what is its function in animals?
Seasonal functions such as reproduction, behavior, coat growth, and camouflage coloring.
Other animals
The change in duration of secretion thus serves as a biological signal for the organization of daylength-dependent (photoperiodic) seasonal functions such as reproduction, behavior, coat growth, and camouflage coloring in seasonal animals. 
the primary high energy molecule in human metabolism is Adenosine triphosphate (ATP) what is catabolism? It is the set of metabolic processes that breaks down large molecules. which hormones are related to it? Cortisol, glucagon, adrenaline, cytokines, orexin and melatonin. what is the emotional response due to the third one? Fear. how does the first hormone related to metabolism of glucose? Cortisol stimulates the synthesis of 'new' glucose from non-carbohydrate sources; this is known as gluconeogenesis.. is process resisted by insulin? Yes. when was this substance which resists the process discovered? 1921. can it be extracted? Yes. from where? Pancreas. can we find in plants the last hormone in the list of hormones mentioned above? Yes. is it responsible for any memory related disease? No. how does it affect immune system? An antiinflammatory effect seems to be the most relevant. is it also found in animals? Yes.
Many animals use the variation in duration of melatonin production each day as a seasonal clock. Onset of melatonin at dusk promotes activity in nocturnal animals that are active at night It promotes activity in nocturnal animals and sleep in diurnal ones.
Melatonin Melatonin Melatonin
Other animals Other animals Other animals
Many animals use the variation in duration of melatonin production each day as a seasonal clock.  the onset of melatonin at dusk promotes activity in nocturnal (night-active) animals and sleep in diurnal ones including humans. Known as "the hormone of darkness", the onset of melatonin at dusk promotes activity in nocturnal (night-active) animals and sleep in diurnal ones including humans.
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Melatonin [SEP] Other animals
The change in duration of secretion thus serves as a biological signal for the organization of daylength-dependent (photoperiodic) seasonal functions such as reproduction, behavior, coat growth, and camouflage coloring in seasonal animals. In seasonal breeders that do not have long gestation periods and that mate during longer daylight hours, the melatonin signal controls the seasonal variation in their sexual physiology, and similar physiological effects can be induced by exogenous melatonin in animals including mynah birds and hamsters. Melatonin can suppress libido by inhibiting secretion of luteinizing hormone and follicle-stimulating hormone from the anterior pituitary gland, especially in mammals that have a breeding season when daylight hours are long.