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Why Do Some Deep-Sea Fish Have Transparent Heads?
为什么某些深海鱼拥有透明的头部？
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The barreleye fish lives 600–800 meters deep where sunlight barely penetrates the ocean surface.
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Its dome-shaped, transparent head shields two upward-facing tubular eyes packed with light-sensitive rods.
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This clear casing protects delicate retinas while allowing maximum photon capture in near-total darkness.
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Inside the dome, fluid-filled tissue maintains optical clarity and internal pressure balance.
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The fish rotates its eyes independently—to scan overhead for bioluminescent prey or predators above.
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Its brain lies directly beneath the dome, surrounded by a gelatinous matrix that transmits light without distortion.
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Unlike opaque skulls, transparency eliminates internal shadows that would blur vision in dim environments.
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CT scans reveal bony struts reinforcing the dome without obstructing visual fields.
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Evolution favored this design because detecting faint glows is more critical than camouflage at such depths.
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Biologists study its optics to improve low-light imaging sensors for underwater exploration.