Neonicotinoid insecticide low doses effects on the olfactory system of the lepidopteran crop pest, Agrotis ipsilon

Durant leur cycle de vie, les insectes doivent faire face à différents perturbateurs pour réussir à survivre et à se reproduire. L’utilisation de plus en plus répandue des insecticides néonicotinoïdes, en raison de leur grande efficacité, a conduit à l’accumulation de résidus dans l’environnement. Ceux-ci ont certainement un effet additif toxique sur les insectes cibles. Cependant il a été montré que ces résidus peuvent aussi avoir un effet positif non désiré sur certains traits de vie des insectes ravageurs.Dans ma thèse, j’ai étudié les effets d’un insecticide néonicotinoïde sur le système olfactif d’un insecte ravageur, la noctuelle Agrotis ipsilon. Nos résultats montrent que l’exposition aigüe des mâles à des faibles doses de clothianidine modifie leurs réponses comportementales à la phéromone sexuelle: une baisse est observée à la dose 0,25 ng/insecte (<DL0) alors que la doses de 10 ng (DL20) induit une augmentation de la réponse chez les adultes naïfs ou pré-exposés à la phéromone. Cet effet biphasique à faible et très faible dose s’apparente à un effet hormétique et les modifications observées sont corrélées avec des changements de sensibilité du système olfactif central et non périphérique. Nous émettons l’hypothèse que la clothianidine agirait sur l’expression des sous-unités des récepteurs nicotiniques pour lesquels elle joue le rôle d’agoniste, changeant leur affinité pour l’acétylcholine et perturbant ou améliorant la transmission synaptique des signaux sensoriels selon la dose. Nos résultats montrent que la prise en compte d’effets de doses sublétales d’insecticides est essentielle non seulement pour les insectes non cibles, mais aussi des insectes cibles.Insects face a multitude of environmental stresses, which they have to bypass in order to survive and reproduce. The extensive use of neonicotinoid insecticides, because of their high efficiency, leads to the accumulation of residues in the environment, which can have an additive toxic effect on target insects. However, such residues can also have unwanted positive effects on certain life traits of pest insects. In my thesis I studied the effects of a neonicotinoid insecticide on the olfactory system of the pest insect Agrotis ipsilon. Our results show that acute oral treatments of males with low doses of clothianidin modify their behavioural responses to the sex pheromone: a treatment with 0.25 ng/moth (<LD0) induces a decrease of pheromone responses whereas intoxication with 10 ng/moth (LD20) leads to an increase in the capacity of naive and pre-exposed males to locate a pheromone source as compared to controls. We propose that this biphasic effect, with low dose stimulation and very low dose inhibition is an hormeticlike effect, that is correlated with sensitivity changes within the central, but not the peripheral olfactory system. We hypothesize that the observed modifications might be due to a differential effect of clothianidin on the expression of different subunits of nicotinic acetylcholine receptors, which might change the affinity of the receptors for acetylcholine, and thus disturb or improve synaptic transmission of sensory signals as a function of the insecticide dose. Our results show that effects of sublethal doses of insecticides need to be taken into account not only for non-target, but also for target insects when evaluating pest management strategies

Effet de faibles doses d'un insecticide néonicotinoïde sur le système olfactif d'un lépidoptère de ravageur des cultures, Agrotis ipsilon

