26 research outputs found
Impacts des polluants métalliques sur l'abeille : de la colonie au cerveau
Les abeilles sont des pollinisateurs essentiels. Une plĂ©thore de facteurs de stress environnementaux, tels que les produits agrochimiques, a Ă©tĂ© identifiĂ©e comme contribuant Ă leur dĂ©clin mondial. En particulier, ces facteurs de stress altĂšrent les processus cognitifs impliquĂ©s dans les comportements fondamentaux. Jusqu'Ă prĂ©sent, cependant, on ne sait pratiquement rien de l'impact de l'exposition Ă des mĂ©taux lourds, dont la toxicitĂ© est avĂ©rĂ©e chez de nombreux organismes. Pourtant, leurs Ă©missions mondiales rĂ©sultant des activitĂ©s humaines ont Ă©levĂ© leurs concentrations bien au-dessus des niveaux naturels dans l'air, le sol, l'eau et la flore, exposant ainsi les abeilles Ă tous les stades de leur vie. Le but de ma thĂšse Ă©tait d'examiner les effets de la pollution mĂ©tallique sur l'abeille domestique en utilisant une approche multi-Ă©chelle, du cerveau Ă la colonie, en laboratoire et sur le terrain. J'ai d'abord observĂ© que les abeilles exposĂ©es Ă une gamme de concentrations de trois mĂ©taux communs (arsenic, plomb et zinc) en laboratoire Ă©taient incapables de percevoir et Ă©viter des concentrations usuelles, nĂ©anmoins nocives, de ces mĂ©taux dans leur nourriture. J'ai ensuite exposĂ© de façon chronique des colonies Ă des concentrations rĂ©alistes de plomb dans la nourriture et dĂ©montrĂ© que la consommation de ce mĂ©tal altĂ©rait la cognition et le dĂ©veloppement morphologique des abeilles. Comme les polluants mĂ©talliques se trouvent souvent dans des mĂ©langes complexes dans l'environnement, j'ai explorĂ© l'effet des cocktails de mĂ©taux, montrant que l'exposition au plomb, Ă l'arsenic ou au cuivre seul Ă©tait suffisante pour ralentir l'apprentissage et perturber le rappel de la mĂ©moire, et que les combinaisons de ces mĂ©taux induisaient des effets nĂ©gatifs additifs sur ces deux processus cognitifs. J'ai finalement Ă©tudiĂ© l'impact de l'exposition naturelle aux polluants mĂ©talliques dans un environnement contaminĂ©, en collectant des abeilles Ă proximitĂ© d'une ancienne mine d'or, et montrĂ© que les individus des populations les plus exposĂ©es aux mĂ©taux prĂ©sentaient des capacitĂ©s d'apprentissage et de mĂ©moire plus faibles, et des altĂ©rations de leur dĂ©veloppement conduisant Ă une rĂ©duction de la taille de leur cerveau. Une analyse plus systĂ©matique des abeilles non exposĂ©es a rĂ©vĂ©lĂ© une relation entre la taille de la tĂȘte, la morphomĂ©trie du cerveau et les performances d'apprentissage dans diffĂ©rentes tĂąches comportementales, suggĂ©rant que l'exposition aux polluants mĂ©talliques amplifie ces variations naturelles. Ainsi, mes rĂ©sultats suggĂšrent que les abeilles domestiques sont incapables d'Ă©viter l'exposition Ă des concentrations rĂ©alistes de mĂ©taux qui sont prĂ©judiciables au dĂ©veloppement et aux fonctions cognitives, et appellent Ă une rĂ©vision des niveaux environnementaux considĂ©rĂ©s comme "sĂ»rs". Ma thĂšse est la premiĂšre analyse intĂ©grĂ©e de l'impact de plusieurs polluants mĂ©talliques sur la cognition, la morphologie et l'organisation cĂ©rĂ©brale chez l'abeille, et vise Ă encourager de nouvelles Ă©tudes sur la contribution de la pollution mĂ©tallique dans le dĂ©clin signalĂ© des abeilles, et plus gĂ©nĂ©ralement, des insectes.Honey bees are crucial pollinators. A plethora of environmental stressors, such as agrochemicals, have been identified as contributors to their global decline. Especially, these stressors impair cognitive processes involved in fundamental behaviours. So far however, virtually nothing is known about the impact of metal pollutants, despite their known toxicity to many organisms. Their worldwide emissions resulting from human activities have elevated their concentrations far above natural baselines in the air, soil, water and flora, exposing bees at all life stages. The aim of my thesis was to examine the effects of metallic pollution on honey bees using a multiscale approach, from brain to colonies, in laboratory and field conditions. I first observed that bees exposed to a range of concentrations of three common metals (arsenic, lead and zinc) in the laboratory were unable to perceive and avoid, low, yet harmful, field-realistic concentrations