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The hypothesis that the inter-individual parameter variability is an unexploited area of ecotoxicology was proposed several decades ago. Although some illustrative examples were presented to support this hypothesis in the last decades, it has never been tested on an extensive, coherent database. In this study, variance changes of 105 dose-response curves were analysed. All data originated from the same experiment, where the effects of the insecticide Trebon EC were investigated in a dose-response manner on 15 traits of the collembolan Folsomia candida in four subsequent generations and two types of insecticide treatments. A consistent relationship between inter-individual variance and insecticide application was found in 2 (first clutch size and growth-reproduction trade-off) out of the 15 of the parameters. Contrary to the mean, the variance of the first clutch size showed consistent differences compared to the control. Furthermore, the variance of the growth-reproduction trade-off was consistently different from the control except in one case (F3 generation of the transgenerational treatment). Higher first clutch size variances were found in F1 and a lower one in the F2 and F3 generations than in that of the control. This overall pattern of the variance changes of the first clutch size and the trade-off seems to be a quick response to the insecticide application. In the short term, we have found that variance increased with insecticide treatment (P and F1 generation), because phenotypic variance generally increases due to environmental stress. Disruptive selection could be another mechanism between the more detoxification less reproduction strategy and the more reproduction less detoxification strategy. However, in the later generations (F2-F3) the variance decreases compared to the control, which could be because on short term selection stronger on the viability parameters and in long-term selection on reproduction becomes stronger. According to our results, analysis of the variance changes of some parameters may give information about the effects of the pesticide even when the mean does not predict any impact. Testing variance changes are important in ecotoxicology because variance change can signalise toxicant impact even when the mean does not change in certain cases.

The standard OECD tests for Folsomia candida should be performed on the standard OECD soil. However, if it is necessary to measure more parameters than the juvenile number and mortality, the use of different substrates is necessary. But these substrates can modify the results of the experiments comparing to the standard OECD soil, resulting in different toxicity values. In our research, we tested the toxicity of an insecticide, Trebon® 10F to F. candida (Collembola). We tested the dose-dependent effect of Trebon® 10F on the egg number and the egg size on the substrates of (i) plaster of Paris mixed with activated charcoal and (ii) in standard OECD soil on two generation of collembolas. Similarly to our previous study, the insecticide had a dose-dependent negative effect on the parent’s egg size in the OECD soil, but on plaster of Paris, no response was found. The egg number did not show any response to the treatments. On the contrary, in the offspring generation, the egg size increased both in OECD and plaster of Paris tests. In the soil test, parent collembolas laid significantly more eggs, while the offspring laid much fewer, compared to the plaster of Paris test. Similar results were found in the case of egg size. In the soil test parent collembolas laid larger, while the offspring laid smaller eggs, compared to the plaster of Paris test. In multigenerational tests (i) Trebon 10F could affect the different generations in the opposite way. The experiment performed on the plaster of Paris (ii) could underestimate toxicity compared to the OECD soil test. This should be taken into account when Ecotoxicologists interpret their data.

Environmental toxicants such as insecticides are able to provoke epigenetic alterations which can be inherited to future generations. The aim of the current study was to assess whether the insecticide Trebon 10F (containing the active ingredient etofenprox) causes multigenerational and/or transgenerational effects on the egg traits of the collembolan Folsomia candida. The parent generation was kept in soil treated with three concentrations of the insecticide. The hatched offspring from each treatment were divided into two groups and were treated in the same manner as their parents (multigenerational effect), or remained untreated (transgenerational effect). The parents reacted with smaller eggs to the insecticide in a concentration dependent manner. Both multigenerational and transgenerational effects were detected in the offspring generations. While neither the number of eggs nor the ratios of the egg diameters (shortest/longest diameter) changed, the egg size increased as the Trebon 10F concent...