Insects face a multitude of environmental stresses, which they have to bypass in order to survive and reproduce. The extensive use of neonicotinoid insecticides, because of their high efficiency, leads to the accumulation of residues in the environment, which can have an additive toxic effect on target insects. However, such residues can also have unwanted positive effects on certain life traits of pest insects. In my thesis I studied the effects of a neonicotinoid insecticide on the olfactory system of the pest insect Agrotis ipsilon. Our results show that acute oral treatments of males with low doses of clothianidin modify their behavioural responses to the sex pheromone: a treatment with 0.25 ng/moth (<LD0) induces a decrease of pheromone responses whereas intoxication with 10 ng/moth (LD20) leads to an increase in the capacity of naive and pre-exposed males to locate a pheromone source as compared to controls. We propose that this biphasic effect, with low dose stimulation and very low dose inhibition is an hormeticlike effect, that is correlated with sensitivity changes within the central, but not the peripheral olfactory system. We hypothesize that the observed modifications might be due to a differential effect of clothianidin on the expression of different subunits of nicotinic acetylcholine receptors, which might change the affinity of the receptors for acetylcholine, and thus disturb or improve synaptic transmission of sensory signals as a function of the insecticide dose. Our results show that effects of sublethal doses of insecticides need to be taken into account not only for non-target, but also for target insects when evaluating pest management strategies.Durant leur cycle de vie, les insectes doivent faire face à différents perturbateurs pour réussir à survivre et à se reproduire. L’utilisation de plus en plus répandue des insecticides néonicotinoïdes, en raison de leur grande efficacité, a conduit à l’accumulation de résidus dans l’environnement. Ceux-ci ont certainement un effet additif toxique sur les insectes cibles. Cependant il a été montré que ces résidus peuvent aussi avoir un effet positif non désiré sur certains traits de vie des insectes ravageurs.Dans ma thèse, j’ai étudié les effets d’un insecticide néonicotinoïde sur le système olfactif d’un insecte ravageur, la noctuelle Agrotis ipsilon. Nos résultats montrent que l’exposition aigüe des mâles à des faibles doses de clothianidine modifie leurs réponses comportementales à la phéromone sexuelle: une baisse est observée à la dose 0,25 ng/insecte (<DL0) alors que la doses de 10 ng (DL20) induit une augmentation de la réponse chez les adultes naïfs ou pré-exposés à la phéromone. Cet effet biphasique à faible et très faible dose s’apparente à un effet hormétique et les modifications observées sont corrélées avec des changements de sensibilité du système olfactif central et non périphérique. Nous émettons l’hypothèse que la clothianidine agirait sur l’expression des sous-unités des récepteurs nicotiniques pour lesquels elle joue le rôle d’agoniste, changeant leur affinité pour l’acétylcholine et perturbant ou améliorant la transmission synaptique des signaux sensoriels selon la dose. Nos résultats montrent que la prise en compte d’effets de doses sublétales d’insecticides est essentielle non seulement pour les insectes non cibles, mais aussi des insectes cibles

Reliability of the tunisian pediatric gait, arms, legs, and spine: toward a valid screening tool for tunisian children with musculoskeletal conditions

Abstract Background Pediatric musculoskeletal disorders account for 10% of first-line consultations in Tunisia. Referral delay and deficiencies in musculoskeletal screening raise a challenge to the early diagnosis and management of rheumatic conditions in children. The pGALS (Pediatric Gait Arms Legs Spine) was developed and translated into many languages to overcome these deficiencies. Our study aimed to adapt and validate pGALS to the Tunisian dialect for school-age children. Methods Using the Delphi method, we carried out a cross-cultural adaptation of the pGALS to the Tunisian dialect. This consensual version was validated in a cross-sectional study, in two pediatric centers. Results Ninety-two patients were enrolled, 43 females (46.7%) and 49 males (53.3%), mean age was 9.4 ± 2.6 years. The mean test duration was 3.4 ± 2.3 min, and the acceptability and comprehension of the test were good. Six patients had a musculoskeletal complaint, 19 had positive pGALS, and 14 were diagnosed with musculoskeletal disease. The internal consistency score (Cronbach’s α) was 0.852. The sensitivity of the test was 92.8%, the specificity was 92.3%, the positive likelihood ratio was 2.16, and the negative likelihood ratio was 0.01. Conclusion The pGALS test adapted to the Tunisian dialect is a relevant, quick, and valid tool for screening musculoskeletal abnormalities in school-age children

Effects of subletal doses of a neonicotinoid insecticide on the olfactory system of the moth Agrotis ipsilon

International audienc

An insecticide further enhances experience-dependent increased behavioural responses to sex pheromone in a pest insect

