Prolonged effects of the insecticide dimethoate on locomotor behaviour in the woodlouse, Porcellio scaber Latr. (isopoda)

Avoidance behaviour toxicity tests should account for animal gregariousness: a case study on the terrestrial isopod Porcellioscaber

Avoidance behaviour enables woodlice to escape suboptimal environmental conditions and to mitigate harmful effects of pollutants. However, several studies have shown that at least in some woodlice species the tendency to aggregate can lead to suboptimal responses as the between-conspecific attraction can outweigh the aversive stimuli. The present study evaluated the influence of gregariousness on the behaviour of Porcellioscaber in a heterogeneously polluted environment. The hypothesis was that the tendency for aggregation outweighs the tendency for exploratory activity, therefore animals in groups will be less active. Consequently, this will affect their avoidance of polluted environmental patches. To test this hypothesis, isolated individuals or pairs of individuals were monitored in free-choice arenas where animals could select between uncontaminated and pyrethrin-contaminated soils. Animals were video recorded for 3 h in darkness using infrared light and analysed for avoidance behaviour and locomotor activity. In general, isolated animals were more locomotory active and avoided the contaminated soil more than paired animals. It can be concluded that aggregation behaviour suppresses exploratory behaviour and consequently also the avoidance of polluted environments. This should be accounted for when interpreting results of avoidance tests with groups of gregarious animals, which may underestimate the effect of pollutants.

Effects of Wolf Spiders’ Captive Environment on Their Locomotor and Exploratory Behaviours

Simple Summary

Since the 1960s, abuses of domestic and of wild animals that have been tamed or are held in captivity have been legally prohibited and laws ensure their well-being. Many scientific investigations carried out in this context recommend ways to adapt farming and thus to avoid physical and/or psychological suffering. Evaluations of animals’ welfare in captivity entail the need to understand in detail the fundamental behaviours of the focus species and to know the degree of their variation to be able to establish objective bases that can ensure breeding conditions that respect the animals’ welfare. Current laws do not apply to invertebrate animals (such as insects or spiders) and consideration of the welfare of these animals in captivity is neglected. Here, I compared the behaviour of wild adult spiders just after collection and that of adult spiders hatched and bred in the laboratory. My results show that captivity induced rapid changes of wild spiders’ behaviour once in captivity. Therefore, it is important to establish the best breeding conditions for the needs of both invertebrate and vertebrate animals in order to promote their well-being.

Abstract

Here I detail the effects of the abiotic/captive environment of an adult wandering spider, Pardosa saltans (Lycosidae) on its behaviour. These studies focused on spiders collected as adults in their natural environment and spiders developed in the laboratory under controlled conditions. Wild-caught spiders were tested either immediately after capture or after being housed for 15 days post-collection. Laboratory reared spiders were kept in different environments: small or large space combined with the presence or absence of litter. Two tests evaluated by sex show the influence of these rearing conditions: an open-field test and a radial-arm maze test. The results show that wild caught spiders of both sexes tested immediately after capture weighed significantly less and were significantly more active than spiders housed in the laboratory for 15 days and spiders reared in the laboratory. Laboratory conditions induced a positive impact on body mass and negative impact on behaviour activities. The locomotor and exploratory activities of spiders of both sexes kept in container without substrate showed lower. My results suggest that the physical enrichment of the environment can reduce these negative effects for females, but not for males that seem to be more affected by being reared under controlled conditions.

Behavioural effects of the neonicotinoid insecticide thiamethoxam on the predatory insect Platynus assimilis

Little information is available regarding sublethal effects of neonicotinoids on insect predators, many of which perform important roles in ecosystem functioning and biocontrol. In this study, dose-dependent sublethal effects of a dietary administered neonicotinoid insecticide thiamethoxam on two basic behaviours, locomotion and feeding, were quantified in the carabid Platynus assimilis (Coleoptera, Carabidae) using automated video-tracking and weighing of consumed food, respectively. Acute toxicity tests showed that, when orally administered, the LD₅₀ of thiamethoxam for P. assimilis beetles was 114.5 ng/g. Thiamethoxam at 108.1 ng/g caused a short-term locomotor hyperactivity within several hours of treatment. Next day after exposure to the insecticide, all the beetles were in a state of locomotor hypoactivity independent of the administered dose ranging from 1.1 to 108.1 ng/g. Reduction in clean food consumption rate (CFCR) is another altered behavioural endpoint of poisoned insect predators as first demonstrated in this study. On the first day of thiamethoxam administration, a remarkable reduction in feeding only occurred in beetles treated at 108.1 ng/g but on the next day, this negative effect appeared even at doses ten to a hundred-fold lower. Recovery from locomotion abnormalities and reduced feeding took several days. Both locomotor activity and CFCR are sensitive and valuable ecotoxicological biomarkers of carabids which should be taken into account in Integrated Pest Management programs where optimal combination of reduced insecticide use and biological control by predatory insects is crucial to achieve best results.

