The chronic toxicity of fenoxycarb to larvae of the grass shrimp,Palaemonetes pugio

Abstract

This study examined effects of fenoxycarb, a carbamate insecticide, on larvae of the grass shrimp, Palaemonetes pugio. In laboratory experiments, grass shrimp larvae were exposed to fenoxycarb from hatch to postlarval metamorphosis in a chronic, static renewal bio assay. LC50's ranged from 0.92 mg/L at 96 h to 0.35 mg/L at the end of the study (24 days). In assessing sublethal effects of fenoxycarb, postlarval emergence was significantly (p < 0.05) reduced in exposed grass shrimp as compared with controls, and the time to reach postlarval status was significantly (p < 0.05) increased in exposed grass shrimp. Significant differences were not found in other sublethal parameters including postlarval dry weight and intermolt duration. Analysis of fenoxycarb from spiked seawater samples showed concentrations declined by 32 to 42% after 24 h.     

Simulation of a Hazardous and Noxious Substances (HNS) spill in the marine environment: Lethal and sublethal effects of acrylonitrile to the European seabass

Despite the extensive maritime transportation of Hazardous and Noxious Substances (HNS), there is a current lack of knowledge on the effects posed by HNS spills on the marine biota. Among the HNS identified as priority, acrylonitrile was selected to conduct ecotoxicological assays. We assessed the acute and subletal effects of acrylonitrile in seabass, followed by a recovery phase to simulate the conditions of a spill incident. The work aimed at testing a broad range of biological responses induced by acrylonitrile. Sublethal exposure to the highest two doses increased the fish mortality rate (8.3% and 25% mortality in 0.75 and 2 mg L⁻¹ acrylonitrile concentrations), whereas no mortality were observed in control and 0.15 mg L⁻¹ treatments. Additionally, important alterations at sub-individual level were observed. Acrylonitrile significantly induced the activities of Catalase– CAT and Glutathione S-Transferase – GST; and the levels of DNA damage were significantly increased. Conversely, Superoxide Dismutase– SOD – activity was found to be significantly inhibited and no effects were found on Lipid Peroxidation– LPO and ethoxyresorufin O-deethylase – EROD – activity. Following a 7 d recovery period, the levels of CAT, GST and EROD fell to levels at or below those in the control. In the 2 mg L⁻¹ group, SOD remained at the levels found during exposure phase. This study has gathered essential information on the acute and subletal toxicity of acrylonitrile to seabass. It also demonstrated that 7 d recovery allowed a return of most endpoints to background levels. These data will be useful to assist relevant bodies in preparedness and response to HNS spills.     

A new challenge—development of test systems for the infochemical effect

Background, aim, and scope

Many—if not all—organisms depend on so-called infochemicals, chemical substances in their surroundings which inform the receivers about their biotic and abiotic environment and which allow them to react adequately to these signals. Anthropogenic substances can interfere with this complex chemical communication system. This finding is called infochemical effect. So far, it is not known to what extent anthropogenic discharges act as infochemicals and influence life and reproduction of organisms in the environment because adequate testing methods to identify chemicals which show the infochemical effect and to quantify their effects have not been developed yet. The purpose of this article is to help and find suitable test designs.

Main features

Test systems used in basic research to elucidate the olfactory cascade and the communication of environmental organisms by infochemicals are plentiful. Some of them might be the basis for a quantified ecotoxicological analysis of the infochemical effect. In principle, test systems for the infochemical effect could be developed at each step of the chemosensory signal transduction and processing cascade.

Results

Experimental set-ups were compiled systematically under the aspect whether they might be usable for testing the infochemical effect of single chemicals in standardized quantifying laboratory experiments. For an appropriate ecotoxicological assessment of the infochemical effect, experimental studies of many disciplines, such as molecular biology, neurobiology, physiology, chemical ecology, and population dynamics, should be evaluated in detail before a decision can be made which test system, respectively which test battery, might be suited best. The test systems presented here are based on the knowledge of the genetic sequences for olfactory receptors, binding studies of odorants, signal transmission, and reactions of the receivers on the level of the organisms or the populations. The following basic approaches are conceivable to identify the role of an infochemical: binding studies to the odorant-binding protein or to the odorant receptor binding protein (e.g., by in situ hybridization and immunohistochemical studies), measurement of electrical signals of the receptor cells in the tissue (e.g., electroolfactograms, electroantennograms), registration of phenotypic changes (e.g., observation under the microscope), behavioral tests (e.g., in situ online biomonitoring, use of T-shaped olfactometers, tests of avoidance responses), measurement of population changes (e.g., cell density or turbidity measurements), and multispecies tests with observation of community structure and community function. The main focus of this study is on aquatic organisms.

