Structural modifications in the gill membranes maintain homeostasis under the influence of temperature changes. We hypothesized that thermal acclimation would result in significant modification of ...phospholipid fatty acids, with modulation of sodium pump activity during acute (24 and 48 h) and chronic (15 days) thermal shifts in the neotropical reophilic catfish Steindachneridion parahybae. Indeed, the time-course experiment showed acute and chronic changes in gill membrane at the lowest temperatures, notably linked to maintenance of membrane fluidity: significant preferential changes in phosphatidylethanolamine, with decrease of saturated fatty acids and increase of C18:1 in all groups kept below 30 °C in chronic trial, increase in polyunsaturated fatty acids n6 and C18:1 at 17 and 12 °C compared to 24 °C, as soon as the temperature was changed (initial time). Additionally, the activity of the sodium pump increased at 12 °C, but without apparent connection with the altered lipid environment. The animals maintained at the lowest temperature showed a higher mortality, possibly because of the approach to the minimum critical temperature for this species, and unexpected results of changes in the fatty acid profile, such as decreased docosahexaenoic acid in phosphatidylethanolamine and increased saturated fatty acids in phosphatidylcholine. This set of mechanisms highlights rheostatic adjustments in this species in the face of temperature changes.
Display omitted
•A migratory fish was used as a model to a thermal regime test of rheostatic responses.•Homeoviscous acclimatization strategies for membrane functionality was detected.•Phosphatidylethanolamine and oleic acid were the tools for maintaining homeostasis•NKA was not responsive to the lipid membrane environment.•12 °C is lethal to Steindachneridion parahybae.
In ectothermic vertebrates, behavioral fever, where an individual actively seeks warmer areas, seems to be a primary response to pathogens. This is considered a broad and evolutionarily conserved ...response among vertebrates. Recent population declines in amphibians are associated with an increase of infectious disease driven largely by climate change, habitat degradation, and pollution. Immediate action through research is required to better understand and inform conservation efforts. The literature available, does not provide unifying concepts that can guide adequate experimental protocols and interpretation of data, especially when studying animals in the field. The aim of this review is to promote common understanding of terminology and facilitating improved comprehension and application of key concepts about the occurrence of both sickness behavior or behavioral fever in ectothermic vertebrates. We start with a conceptual synthesis of sickness behavior and behavioral fever, with examples in different taxa. Through this discussion we present possible paths to standardize terminology, starting from original use in endothermic tetrapods which was expanded to ectothermic vertebrates, particularly amphibians and reptiles. This conceptual expansion from humans (endothermic vertebrates) and then to ectothermic counterparts, gravitates around the concept of ‘normality'. Thus, following this discussion, we highlight caveats with experimental protocols and state the need of a reference value considered normal (RVCN), which is different from experimental control and make recommendations regarding experimental procedures and stress the value of detailed documentation of behavioral responses. We also propose some future directions that could enhance interaction among disciplines, emphasizing relationships at different levels of biological organization. This is crucial given the increasing convergence of fields such as thermal physiology, immunology, and animal behavior due to emerging diseases and other global crises impacting biodiversity.
•Independently of metabolic profile, sickness behavior and (behavioral) fever mark the onset of the acute phase response of the immune system, sharing signaling pathways and autonomic mechanisms.•Reptiles and anurans exhibit sickness behavior and/or behavioral fever face pathogens and illnesses. The interaction between these two responses is poorly understood, as the correlations of thermal landscape and behavioral thermoregulation.•A reference system is crucial to define fever. The choice of a given reference has analytical consequences for experimentation. Careful experimental control is essential to unambiguously define sickness behavior or behavioral fever.•For poorly known species, febrile and sickness responses must be considered as hypotheses, not a priori assumptions. Experimental protocols must be designed to encompass the multiple behavioral responses that may emerge.•We encourage deeper examination of this phenomenon in anurans, and a phylogenetically diverse approach.
Task partitioning in eusocial animals is most likely an evolutionary adaptation that optimizes the efficiency of the colony to grow and reproduce. It was investigated indirect task partitioning in ...two castes sizes; this involves task partitioning in which the material transported is not transferred directly from one individual to another, but where it is dropped by one ant to be picked up by another. In two separate approaches, it was confirmed previous results pertaining to leaf caching activities among Atta colombica with task partitioning activities involving leaf dropping among Atta sexdens rubropilosa, in which there is a correlation between the size of an individual ant and the leaf fragment it transports. It was also suggested that this correlation exists only in individual ants that cut and transport (CaT) the same fragment to the nest. When task partitioning occurs and individual ants transporting (T) leaf fragments cut by other ants, the correlation becomes looser or disappears. We also observed that CaT ants are smaller than T ants. Key words: Atta, ant behavior, leaf cutting, ecological adaptation. Particionamento de tarefas em animais eusociais e provavelmente uma adaptacao evolutiva, que otimiza a eficiencia de forrageio da colonia, gerando maior capacidade de crescimento e reproducao. Nos investigamos o particionamento indireto de tarefas, com o envolvimento de castas de dois tamanhos distintos. Assim, o material coletado por uma formiga nao era transportado diretamente ao ninho, nem transferido diretamente de um individuo para outro, mas sim descartado por uma formiga e coletado por outra. Em duas abordagens distintas, nos confirmamos em Atta sexdens rubropilosa resultados anteriores relativos a ocorrencia deste particionamento indireto de tarefas, observado em Atta colombica. Mostramos tambem que, assim como em Atta colombica, ha uma correlacao entre os tamanhos da formiga e do fragmento de folha transportado quando esta corta e transporta este fragmento ao ninho (CaT). Mais ainda, confirmamos em Atta sexdens que, quando o particionamento de tarefas ocorre e as formigas apenas transportam o fragmento de folhas (T) cortadas por outras formigas, a correlacao desaparece. Nos tambem descrevemos que as formigas CaT sao menores do que as T. Palavras-chave: Atta, o comportamento das formigas, o corte de folha, adaptacao ecologica.
PDF