Cytochemical characterization of gill and hepatopancreatic cells of the crab Ucides cordatus (Crustacea, Brachyura) validated by cell metal transport

Microplastics and 17α Ethinylestradiol: How Do Different Aquatic Invertebrates Respond to This Combination of Contaminants?

The synthetic hormone 17α ethinyl estradiol (EE2) is a molecule widely used in female contraceptives and recognized as a contaminant of attention (Watch List) in the European Union due to its high consumption, endocrine effects and occurrence in aquatic environments. Its main source of introduction is domestic sewage where it can be associated with other contaminants such as microplastics (MPs). Due to their characteristics, they can combine with each other and exacerbate their isolated effects on biota. This study evaluated the combined effects of microplastics (MPs) and 17α ethinylestradiol (EE2) on two tropical estuarine invertebrate species: Crassostrea gasar and Ucides cordatus. Polyethylene particles were spiked with EE2 and organisms were exposed to three treatments, categorized into three groups: control group (C), virgin microplastics (MPs), and spiked microplastics with EE2 (MPEs). All treatments were evaluated after 3 and 7 days of exposure. Oysters exhibited changes in phase 2 enzymes and the antioxidant system, oxidative stress in the gills, and reduced lysosomal membrane stability after exposure to MPs and MPEs. Crabs exposed to MPs and MPEs after seven days showed changes in phase 1 enzymes in the gills and changes in phases 1 and 2 enzymes in the hepatopancreas, such as disturbed cellular health. The combined effects of microplastics and EE2 increased the toxicity experienced by organisms, which may trigger effects at higher levels of biological organization, leading to ecological disturbances in tropical coastal ecosystems.

Combined effects of polyethylene spiked with the antimicrobial triclosan on the swamp ghost crab (Ucides cordatus; Linnaeus, 1763)

Domestic sewage is an important source of pollutants in aquatic ecosystems and includes both microplastics (MPs) and pharmaceuticals and personal care products (PPCPs). This study sought to assess the biological effects of the interaction between plastic particles and the antibacterial agent triclosan (TCS). The study relied on the swamp ghost crab Ucides cordatus as a model. Herein polyethylene particles were contaminated with triclosan solution. Triclosan concentrations in the particles were then chemically analyzed. Swamp ghost crab specimens were exposed to experimental compounds (a control, microplastics, and microplastics with triclosan) for 7 days. Samplings were performed on days 3 (T3) and 7 (T7). Gill, hepatopancreas, muscle and hemolymph tissue samples were collected from the animals to evaluate the biomarkers ethoxyresorufin O-deethylase (EROD), dibenzylfluorescein dealkylase (DBF), glutathione S-transferase (GST), glutathione peroxidase (GPx), reduced glutathione (GSH), lipid peroxidation (LPO), DNA strands break (DNA damage), cholinesterase (ChE) through protein levels and neutral red retention time (NRRT). Water, organism, and microplastic samples were collected at the end of the assay for post-exposure chemical analyses. Triclosan was detected in the water and crab tissue samples, results which indicate that microplastics serve as triclosan carriers. Effects on the gills of organisms exposed to triclosan-spiked microplastics were observed as altered biomarker results (EROD, GST, GPx, GSH, LPO, DNA damage and NRRT). The effects were more closely associated with microplastic contaminated with triclosan exposure than with microplastic exposure, since animals exposed only to microplastics did not experience significant effects. Our results show that microplastics may be important carriers of substances of emerging interest in marine environments in that they contaminate environmental matrices and have adverse effects on organisms exposed to these stressors.

Diluted Seawater and Ammonia-N Tolerance of Two Mangrove Crab Species. New Insights to Understand the Vulnerability of Pristine Islands Ecosystems Organisms