Discussion

It is evident that the infochemical effect is a very complex sublethal endpoint, and it needs further studies with standardized quantitative methods to elucidate whether and to what extent the ecosystem is affected. The collection of approaches presented here is far from being complete but should serve as a point of depart for further experimental research.

Conclusions

This article is the first to compare various approaches for testing the infochemical effect. The development of a suitable test system will not be easy as there are a multitude of relevant chemicals, a multitude of relevant receptors, and a multitude of relevant reactions, and it must be expected that the effective concentrations are very low. The chemical communication is of utmost importance for the ecosystem and justifies great endeavors to find solutions to these technical problems.

Recommendations and perspectives

The infochemical effect is a new chapter in ecotoxicology. Will a new endpoint, the so-called infochemical effect, be required in addition to the actual standard test battery of Annex 5 to Commission Directive 92/69/EEC (EC 1992)? Finding the answer to this question is a big challenge that could be met by a comprehensive research project.     

Oxidative stress and changes in locomotor behavior and gill morphology of Gambusia affinis exposed to chromium

Sublethal effects of chromium trioxide on mosquito fish, Gambusia affinis, were carried out for 28 days on day 4, 8, 12, 16, 20, 24, and 28. The sublethal effects of chromium (LC₁₀, 77.62?mg?L^?1) on antioxidant enzymes, thiobarbituric acid reactive substance (TBARS), locomotor behavior, and gill morphology were studied. The antioxidant enzymes like superoxide dismutase (SOD) and catalase were induced throughout the exposure span of 28 days. Percent induction was also increase with the days of exposure. Lipid peroxidation product, malondialdehyde was enhanced in the viscera tissue of chromium-exposed fish. Perturbation of locomotor behavior like decrease in distance travelled (m?min^?1) and in swimming speed (cm?s^?1) was observed in exposed fish. Chromium toxicity caused alterations in gill morphology like hypertrophy and hyperplasia in secondary lamellae followed by detached epithelium with severe necrosis. It can be concluded from the results that Cr intoxication in Gambusia fish, caused induction in antioxidant enzymes and lipid peroxidation, plus changes in gill morphology and locomotor behavior.     

Copper oxide nanoparticles can induce toxicity to the freshwater shredder Allogamus ligonifer

Increased commercialisation of nanometal-based products augments the possibility of their deposition into aquatic ecosystems; this, in turn, may pose risks to aquatic biota and associated ecological functions. Freshwater invertebrate shredders mostly use microbially-colonized plant litter as food resource and play an important role in aquatic detritus food webs. We assessed lethal effects of nanoCuO on the shredder Allogamus ligonifer (Trichoptera, Limnephilidae) by determining the concentration that induced 50% of death (LC₅₀), and sublethal effects of nanoCuO on the feeding behaviour and growth of the shredder by exposing the animals to: (i) stream water supplemented with nanoCuO and microbially-colonized leaves, and (ii) stream water (without nanoCuO) and microbially-colonized leaves pre-exposed to nanoCuO. Results from acute lethal tests showed that the 96 h LC₅₀ of nanoCuO was very high (569 mg L⁻¹). In the absence of nanoparticles, leaf consumption rate was 0.27 mg leaf DM mg⁻¹ animal DM d⁻¹ and the shredder growth rate was 56 μg animal DM mg⁻¹ animal DM d⁻¹. A significant inhibition in leaf consumption rate (up to 47%) and invertebrate growth rate (up to 46%) was observed when shredders were exposed to the higher tested sublethal concentration of nanoCuO (75 mg L⁻¹) through either contaminated stream water or pre-contaminated food. The exposure to increased nanoCuO concentration via water or pre-contaminated food led to higher accumulation of copper in the larval body. Leached water-soluble ionic copper from the nanoCuO adsorbed or accumulated in the shredder (up to 10.2% of total Cu) seemed to influence the feeding behaviour and growth of the shredder.     

