十万个为什么·科学阅读30篇（2）
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Why Do Certain Clams Produce Light When Disturbed — But Only at Night?
为什么某些蛤蜊受惊时会发光，但仅限于夜间？
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These clams contain symbiotic bacteria that emit blue-green light through bioluminescent chemical reactions.
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Light production occurs only in darkness because daylight suppresses the enzyme luciferase activity.
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The flash startles predators, giving the clam time to bury itself deeper in sand quickly.
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Nocturnal behavior aligns with peak predator activity, maximizing survival advantage.
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Researchers discovered that melatonin levels in clam tissues regulate light sensitivity rhythmically.
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Unlike fireflies, clams cannot control flashes voluntarily—they respond purely to mechanical shock.
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Oceanographers use this trait to monitor coastal health and plankton bloom timing.
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The light wavelength matches deep-water transmission peaks, enhancing visibility underwater.
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Genetic studies show light-emission genes activate only under low-light transcription factors.
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This circadian-linked defense reveals how marine life times responses to environmental cycles.