How do fish breathe underwater?

Introduction

Fish have evolved various mechanisms to extract oxygen from their environment, allowing them to thrive in diverse aquatic habitats. While most fish rely on gills to breathe underwater, some species have developed the ability to breathe air, using specialized organs. This synthesis explores the mechanisms and conditions under which fish breathe underwater and the factors influencing their respiratory modes.

Key Insights

Dual Respiratory Modes in Fish:
- Many fish species can obtain oxygen from both air and water, using gills and lungs or other air-breathing organs. This bimodal breathing is observed in species like bowfin (Amia calva) and spotted gar (Lepisosteus oculatus), which consume significant amounts of oxygen from the air during low-level exercise in oxygen-rich water.
Sensory Control of Respiratory Mode:
- The transition between water and air breathing in bimodal fish is regulated by sensory information from peripheral receptors. Oxygen-sensitive chemoreceptors play a dominant role, with internal chemoreceptors increasing both aquatic and aerial respiration, and external chemoreceptors shifting the emphasis to air breathing. Mechanoreceptors in air-breathing organs also help match ventilation to perfusion, while defense receptors can inhibit gill ventilation in favor of air breathing when stimulated by waterborne irritants or emersion.
Environmental Influence on Respiratory Patterns:
- The climbing perch (Anabas testudineus) adjusts its respiratory patterns based on the oxygen and carbon dioxide concentrations in the water. In high CO2 environments, the fish increases air-breathing frequency and may stop aquatic respiration entirely, relying solely on aerial respiration. This adaptation allows the climbing perch to survive in hypercarbic water by using its air-breathing organs exclusively.

Conclusion

Fish exhibit a range of respiratory adaptations that allow them to extract oxygen from both water and air. Bimodal breathing is controlled by sensory receptors that respond to environmental conditions, such as oxygen and carbon dioxide levels. These adaptations enable fish to survive in various aquatic environments, including those with low oxygen or high carbon dioxide concentrations.

How do fish breathe underwater?

Summary

Introduction

Key Insights

Conclusion

Sources and full results

Air-breathing during activity in the fishes amia calva and lepisosteus oculatus

During low-level exercise in oxygen-rich water, more than 50% of oxygen consumed by bowfin and spotted gar fishes is from air, suggesting that air-breathing may play a significant role in their survival.

Control of the respiratory mode in air-breathing fishes

Control of respiratory mode in air-breathing fishes relies on sensory information from three major peripheral receptors, with external chemoreceptors shifting the ventilatory emphasis from water to air breathing and internal chemoreceptors increasing both aquatic and aerial respiration.

Respiration in an Air-Breathing Fish, the Climbing Perch, Anabas Testudineus : II. Respiratory Patterns and the Control of Breathing

Climbing perch fish's respiratory patterns are influenced by carbon dioxide content, pH, and oxygen content, with air-breathing increasing in high CO2 water and aquatic respiration stopping when more than 20% CO2 is bubbled in.

Swimming in air-breathing fishes.

Air-breathing fishes exhibit diverse swimming physiology, with some relying on air breathing for aerobic metabolism, while others prefer aquatic respiration for recovery and predator avoidance.

Breaking wind to survive: fishes that breathe air with their gut.

Gut air breathing (GAB) in fishes has evolved multiple times, allowing them to extract oxygen from the air, supplementing aquatic respiration in hypoxic waters, and influencing their behavior in various ecological contexts.

Respiration in the African lungfish Protopterus aethiopicus. II. Control of breathing.

African lungfish exhibit irregular breathing patterns, with branchial breathing often preceding air breathing, and breathing from hypoxic gas mixtures increases air breathing rate.

The Biology of Air-Breathing Fishes

Fish air breathing has played a fundamental role in vertebrate evolution and can be observed in various freshwater and marine habitats.

Air- breathing in fish: Air- breathing organs and control of respiration: Nerves and neurotransmitters in the air-breathing organs and the skin.

Fishes' air-breathing control is influenced by peripheral and central nervous system receptors, with neuroepithelial cells in gills and lungs playing a role in respiratory reflexes.

Comparative transcriptome analysis between aquatic and aerial breathing organs of Channa argus to reveal the genetic basis underlying bimodal respiration.

The genetic basis for bimodal breathing in fish, such as Channa argus, involves angiogenesis, elastic fiber formation, ion uptake, and acid-base balance, with the aerial breathing organ being more efficient for gas exchange.

Respiration of Air by the Primitive Fish Polypterus senegalus

Polypterus senegalus fish uses spiracles to inhale air, which is passed to the lungs, for respiration in low oxygen concentrations and during periods of excessive activity.

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