What causes men to ejaculate different amounts of semen?

I was curious, why do some men ejaculate much more semen than other men? . And how come sometimes, a man can have a huge amount of semen and other times, not as much? . Does it mean that he's more aroused when he produces more? . And I don't mean in succession. I mean one day he ejaculates A LOT of... show more I was curious, why do some men ejaculate much more semen than other men?
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And how come sometimes, a man can have a huge amount of semen and other times, not as much?
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Does it mean that he's more aroused when he produces more?
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And I don't mean in succession. I mean one day he ejaculates A LOT of sperm, and then another not so much?
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Just curious, couldn't find the answer. Haha.
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