Melatonin Counteracts the Stimulatory Effects of Blinding or Exposure to Red Light on Reproduction in the Skipper Frog Rana cyanophlyctis

Red light accelerates and melatonin retards metamorphosis of frog tadpoles

“…The extra ocular perception could be through the frontal organ-photoreceptor elements. At least in adult Rana cyanophlyctis frontal organ not only perceives but also differentiates different colours of light [3]. However perception of light through other photoreceptor elements located elsewhere in the skin or brain regions cannot be ruled out.…”

“…In other words the observed effects of red light may not be associated with actually 'seeing' the colours. Even the red light-induced stimulation of ovarian function in this species occurred irrespective of whether the perception of light was ocular or non-ocular [3]. Since red light had its effect on metamorphosis even in blinded tadpoles it is necessary to study the biological importance of non-ocular photoreceptors, especially those present in the frontal organ.…”

“…Whether the effects of light and its spectra on metamorphosis of the tadpoles are mediated by changes in thyroid physiology, directly or indirectly, needs to be ascertained. While reporting on the effects of enucleation and exposure to red light on ovarian function in Rana cyanophlyctis Joshi and Udaykumar [3] suggested that enucleation-induced ovarian stimulation was probably due to elimination of ocular source of melatonin, which is a major source of melatonin in frogs [11]. Metamorphosis of tadpoles involves a complex sequence of changes in which variations in tissue sensitivity occur during various stages of development [15].…”

“…Anuran amphibians are unique in possessing an extracranially located frontal organ having photoreceptor elements [2]. An earlier study from this laboratory reported that perception of light either through ocular or extra ocular (through frontal organ) pathways modulates ovarian function in the Indian skipper frog Rana cyanophlyctis [3]. Recently, in a follow up study we set up an experiment to examine chromotactic behaviour of the tadpoles.…”