I agree. The animal kingdom, as such, is a completely agnostic in its definition toward sentience. I once asked my cousin, a vegetarian for twenty or so years, whether she had any moral qualms about eating an anemone, for example, a creature that likely can't feel pain in any way that we would describe as pain, given that it lacks the mechanisms to do so from a neurobiological point of view. She told me yes, but couldn't articulate why. Not that her opinion isn't valid, but it perhaps points to a critical lack of knowledge of how organisms interact with their environment, and how pain is processed. In my world view, the grey area is around birds and mammals. That is, I have no objection whatever to boiling a lobster.[W]hen a living thing has a primitive or no nervous system the word "suffering" may not even be meaningful.