frogs (IMAGE) Penn State Caption A new study led by a Penn State biologist reveals that frogs have maintained a surprising number of nonvisual light-sensing proteins over evolutionary time. These proteins, called opsins, play a role in a variety of biological functions including calibration of circadian rhythm, melatonin release, pupil response, and detection and response to seasonal changes. Credit John L. Boyette/Penn State Usage Restrictions Credit must be given to the creator. Only noncommercial uses of the work are permitted. No derivatives or adaptations of the work are permitted. License CC BY-NC-ND Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.