Facing other minds: An ecological, behavioral, and evolutionary investigation into sentience and welfare in Octopuses (Cephalopoda: Mollusca: Conchifera)
The question of the existence and nature of minds other than the human mind is one of the most profound challenges in philosophy and science. Recognizing sentience in other species impacts ethical responsibilities; however, when we move away from vertebrates, the challenge of understanding which species are sentient becomes exponentially greater. In this scenario, octopuses (Cephalopoda) emerge as an important and unique case study. The objective of this thesis was to investigate octopus sentience with an integrative approach, combining theoretical, behavioral, and evolutionary studies. Theoretically and evolutionarily, we propose a hypothesis of deep homology as the evolutionary root of sentience, suggesting that its genetic mechanisms are ancestral, inherited from Urbilateria. This basis supports the applicability of the study of introspection through the analysis of behavioral discontinuities (perceptions, beliefs, intentions) to infer mental processes. Empirically, the study used Octopus insularis in the wild, a medium-sized benthic octopus that lives in shallow, clear waters off the coast of Northeast Brazil. The thesis validated negative welfare metrics in these animals, identifying new indicators and associating lesions and irregular color expression with interaction with fishermen. The analysis of interspecific interactions between octopuses and fish demonstrated the cognitive capacity of octopuses to strategically modulate their behavior, depending on the type of fish in the interaction. In a comparative dimension, the thesis also describes foraging strategies and establishes a morphological differentiation of juvenile Octopus hummelincki, an elusive and neglected species, enriching systematics and behavioral ecology. Finally, the proposed ethical development is post-Darwinian morality, which expands rights to all sentient beings, combating speciesism. Taken together, our results strengthen the evidence for octopuses as sentient beings, contributing empirical data to ethical debates about the welfare of wild animals, as well as their conservation.