Neonicotinoid insecticides are widely used to protect plants against pest insects, and insecticide residues remaining in the environment affect both target and non-target organisms. Whereas low doses of neonicotinoids have been shown to disturb the behaviour of pollinating insects, recent studies have revealed that a low dose of the neonicotinoid clothianidin can improve behavioural and neuronal sex pheromone responses in a pest insect, the male moth Agrotis ipsilon, and thus potentially improve reproduction. As male moth behaviour depends also on its physiological state and previous experience with sensory signals, we wondered if insecticide effects would be dependent on plasticity of olfactory-guided behaviour. We investigated, using wind tunnel experiments, whether a brief pre-exposure to the sex pheromone could enhance the behavioural response to this important signal in the moth A. ipsilon at different ages (sexually immature and mature males) and after different delays (2 h and 24 h), and if the insecticide clothianidin would interfere with age effects or the potential pre-exposure-effects. Brief pre-exposure to the pheromone induced an age-independent significant increase of sex pheromone responses 24 h later, whereas sex pheromone responses did not increase significantly 2 h after exposure. However, response delays were significantly shorter compared to naive males already two hours after exposure. Oral treatment with clothianidin increased sex pheromone responses in sexually mature males, confirming previous results, but did not influence responses in young immature males. Males treated with clothianidin after pre-exposure at day 4 responded significantly more to the sex pheromone at day 5 than males treated with clothianidin only and than males pre-exposed only, revealing an additive effect of experience and the insecticide. Plasticity of sensory systems has thus to be taken into account when investigating the effects of sublethal doses of insecticides on behaviour

Effect of the 10-ng and 0.25-ng low doses of clothianidin on oriented responses (A) and general flight activity (B) of <i>A. ipsilon</i> males in presence of a linden flower extract.

<p>Responses to the linden flower extract were not significantly different between clothianidin- and DMSO-treated males for both 0.25 ng and 10 ng clothianidin. N>50 for all groups, G-test, P<0.05.</p

Effect of low doses of clothianidin on oriented responses of <i>A. ipsilon</i> males towards a 20-ng sex pheromone blend.

<p>The percentage of responses of clothianidin-treated males divided by that of DMSO-treated males is represented. The 0.25-ng dose induced a significant decrease in oriented responses whereas the 10-ng dose induced a significant increase in sex pheromone oriented responses. Bars with same letters are not significantly different (G-test, P<0.05). The dashed line represents an equal response of males treated with clothianidine and the corresponding DMSO dose. N>50 for all groups.</p

Effect of pheromone pre-exposure on pheromone responses of <i>A</i>. <i>ipsilon</i> males of different ages tested 24 h after treatment.

<p>One-day-, 4-day- and 5-day-old males were pre-exposed for 3 min with 10 ng of the pheromone blend, and their oriented response to a 1 ng pheromone blend was analyzed in wind tunnel experiments 24 h later (D2-PE1, D5-PE4 and D6-PE5 respectively). Unexperienced 2-day-, 5-day- and 6-day-old males (D2, D5, and D6 males respectively) were used as controls. <b>(A)</b> Percentage of males showing oriented response. <b>(B)</b> Response delay and standard deviation of males showing oriented responses. The lower whisker presents the minimum, the lower hinge of the box is the first quartile, the line inside the box is the median, the upper hinge is the third quartile, and the extreme of the upper whisker is the maximum. Oriented pheromone responses are increased 24 h after brief pre-exposure independently of age. Numbers in bars indicate the numbers of males tested (A) and the number of males that showed an oriented response (B). Bars with the same letter are not significantly different (G-test for (A), Mann-Whitney test for (B), P < 0.05).</p

Effect of the combined treatment of pre-exposure and clothianidin on pheromone responses of 5-day-old <i>A</i>. <i>ipsilon</i> males.

<p>Four-day-old males were pre-exposed with 10 ng of the pheromone blend and subsequently orally treated with 10 ng of clothianidin. Behavioural responses to 1 ng of the pheromone blend were observed in the wind tunnel 24 h later (D5-PE4-CLO). Unexperienced and solvent-treated males, as well as pre-exposure- or clothianidin-treated males were used as controls. <b>(A)</b> Percentage of males showing oriented response. <b>(B)</b> Response delay and standard deviation of males showing oriented responses. The lower whisker presents the minimum, the lower hinge of the box is the first quartile, the line inside the box is the median, the upper hinge is the third quartile, and the extreme of the upper whisker is the maximum. Clothianidin further enhances oriented pheromone responses of <i>A</i>. <i>ipsilon</i> males after brief pre-exposure. Numbers in bars indicate the numbers of males tested (A) and number of males that showed an oriented response (B). Bars with the same letter are not significantly different (G-test for (A), Mann-Whitney test for (B), P < 0.05).</p

Design of experiments.

<p>Treatments were performed on 1-day-, 4-day-, and 5-day-old males, and behavioral tests in wind tunnel were performed either the same day of treatment or 24 h later. Test: behavioral test in wind tunnel.</p