Do Invertebrates Have Emotions?

Recommendable! This is a comprehensive overview article. Why should emotions be confined to vertebrates? How necessary is a nervous system or are there alternatives?

"... Decades ago, scientists and lawmakers had all but reached a consensus that invertebrates could not feel pain, let alone other emotions like joy or fear. Recently, however, evidence is mounting that invertebrates are more than just reflexive beings. Experiments in bees, crabs, and octopuses show that some invertebrate animals can learn from painful experiences, have positive and negative emotion-like states, and might even experience a range of other emotions beyond pain and pleasure. ...
Still, many scientists remain extremely skeptical, and the question of whether invertebrates can experience emotions is hotly debated. ..."

From the abstract:

"If the UK joins a handful of other nations to recognize the sentience of invertebrates, such as cephalopod mollusks and decapod crustaceans, by, for example, prohibiting the boiling of live lobsters, this will be based on evidence that emotions and felt experiences (i.e., sentience) are not limited to animals close to humans, such as the mammals. This topic has been heavily debated in both affective neuroscience (how to define an emotion?) and philosophy (what is the moral relevance of animal experiences?), but a consensus on the criteria for and implications of recognizing animal sentience seems to be emerging"

Do Invertebrates Have Emotions? | The Scientist Magazine® And how do scientists go about answering that question?

The question of animal emotions (no public access) Do animals, including invertebrates, have felt emotions and does this morally matter?