Meeting Abstract
45.6 Jan. 6 Energy and predation costs of firefly courtship signals WOODS, W. A. Jr.*; HENDRICKSON, H.; MASON, J.; LEWIS, S. M.; Tufts University; Tufts University; Tufts University; Tufts University william.woods@tufts.edu
A courtship signal may impose more than one cost, and despite the acknowledged theoretical importance of these multiple costs, little is known about their relative importance. In addition, although bioluminescent signals are widespread in the animal kingdom, the costs associated with light production have never been measured. We quantified separately the energy and predation costs associated with the bioluminescent courtship signals of fireflies. We made respirometry measurements of the energy required to generate bioluminescent flashes, and found that energy expenditure during periods of flash production averaged a nominal 37 ±6% (mean ± SEM, n = 13) higher than when the same beetles were measured when not flashing (paired t = 5.83, 12 df, P < 0.0001). Percent elevation of metabolic rates above resting values increased as a direct function of bioluminescent pulse rates recorded by time-synchronized video imaging (regression r2 = 0.60, F1,10 = 13.47, P < 0.01). We also conducted field experiments in which light emitting diodes (LEDs) were used to accurately simulate courtship flashes of Photinus greeni females. Predatory Photuris fireflies were attracted significantly more often to traps with LEDs than to control traps (paired t = 12.04, 30 df, P < 0.0001). Furthermore, higher rates of signaling significantly increased the risk of Photuris predation (logistic regression likelihood ratio chi-square = 8.57, n = 31, P < 0.01). These results demonstrate that while energy expenditure of flashing is small, predation cost can be considerable, and suggest the importance of thinking beyond dyadic interactions toward a broader framework of communication networks involving multiple categories of receivers.
