Exploring ethical reasoning and welfare perceptions of <i>Octopus vulgaris</i> paralarvae among scientific and non-scientific communities

Live cephalopods used in scientific research are protected under European Directive 2010/63/EU due to growing evidence that adult cephalopods can experience pain. This protection also extends to paralarval Octopus vulgaris , despite the absence of evidence that these early life stages are capable of nociception or pain. Consequently, the question arises whether welfare protection should be applied as a precaution when evidence of sentience is lacking, or only once it has been empirically demonstrated. Ethical reasoning under such uncertainty is influenced by views about sentience, scientific necessity, and societal relevance, and prior work suggests these views differ between scientists and laypeople. However, it remains unclear how these considerations combine when evidence for sentience is incomplete. This study investigated what influences ethical reasoning about the use of O. vulgaris paralarvae in research. An online survey ( N = 205) presented cephalopod biologists, other biologists, and non-biologists with one of three scenarios describing a gene expression experiment on O. vulgaris paralarvae in which nociception-related genes were expressed, not expressed, or not yet investigated. The provided scientific information did not significantly affect ethical judgments, but beliefs about pain capacity, disciplinary background, and gender did. These findings suggest that ethical evaluations in the context of uncertain biological evidence are driven more by prior beliefs, disciplinary background, and gender than by scientific information and familiarity with research ethics. This underscores the need for more accessible science communication, improved ethical engagement, and more objective evaluation of ethics education to support well-informed and inclusive decision-making in animal research governance.