Chronic exposure of soil animals with insecticides over multiple generations can induce modifications to their life-history. Moreover, insecticide effects over generations may be substantially different if subsequent generations get direct exposure repeatedly (multigenerational effect), or direct exposure affects only the parent generation, but the subsequent ones not (transgenerational effect). These are essential but understudied aspects of the environmental risk assessment. The present study assessed the multi- and transgenerational effects of the insecticide Trebon® 30 EC (active ingredient etofenprox) on 15 life-history traits (initial length, final length, absolute growth, total number of eggs, number of clutches, time of maturation, ratio of egg diameters, egg volume, unhatched ratio, reproduction investment, mortality, food consumption, velocity, movement energy, growth-reproduction trade-off) of the collembolan Folsomia candida Willem, 1902 in a four-generation long laboratory study. In the multigenerational treatment, all four generations were treated by the insecticide, while in the transgenerational one, only the parent generation was treated, but the consecutive three generations were not. When a generation was treated with the insecticide, six sublethal concentrations of the Trebon® 30 EC (0, 0.766, 1.303, 2.215, 3.765, and 6.4 ml insecticide L−1 water) were applied to see dose-response effects. In the multigenerational treatment, dose-dependent effects of the insecticide were pronounced from the parent to the F2 generation, with high mortality, especially in the highest concentration. Conversely, in the transgenerational treatment the most effects on life-history traits were found in the F3 generation. The results show that in the multigenerational treatment, either the population becomes resistant, or it could compensate for the effects of the insecticide in the long term. In the F1 generation, the number of eggs and clutches decreased, the mortality increased, and the growth-reproduction trade-off shifted in the direction of growth. Rather similar results were found in the F2 generation, with the difference that all animals died in that case if the insecticide was applied for consecutive generations repeatedly, and five to eight times higher than the recommended field concentration (0.766–1.303 ml L−1). Furthermore, our experiment detected evidence of an apparent transgenerational effect. While in the F1 and F2 generation of the transgenerational treatment, few effects were found, in the F3 generation, 10 out of the 15 traits showed a dose-response relationship. This finding indicates the long-term transgenerational effects of the Trebon® 30 EC insecticide on several F. candida life-history traits. We concluded that the influence of both treatment methods on life-history traits is strong but appreciably distinct. Our results support the view that transgenerational epigenetic heritability should be taken into account in environmental risk assessment.

Zn uptake by maize plants may be affected by the presence of arbuscular mycorrhizal fungi (AMF). Collembola often play an important controlling role in the inter-relationship between AMF and host plants. The objective of this experiment was to examine whether the presence of Collembola at different densities (0.4 and 1 individuals g−1 dry soil) and their activity have any effect on Zn uptake by maize through the plant–AMF system. The presence of the AMF (Glomus intraradices) and of the Collembola species Folsomia candida was studied in a laboratory microcosm experiment, applying a Zn exposure level of 250 mg kg−1 dry soil. Biomass and water content of the plants were no different when only AMF or when both AMF and Collembola were present. In the presence of AMF the Zn content of the plant shoots and roots was significantly higher than without AMF. This effect was reduced by Collembola at both low and high density. High densities of Collembola reduced the extent of AMF colonization of the plant roots and hyphal length in the soil, but low densities had no effect on either. The results of this experiment reveal that the F. candida–G. intraradices interaction affects Zn uptake by maize, but the mechanisms are still unknown.

The effect of long-term feeding on Bt-maize by collembolans in the laboratory is virtually unestablished. That is why the aim of the present study was to test whether the reproduction, fecal pellet production or food preference of the collembolan F. candida is affected when fed on Bt-maize for several consecutive generations. The collembolans were fed with Bt-maize for 0, 6, 16 and 22 months and the number of eggs and fecal pellets were determined. The experiment was repeated seven months later with the same populations. Food preference tests were additionally performed. Significant differences were found in food consumption, egg production and food preference between populations in some cases, but no time-response effect was observed. In conclusion, several generations feeding of F. candida on Cry1Ab toxin containing Bt-maize seems not to be harmful to this collembolan species.