A estivação é caracterizada como um conjunto de alterações fisiológicas e comportamentais relacionadas com a redução do metabolismo e a permanência em micro-habitats específicos durante a fase de estiagem. Na caatinga brasileira foram observadas ao menos três espécies que estivam, sendo duas da família Leiuperidae, Pleurodema diplolistris e Physalaemus albifrons e uma da família Cycloramphidae, Proceratophrys cristiceps. Ainda que encontradas no mesmo micro-habitat durante a estivação, estas três espécies exibiram padrões distintos de alteração do desempenho locomotor entre as duas estações marcantes do ano (seca e chuvosa). Enquanto P. diplolistris reduziu em cerca de 47% a velocidade de seu desempenho locomotor durante a fase de estiagem, as outras duas espécies, P. cristiceps e P. albifrons, reduziram cerca de 87 e 83%, respectivamente. Mais ainda, apenas P. diplolistris exibiu mudança de profundidade ao longo da estiagem. A redução da taxa metabólica aeróbia foi de aproximadamente 50% para as três espécies. A comparação entre as estações marcantes do ano ainda revelou que as três espécies estudadas apresentam diferentes padrões de alteração na concentração de substrato energéticos e na atividade de enzimas representativas do metabolismo energético no fígado e musculatura dos membros posteriores. A manutenção hídrica também foi diferente entre as três espécies, o que indica a ocorrência de estratégias diversas de regulação hídrica / Estivation is defined as a set of physiological and behavioral changes associated to decreased metabolism and permanence in specific microhabitats during the dry season. In the Brazilian Caatinga was observed at least three estivating species: Pleurodema diplolistris and Physalaemus albifrons (Leiuperidae) and Proceratophrys cristiceps (Cycloramphidae). Although found in the same micro-habitat during aestivation, these three species differ in the variation patterns of locomotor performance when compared between the two seasons (dry and rainy season). During the dry phase, speed in P. diplolistris is reduced by about 47% whereas in P. cristiceps and P. albifrons values decrease by 87% and 83%, respectively. Moreover, only P. diplolistris exhibited changes of depth along the drought. The reduction of aerobic metabolic rate was of approximately 50% for the three species. The comparison between seasons also revealed that the three species differ in relation to the variation patterns of the concentration of substrate energy and activity of representative enzymes of energy metabolism in the liver and muscles of the hindlimb. The water maintenance was also different among the three species, indicating the occurrence of several strategies of hidric regulation

A estivação é caracterizada como um conjunto de alterações fisiológicas e comportamentais relacionadas com a redução do metabolismo e a permanência em micro-habitats específicos durante a fase de estiagem. Na caatinga brasileira foram observadas ao menos três espécies que estivam, sendo duas da família Leiuperidae, Pleurodema diplolistris e Physalaemus albifrons e uma da família Cycloramphidae, Proceratophrys cristiceps. Ainda que encontradas no mesmo micro-habitat durante a estivação, estas três espécies exibiram padrões distintos de alteração do desempenho locomotor entre as duas estações marcantes do ano (seca e chuvosa). Enquanto P. diplolistris reduziu em cerca de 47% a velocidade de seu desempenho locomotor durante a fase de estiagem, as outras duas espécies, P. cristiceps e P. albifrons, reduziram cerca de 87 e 83%, respectivamente. Mais ainda, apenas P. diplolistris exibiu mudança de profundidade ao longo da estiagem. A redução da taxa metabólica aeróbia foi de aproximadamente 50% para as três espécies. A comparação entre as estações marcantes do ano ainda revelou que as três espécies estudadas apresentam diferentes padrões de alteração na concentração de substrato energéticos e na atividade de enzimas representativas do metabolismo energético no fígado e musculatura dos membros posteriores. A manutenção hídrica também foi diferente entre as três espécies, o que indica a ocorrência de estratégias diversas de regulação hídrica / Estivation is defined as a set of physiological and behavioral changes associated to decreased metabolism and permanence in specific microhabitats during the dry season. In the Brazilian Caatinga was observed at least three estivating species: Pleurodema diplolistris and Physalaemus albifrons (Leiuperidae) and Proceratophrys cristiceps (Cycloramphidae). Although found in the same micro-habitat during aestivation, these three species differ in the variation patterns of locomotor performance when compared between the two seasons (dry and rainy season). During the dry phase, speed in P. diplolistris is reduced by about 47% whereas in P. cristiceps and P. albifrons values decrease by 87% and 83%, respectively. Moreover, only P. diplolistris exhibited changes of depth along the drought. The reduction of aerobic metabolic rate was of approximately 50% for the three species. The comparison between seasons also revealed that the three species differ in relation to the variation patterns of the concentration of substrate energy and activity of representative enzymes of energy metabolism in the liver and muscles of the hindlimb. The water maintenance was also different among the three species, indicating the occurrence of several strategies of hidric regulation