of those metals in their food. I then chronically exposed colonies to field-realistic concentrations of lead in food and demonstrated that consumption of this metal impaired bee cognition and morphological development, leading to smaller adult bees. As metal pollutants are often found in complex mixtures in the environment, I explored the effect of cocktails of metals, showing that exposure to lead, arsenic or copper alone was sufficient to slow down learning and disrupt memory retrieval, and that combinations of these metals induced additive negative effects on both cognitive processes. I finally investigated the impact of natural exposure to metal pollutants in a contaminated environment, by collecting bees in the vicinity of a former gold mine, and showed that individuals from populations most exposed to metals exhibited lower learning and memory abilities, and development impairments conducing to reduced brain size. A more systematic analysis of unexposed bees revealed a relationship between head size, brain morphometrics and learning performances in different behavioural tasks, suggesting that exposure to metal pollutants magnifies these natural variations. Hence, altogether, my results suggest that honey bees are unable to avoid exposure to field-realistic concentrations of metals that are detrimental to development and cognitive functions; and call for a revision of the environmental levels considered as 'safe'. My thesis is the first integrated analysis of the impact of several metal pollutants on bee cognition, morphology and brain structure, and should encourage further studies on the contribution of metal pollution in the reported decline of honey bees, and more generally, of insects
Contrasting coral community structures between natural and artificial substrates at Koh Tao, Gulf of Thailand
Concrete cubic frames and decommissioned steel naval vessels have been deployed in Thailand liberally to act as artificial substrates for coral restoration and marine recreation. We assessed recruitment at such substrate types at Koh Tao, Gulf of Thailand, and compared the community structure of scleractinian corals between artificial substrates and nearby natural reefs. Our results from a sample of 2677 recruits from nine sites highlighted significant differences in community structure between both reef types. Investigations of variables including time since deployment, distance from the natural reef, and seafloor depth revealed only the latter as a possible influencing factor. The diversity of recruits could not be explained by dynamics in coral spawning, and were found to represent groups with lower structural complexity. Our results suggest that coral community structure on artificial and natural reefs differs and supports distinct ecological and functional roles
Impacts des polluants mĂ©talliques sur lâabeille : de la colonie au cerveau
Honey bees are crucial pollinators. A plethora of environmental stressors, such as agrochemicals, have been identified as contributors to their global decline. Especially, these stressors impair cognitive processes involved in fundamental behaviours. So far however, virtually nothing is known about the impact of metal pollutants, despite their known toxicity to many organisms. Their worldwide emissions resulting from human activities have elevated their concentrations far above natural baselines in the air, soil, water and flora, exposing bees at all life stages. The aim of my thesis was to examine the effects of metallic pollution on honey bees using a multiscale approach, from brain to colonies, in laboratory and field conditions. I first observed that bees exposed to a range of concentrations of three common metals (arsenic, lead and zinc) in the laboratory were unable to perceive and avoid, low, yet harmful, field-realistic concentrations of those metals in their food. I then chronically exposed colonies to field-realistic concentrations of lead in food and demonstrated that consumption of this metal impaired bee cognition and morphological development, leading to smaller adult bees. As metal pollutants are often found in complex mixtures in the environment, I explored the effect of cocktails of metals, showing that exposure to lead, arsenic or copper alone was sufficient to