4 public questions tagged with this topic.
Aquatic arthropods and mollusks use branchial respiration, where gaseous exchange occurs through gills.
Ref: NCERT Class 11 Biology Chapter 14: Breathing and Exchange of Gases Respiratory Organs and Human Respiratory System
Aquatic arthropods predominantly respire using gills, diverse filamentous or lamellate outgrowths with large surface area and thin diffusion barrier. Crustacean gills classified as phyllobranchiate or trichobranchiate, located in branchial chambers ventilated by bailer appendage scaphognathite. Horseshoe crabs possess book gills, leaf-like lamellae attached to opisthosomal appendages. Book lungs and internal tracheal tubes are terrestrial adaptations reducing evaporative loss, forming air-filled invaginations with hemolymph counterflow. Cutaneous skin diffusion insufficient for larger active arthropods. Hence gill retention reflects secondary aquatic lifestyle and requirement for efficient oxygen extraction from water.
Ref: Brusca & Brusca, Invertebrates, 3rd ed., Arthropod Respiration Gills; Campbell Biology, 12th ed., Chap 42
Fish respiration primarily involves branchial gills supported by pharyngeal arches. Each gill arch bears filaments further divided into lamellae containing dense capillary networks. Water flows unidirectionally, driven by buccal-opercular pumping in osteichthyans or ram ventilation, counter to blood flow within lamellae, maximizing oxygen extraction via countercurrent exchange with efficiency exceeding 80%. Lungs are present only in dipnoan lungfishes for air breathing, skin respiration minor, tracheae characteristic of insects. Such branchial adaptation supports active swimming, reflecting aquatic oxygen availability and metabolic demands of ectothermic vertebrates living in water.
Ref: NCERT Class 11 Biology, Chapter 4: Pisces – Gills; Campbell Biology, 12th ed., Chapter 42, Gills
Gills in amphibians appear predominantly during aquatic larval phase as external filamentous branched structures richly vascularized serving tadpole respiration in water, subsequently resorbed during metamorphic climax triggered by thyroxine surge inducing apoptosis of branchial tissue and maturation of lungs. Adult terrestrial frogs lack functional gills entirely, relying on skin, lungs and buccopharynx. Aquatic salamanders like Necturus and axolotl exhibit neoteny retaining larval external gills throughout life capable of reproduction. Embryonic gill grooves transient, not permanent, distinguishing typical biphasic development. This concept holds high importance for NEET, CBSE board, CUET and competitive examinations focusing on comparative
Ref: Campbell Biology 12th ed. Chapter 34 Amphibian Development Life Cycle; Gilbert Developmental Biology Metamorphosis
