Your goldfish may not have a ton of personality, but he has feelings too (well, in a rudimentary physiological sense). A new Norwegian study proposes that fish can perceive pain.
In her recent doctoral dissertation, Janicke Nordgreen of the Norwegian School of Veterinary Science posited that fish can feel pain. Unfortunately for some of Nordgreen's test subjects, this meant turning up the heat:
In her project, Nordgreen used Atlantic salmon (Salmo salar), goldfish (Carassius auratus) and rainbow trout (Oncorhynchus mykiss). Her research showed that noxious galvanic stimulation elicited activity in the Atlantic salmon telecephalon, and that the response was graded with stimulus intensity. In another experiment, the goldfish showed escape responses when the temperature exceeded 38 degrees C, which is within the temperature range that is deadly to goldfish. This suggests that the ability to respond to harmful point heat is a conserved feature among vertebrates.
Other experiments in Nordgreen's study included analyzing how Atlantic Salmon broke down morphine and conditioning rainbow trout to follow certain stimuli. In sum, Nordgreen's research makes those restaurants that serve still-flopping fish more or less the Eighth Circle of Ichthyological Hell.