slow down learning and disrupt memory retrieval, and that combinations of these metals induced additive negative effects on both cognitive processes. I finally investigated the impact of natural exposure to metal pollutants in a contaminated environment, by collecting bees in the vicinity of a former gold mine, and showed that individuals from populations most exposed to metals exhibited lower learning and memory abilities, and development impairments conducing to reduced brain size. A more systematic analysis of unexposed bees revealed a relationship between head size, brain morphometrics and learning performances in different behavioural tasks, suggesting that exposure to metal pollutants magnifies these natural variations. Hence, altogether, my results suggest that honey bees are unable to avoid exposure to field-realistic concentrations of metals that are detrimental to development and cognitive functions; and call for a revision of the environmental levels considered as âsafeâ. My thesis is the first integrated analysis of the impact of several metal pollutants on bee cognition, morphology and brain structure, and should encourage further studies on the contribution of metal pollution in the reported decline of honey bees, and more generally, of insects.Les abeilles sont des pollinisateurs essentiels. Une plĂ©thore de facteurs de stress environnementaux, tels que les produits agrochimiques, a Ă©tĂ© identifiĂ©e comme contribuant Ă leur dĂ©clin mondial. En particulier, ces facteurs de stress altĂšrent les processus cognitifs impliquĂ©s dans les comportements fondamentaux. Jusqu'Ă prĂ©sent, cependant, on ne sait pratiquement rien de l'impact de lâexposition Ă des mĂ©taux lourds, dont la toxicitĂ© est avĂ©rĂ©e chez de nombreux organismes. Pourtant, leurs Ă©missions mondiales rĂ©sultant des activitĂ©s humaines ont Ă©levĂ© leurs concentrations bien au-dessus des niveaux naturels dans l'air, le sol, l'eau et la flore, exposant ainsi les abeilles Ă tous les stades de leur vie. Le but de ma thĂšse Ă©tait d'examiner les effets de la pollution mĂ©tallique sur lâabeille domestique en utilisant une approche multi-Ă©chelle, du cerveau Ă la colonie, en laboratoire et sur le terrain. J'ai d'abord observĂ© que les abeilles exposĂ©es Ă une gamme de concentrations de trois mĂ©taux communs (arsenic, plomb et zinc) en laboratoire Ă©taient incapables de percevoir et Ă©viter des concentrations usuelles, nĂ©anmoins nocives, de ces mĂ©taux dans leur nourriture. J'ai ensuite exposĂ© de façon chronique des colonies Ă des concentrations rĂ©alistes de plomb dans la nourriture et dĂ©montrĂ© que la consommation de ce mĂ©tal altĂ©rait la cognition et le dĂ©veloppement morphologique des abeilles. Comme les polluants mĂ©talliques se trouvent souvent dans des mĂ©langes complexes dans l'environnement, j'ai explorĂ© l'effet des cocktails de mĂ©taux, montrant que l'exposition au plomb, Ă l'arsenic ou au cuivre seul Ă©tait suffisante pour ralentir l'apprentissage et perturber le rappel de la mĂ©moire, et que les combinaisons de ces mĂ©taux induisaient des effets nĂ©gatifs additifs sur ces deux processus cognitifs. J'ai finalement Ă©tudiĂ© l'impact de l'exposition naturelle aux polluants mĂ©talliques dans un environnement contaminĂ©, en collectant des abeilles Ă proximitĂ© d'une ancienne mine d'or, et montrĂ© que les individus des populations les plus exposĂ©es aux mĂ©taux prĂ©sentaient des capacitĂ©s d'apprentissage et de mĂ©moire plus faibles, et des altĂ©rations de leur dĂ©veloppement conduisant Ă une rĂ©duction de la taille de leur cerveau. Une analyse plus systĂ©matique des abeilles non exposĂ©es a rĂ©vĂ©lĂ© une relation entre la taille de la tĂȘte, la morphomĂ©trie du cerveau et les performances d'apprentissage dans diffĂ©rentes tĂąches comportementales, suggĂ©rant que l'exposition aux polluants mĂ©talliques amplifie ces variations naturelles. Ainsi, mes rĂ©sultats suggĂšrent que les abeilles domestiques sont incapables d'Ă©viter lâexposition Ă des concentrations rĂ©alistes de mĂ©taux qui sont prĂ©judiciables au dĂ©veloppement et aux fonctions cognitives, et appellent Ă une rĂ©vision des niveaux environnementaux considĂ©rĂ©s comme «sĂ»rs». Ma thĂšse est la premiĂšre analyse intĂ©grĂ©e de l'impact de plusieurs polluants mĂ©talliques sur la cognition, la morphologie et lâorganisation cĂ©rĂ©brale chez lâabeille, et vise Ă encourager de nouvelles Ă©tudes sur la contribution de la pollution mĂ©tallique dans le dĂ©clin signalĂ© des abeilles, et plus gĂ©nĂ©ralement, des insectes