Sub-lethal effects of the neurotoxic pyrethroid insecticide Fastac 50EC on the general motor and locomotor activities of the non-targeted beneficial carabid beetle Platynus assimilis (Coleoptera: Carabidae)

BACKGROUND

Sub-lethal effects of pesticides on behavioural endpoints are poorly studied in carabids (Coleoptera: Carabidae) though changes in behaviour caused by chemical stress may affect populations of these non-targeted beneficial insects. General motor activity and locomotion are inherent in many behavioural patterns, and changes in these activities that result from xenobiotic influence mirror an integrated response of the insect to pesticides. Influence of pyrethroid insecticides over a wide range of sub-lethal doses on the motor activities of carabids still remains unclear.

RESULTS

Video tracking of Platynus assimilis showed that brief exposure to alpha-cypermethrin at sub-lethal concentrations ranged from 0.01 to 100 mg L(-1) caused initial short-term (< 2 h) locomotor hyperactivity followed by a long-term (>24 h) locomotor hypo-activity. In addition, significant short- and long-term concentration and time-dependent changes occurred in general motor activity patterns and rates.

CONCLUSION

Conspicuous changes in motor activity of Platynus assimilis beetles treated at alpha-cypermethrin concentrations up to 75,000-fold lower than maximum field recommended concentration (MFRC) suggest that many, basic fitness-related behaviours might be severely injured as well. These changes may negatively affect carabid populations in agro-ecosystems. Long-term hypo-activity could directly contribute to decreased trap captures of carabids frequently observed after insecticide application in the field.

Joint effects of three plant protection products to the terrestrial isopod Porcellionides pruinosus and the collembolan Folsomia candida

The effects of simultaneous application of plant protection products are of concern since the uses of different products pose an additional risk to non-target soil organisms. The effects of binary combinations of dimethoate, glyphosate and spirodiclofen, an insecticide an herbicide and an acaricide, on the avoidance behaviour of the terrestrial isopod Porcellionides pruinosus and the reproductive effort of Folsomia candida were assessed using the two reference models of concentration addition (CA) and independent action (IA). Results of single exposure to the three pesticides indicated a clear dose related avoidance response of the isopods in the highest concentrations tested of the three as well as a strong decrease in collembolan adult survival and concomitant number of juveniles produced. In the combined experiments, antagonism was found in 7 out of the 12 combinations, four combinations followed the reference models, and only in one combination synergism was detected (lower doses of glyphosate and spirodiclofen applied to P. pruinosus). In conclusion, it seems that mixing and applying these products, at the recommended field application rate, does not lead to enhanced toxicity, hence limited risk is associated with the joint application of these pesticides.

Assessing joint toxicity of chemicals in Enchytraeus albidus (Enchytraeidae) and Porcellionides pruinosus (Isopoda) using avoidance behaviour as an endpoint

Contamination problems are often characterized by complex mixtures of chemicals. There are two conceptual models usually used to evaluate patterns of mixture toxicity: Concentration Addition (CA) and Independent Action (IA). Deviations from these models as synergism, antagonism and dose dependency also occur. In the present study, single and mixture toxicity of atrazine, dimethoate, lindane, zinc and cadmium were tested in Porcellionides pruinosus and Enchytraeus albidus, using avoidance as test parameter. For both species patterns of antagonism were found when exposed to dimethoate and atrazine, synergism for lindane and dimethoate exposures (with the exception of lower doses in the isopod case study) and concentration addition for cadmium and zinc occurred, while the exposure to cadmium and dimethoate showed dissimilar patterns. This study highlights the importance of dose dependencies when testing chemical mixtures and that avoidance tests can also be used to asses the effects of mixture toxicity.

Toxicity of organophosphates on morphology and locomotor behavior in brine shrimp, Artemia salina

The acute toxicity and hatching success of four organophosphorus insecticides--acephate (ACEP), chlorpyrifos (CPP), monocrotophos (MCP), and profenofos (PF)--was studied in a short-term bioassay using brine shrimp, Artemia salina. Fifty percent hatchability inhibition concentration and median lethal concentration (LC(50)) values were calculated after probit transformation of the resulting data. Among the insecticides tested, CPP is found to be the most toxic and also to inhibit hatching success of A. salina cysts in a concentration-dependent manner. In addition, the effect of these pesticides on locomotor behavior (swimming speed) and morphologic differences were studied in LC(50)-exposed nauplii after 24 hours. The in vivo effect of these insecticides on acetylcholinesterase (Enzyme commission number (EC 3.1.1.7) activity was also determined in LC(50)-exposed nauplii after 24 hours. Maximum percent decrease in their swimming speed and significant morphologic alterations were noticed in CPP-exposed brine shrimps. The order of toxicity was CPP > PF > MCP > ACEP in all the parameters studied.

