The concept of sentience concerns the capacity to have feelings. There is evidence for sophisticated cognitive concepts and for both positive and negative feelings in a wide range of nonhuman animals. All vertebrates, including fish, as well as some molluscs and decapod crustaceans have pain systems. Most people today consider that their moral obligations extend to many animal species. Moral decisions about abortion, euthanasia, and the various ways we protect animals should take into account the research findings about sentience. In addition, all animal life should be respected and studies of the welfare of even the simplest invertebrate animals should be taken into consideration when we interact with these animals