Impacts des polluants mĂ©talliques sur lâabeille : de la colonie au cerveau
Honey bees are crucial pollinators. A plethora of environmental stressors, such as agrochemicals, have been identified as contributors to their global decline. Especially, these stressors impair cognitive processes involved in fundamental behaviours. So far however, virtually nothing is known about the impact of metal pollutants, despite their known toxicity to many organisms. Their worldwide emissions resulting from human activities have elevated their concentrations far above natural baselines in the air, soil, water and flora, exposing bees at all life stages. The aim of my thesis was to examine the effects of metallic pollution on honey bees using a multiscale approach, from brain to colonies, in laboratory and field conditions. I first observed that bees exposed to a range of concentrations of three common metals (arsenic, lead and zinc) in the laboratory were unable to perceive and avoid, low, yet harmful, field-realistic concentrations of those metals in their food. I then chronically exposed colonies to field-realistic concentrations of lead in food and demonstrated that consumption of this metal impaired bee cognition and morphological development, leading to smaller adult bees. As metal pollutants are often found in complex mixtures in the environment, I explored the effect of cocktails of metals, showing that exposure to lead, arsenic or copper alone was sufficient to slow down learning and disrupt memory retrieval, and that combinations of these metals induced additive negative effects on both cognitive processes. I finally investigated the impact of natural exposure to metal pollutants in a contaminated environment, by collecting bees in the vicinity of a former gold mine, and showed that individuals from populations most exposed to metals exhibited lower learning and memory abilities, and development impairments conducing to reduced brain size. A more systematic analysis of unexposed bees revealed a relationship between head size, brain morphometrics and learning performances in different behavioural tasks, suggesting that exposure to metal pollutants magnifies these natural variations. Hence, altogether, my results suggest that honey bees are unable to avoid exposure to field-realistic concentrations of metals that are detrimental to development and cognitive functions; and call for a revision of the environmental levels considered as âsafeâ. My thesis is the first integrated analysis of the impact of several metal pollutants on bee cognition, morphology and brain structure, and should encourage further studies on the contribution of metal pollution in the reported decline of honey bees, and more generally, of insects.Les abeilles sont des pollinisateurs essentiels. Une plĂ©thore de facteurs de stress environnementaux, tels que les produits agrochimiques, a Ă©tĂ© identifiĂ©e comme contribuant Ă leur dĂ©clin mondial. En particulier, ces facteurs de stress altĂšrent les processus cognitifs impliquĂ©s dans les comportements fondamentaux. Jusqu'Ă prĂ©sent, cependant, on ne sait pratiquement rien de l'impact de lâexposition Ă des mĂ©taux lourds, dont la toxicitĂ© est avĂ©rĂ©e chez de nombreux organismes. Pourtant, leurs Ă©missions mondiales rĂ©sultant des activitĂ©s humaines ont Ă©levĂ© leurs concentrations bien au-dessus des niveaux naturels dans l'air, le sol, l'eau et la flore, exposant ainsi les abeilles Ă tous les stades de leur vie. Le but de ma thĂšse Ă©tait d'examiner les effets de la pollution mĂ©tallique sur lâabeille domestique en utilisant une approche multi-Ă©chelle, du cerveau Ă la colonie, en laboratoire et sur le terrain. J'ai d'abord observĂ© que les abeilles exposĂ©es Ă une gamme de concentrations de trois mĂ©taux communs (arsenic, plomb et zinc) en laboratoire Ă©taient incapables de percevoir et Ă©viter des concentrations usuelles, nĂ©anmoins nocives, de ces mĂ©taux dans leur nourriture. J'ai ensuite exposĂ© de façon chronique des colonies Ă des concentrations rĂ©alistes de plomb dans la nourriture