Bryan Wilson
Most fish reproduce seasonally or on a regular basis, with spawning taking place at the right time to guarantee maximal progeny survival. A species-specific endogenous timing system, which fundamentally relies on a well-equipped physiological response mechanism to changing environmental stimuli, controls the order of reproductive events in an annual cycle. A huge variety of animals, including fish, use the length of solar light, or photoperiod, as one of the most dependable environmental signals to coordinate their seasonal spawning. The pineal gland is a significant photoneuroendocrine component of the brain in vertebrates that synthesises and releases melatonin (N-acetyl5-methoxytryptamine) into the blood in synchrony with the lightdark cycle of the environment.
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