Why high temperatures limit reproduction in cephalopods? The case of Octopus maya

Since thermal stress enhances the energy demands, it is possible to hypothesize that the harmful effects of high temperatures observed in Octopus maya are the result of the limited capacity of adults to channel more energy that reproductive activity demands. The present study was designed to know how temperature modulates the energy physiology of O. maya adults. It was evaluated through the relationship between temperature, respiratory metabolism (measured as thermal metabolic scope: TMS), antioxidant defence mechanisms (ANTIOX) and oxidative damage indicators (ODI). Groups of males and females of O. maya were individually distributed at 24℃, 26℃ and 30℃. TMS resulted lower in animals acclimated to 30℃. Also, higher values of ANTIOX and ODI were registered in the branchial hearts in octopus acclimated to 30℃. Results demonstrate that 30℃ is a temperature that limits the energy production in O. maya, probably because of the incapacity of animals to transport oxygen to mitochondria. Although the animals are adapted to satisfy their basic energy requirements at 30℃, we hypothesize that it is not enough to cover all the energy demands needed for reproduction. At 30℃, joint with a reduction on physiologically available energy a high level of oxidative stress was observed, both explaining the previously reported reduction in the production of eggs, in the production of viable sperm and therefore in the quality of the progeny.