et dĂ©montrĂ© que la consommation de ce mĂ©tal altĂ©rait la cognition et le dĂ©veloppement morphologique des abeilles. Comme les polluants mĂ©talliques se trouvent souvent dans des mĂ©langes complexes dans l'environnement, j'ai explorĂ© l'effet des cocktails de mĂ©taux, montrant que l'exposition au plomb, Ă l'arsenic ou au cuivre seul Ă©tait suffisante pour ralentir l'apprentissage et perturber le rappel de la mĂ©moire, et que les combinaisons de ces mĂ©taux induisaient des effets nĂ©gatifs additifs sur ces deux processus cognitifs. J'ai finalement Ă©tudiĂ© l'impact de l'exposition naturelle aux polluants mĂ©talliques dans un environnement contaminĂ©, en collectant des abeilles Ă proximitĂ© d'une ancienne mine d'or, et montrĂ© que les individus des populations les plus exposĂ©es aux mĂ©taux prĂ©sentaient des capacitĂ©s d'apprentissage et de mĂ©moire plus faibles, et des altĂ©rations de leur dĂ©veloppement conduisant Ă une rĂ©duction de la taille de leur cerveau. Une analyse plus systĂ©matique des abeilles non exposĂ©es a rĂ©vĂ©lĂ© une relation entre la taille de la tĂȘte, la morphomĂ©trie du cerveau et les performances d'apprentissage dans diffĂ©rentes tĂąches comportementales, suggĂ©rant que l'exposition aux polluants mĂ©talliques amplifie ces variations naturelles. Ainsi, mes rĂ©sultats suggĂšrent que les abeilles domestiques sont incapables d'Ă©viter lâexposition Ă des concentrations rĂ©alistes de mĂ©taux qui sont prĂ©judiciables au dĂ©veloppement et aux fonctions cognitives, et appellent Ă une rĂ©vision des niveaux environnementaux considĂ©rĂ©s comme «sĂ»rs». Ma thĂšse est la premiĂšre analyse intĂ©grĂ©e de l'impact de plusieurs polluants mĂ©talliques sur la cognition, la morphologie et lâorganisation cĂ©rĂ©brale chez lâabeille, et vise Ă encourager de nouvelles Ă©tudes sur la contribution de la pollution mĂ©tallique dans le dĂ©clin signalĂ© des abeilles, et plus gĂ©nĂ©ralement, des insectes
Impacts des polluants mĂ©talliques sur lâabeille : de la colonie au cerveau
Honey bees are crucial pollinators. A plethora of environmental stressors, such as agrochemicals, have been identified as contributors to their global decline. Especially, these stressors impair cognitive processes involved in fundamental behaviours. So far however, virtually nothing is known about the impact of metal pollutants, despite their known toxicity to many organisms. Their worldwide emissions resulting from human activities have elevated their concentrations far above natural baselines in the air, soil, water and flora, exposing bees at all life stages. The aim of my thesis was to examine the effects of metallic pollution on honey bees using a multiscale approach, from brain to colonies, in laboratory and field conditions. I first observed that bees exposed to a range of concentrations of three common metals (arsenic, lead and zinc) in the laboratory were unable to perceive and avoid, low, yet harmful, field-realistic concentrations of those metals in their food. I then chronically exposed colonies to field-realistic concentrations of lead in food and demonstrated that consumption of this metal impaired bee cognition and morphological development, leading to smaller adult bees. As metal pollutants are often found in complex mixtures in the environment, I explored the effect of cocktails of metals, showing that exposure to lead, arsenic or copper alone was sufficient to slow down learning and disrupt memory retrieval, and that combinations of these metals induced additive negative effects on both cognitive processes. I finally investigated the impact of natural exposure to metal pollutants in a contaminated environment, by collecting bees in the vicinity of a former gold mine, and showed that individuals from populations most exposed to metals exhibited lower learning and memory abilities, and development impairments conducing to reduced brain size. A more systematic analysis of unexposed bees revealed a relationship between head size, brain morphometrics and learning performances in different behavioural tasks, suggesting that exposure to metal pollutants magnifies these natural variations. Hence, altogether, my results suggest that honey bees are unable to avoid exposure to field-realistic concentrations of metals that are detrimental to