Effect of chlorpyrifos and monocrotophos on locomotor behaviour and acetylcholinesterase activity of subterranean termites, Odontotermes obesus

The acute toxicity of chlorpyrifos and monocrotophos to subterranean termites, Odontotermes obesus (Rambur), has been studied by a paper contact method. The LC50 values for chlorpyrifos and monocrotophos were 0.046 and 0.148 microg cm(-2), respectively. Chlorpyrifos was 3.22-fold more toxic than monocrotophos. The effect of the pesticides on locomotor behaviour (velocity) and head acetylcholinesterase (AChE: EC 3.1.1.7) activity was estimated in LC50-exposed termites at intervals of 4, 8, 12, 16, 20 and 24 h. Chlorpyrifos- and monocrotophos-treated termites showed, respectively, 97 and 88% reduction in locomotor behaviour (velocity) after 24 h. At all time intervals the chlorpyrifos-treated termites exhibited more AChE inhibition and showed greater distorted behaviour than those exposed to monocrotophos. In vitro studies indicated that the I50 value (50% inhibition) for chlorpyrifos against AChE was 8.75 times that of monocrotophos.

Optimization of culture conditions of Porcellio dilatatus (Crustacea: Isopoda) for laboratory test development

This paper describes the experimental results for optimizing isopod culture conditions for terrestrial ecotoxicity testing. The influence of animal density and food quality on growth and reproduction of Porcellio dilatatus was investigated. Results indicate that density influences isopod performance in a significant way, with low-density cultures having a higher growth rate and better reproductive output than medium- or high-density cultures. Alder leaves, as a soft nitrogen-rich species, were found to be the best-quality diet; when compared with two other food mixtures, alder leaves induced the best results, particularly in terms of breeding success. Guidance regarding culture conditions of isopod species, especially in terms of culture density and diet, is given.

Guppy sexual behavior as an effect biomarker of estrogen mimics

There is widespread concern that some environmental chemicals can reduce the reproductive capability of humans and wildlife by mimicking natural estrogens and disrupting endocrine function. This potential threat to animal populations posed by xenoestrogens has, hardly surprisingly, been met by an intensive global effort to identify and develop biomarkers suitable for screening chemicals for estrogen mimicking capacity. Despite this effort, there are few biomarkers capable of linking exposure to xenoestrogens to impaired reproductive capability. The reproductive success of most animals depends strongly on the ability to perform the appropriate sexual behavior. The sexual display of the male guppy is strongly linked to reproductive success and is readily quantified under laboratory conditions. This preliminary study demonstrates that exposure of adult male guppies to water weakly contaminated with either natural estrogen (17beta-estradiol) or the xenoestrogen (4-tert-octylphenol) causes a dramatic decrease in the rate and intensity of sexual display. It is concluded that quantitative analysis of the sexual display of male guppies holds great promise as a biomarker at the organismal level for the effects of estrogen mimicking xenobiotics.

Evaluation of hyperactivity produced by pyrethroid treatment on third instar nymphs of Triatoma infestans (Hemiptera:Reduviidae)

The hyperactivity produced in third instar nymphs of Triatoma infestans by their exposure to films of deltamethrin or cis-permethrin was evaluated. Both pyrethroids produced a significant increase in locomotor activity at 26 and 36 degrees C but not at 16 degrees C. At 26 degrees C, only deltamethrin produced hyperactivity when topically applied on the dorsal side of the nymph's abdomen. However, both pyrethroids produced hyperactivity when topically applied on the head of the nymphs. Hyperactivity was not observed when nymphs were treated with N-ethylmaleimide (20 micrograms/insect) before exposure to the pyrethroids. The effect of both insecticides on locomotor activity reversed the inhibitory influence on locomotion elicited by contact with the walls of the experimental arena (thigmotaxis).

Pesticide uptake and locomotor behaviour in the woodlouse: an experimental study employing video tracking and (14)C-labelling

: The toxicity of soil pesticide residues to target and non-target organisms depends on the amount of chemical absorbed by the organism. One of the principle factors governing chemical uptake is the amount of chemical encountered by the animal and, hence, the area of soil contacted. This in turn, depends on the locomotor behaviour of the animal. In the present study, the relationship between the uptake of soil residues of an organophosphate insecticide and locomotor behaviour was examined, employing (14)C-labelled dimethoate and computer-aided video tracking. Groups of male woodlice, Porcellio scaber (Isopoda), walked freely for 22 h on a soil substrate treated with three application rates of the pesticide. A strong correlation was found between pesticide uptake and path length, mean velocity and time spent in locomotor acivity, which is consistent with previously reported modelling studies. Our data suggest a linear relationship for all locomotor parameters except for path length at the highest application rate, where uptake was best described by an inverse exponential relationship. All doses induced hyperactivity in terms of time spent in locomotor activity. However, when compared with a untreated control group, the most pronounced effects were displayed at the lowest dose where path length, mean velocity and turning rate were also significantly different. The number of shifts between locomotor active and inactive periods in the experimental period increased with increasing application rate.