Ichthyology (fish buoyancy): Identify the anatomical feature that prevents most bony fishes from sinking. Full question: Most fish do not sink in water primarily because of which internal structure? Choose the correct option.
General Knowledge
Biology
Difficulty: Easy
Choose an option
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ASwim bladder (air bladder)
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BAir sacs like birds
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CAir trapped in spongy bones
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DFatty liver alone (as in sharks)
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EExpanded stomach
Answer
Correct Answer: Swim bladder (air bladder)
Explanation
ConceptMost bony fishes (teleosts) possess a swim bladder—a gas-filled sac that regulates buoyancy via gas secretion/resorption. Cartilaginous fishes (e.g., sharks) lack a swim bladder and partly offset density with large oil-rich livers.
Why others are incorrectBird-like air sacs are absent; spongy bone air does not control buoyancy; fatty liver is species-specific and not the general teleost mechanism; stomach inflation is not a controlled buoyancy organ.
Final AnswerSwim bladder (air bladder).