development and cognitive functions; and call for a revision of the environmental levels considered as âsafeâ. My thesis is the first integrated analysis of the impact of several metal pollutants on bee cognition, morphology and brain structure, and should encourage further studies on the contribution of metal pollution in the reported decline of honey bees, and more generally, of insects.Les abeilles sont des pollinisateurs essentiels. Une plĂ©thore de facteurs de stress environnementaux, tels que les produits agrochimiques, a Ă©tĂ© identifiĂ©e comme contribuant Ă leur dĂ©clin mondial. En particulier, ces facteurs de stress altĂšrent les processus cognitifs impliquĂ©s dans les comportements fondamentaux. Jusqu'Ă prĂ©sent, cependant, on ne sait pratiquement rien de l'impact de lâexposition Ă des mĂ©taux lourds, dont la toxicitĂ© est avĂ©rĂ©e chez de nombreux organismes. Pourtant, leurs Ă©missions mondiales rĂ©sultant des activitĂ©s humaines ont Ă©levĂ© leurs concentrations bien au-dessus des niveaux naturels dans l'air, le sol, l'eau et la flore, exposant ainsi les abeilles Ă tous les stades de leur vie. Le but de ma thĂšse Ă©tait d'examiner les effets de la pollution mĂ©tallique sur lâabeille domestique en utilisant une approche multi-Ă©chelle, du cerveau Ă la colonie, en laboratoire et sur le terrain. J'ai d'abord observĂ© que les abeilles exposĂ©es Ă une gamme de concentrations de trois mĂ©taux communs (arsenic, plomb et zinc) en laboratoire Ă©taient incapables de percevoir et Ă©viter des concentrations usuelles, nĂ©anmoins nocives, de ces mĂ©taux dans leur nourriture. J'ai ensuite exposĂ© de façon chronique des colonies Ă des concentrations rĂ©alistes de plomb dans la nourriture et dĂ©montrĂ© que la consommation de ce mĂ©tal altĂ©rait la cognition et le dĂ©veloppement morphologique des abeilles. Comme les polluants mĂ©talliques se trouvent souvent dans des mĂ©langes complexes dans l'environnement, j'ai explorĂ© l'effet des cocktails de mĂ©taux, montrant que l'exposition au plomb, Ă l'arsenic ou au cuivre seul Ă©tait suffisante pour ralentir l'apprentissage et perturber le rappel de la mĂ©moire, et que les combinaisons de ces mĂ©taux induisaient des effets nĂ©gatifs additifs sur ces deux processus cognitifs. J'ai finalement Ă©tudiĂ© l'impact de l'exposition naturelle aux polluants mĂ©talliques dans un environnement contaminĂ©, en collectant des abeilles Ă proximitĂ© d'une ancienne mine d'or, et montrĂ© que les individus des populations les plus exposĂ©es aux mĂ©taux prĂ©sentaient des capacitĂ©s d'apprentissage et de mĂ©moire plus faibles, et des altĂ©rations de leur dĂ©veloppement conduisant Ă une rĂ©duction de la taille de leur cerveau. Une analyse plus systĂ©matique des abeilles non exposĂ©es a rĂ©vĂ©lĂ© une relation entre la taille de la tĂȘte, la morphomĂ©trie du cerveau et les performances d'apprentissage dans diffĂ©rentes tĂąches comportementales, suggĂ©rant que l'exposition aux polluants mĂ©talliques amplifie ces variations naturelles. Ainsi, mes rĂ©sultats suggĂšrent que les abeilles domestiques sont incapables d'Ă©viter lâexposition Ă des concentrations rĂ©alistes de mĂ©taux qui sont prĂ©judiciables au dĂ©veloppement et aux fonctions cognitives, et appellent Ă une rĂ©vision des niveaux environnementaux considĂ©rĂ©s comme «sĂ»rs». Ma thĂšse est la premiĂšre analyse intĂ©grĂ©e de l'impact de plusieurs polluants mĂ©talliques sur la cognition, la morphologie et lâorganisation cĂ©rĂ©brale chez lâabeille, et vise Ă encourager de nouvelles Ă©tudes sur la contribution de la pollution mĂ©tallique dans le dĂ©clin signalĂ© des abeilles, et plus gĂ©nĂ©ralement, des insectes
Impacts of metallic pollutants on honey bees : from the colony to the brain
