Behavioural, developmental and morphological responses of Chironomus gr. thummi larvae (Diptera, Nematocera) to aquatic pollution

Biological responses of midge (Chironomus riparius) and lamprey (Lampetra fluviatilis) larvae in ecotoxicity assessment of PCDD/F-, PCB- and Hg-contaminated river sediments

We evaluated the utility of chironomid and lamprey larval responses in ecotoxicity assessment of polychlorinated dibenzo-p-dioxins, dibenzofurans (PCDD/F)-, polychlorinated biphenyls (PCB)- and mercury (Hg)-contaminated river sediments. Sediment samples were collected from the River Kymijoki with a known industrial pollution gradient. Sediment for the controls and lamprey larvae were obtained from an uncontaminated river nearby. Contamination levels were verified with sediment and tissue PCDD/F, PCB and Hg analyses. Behaviour of sediment-exposed chironomid and lamprey larvae were measured with Multispecies Freshwater Biomonitor© utilizing quadrupole impedance conversion technique. In addition, mortality, growth and head capsule deformity incidence of chironomids were used as ecotoxicity indicators. WHOPCDD/F+PCB-TEQ in the R. Kymijoki sediments ranged from the highest upstream 22.36 ng g(-1) dw to the lowest 1.50 ng g(-1) near the river mouth. The sum of PCDD/Fs and PCBs correlated strongly with Hg sediment concentrations, which ranged from <0.01 to 1.15 μg g(-1). Lamprey tissue concentrations of PCDD/Fs were two orders and PCBs one order of magnitude higher in the R. Kymijoki compared to the reference. Chironomid growth decreased in contaminated sediments and was negatively related to sediment ∑PCDD/Fs, WHOPCDD/F+PCB-TEQ and Hg. There were no significant differences in larval mortality or chironomid mentum deformity incidence between the sediment exposures. The distinct behavioural patterns of both species indicate overall applicability of behavioural MFB measurements of these species in sediment toxicity bioassays. Chironomids spent less and lampreys more time in locomotion in the most contaminated sediment compared to the reference, albeit statistically significant differences were not detected. Lamprey larvae had also a greater activity range in some of the contaminated sediments than in the reference. High pollutant levels in lamprey indicate risks for biomagnification in the food webs, with potential health risks to humans consuming fish.

Effects of inbreeding on mouthpart deformities of Chironomus riparius under sublethal pesticide exposure

Mouthpart deformities in chironomids have been reported to indicate adverse effects of environmental pollutants. The authors assessed rates of mouthpart deformities in tributyltin-exposed, inbred, and outcrossed Chironomus riparius larvae over multiple generations. The authors found that the occurrence of mouthpart deformities was significantly correlated with inbreeding, whereas no correlation was found with the tributyltin exposure. The present study confirms the strong effect of high inbreeding rates on developmental deformities in chironomids.

Effects of mercury on growth, emergence, and behavior of Chironomus riparius Meigen (Diptera: Chironomidae)

Mercury is a pervasive toxicant that can be found in the environment due to anthropogenic activity as well as natural sources. The majority of studies in freshwater environments focus mainly on bioaccumulation, population dynamics, and biomagnification. Here, we study the effects of mercuric chloride on Chironomus riparius Meigen, simulating a mercury discharge on a freshwater ecosystem. Growth, emergence, development time, and behavior were the end points assessed. Growth was measured after 8 days of exposure and behavior was recorded on days 4 and 10 of the experimental period. The behavioral responses of C. riparius to different mercury treatments were recorded with an online biomonitor, which allows a more objective and precise behavioral understanding than visual observation. Mercury exposure resulted in reductions in growth and emergence, a delayed development time, and a decrease in locomotor activity of the larvae. Our results demonstrate that mercury exposure can impair life-history responses of chironomids.

Assessing toxicity of the insecticide thiacloprid on Chironomus riparius (Insecta: Diptera) using multiple end points

Since data documentation on neonicotinic toxicity to nontarget organisms should be enhanced, we investigate the effects of thiacloprid, a novel neonicotinoid insecticide, on the sediment-dwelling nontarget insect Chironomus riparius. Further, we wanted to validate the sensitivity of end points on different biological levels and obtain the greatest amount of information regarding the effects of this compound by using a battery of several end points such as larval mortality, behavior, body weight gain, emergence rate, time of development, gender ratio, Hsp70 stress protein level, and larval mouthpart deformities after exposure at a concentration range of 0.1 to 1000 microg/L thiacloprid. C. riparius was impacted starting at concentrations of 0.5 microg/L, a concentration that can be considered environmentally relevant. Larval mortality, behavior, emergence, and Hsp70 protein level were sensitive indicators for the toxic effect of thiacloprid, whereas gender ratio and mouthpart morphology were not affected. In our case life-cycle end points like survival rate (LC(50): 1.57 microg/L) and emergence rate (EC(50): 0.54 microg/L) proved to be more sensitive than tested physiological end points for the neurotoxic insecticide.

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.

