Abstract
We studied the light-triggered current of crayfish photoreceptors. We found that when a train of light flashes of either increasing or decreasing intensity is applied, the current waveform presents the non-linear behavior known as hysteresis. Additionally, we observed that the extent of this response depends on the circadian time at which the pulses are applied. We hypothesize that positive feedback loops of biochemical networks underlying light energy transduction are responsible of the observed behavior. It has been demonstrated that a dynamical system hysteresis provides a mechanism that enhances its robustness against random perturbations. Taking into account this characteristic we hypothesize that the electrical-response hysteresis of crayfish photoreceptors: 1) makes the visual system more stable to environmental noise, and hence 2) adds stability to circadian clock oscillations.