Around the word stress: its biological and evolutive implications

Abstract

Stress is a general adaptive reaction crucial for survival and basically positive that involves the
neuroendocrine and the immune systems. In all bilaterian metazoans, the molecular mediators of the
stress response, i.e., corticotrophin-releasing hormone, corticotrophin, catecholamines and
glucocorticoids, have been preserved during evolution, even if the increased complexity of animals
have corresponded to a more articulated stress response that, following the eco-immunology
perspective, we speculate to be hierarchically organized along three levels.