How do octopuses deal with stress?

Abstract

The importance of cephalopods and specifically octopuses as a highly appreciated culinary product and as an important fishing resource is widely known worldwide. This, together with its biological characteristics (short life cycle and high growth rate) make it as important potential species for its cultivation and domestication. However, many basic aspects of the biology and physiology of this species are still a mystery. Recognizing signs of stressed octopus, defining reliable stress biomarkers and knowing how to manage stress levels is key in ensuring octopus domestication and cultivation. In verterbrates, Glucocorticoids (GCs) are the final effector products of the neuroendocrine HPA/HPI axis governing energy balance and stress response, but what happens in cephalopods and specifically in octopuses?. Therefore, the main objective of this study is to demonstrate whether glucorticoids, as in vertebrates, are involved in the response to stress in octopuses and therefore can be used as reliable stress biomarkers in this species. Our data show, for first time, the absence of the two main glucocorticoids governing energy balance and stress response in vertebrates (cortisol and corticosterone) in the hemolymph samples of cultured octopus. These results, along with the idea that just because it is possible to measure vertebrate glucocorticoids in the tissues of mollusks and the surprisingly large number of studies showing that they can readily absorb, conjugate and retains vertebrate steroids from the environment, calls into doubt the claims that glucocorticoid concentrations are functionally linked to stress response and they can be used as a biomarker in mollusks