Mangrove ecosystems are the primary receptors of anthropogenic pollution in tropical areas. Assessing the vulnerability of these ecosystems can be expressed, among other indicators, by studying the health of ‘ecosystem engineers’. In this study, mangrove forests facing opposing anthropogenic pressures were studied (i) in the uninhabited island of Europa (Mozambique Channel), considered as a pristine ecosystem, and, (ii) on the island of Mayotte, facing regular domestic wastewater discharges. Using an ecophysiological approach, the effects of diluted seawater (DSW) and increased ammonia-N were studied for two fiddler crab species: Gelasimus tetragonon (GT) on the island of Europa and Paraleptuca chlorophthalmus (PC) on the island of Mayotte. Osmoregulation curves and osmoregulatory capacity were determined along with O2 consumption rates after a 96 h exposure period. Histological analyses were also carried out on two important metabolic organs: the hepatopancreas and the posterior gills. Results indicate that both crab species are good hyper-hypo-osmoregulators but only PC can maintain its osmoregulatory capacity when exposed to ammonia-N. Oxygen consumption is increased in GT after 96 h of exposure to ammonia-N but this does not occur in PC. Finally, a thickening of the gill osmoregulatory epithelium was observed after 96 h in PC when exposed to ammonium but not in GT. Therefore, the two species do not have the same tolerance to DSW and increased ammonia-N. PC shows physiological acclimation capacities in order to better manage nitrogenous enrichments. GT did not show the same physiological plasticity when exposed to ammonia-N and could be more at risk by this kind of stress. These results along with those from other studies regarding the effects of domestic effluents on mangrove crabs are discussed. Therefore, the greater vulnerability of organisms occupying pristine ecosystems could induce major changes in mangrove functioning if crabs, that are engineer species of the ecosystem, are about to reduce their bioturbation activity or, even, disappear from the mangrove forests.

The hepatopancreas of the mangrove crab Neosarmatium africanum: a possible key to understanding the effects of wastewater exposure (Mayotte Island, Indian Ocean)

Mangrove crabs are ecosystem engineers through their bioturbation activity. On Mayotte Island, the abundance of Neosarmatium africanum decreased in wastewater-impacted areas. Previous analyses showed that global crab metabolism is impacted by wastewater, with a burst in O₂ consumption that may be caused by osmo-respiratory trade-offs since gill functioning was impacted. As the hepatopancreas is a key metabolic organ, the purpose of this study was to investigate the physiological effects of wastewater and ammonia-N 5-h exposure on crabs to better understand the potential trade-offs underlying the global metabolic state. Catalase, superoxide dismutase, glutathione S-transferase, total digestive protease, and serine protease (trypsin and chymotrypsin) activities were assessed. Histological analyses were performed to determine structural modifications. No effect of short-term wastewater and ammonia-N exposure was found in antioxidant defenses or digestive enzyme activity. However, histological changes of B-cells indicate an increase in intracellular digestive activity through higher vacuolization processes and tubule dilation in wastewater-exposed crabs.

Co-exposure of graphene oxide with trace elements: Effects on acute ecotoxicity and routine metabolism in Palaemon pandaliformis (shrimp)

Graphene oxide (GO) has been evaluated for application in environmental remediation and pollution control strategies. However, the side effects caused by the interactions of GO with classical pollutants in aquatic environments are still largely unknown. In this work, the ecotoxicological effects of GO, cadmium, zinc and the interactions between GO and these trace elements (co-exposure) were evaluated through acute toxicity tests and routine metabolism (i.e., oxygen consumption and ammonia excretion) in Palaemon pandaliformis (shrimp). After 96 h of exposure, GO did not present acute ecotoxicity at concentrations up to 5.0 mg L^-1. However, the association of GO with Cd or Zn increased the toxicity of these trace elements as demonstrated by the decrease in LC₅₀ values. The 96 h LC₅₀ of Cd associated with GO was 1.7 times less than the 96 h LC₅₀ of Cd alone. Similarly, the 96 h LC₅₀ of Zn associated with GO was 1.8 times less than the 96 h LC₅₀ of Zn alone. Additionally, the co-exposure of GO with trace elements impaired the routine metabolism of P. pandaliformis. Finally, the GO potentiated the ecotoxicological effects of Cd and Zn in the shrimp model. Future research on this emerging nanomaterial should focus on its use and disposal in aquatic ecosystems.

