James Devillers

Ecotoxicity of Neonicotinoid Insecticides to Bees

This chapter reviews the available data on the toxicity of neonicotinoid insecticides to bees that are the prominent and the most economically important group of pollinators worldwide. Classical and new methods developed to take into account the characteristics and different types of effects of the neonicotinoid insecticides to bees are described. The available toxicity results are critically analyzed. Thus, the nitro-substituted compounds (clothianidin, dinotefuran, imidacloprid and its metabolites, thiamethoxam, nitenpyram) appear the most toxic to bees. The cyano-substituted neonicotinoids seem to exhibit a much lower toxicity (acetamiprid and thiacloprid). The chapter ends with suggestions for additional studies aiming at better assess the hazard of this important insecticide family to bees.

Honeybee tracking with microchips: a new methodology to measure the effects of pesticides

Losses of foraging bees are sometimes attributed to altered flight pattern between a meliferous plant treated with an insecticide and the hive. Only a limited number of studies has investigated the impact of pesticides on homing flight due to the difficulty of measuring the flight time between the food source and the hive. Monitoring the flights of the foraging bees needs their individual identification. The number of bees monitored simultaneously and the time span during which observations can be made limit most of the monitoring techniques. However, techniques of automatic tracking and identification of individuals have the potential to revolutionize the study of the ecotoxicological effects of xenobiotics on the bee behaviors. Radio Frequency Identification (RFID) offer numerous advantages such as an unlimited number of codes, a large number of simultaneous recording, and a quick reading, especially through materials (e.g., wood). The aim of this study was to show how the RFID device can be used to study the effects of pesticides on both the behavioral traits and the lifespan of bees. In this context, we have developed a method under tunnel to automatically record the displacements of foragers individualized with RFID tags and to detect the alteration of the flight pattern between an artificial feeder and the hive. Fipronil was selected as test substance due to the lack of information on the effects of this insecticide on the foraging behavior of free-flying bees. We showed that oral treatment of 0.3xa0ng of fipronil per bee (LD50/20) reduced the number of foraging trips. The strengths of our approach were briefly discussed.

Larval Exposure to the Juvenile Hormone Analog Pyriproxyfen Disrupts Acceptance of and Social Behavior Performance in Adult Honeybees.

Background Juvenile hormone (JH) plays an important role in honeybee development and the regulation of age-related division of labor. However, honeybees can be exposed to insect growth regulators (IGRs), such as JH analogs developed for insect pest and vector control. Although their side effects as endocrine disruptors on honeybee larval or adult stages have been studied, little is known about the subsequent effects on adults of a sublethal larval exposure. We therefore studied the impact of the JH analog pyriproxyfen on larvae and resulting adults within a colony under semi-field conditions by combining recent laboratory larval tests with chemical analysis and behavioral observations. Oral and chronic larval exposure at cumulative doses of 23 or 57 ng per larva were tested. Results Pyriproxyfen-treated bees emerged earlier than control bees and the highest dose led to a significant rate of malformed adults (atrophied wings). Young pyriproxyfen-treated bees were more frequently rejected by nestmates from the colony, inducing a shorter life span. This could be linked to differences in cuticular hydrocarbon (CHC) profiles between control and pyriproxyfen-treated bees. Finally, pyriproxyfen-treated bees exhibited fewer social behaviors (ventilation, brood care, contacts with nestmates or food stocks) than control bees. Conclusion Larval exposure to sublethal doses of pyriproxyfen affected several life history traits of the honeybees. Our results especially showed changes in social integration (acceptance by nestmates and social behaviors performance) that could potentially affect population growth and balance of the colony.

Interspecies Correlations for Predicting the Acute Toxicity of Xenobiotics

LD50 tests on rat and mouse are commonly used to express the relative hazard associated with the acute toxicity of new and existing substances. These tests are expensive, time consuming, and actively fought by Animal Rightists. Consequently, there is a need to find alternative methods. If the design of QSAR models can be used as surrogate, the search for interspecies correlations also represents a valuable alternative to the classical mammalian laboratory tests. In this chapter, the different toxicityu200b = u200b f(ecotoxicity) models available in the literature were first critically analyzed. In a second step, a strong bibliographical investigation was performed to collect oral, intraperitoneal, and intravenous rat and mouse LD50 data for a large collection of structurally diverse chemicals. In the meantime, EC50 data on Vibrio fischeri (MicrotoxTM test) and Daphnia magna were also retrieved from literature. Numerous oral, intraperitoneal, and intravenous rat and mouse toxicity models were derived using Vibrio fischeri and Daphnia magna as independent variables alone or together through a stepwise regression analysis. Most of the models on Daphnia magna were totally new and some of them presented acceptable quality. They outperformed the MicrotoxTM models. The usefulness of the 1-octanol/water partition coefficient (log P) as additional independent variable was also tested. The interest of nonlinear statistical tools for deriving toxicityu200b = u200b f (ecotoxicity) models was also experienced.

Use of Multicriteria Analysis for Selecting Ecotoxicity Tests

It is now well admitted that a battery of ecotoxicity tests should be designed by accounting for the requirements of a specific scenario such as classification of wastes or remediation efficiency of contaminated soils. The development of a single battery of tests for all applications is thereafter recognized not to be relevant. The selection of tests for constituting a battery may be established according to expert judgments, decision criteria such as cost, ecological relevance, sensitivity of selected organisms, standardization of the methods, implementation of the test protocols or after statistical analysis of test results obtained on a large series of bioassays. In this chapter, a methodological framework, based on the combination of an original multicriteria method called SIRIS and multivariate analyses, is presented for selecting ecotoxicity tests for assessing the level of contamination of soils. The interest of this approach that simultaneously accounts for ecological, technical, and economical constraints is discussed.