The infochemical effect-a new chapter in ecotoxicology

BACKGROUND, AIM, AND SCOPE

Organisms use chemical cues in their surrounding, so-called infochemicals, as important source of information about their biotic and abiotic environment. The scope of this work is to transfer the knowledge on infochemicals obtained in chemical ecology into ecotoxicology, compare the observations with ecotoxicological standard tests, with other sublethal effects, and deduce consequences for the legal situation of environmental chemicals.

MAIN FEATURES

General principles were elaborated from the compiled information from literature on the structures and roles of natural infochemicals. The experiences gained in chemical ecology and in ecotoxicology led to the discovery of the infochemical effect: Anthropogenic substances can influence the chemical communication of environmental organisms. This finding is supported by a close look at fragrances and other common anthropogenic substances in the environment.

RESULTS

Increasing scientific knowledge shows how complex the chemical communication of environmental organisms is. Infochemicals are released by senders and detected by receivers. The relevant concentrations of infochemicals are very low, usually in the nano- to micromolar range and they do not seem to have common structural features. Knowledge about natural infochemicals is still poor and not consistent. The chemical cues fluctuate specifically in time and space resulting in dynamic response patterns in the ecosystem. Organisms can react to infochemicals in very specific ways by behavioral, morphological, or physiological responses; activities that are relevant for their survival as vital reactions such as flight, food uptake, or mating are affected. Anthropogenic substances at minor concentrations can interfere in the complex chemical communication web of infochemicals, possibly leading to increased vulnerability of populations.

DISCUSSION

The findings show clearly that the actual description of the interplay of organisms in the ecosystem is still very simplified and we are far from understanding the interactions completely. Anthropogenic discharges may play a role on the chemical communication and, hence, on the behavior and interactions of organisms in the ecosystem. The description of the infochemical effect opens a new chapter in ecotoxicology. It is a challenge to develop a suitable test system for the infochemical effect with the knowledge of the multitude of possible reactions and of the high specificity of infochemicals. Problems during the performance and evaluation of standard tests might be related to reactions due to infochemicals in the test systems which have not been considered so far.

CONCLUSIONS

The roles of anthropogenic infochemicals in the environment and the role of natural infochemicals in laboratory tests have been underestimated up to now.

RECOMMENDATIONS AND PERSPECTIVES

The discrepancy between the biological relevance and the lack of data about infochemicals in the environment reveals the necessity of further research. According to the actual findings, infochemicals are so decisive for the interactions in the ecosystem that they should not be neglected in ecotoxicology. The discovery of the infochemical effect is comparable to the detection that environmental substances can act as hormones. Sublethal effects with impacts on the ecosystem, such as the infochemical effect, will receive higher appraisal in the ecotoxicology of the future. It needs to be clarified to which extent anthropogenic discharges disturb the natural chemical communication web. A systematic analysis of this very complex field will be needed to know whether a new ecotoxicological endpoint, the infochemical effect, will have to be taken up in the standard repertoire. The knowledge on infochemicals might require some adjustments of the legal framework on environmental chemicals in future. Looking closer at the infochemical effect will lead to a new understanding of the complexity of environmental communities.

Antennal deformities of chironomid larvae and their use in biomonitoring of heavy metal pollutants in the river Damodar of West Bengal, India

Analyses of sediment and water indicate the presence of heavy metal pollutants like lead, zinc, copper, mercury and cadmium of the river Damodar of India. These metals are responsible for causing morphological deformities of antennae and other parts of chironomid larvae. Percentage of deformity correlated positively with the concentrations of Pb in water and sediment (r > 0.6) at the confluence point. A new severity index, SISS((antenna)) has been proposed here to assess deformity at the family or subfamily level.

Behavioural early warning responses to polluted water : Performance ofGammarus pulex L. (Crustacea) andHydropsyche angustipennis (Curtis) (Insecta) to a complex industrial effluent

Behavioural early warning responses to polluted surface water from an industrial effluent have been measured in two freshwater macroinvertebrate species using the four electrode impedance conversion technique. Specimens ofGammarus pulex (L.) andHydropsycho angustipennis (Curtis) were caught from reference streams and exposed to water from above and below the factory and to reference water for about 1 h with different kinds of behaviour being registered on-line every 10 min, such as time spent on locomotion, number of "high swimming peaks", number of activity phases, cleaning, time spent on ventilation, ventilation frequency and netspinning. Additionally, G.pulex was exposedin situ above and 100 m, 500 m and 1000 m below the factory for 24 h.G.pulex reacted to water pollution within 1 h with less time spent on locomotion, fewer "high swimming peaks" and lower number of activity phases (p < 0.01). The same results were found after thein situ exposure (p < 0.05) and the pollution gradient mirrored survival and behavioural performance of the organisms.H. angustipennis reacted to water pollution within 1 h with decreased time spent on ventilation (p < 0.001), no change in locomotion and netspinning during daytime. During the night, exposure to water pollution resulted in increased locomotion (p < 0.0001).Simultaneous multispecies on-line biomonitoring of industrial effluents is recommended for reliable risk assessment.