Q.85 Which one of the following animals has “Book Lungs” as a respiratory organ?
(A) Earthworm
(B) Scorpion
(C) Octopus
(D) Starfish
Scorpion is the correct answer (Option B). Book lungs serve as the respiratory organ exclusively in arachnids like scorpions, enabling efficient gas exchange in terrestrial environments.
Option Analysis
Earthworms (A) respire through their moist skin via cutaneous respiration, lacking specialized organs like lungs.
Octopus (C), a cephalopod mollusk, uses gills in the mantle cavity to extract oxygen from water.
Starfish (D), an echinoderm, relies on dermal branchiae or skin gills for diffusion-based gas exchange.
Scorpion (B) possesses four pairs of book lungs, stacked lamellae-filled structures opening via spiracles for atmospheric oxygen uptake.
Book Lungs Overview
Book lungs consist of thin, vascularized plates resembling book pages, maximizing surface area for O₂ and CO₂ diffusion in air-breathing arachnids. Scorpions have these on abdominal segments 3-6, adapted from aquatic book gills in ancestors like horseshoe crabs.
Animals with book lungs possess a unique respiratory adaptation vital for terrestrial survival, particularly in arachnids preparing for exams like CSIR NET Life Sciences.
Structure of Book Lungs
Book lungs feature lamellae—thin, hemolymph-filled plates stacked like book pages within an atrial chamber, connected to spiracles for air entry. This design supports diffusion in low-oxygen air, unlike aquatic gills.
Animals with Book Lungs
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Scorpions: Four pairs on ventral abdomen for atmospheric gas exchange.
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Spiders: Up to two pairs, often supplemented by tracheae.
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Whip scorpions: Tetrapulmonates retain pairs on abdominal segments.
Incorrect Options Explained
Earthworm respiration occurs cutaneously through moist, vascular skin. Octopus gills filter waterborne oxygen via mantle pumping. Starfish use dermal branchiae and tube feet for diffusion.
Exam Relevance
For CSIR NET, recognize book lungs as arachnid-specific (Arthropoda: Chelicerata), distinguishing from annelid skin, mollusk gills, or echinoderm papulae.
