Subterranean Fishes of the World

5635

2022

AIM 2022

39

We conducted several multi-year, longitudinal field studies. Our first results concern foraging behaviors. Cavefish respond to a host of multisensory signals such as water vibration, sound, and smell to find food. Previous studies showed asymmetries: VAB correlates only with the left side number of neuromast, cavefish have a bent skull preferentially to the left, and a QTL signal for the right-side number of neuromast. Our field studies in 5 different caves throughout three years suggest preference of side with which to examine potential prey. Several cavefish populations showed behavioral lateralization or “handedness” by preferentially circling a vibrating device counterclockwise, using the left-side neuromasts of their face. In the lab, Pachón 10-13 postfertilization fry preferred their right side to strike at nauplii shrimp. The laterality resulted in differently sized semicircular asymmetric striking ranges, whose combined area/volume were larger than if striking preference was symmetrical. We discuss a mathematic model that incorporates these semicircular asymmetric response ranges. Model predicts that under low food availability, enlarged behavioral ranges due to laterality are favored, but under high food availability, the disadvantages caused by laterality dominate and symmetry is favored. Our 3-year study also showed that while Astyanax is a year-long spawner, its peak of reproduction may occur at the end of January, when temperatures increase. The fry’s stomach contents show food is more available during the dry season. For adult Pachón cave, on the contrary, organic carbon contents of the mud, adults’ stomach contents, and their length and weight throughout the year suggest nutrition levels are relatively constant year-round. Food regimes change between post-larval and adult stages, so seasons have a strong impact on reproduction or survival of fry, but are less important to adults in Pachón cave.

1