Meeting Abstract
Euryhaline fish species are able to tolerate a wide range of salinities. However, the extent to which fish populations cope with the energetic costs associated with fluctuating salinity levels through plasticity remains understudied. Moving from freshwater to brackish water should increase the minimum amount of energy required for basic physiological processes, or routine metabolic rate (RMR), and could decrease the maximum metabolic rate (MMR) if fish decrease gill permeability. An increase in RMR along with a decrease in MMR can result in an insufficient scope of activity, or aerobic scope (AS) to promote osmotic homeostasis. In Trinidad, the guppy (Poecilia reticulata) is confined to freshwater and behaviorally avoids brackish water, despite being considered euryhaline. To test if reduced AS contributes to the avoidance of brackish water, we conducted a common garden experiment that examined how long- and short-term acclimation to salinity altered AS. Wild-caught guppies were bred out to the second generation, and upon birth were split into either fresh- (0ppt) or saltwater (30ppt). RMR and MMR were measured, and AS was calculated in their rearing salinity to test long-term acclimation. We also used a gradual, step-wise acclimation to 5, 15, and 30ppt to test the effects of short-term acclimation. We predict AS should be maintained after long-term acclimation to saltwater, but should decline in response short-acclimation. Although the mechanisms of salinity acclimation are known in euryhaline fish, less is known about the potential trade-off between acclimation ability to salinity changes and other performance traits associated with fitness.
