engleski

Adaptive differences between dopamine-related locomotor activity in cave and surface dwelling Astyanax mexicanus

Many behavioral differences have evolved between cave and surface dwelling Astyanax mexicanus. Here we explore locomotor activity and its relationship to dopamine between these two subgroups. Three different assays were used to quantify locomotor activity between cave and surface Astyanax mexicanus by varying the size and shape of a swimming arena. The number of times that fish crossed a line drawn in the center of each arena during a specific time period was recorded. Our results show that the independently evolved Pachon and Tinaja cavefish populations have increased activity levels compared to conspecific surface dwelling fish. To test the hypothesis that cavefish have increased activity levels because of the need to be constantly searching for food in nutrient depleted cave environments, we studied the differences in activity between fish that had been fed varying amounts. We found that fish fed more have decreased activity confirming the hypothesis and suggesting that increased locomotor activity is adaptive in cavefish. Recently we discovered that Pachon cavefish have higher dopamine levels than surface fish. To understand the effect of increased dopamine levels on locomotor activity we tested different fish populations in arenas containing exogenous dopamine. The addition of dopamine increased the activity of Pachon cavefish, Tinaja cavefish, and surface fish. In order to understand the effects of dopamine on the activity levels, we explored the effects of the dopaminergic agonist quinpirole and the antagonist haloperidol on locomotor activity. The agonist and antagonist resulted in increased and decreased activity levels in cavefish respectively but had little or no effects on surface fish, confirming that activity changes in cavefish are related to dopamine. Our future goal is to understand the causes and mechanisms for the differences in locomotor activity and their relationship to dopamine levels in cave and surface Astyanax.

cave fish ; locomotor activity ; dopamine

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