Magnetite nanoparticles coated with oleic acid: accumulation in hepatopancreatic cells of the mangrove crab Ucides cordatus

The field of nanotechnology had enormous developments, resulting in new methods for the controlled synthesis of a wide variety of nanoscale materials with unique properties. Efficient methods such as thermal decomposition for efficient size control have been developed in recent years for the synthesis of oleic acid (OA)-coated magnetite (Fe₃O₄) nanoparticles (MNP-OA). These nanostructures can be a source of pollution when emitted in the aquatic environment and could be accumulated by vulnerable marine species such as crustaceans. In this work, we synthesized and characterized MNP-OA of three different diameters (5, 8, and 12 nm) by thermal decomposition. These nanoparticles were remarkably stable after treatment with high affinity iron chelators (calcein, fluorescent desferrioxamine, and fluorescent apotransferrin); however, they displayed pro-oxidant activity after being challenged with ascorbate under two physiological buffers. Free or nanoparticle iron displayed low toxicity to four types of hepatopancreatic cells (E, R, F, and B) of the mangrove crab Ucides cordatus; however, they were promptly bioavailable, posing the risk of ecosystem disruption due to the release of excess nutrients.

Evaluation of iron loading in four types of hepatopancreatic cells of the mangrove crab Ucides cordatus using ferrocene derivatives and iron supplements

The mangrove crab Ucides cordatus is a bioindicator of aquatic contamination. In this work, the iron availability and redox activity of saccharide-coated mineral iron supplements (for both human and veterinary use) and ferrocene derivatives in Saline Ucides Buffer (SUB) medium were assessed. The transport of these metallodrugs by four different hepatopancreatic cell types (embryonic (E), resorptive (R), fibrillar (F), and blister (B)) of U. cordatus were measured. Organic coated iron minerals (iron supplements) were stable against strong chelators (calcein and transferrin). Ascorbic acid efficiently mediated the release of iron only from ferrocene compounds, leading to redox-active species. Ferrous iron and iron supplements were efficient in loading iron to all hepatopancreatic cell types. In contrast, ferrocene derivatives were loaded only in F and B cell types. Acute exposition to the iron compounds resulted in cell viability of 70-95%, and to intracellular iron levels as high as 0.40 μmol L^-1 depending upon the compound and the cell line. The easiness that iron from iron metallodrugs was loaded/transported into U. cordatus hepatopancreatic cells reinforces a cautionary approach to the widespread disposal and use of highly bioavailable iron species as far as the long-term environmental welfare is concerned.

Characterization of cadmium transport in hepatopancreatic cells of a mangrove crab Ucides cordatus: The role of calcium

Cadmium is a toxic metal, present in batteries and discarded in estuaries and mangrove habitats. Apart from that, it is a non-essential metal that causes toxic effects in many organisms. Cadmium accumulates in gills and hepatopancreas of crustaceans and its route into the cell is unknown. It is possible that occurs by calcium channels or calcium transporters. The objective of this study was to characterize the transport of cadmium and the role of calcium in different cell types from hepatopancreas of the mangrove crab Ucides cordatus. For this, the hepatopancreas was dissociated by magnetic stirring and after that separated by a sucrose gradient. Then, the cells were labeled with FluoZin-3 AM and different CdCl₂ concentrations were added together with a variety of inhibitors. The results showed that Cd²⁺ transport occurs differently in each cell type from hepatopancreas and is partially explained by the function the cells perform in this organ. Embryonic (E) and Resorptive (R) cells transported more Cd²⁺ compared to Fibrillar (F) and Blister (B) cells. R cells responded to Ca²⁺ channel inhibitors and intracellular Ca²⁺ manipulations positively, as the other cell types and in a stronger way. B cells were the least responsive to Ca²⁺ channel inhibitors and, unlike the other cells, showed a competition of Cd²⁺ with intracellular Ca²⁺ manipulations. The results indicate that Ca²⁺ affects the transport of Cd²⁺ in hepatopancreatic cells of Ucides cordatus and uses Ca²⁺ channels to enter these cells. In addition, information about Ca concentration could be used as a mitigating factor for Cd accumulation in crabs' hepatopancreas.

