engleski

Understanding the colonization of caves: Effects of constant darkness on surface form of Astyanax mexicanus

The fish Astyanax mexicanus are able to survive in normal conditions of sunlight as well in the depths of caves concealed in complete darkness. Those living in the light conditions are called surface fish and those in the dark are called cavefish. However, on occasion one could encounter a surface fish deep in caves. It is not clear how or what adaptations the surface fish had to make in order to thrive in such different conditions. This research used two cave populations of surface fish from separate caves in Mexico: Pachon and Tinaja. The purpose of this research is to understand the effects of darkness on surface fish by looking at a suite of physiological traits and changes at the molecular level. The study groups include surface fish born at the same time and raised separately, half kept in completely dark conditions, and the other half kept in normal 14 hour light/10 hour dark conditions. All other factors were kept identical between the two groups of fish. Our results showed that fish kept in constant darkness began to show physical changes. It was determined that darkness causes increased stress, measured by cortisol levels, in fish kept in completely dark conditions compared to their counterparts in the light. Surface fish kept in the completely dark conditions also showed a lower metabolic rate as measured by oxygen consumption and a higher tolerance to starvation. Future testing will be conducted to determine if any other physiological or molecular differences exist between the two groups of fish.

cavefish ; effects of darkness ; stress ; metabolic rate ; starvation

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