Pain and aversive states in fish: role of aversive and predatory stimuli and evolutionary considerations
|Institute of Evolutionary Biology, University of Edinburgh, UK|
|(currently on sabbatical at the Institute for Advanced Studies, Berlin )|
Until recently, fish were considered to be little more than automata generating simple stimulus response behaviours. However, recent research is challenging this view. There is now good evidence that some fish have impressive cognitive abilities. The realisation that several fish species are capable of complex cognition has raised two key issues. First, the question of whether fish are capable of perceiving and suffering from pain. And second, work has begun to consider how stressful experiences affect the life history traits and behaviours of these fish. To address these two aspects, I will first present data demonstrating that fish have nociceptors and that behaviour and cognition is adversely affected by noxious stimulation of these pain receptors. Importantly, these adverse changes can be reversed when analgesics are given to the fish. I will also review some recent brain ablation work demonstrating that teleost fish have two forebrain regions that are analogous to the mammalian hippocampus and amygdala. To address the second issue, I will explain how stressors, such as predation pressure, affect the physiology, cognition and behaviour of fish. For example, fish living in high predation sites are typically bolder and take more risks compared to conspecifics that live in areas with low risks of predation. When the abilities of these different types of fish are compared the fish from low predation sites show a quicker more accurate ability to learn compared to their high predation counterparts. Using these types of data we can see how selection favours different phenotypes in different types of environment, and I will discuss the implications of this for selection processes.