Circadian rhythms affect the electroretinogram, compound eye color, striking behavior, and locomotion of the praying mantis, Hierodula patellifera (Serville)

Abstract

Abstract Many behaviors and physiological processes oscillate with daily, or circadian rhythms that are synchronized to environmental cues (e.g., light onset), but persist with periods of approximately 24 hours in the absence of such cues. We used a multilevel experimental approach to assess whether circadian rhythms modulate several aspects of the visual physiology and behavior of the praying mantis, Hierodula patellifera. The approach included electroretinograms (ERG) to assess compound eye sensitivity, colorimetric photographic analyses to assess compound eye color changes (i.e., screening pigment migration), behavioral assays of responsiveness to computer generated, prey-like visual stimuli, and analyses of locomotor activity patterns on a modified treadmill apparatus. Our results indicate that circadian clocks control and/or modulate each of the target behaviors. Strong rhythms, persisting under constant conditions, with periods of approximately 24 hours were evident in photoreceptor sensitivity to light, appetitive responsiveness to prey-like stimuli, and gross locomotor activity. In the former two cases, responsiveness was highest during the subjective night and lowest during the subjective day. Locomotor activity was strongly clustered around the transition time from day to night. In addition, pigment migration and locomotor behavior responded strongly to light/dark cycles and anticipated the light/dark transition suggesting that the circadian clocks modulating both were entrained to environmental light cues. Together, these data indicate that circadian rhythms operate at the cellular, cellular systems, and organismal level in the mantis H. patellifera. Our results represent an intriguing first step in uncovering the complexities of circadian rhythms in the Mantodea.