Senescence in common octopus, Octopus vulgaris : Morphological, behavioural and functional observations

Understanding senescence in semelparous species not only deepens our knowledge of the evolution of aging but also highlights the diversity of life strategies that have evolved in the natural world. This terminal phase occurs at the end of the lifecycle and is particularly evident in the common octopus, Octopus vulgaris, Cuvier 1797, a semelparous species with terminal reproduction. The aim of the present work was to document the natural process of senescence in specimens raised in captivity for two consecutive generations and the differences in morphology, behaviour and functional traits between the two sexes. Both sexes showed similar affections in the skin, with unhealed wounds, paler colors, and white lesions. At the same temperature males lived longer (six to seven months) than females, and showed extensive arm tip damage, with the exception of the hectocotylus that was fully functional until the very last day. Females, contrarily to males, lose 35.4-46.8% of their body weight during brooding and senescence. Uncommon behaviours were registered during this terminal phase like egg laying outside of the den, egg ingestion or copulation between males. These observations provide new data that will help to better understand this terminal phase and the natural processes occurring in both sexes at the end of their life cycle.