Circadian rhythms and food entrainment of lionfish (Pterois volitans)
Circadian rhythms are common in many organisms and provide an organism synchrony with its environment, which is vital for survival. Entraining factors, called Zeitgebers, can modulate and synchronize the internal clock. Prey availability can change circadian rhythms and has been modeled in the laboratory with the presentation of food. The anticipation of the presentation of food, called food-anticipatory activity (FAA), has been studied extensively in mammals but is poorly understood in fish. The aim of the present study was to examine circadian rhythms and FAA of the Indo-Pacific lionfish, Pterois volitans. P. volitans is an invasive species of fish that may alter the composition of coral reefs. Lionfish have become established from the southeastern coast of the United States through the Caribbean Islands and parts of South America. In the wild, lionfish are most active around the crepuscular periods, dawn and dusk, and least active at midday. Lionfish maintained under constant conditions (CC) for two weeks did not demonstrate the same patterns of activity observed in the wild. The pattern that emerged was similar overall but much less distinct, suggesting that the pattern observed in the wild requires a specific Zeitgeber to persist. When fed consistently at 1300 hrs for two weeks under CC, a significant change in activity levels occurred. Lionfish demonstrated clear evidence of FAA through a significant increase in time spent active during the hour preceding prey availability. This study adds to the literature on fish chronobiology and provides insight into the adaptive nature of lionfish.