Pineal GlandMelatoninReceptors, MelatoninReceptor, Melatonin, MT1Receptor, Melatonin, MT2Acetylserotonin O-MethyltransferaseArylalkylamine N-AcetyltransferasePinealomaCircadian RhythmSalivary GlandsPhotoperiodLightArylamine N-AcetyltransferaseMammary Glands, AnimalExocrine GlandsSubmandibular GlandTryptaminesDarknessParotid GlandRetinaSweat GlandsChickensSebaceous GlandsRod OpsinsPeriodicity