Spectral tuning of bioluminescence and visual sensitivity in males of Brazilian firefly species inhabiting dim light environments (Coleoptera: Elateroidea: Lampyridae).

Bioluminescence in fireflies is essential for sexual communication, and each species has evolved a specific bioluminescence emission capable of being detected by its visual system. This spectral "tuning" between visual sensitivity and bioluminescent emission has been established in 14 species of North American fireflies inhabiting diverse photoecological niches. Here we extend that research to three Brazilian species. Macrolampis omissa inhabits the Cerrado (savannas), while Photinus sp1 and Pyrogaster moestus are often sympatric species inhabiting borders of mesophyll rain forests and secondary growth. P. moestus particularly favors humid areas of the forest. M. omissa and Photinus sp1 are twilight-active fireflies emitting yellow bioluminescence. P. moestus is a "twi-night" species emitting green bioluminescence. It initiates flashing at the end of twilight and continues activity into the night. The visual spectral sensitivity of dark-adapted compound eyes in these three species is similar, showing a maximum in the yellow-green wavelengths and a secondary peak in the near-UV, suggesting the presence of two receptors. The bioluminescence emission spectrum in each species is tuned to its yellow-green visual sensitivity peak. Green chromatic adaptation experiments on Photinus sp1 and P. moestus suggest the presence of a blue receptor. The presence of near-UV, blue, and long-wavelength receptors in the compound eyes would enable a trichromatic color vision in Brazilian firefly species active in dim illumination.