Boing Boing considers the lobster, or the most humane way to kill one:
According to Jennifer Basil, associate professor of Biology at City University of New York, Brooklyn College, it’s boiling. That’s because lobsters, like most invertebrates, don’t have the same kind of brain we do. Instead of having one, big central mass of neurons — i.e., the brain — lobsters spread their thinking around their bodies in several smaller masses, called ganglia.But consider David Foster Wallace’s essay “Consider the Lobster”, which begins its examination of these matters (in the pages of Gourmet) by quoting a statement of the Maine Lobster Promotion Council: “‘The nervous system of a lobster is very simple, and is in fact most similar to the nervous system of the grasshopper. It is decentralized with no brain. There is no cerebral cortex, which in humans is the area of the brain that gives the experience of pain.’” Says Wallace,
“Every segment has its own little brain doing its own thing,” says Basil. Which is why, she says, it’s better to boil the lobster and kill all those mini-brains at once. “Cutting it up just creates two uncomfortable lobsters.”
Though it sounds more sophisticated, a lot of the neurology in this latter claim is still either false or fuzzy. The human cerebral cortex is the brain-part that deals with higher faculties like reason, metaphysical self-awareness, language, etc. Pain reception is known to be part of a much older and more primitive system of nociceptors and prostaglandins that are managed by the brain stem and thalamus. On the other hand, it is true that the cerebral cortex is involved in what’s variously called suffering, distress, or the emotional experience of pain — i.e., experiencing painful stimuli as unpleasant, very unpleasant, unbearable, and so on.Endnote  adds:
To elaborate by way of example: The common experience of accidentally touching a hot stove and yanking your hand back before you’re even aware that anything’s going on is explained by the fact that many of the processes by which we detect and avoid painful stimuli do not involve the cortex. In the case of the hand and stove, the brain is bypassed altogether; all the important neurochemical action takes place in the spine.I’m in no position to decide who’s right here. I only invite you to consider what Jennifer Basil has to say, what David Foster Wallace has to say, and what the lobster might have to say.