form was an As-thiol. In Cx. tarsalis, As was not found in high enough concentrations to determine As speciation, but the element was distributed throughout the larva. In adults, As was concentrated in the thorax and eyes of adults. These results have implications for understanding the biotransformation of As and its movement from aquatic to terrestrial environments.

Copper and zinc detoxification in Gammarus pulex (L.)

To negate the toxicity of labile intracellular metals, some aquatic organisms partition metals into specific subcellular locations for detoxification, namely the soluble heat-stable cytosol and insoluble metal-rich granules. The aim of the present study was to characterise these subcellular storage sites in the freshwater crustacean Gammarus pulex (Linnaeus) following in situ exposures upstream (Drym, low metal) and downstream (Relubbus, elevated metal) of copper- and zinc-rich inflows into the River Hayle (Cornwall, UK). In the cytosol of gammarids exposed at Relubbus, copper and zinc associated to a 7.5-kDa metallothionein-like protein (MTLP) that was largely absent from gammarids prior to exposure. Exposure at Relubbus caused MTLP concentrations to increase 4- to 5-fold between days 2 and 4, indicating an induction response to increased labile intracellular metal. On day 16, spherical calcium-rich granules (0.5–2.5 μmol l–1) were visualised and analysed in the posterior caeca of gammarids exposed at both sites. Following exposure at Relubbus, granules contained trace amounts of copper, but zinc was absent. Granules in gammarids exposed at Drym contained no detectable copper or zinc. Granule formation appeared to be independent of exposure. Within the posterior caeca, granules have been associated with calcium storage during the crustacean molt, rather than in detoxification of trace metals. However, the granular copper burden appeared to follow environmental Cu availabilities. Thus, we describe Cu sequestration within molt-cycle calcium storage granules. As both MTLP concentrations and granule formation in crustaceans are affected upon by molting, we hypothesise that detoxification might impact upon this existing process.

Metallothioneins and energy budget indices in cadmium and copper exposed spiders Agelena labyrinthica in relation to their developmental stage, gender and origin

The aim of our studies was to explain the role of metallothioneins (MTs) in the neutralization of excessive amounts of metals (essential: copper (Cu) and toxic: cadmium (Cd)) and to describe the energy status in metal-exposed spiders Agelena labyrinthica in relation to its developmental stage, gender and origin. Juvenile, female and male spiders were collected from three variously polluted habitats, transferred to the laboratory and exposed to the metals in their diet. Cu and Cd accumulation in the body and exuviae, bioaccumulation factor, percentage of metallothionein positive cells, MT concentration, percentage of cells with depolarized mitochondria, ATP concentration and ADP/ATP ratio were measured and calculated. Cu appeared to be regulated and its excess is eliminated via, among others, the molting process, while Cd was rather accumulated by the spiders. The level of MTs increased significantly mainly in females exposed to both metals, irrespectively of the pollution degree of their site of origin, indicating a defensive role of the proteins. In general, even if both the MT level and the energy status indices were positively correlated with Cd and Cu concentrations in the spider body, the energy status of A. labyrinthica did not seem disturbed.