Animals that can breathe both air and water possess a unique biological adaptation, allowing them to extract oxygen from two distinct environments. This dual respiratory capability enables certain species to thrive in diverse habitats, bridging the gap between aquatic and terrestrial life. This ability provides flexibility for survival in conditions where oxygen availability might fluctuate.
Animals with Dual Breathing Abilities
A variety of animals exhibit the unique ability to breathe both air and water. Among the most recognized are amphibians, including frogs, salamanders, and newts, which typically begin life in water with gills before developing lungs for air breathing as adults. Many amphibians also retain the capacity for cutaneous respiration, absorbing oxygen through their skin.
Lungfish represent another example, possessing both gills for aquatic respiration and lung-like organs that allow them to breathe atmospheric air. This adaptation is useful for surviving periods of drought when their aquatic habitats dry up, as they can burrow into mud and aestivate. Mudskippers, a type of amphibious fish, spend significant time out of water, using their pectoral fins to “walk” on land and absorbing oxygen through their skin and specialized gill chambers that hold water.
Some species of turtles, such as the common snapping turtle, can also engage in dual respiration to a limited extent. While primarily air-breathers with lungs, they can absorb some oxygen through specialized vascularized membranes in their cloaca, particularly during prolonged underwater periods or hibernation. Certain aquatic insects, like mosquito larvae, utilize siphons to access atmospheric air while submerged.
How Animals Breathe Both Air and Water
Animals employ various biological mechanisms to facilitate breathing in both air and water. Gills are a primary structure for aquatic respiration, featuring numerous thin filaments with a large surface area for efficient oxygen absorption from water. Fish, including lungfish and mudskippers, utilize gills when submerged, allowing water to pass over these structures and exchange gases.
For air breathing, many of these animals have developed lungs, which are internal organs designed to extract oxygen from the atmosphere. Amphibians, for instance, transition from gill-based respiration as larvae to lung-based breathing as adults, enabling them to spend significant time on land. Some amphibians and mudskippers also use a process called buccal pumping, where they rhythmically lower and raise the floor of their mouth to draw air in and force it into their lungs.
Cutaneous respiration, or breathing through the skin, is a widespread method for dual breathers, especially for oxygen uptake from water or moist environments. The skin must remain moist for this to occur, as oxygen needs to dissolve into a thin film of water before diffusing across the skin surface into capillaries. Many amphibians rely heavily on their permeable skin for a substantial portion of their oxygen intake, both in and out of water.
Why Dual Breathing is Essential for Survival
The ability to breathe both air and water provides significant survival advantages, particularly in environments prone to change. Fluctuating water levels, such as those caused by droughts, can render aquatic habitats uninhabitable for purely water-breathing organisms. Dual breathers, like lungfish, can survive these periods by switching to air breathing and burrowing into the mud, allowing them to persist until water returns.
Accessing atmospheric oxygen is crucial in aquatic environments with low dissolved oxygen levels, a common occurrence in stagnant ponds or warm waters. By surfacing to breathe air, animals like mudskippers and many amphibians can escape oxygen-depleted water, preventing suffocation. This adaptability allows them to exploit niches that are inaccessible to less versatile species.
Dual breathing also offers advantages for predator avoidance and foraging. Animals can move between aquatic and terrestrial environments to escape threats, finding refuge where their predators cannot follow. This flexibility also opens up diverse food sources across both land and water, expanding their dietary options. This capacity is a strong adaptation for inhabiting transitional or unstable ecosystems.