The desert-adapted frogs Cyclorana platycephala and Cyclorana maini survive long periods of inhospitably hot and dry conditions by retreating underground and aestivating. While aestivating they suspend food and water intake as well as physical activity, depress their metabolic rate by ~80 %, and form cocoons that protect them against desiccation. How these frogs function during this exceptional state is largely unknown. This work characterized a number of physiological parameters in three metabolic states spanning their natural metabolic range: during aestivation (depressed metabolism), at rest (normal metabolism), and where possible, during exercise (elevated metabolism). The primary objective was to identify by comparison, physiological adjustments in these parameters to metabolic depression, as well as the scope of these parameters in frogs capable of aestivation. The parameters measured for C. maini were (a) the glucose transport kinetics and (b) the fluid balance of an extensive number of their individual organs. For C. platycephala, the parameters measured were (a) the activity of the cardiovascular system as indicated by heart rate and blood pressure and (b) the roles of pulmonary and cutaneous respiratory systems in gas exchange

Dans les savanes d'Afrique de l'Ouest, les moustiques Anopheles coluzzii et An. gambiae, qui transmettent le paludisme, pullulent en saison des pluies et disparaissent en saison sèche. Les mécanismes permettant le maintien des populations d'Anophèles d'une année sur l'autre restent inconnus et difficiles à mettre en évidence sur le terrain. Au cours de ce travail, nous avons étudié, par des approches comparatives et expérimentales, la plasticité physiologique et morphologique des femelles An. coluzzii et An. gambiae exprimée en réponse aux conditions déshydratantes de la saison sèche. Des analyses métabolomiques, protéomiques, morphométriques et respirométriques, nous ont permis de mettre en évidence une grande variabilité des profils exprimés entre les espèces et entre les différentes populations d'An. coluzzii. / In dry savannahs of West Africa, the malarial mosquitoes Anopheles coluzzii and An. gambiae swarm during the rainy season but almost disappear at the onset of the dry season. Interestingly, the ecological and physiological bases enhancing the survival of these insects during the desiccating conditions of the dry season remain unknown, and hard to understand with field studies. In the present work, we conducted experimental and comparative studies to analyse the physiological and morphological plasticity of female An. coluzzii and An. gambiae mosquitoes in response to the environmental conditions of the dry season. Metabolomic, proteomic, morphometric and gas exchange analyses highlighted a wide range of responses to the dry season conditions in these species, and enables distinguishing the two considered species.

L'acquisition et l'allocation de ressources sont des tâches fondamentales chez tous les animaux. Les organismes rencontrent souvent de l'hétérogénéité dans l'espace et dans le temps et devront adapter leur traits d'histoire de vie, décrits comme un ensemble héritable de règles qui déterminent l'allocation vers la croissance ou la mise en réserve pour la survie versus la reproduction. Chez Cornu aspersum, la stratégie de reproduction dépend des contraintes saisonnières et l'investissement dans la reproduction est influencé par l'énergie disponible dans l'environnement. Des nutriments présents dans l'alimentation, notamment des lipides, sont déposés dans les oeufs, et une source mixte de calcium a pour effet que la coque des oeufs est plus épaisse. Ceci pourrait augmenter la probabilité de survie des juvéniles. Des bactéries présentes dans l'alimentation et dans la terre pourraient être responsables d'une diminution de la capacité de surfusion, et elles pourraient persister dans l'intestin pendant l'hibernation. Chez Helix pomatia, qui est utilisé dans des élevages biologiques afin de maintenir cette espèce menacée comme spécialité régionale sous le nom Albschneck®, le succès reproducteur est faible même avec une alimentation riche en énergie, comparativement à une population en provenance d'un élevage intensif Italien. Helix pomatia préserve une riche communauté bactérienne dans l'intestin qui pourrait contenir des bactéries nucléantes, mais accumule aussi des cryoprotecteurs, comme des acides aminés, des triglycérides et du glycérol, pour améliorer la résistance au froid pendant l'hiver. Toutefois, la mortalité pourrait être liée à un ajustement perpétuel des processus physiologiques aux variations importantes de la température et aux situations climatiques extrêmes ainsi qu'à une allocation limitée vers des processus de survie. Des mesures de protection devront donc inclure la préservation de refuges dans l'habitat naturel et artificiel.