Malathion-induced sublethal toxicity on the intestine of cricket frog (Fejervarya limnocharis)

The effect of malathion [diethyl(dimethoxythiophosphorylthio)succinate] at sublethal concentration (0.006 ppm) on intestinal parameters of cricket frog (Fejervarya limnocharis) was studied for 24 hrs to 240 hrs of exposure and remarkable histopathological alterations were observed. The study on intestinal parameters revealed acute pathological conditions in the intestinal wall. The toxic effect became evident as the cytoplasm of the cells disintegrated and the cells became empty and vacuolated. The cell membranes were also ruptured. Degenerative changes of the absorptive surface (villi) of the intestine in the different periods of exposure were pronounced. Severe atrophic nature (necrotic mucosa) of the intestine began from 48 hrs onwards to 96 hrs of exposure.     

Effects of previous sublethal pulse to ammonium nitrate on mortality and total length on Epidalea calamita larvae

Ammonium nitrate is one of the most widespread contaminants related with the viability of natural amphibian populations. In this study we have evaluated in terms of mortality and total length the effects that a previous sublethal pulse to ammonium nitrate generates in Epidalea calamita. Experiments were divided in two phases. In the first one, tadpoles were exposed to two different treatments, with and without a low ammonium nitrate concentration (22 mg NH₄NO₃ L⁻¹). The second phase consisted in static toxicity experiments from both origin treatments with five different nominal concentrations (0, 22, 45, 90 and 180 mg NH₄NO₃ L⁻¹). Results showed that tadpoles that had experienced a previous sublethal exposure showed a negative effect on survival (57% of reduction in the LC₅₀ value) and total length, throughout an increase in their sensitivity. These results could help us to understand the situation of amphibian populations inhabiting aquatic ecosystems exposed to discontinuous and variable pulses of pollutants.     

Effects of mercury on behavior and performance of northern two-lined salamanders (Eurycea bislineata)

Mercury (Hg) causes a range of deleterious effects in wildlife, but little is known about its effects on amphibians. Our objective was to determine whether Hg affects performance and behavior in two-lined salamanders (Eurycea bislineata). We collected salamanders from Hg-contaminated and reference sites and assessed speed, responsiveness, and prey capture ability. Mercury concentrations were >17× higher in salamanders from the contaminated sites and were among the highest documented in amphibians. In the first, but not in the second, locomotion trial, we found a significant effect of Hg on speed and responsiveness. In the prey capture experiment, reference salamanders ate approximately twice as many prey items as the contaminated salamanders. Together, our results suggest that sublethal Hg concentrations may negatively affect salamanders by reducing their ability to successfully execute tasks critical to survival. Future work is warranted to determine whether Hg has other sublethal effects on salamanders and whether other amphibians are similarly affected.     

Malathion-induced sublethal toxicity on the hematology of cricket frog (Fejervarya limnocharis)

The effect of malathion [diethyl(dimethoxythiophosphorylthio)succinate] at sublethal concentration (0.006 ppm) on hematological parameters of the cricket frog (Fejervarya limnocharis) was studied for 24 hrs to 240 hrs of exposure and remarkable hematological alterations were observed. The study on hematological parameters revealed a highly significant decrease (P < 0.01) in the total erythrocytes count in malathion-exposed animals from 24 hours to 96 hrs of exposure as compared to control. Significant decreases (P < 0.01) of hemoglobin and packed cell volume were also observed from 48 hrs to 240 hrs. A significant increase (P < 0.01) in leucocytes count was noted throughout the exposure period. Elevated numbers of lymphocytes and eosinophils as found in the present study revealed lymphocytosis as well as eosinophilia, suggesting that this was a result of direct stimulation of the immunological defense due to the presence of a toxic substance or may be associated with tissue damage. The cytomorphological and cytopathological study of erythrocytes and leucocytes in malathion-exposed frogs at 0.006 ppm concentration revealed various cytotoxic effects at different exposure times. It was noted that the size and the shape of the erythrocytes were subjected to variation in different blood disorders.