Les abeilles sont des pollinisateurs essentiels. Une plĂ©thore de facteurs de stress environnementaux, tels que les produits agrochimiques, a Ă©tĂ© identifiĂ©e comme contribuant Ă leur dĂ©clin mondial. En particulier, ces facteurs de stress altĂšrent les processus cognitifs impliquĂ©s dans les comportements fondamentaux. Jusqu'Ă prĂ©sent, cependant, on ne sait pratiquement rien de l'impact de lâexposition Ă des mĂ©taux lourds, dont la toxicitĂ© est avĂ©rĂ©e chez de nombreux organismes. Pourtant, leurs Ă©missions mondiales rĂ©sultant des activitĂ©s humaines ont Ă©levĂ© leurs concentrations bien au-dessus des niveaux naturels dans l'air, le sol, l'eau et la flore, exposant ainsi les abeilles Ă tous les stades de leur vie. Le but de ma thĂšse Ă©tait d'examiner les effets de la pollution mĂ©tallique sur lâabeille domestique en utilisant une approche multi-Ă©chelle, du cerveau Ă la colonie, en laboratoire et sur le terrain. J'ai d'abord observĂ© que les abeilles exposĂ©es Ă une gamme de concentrations de trois mĂ©taux communs (arsenic, plomb et zinc) en laboratoire Ă©taient incapables de percevoir et Ă©viter des concentrations usuelles, nĂ©anmoins nocives, de ces mĂ©taux dans leur nourriture. J'ai ensuite exposĂ© de façon chronique des colonies Ă des concentrations rĂ©alistes de plomb dans la nourriture et dĂ©montrĂ© que la consommation de ce mĂ©tal altĂ©rait la cognition et le dĂ©veloppement morphologique des abeilles. Comme les polluants mĂ©talliques se trouvent souvent dans des mĂ©langes complexes dans l'environnement, j'ai explorĂ© l'effet des cocktails de mĂ©taux, montrant que l'exposition au plomb, Ă l'arsenic ou au cuivre seul Ă©tait suffisante pour ralentir l'apprentissage et perturber le rappel de la mĂ©moire, et que les combinaisons de ces mĂ©taux induisaient des effets nĂ©gatifs additifs sur ces deux processus cognitifs. J'ai finalement Ă©tudiĂ© l'impact de l'exposition naturelle aux polluants mĂ©talliques dans un environnement contaminĂ©, en collectant des abeilles Ă proximitĂ© d'une ancienne mine d'or, et montrĂ© que les individus des populations les plus exposĂ©es aux mĂ©taux prĂ©sentaient des capacitĂ©s d'apprentissage et de mĂ©moire plus faibles, et des altĂ©rations de leur dĂ©veloppement conduisant Ă une rĂ©duction de la taille de leur cerveau. Une analyse plus systĂ©matique des abeilles non exposĂ©es a rĂ©vĂ©lĂ© une relation entre la taille de la tĂȘte, la morphomĂ©trie du cerveau et les performances d'apprentissage dans diffĂ©rentes tĂąches comportementales, suggĂ©rant que l'exposition aux polluants mĂ©talliques amplifie ces variations naturelles. Ainsi, mes rĂ©sultats suggĂšrent que les abeilles domestiques sont incapables d'Ă©viter lâexposition Ă des concentrations rĂ©alistes de mĂ©taux qui sont prĂ©judiciables au dĂ©veloppement et aux fonctions cognitives, et appellent Ă une rĂ©vision des niveaux environnementaux considĂ©rĂ©s comme «sĂ»rs». Ma thĂšse est la premiĂšre analyse intĂ©grĂ©e de l'impact de plusieurs polluants mĂ©talliques sur la cognition, la morphologie et lâorganisation cĂ©rĂ©brale chez lâabeille, et vise Ă encourager de nouvelles Ă©tudes sur la contribution de la pollution mĂ©tallique dans le dĂ©clin signalĂ© des abeilles, et plus gĂ©nĂ©ralement, des insectes.Honey bees are crucial pollinators. A plethora of environmental stressors, such as agrochemicals, have been identified as contributors to their global decline. Especially, these stressors impair cognitive processes involved in fundamental behaviours. So far however, virtually nothing is known about the impact of metal pollutants, despite their known toxicity to many organisms. Their worldwide emissions resulting from human activities have elevated their concentrations far above natural baselines in the air, soil, water and flora, exposing bees at all life stages. The aim of my thesis was to examine the effects of metallic pollution on honey bees using a multiscale approach, from brain to colonies, in laboratory and field conditions. I first observed that bees exposed to a range of concentrations of three common metals (arsenic, lead and zinc) in the laboratory were unable to perceive and avoid, low, yet harmful, field-realistic concentrations of those metals in their food. I then chronically exposed colonies to field-realistic concentrations of lead in food and demonstrated that consumption of this metal impaired bee cognition and morphological development, leading to smaller adult bees. As metal pollutants are often found in complex mixtures in the environment, I explored the effect of cocktails of metals, showing that exposure to lead, arsenic or copper alone was sufficient to slow down learning and disrupt memory retrieval, and that combinations of these metals induced additive negative effects on both cognitive processes. I finally investigated the impact of natural exposure to metal pollutants in a contaminated