Les médicaments sont fréquement retrouvés dans les effluents de STEP relargués dans l’environnement aquatique. Dans le but de prévenir et de mieux comprendre les impacts des médicaments sur les écosystèmes aquatiques, il semble pertinent d’évaluer les perturbations comportementales, physiologiques et transcriptomiques des psychotropes sur les organismes aquatiques. Dans ce contexte, l’objectif de cette étude a été d’évaluer les perturbations induites par 4 psychotropes (oxazépam, carbamazépine, cyamémazine et sertraline) chez deux organismes, Radix balthica et Schmidtea polychroa. Pour ce faire, des embryons de Radix au stade trochophore et des planaires adultes ont été exposés à chaque psychotrope (du μg/L jusqu’à 100 μg/L). Il en ressort que les psychotropes allongent la durée du développement embryonnaire du Radix et perturbent le déplacement, la reproduction et la digestion, mais pas la régénération de la planaire. D’un point de vue transcriptomique, nous avons réalisé le séquençage du transcriptome en conditions différentielles chez le Radix. Ainsi, nous avons obtenu d’une part les séquences du transcriptome et d’autre part, après analyse en différentiel, 144 contigs différentiellement exprimés par l’oxazépam parmi lesquels 94 ont été vérifiés en RT-qPCR chez des Radix exposés à chaque psychotrope. Il ressort de cette analyse que les psychotropes impactent principalement la voie de signalisation Notch, mais aussi les voies de biosynthèse des polyamines et des catécholamines. Les psychotropes modulent aussi l’expression de gènes codant des protéines de la Matrice Extra Cellulaire (MEC), comme la Matriline ou encore la Dentine sialophosphoprotéine. Chez la planaire, nous avons analysé l’expression de 87 gènes impliqués dans différentes fonctions. Il ressort de cette étude que les 4 psychotropes modulent l’expression de nombreux gènes impliqués dans la mobilité ciliaire et musculaire et dans les systèmes nerveux, reproducteur, excréteur et digestif. / Pharmaceuticals are often found in WWTP effluents realesed in surface water. In order to prevent and to understand the pharmaceuticals impact on aquatic ecosystems, it seems relevant to evaluate behavioural, physiological and transcriptomic disturbances of psychotropics on freshwater organisms. The aim of this study was thus to analyse disturbances of 4 psychotropics (oxazepam, carbamazepine, cyamemazine and sertraline) on 2 freshwater organisms, Radix balthica and Schmidtea polychroa. In our experiments, both Radix embryos at the trochophore stage and mature planarian were exposed to each psychotropic (from 1 to 100 μg/L). This psychotropic exposure results in an increase of the duration of Radix embryonic development and a disturbance of the mobility, the reproduction and the digestion but not the regeneration of planarian. Regarding the transcriptomic impact, we performed RNA sequencing in differential conditions of Radix embryos exposed or not to oxazepam. On one hand, this analysis allowed us to obtain the transcriptome sequences and, on the other hand, 144 contigs differentially expressed among which 94 genes were verified by RT-qPCR. The results showed that psychotropics impact mainly the Notch signalling pathways, but also the biosynthetic pathways of polyamines and catecholamines. Psychotropics also disturb the gene expression encoding some Extra Cellular Matrix (ECM) protein such as Matrilin and Dentin sialophosphoprotein. Regarding the molecular study of the psychotropics impact on planarian, we analysed the expression of 87 genes involved in different functions. The results showed that the 4 psychotropics modulate expression of genes involved in ciliary and muscular motility and in the nervous, reproductive and excretory systems. Genes from the digestive system are also impacted by the psychotropics. All the observed impacts on the 2 organisms suggest a possible disturbance on the population fitness and therefore on the freshwater ecosystems.

Temperature is a ubiquitous force influencing biological processes ranging from cellular responses to life span. The thermal environment for many organisms is predicted to change with globally increasing temperatures and studies conducted in natural systems incorporating various evolutionary forces, such as gene flow, is needed. In my thesis, I investigate how snails (Radix balthica) originating from distinct geothermal environments within Lake Mývatn in northern Iceland have adapted, both genetically and phenotypically, to the respective thermal regime. Locations were classified as either cold, warm or seasonal depending on the average and variance in temperature. A high resolution spatial distribution of genetic variation within Mývatn was obtained using both neutral and outlier AFLPs. In addition, the genetic profile enabled me identify warm origin snails irrespective of geographic location in Iceland. Warm environments were often more stressful than cold or seasonal environments but snails originating from a high temperature location benefited from increased performance elsewhere. Patterns of growth were identical in both common garden and reciprocal transplant experiment; warm origin snails grew faster than both cold and seasonal origin snails. This result is in concordance with quantitative genetics models of thermal adaptation but suggesting cogradient rather than countergradient variation. Although warm origin snails generally had superior performance, survival at cold temperatures (< 12 °C) was reduced. All snails matured at similar size in the common garden experiment but cold origin snails were observed to mature later and lay fewer eggs. Also, snails had a common optimum for growth rate at 20 °C irrespective of thermal origin. This is arguably the reason why snails were observed to have a common thermal preference. Interestingly, warm origin snails had a reduced tolerance to high temperatures compared to cold and seasonal origin snails which did not differ in tolerance. Putatively, natural selection has reduced a putatively unnecessary trait (high temperature tolerance in a stable thermal environment) in favour of higher growth rate and performance in warm habitats. In conclusion, the price of high performance in a warm environment was paid in terms of reduced survival at low temperatures and a potential disadvantage of reduced genetic variability.