Hepatopancreatic cells of a stone crab Menippe frontalis from Perú: separation, viability study, and evaluation of lipoperoxidation against cadmium contamination

Crustaceans are frequently used as bioindicators, and changes in their metabolism at the hepatopancreas (HP) level are often followed in these studies. The HP is the site of digestion, absorption, nutrient storage, and toxic metal detoxification, enabling crabs to survive in metal contaminated regions. Cellular damage and high lipid peroxidation (LPO) levels have been found in crab populations under high cadmium (Cd) concentrations. The aim of this work was to separate and characterize the HP cells of the stone crab Menippe frontalis from the Pacific Ocean, Perú (5° 5' 21″ S-81° 6' 51″ W) and to measure the cellular viability and LPO after exposure to the non-essential metal Cd. The HP cells were dissociated by magnetic stirring, with posterior separation by sucrose gradient at concentrations of 10, 20, 30, and 40%. We found the same cell types that were described for other species (e.g., Ucides cordatus, Atlantic Ocean, Brazil). High cellular viability against 1 mmol L^-1 of Cd was observed for resorptive (R) cells in 20% sucrose layer (88 ± 8%, *P < 0.05, ANOVA), and blister (B) cells in the 40% sucrose layers (92 ± 7%, *P < 0.05, ANOVA). Cd (1 mmol L^-1) caused an increase in LPO levels, suggesting that crabs from polluted areas can be affected by toxic metals, generating a physiological stress. The gradient sucrose methodology can be used for different species and results in a similar separation, viability, and cellular identification. The results are a starting point for toxic metal studies for species distributed across different geographic coordinates.

Physiological differences in the crab Ucides cordatus from two populations inhabiting mangroves with different levels of cadmium contamination

Crustaceans found in metal-contaminated regions are able to survive, and the authors investigated the physiological mechanisms involved by comparing populations from contaminated and noncontaminated areas. The objective of the present study was to measure the cellular transport of a nonessential metal (cadmium [Cd]) in gills and hepatopancreas of Ucides cordatus, together with cell membrane fluidity, metallothionein levels, and lipid peroxidation. The 2 populations compared were from a polluted and a nonpolluted mangrove area of São Paulo State, Brazil. The authors found, for the first time, larger Cd transport in gills and hepatopancreatic cells from crabs living in polluted mangrove areas. The cells also had lower plasma membrane fluidity, increased lipid peroxidation and less metallothionein compared to those from nonpolluted regions. The authors also found larger amounts of Cd in intracellular organelles of gills, but not in the hepatopancreas, from crabs in polluted regions. Therefore, in polluted areas, these animals showed higher Cd transport and lower plasma membrane fluidity and storage of Cd intracellularly in gill cells, whereas hepatopancreatic cells used metallothionein as their main line of defense. The findings suggest that crabs from polluted areas can accumulate Cd more easily than crabs from nonpolluted areas, probably because of an impairment of the regulatory mechanisms of cell membrane transport. Environ Toxicol Chem 2017;36:361-371. © 2016 SETAC.

Characterization of cadmium plasma membrane transport in gills of a mangrove crab Ucides cordatus

Membrane pathway for intracellular cadmium (Cd(2+)) accumulation is not fully elucidated in many organisms and has not been studied in crab gill cells. To characterize membrane Cd(2+) transport of anterior and posterior gill cells of Ucides cordatus, a hypo-hyper-regulating crab, a change in intracellular Cd(2+) concentration under various experimental conditions was examined by using FluoZin, a fluorescent probe. The membrane Cd(2+) transport was estimated by the augmentation of FluoZin fluorescence induced by extracellular application of CdCl2 and different inhibitors. Addition of extracellular calcium (Ca(2+)) to the cells affected little the fluorescence of FluoZin, confirming that Cd(2+) was the main ion increasing intracellular fluorescence. Ca(2+) channels blockers (nimodipine and verapamil) decreased Cd(2+) influx as well as vanadate, a Ca(2+)-ATPase blocker. Chelating intracellular Ca(2+) (BAPTA) decreased Cd(2+) influx in gill cells, while increasing intracellular Ca(2+) (caffeine) augmented Cd influx. Cd(2+) and ATP added at different temporal conditions were not effective at increasing intracellular Cd(2+) accumulation. Ouabain (Na(+)/K(+)-ATPase inhibitor) increased Cd(2+) influx probably through a change in intracellular Na and/or a change in cell membrane potential. Routes of Cd(2+) influx, a non-essential metal, through the gill cell plasma membrane of crabs are suggested.