Abstract
Although behavioral studies of whole animals are usually undertaken on rats and mice, studies in crustaceans offer an alternative group that provides new evolutionary insights into the relationship between physiology and behavior. In the cherry shrimp Neocaridina davidi (Bouvier, 1904), food-seeking movement increases in response to glutamate (MSG), decreases when exposed to dopamine, and increases when exposed to glucose. Activity of shrimp individuals was observed in 4l tanks over twenty minutes after individuals were exposed to treatments applied directly into the water. Glutamate-stimulated seeking behavior was statistically similar to seeking behavior after exposure to food pellet filtrate. Glucose also stimulated seeking behavior, but with a reduction over time, whereas MSG-stimulated seeking behavior increased over time. Insulin reduced activity but showed no effect when paired with glucose, whereas dopamine increased activity when paired with glucose. This was contrary to the reduced activity observed when dopamine was paired with MSG. The decrease in activity after exposure to dopamine also contrasts with vertebrate (rat) models where dopaminergic drugs such as caffeine and cocaine are stimulants. The stimulatory effect of dopamine paired with glucose was unexpected given its inhibitory effect on its own or when paired with MSG. This crustacean-based model aims to give new insights regarding the role of inhibitory and stimulatory neurotransmitters on the behavior of whole crustacean individuals. These mechanisms show different results than predicted by vertebrate models, implying either differences in underlying physiology, problems with the vertebrate models, or both.
The sigma-1 receptor as key common factor in cocaine and food-seeking behaviors