environment, by collecting bees in the vicinity of a former gold mine, and showed that individuals from populations most exposed to metals exhibited lower learning and memory abilities, and development impairments conducing to reduced brain size. A more systematic analysis of unexposed bees revealed a relationship between head size, brain morphometrics and learning performances in different behavioural tasks, suggesting that exposure to metal pollutants magnifies these natural variations. Hence, altogether, my results suggest that honey bees are unable to avoid exposure to field-realistic concentrations of metals that are detrimental to development and cognitive functions; and call for a revision of the environmental levels considered as âsafeâ. My thesis is the first integrated analysis of the impact of several metal pollutants on bee cognition, morphology and brain structure, and should encourage further studies on the contribution of metal pollution in the reported decline of honey bees, and more generally, of insects
A toxic error
International audienceHeavy metal pollution limits shouldn't just keep humans safe, but other animals too, say Coline Monchanin and Mathieu Lihorea
Biodiversity, ecology, and taxonomy of sediment-dwelling Dendrophylliidae (Anthozoa, Scleractinia) in the Gulf of Thailand
Dendrophylliidae represents one of the most speciose families of scleractinian coral, expressing a wide range of morphological and ecological traits. Recent phylogenetic analyses of the family have indicated that several conventional genera are in need of revision. In the Gulf of Thailand, dendrophylliids are predominantly found on hard-substrate reefs and pinnacles, or on soft-substrate habitats. Soft-substrate habitats in the Gulf of Thailand have been shown to host unique species assemblages and faunal ecology. Here we provided an updated phylogenetic hypothesis for the Dendrophylliidae based on newly sequenced species, and analyses integrating morphology, genetics and ecology. High-resolution Micro-ct was used to create digital versions of the studied species, allowing for non-destructive examination of internal and external features. Our findings allowed for a taxonomic assessment of the genera Heteropsammia and Tubastraea, with the species Balanophyllia (Eupsammia) stimpsonii, moved to the genus Tubastraea. They also support the polyphyly of Dendrophyllia and Cladopsammia. In-situ surveys provided population-density information for four dendrophylliid species from soft substrate habitats, indicating that the species Heteropsammia moretonensis may be the most widespread within the Gulf of Thailand. These surveys also provided novel ecological documentation associated with these corals, including protocooperative feeding upon a sea pen by Tubastraea stimpsonii comb. nov., and feeding upon other cnidarians by Heteropsammia spp.</p
Pesticide dosing must be guided by ecological principles
International audienceInsecticide use could be reduced if dose recommendations move from a toxicological perspective (how much is needed to kill an insect pest) to an ecological perspective (how much is needed to protect a crop)
Current permissible levels of metal pollutants harm terrestrial invertebrates
International audienceThe current decline of invertebrates worldwide is alarming. Several potential causes have been proposed but metal pollutants, while being widespread in the air, soils and water, have so far been largely overlooked. Here, we reviewed the results of 527 observations of the effects of arsenic, cadmium, lead and mercury on terrestrial invertebrates. These four well-studied metals are considered as priorities for public health and for which international regulatory guidelines exist. We found that they all significantly impact the physiology and behavior of invertebrates, even at levels below those recommended as âsafeâ for humans. Our results call for a revision of the regulatory thresholds to better protect terrestrial invertebrates, which appear to be more sensitive to metal pollution than vertebrates. More fundamental research on a broader range of compounds and species is needed to improve international guidelines for metal pollutants, and to develop conservation plans to protect invertebrates and ecosystem services