Do lizards have gills? No, lizards do not possess gills. This article will delve into the mechanisms by which lizards respire, explore the fundamental workings of gills, and clarify why these aquatic respiratory organs are not part of lizard biology.
How Lizards Respire
Lizards are reptiles, and like all other terrestrial vertebrates, they breathe air using lungs. Their respiratory system is adapted for life on land, enabling them to efficiently extract oxygen from the atmosphere. Air enters a lizard’s body through the external nares, or nostrils, moving through nasal chambers before passing into the internal nares.
From there, air travels down the glottis and larynx into the trachea. The trachea then branches into two bronchi, which lead to the lungs. Lizard lungs are typically sac-like structures with internal folds or small chambers called faveoli, which increase the surface area available for gas exchange. Unlike mammals, lizards generally lack a diaphragm and instead rely on muscles between their ribs to expand and contract their body cavity, drawing air into and pushing it out of their lungs.
The Mechanics of Gills
Gills are specialized organs designed to extract dissolved oxygen from water. These delicate structures are typically composed of numerous thin filaments or lamellae, which are richly supplied with blood vessels. This intricate, folded design provides a large surface area, maximizing the efficiency of gas exchange in an aquatic environment.
As water flows over the gill filaments, oxygen diffuses from the water into the bloodstream, while carbon dioxide is released from the blood into the water. Many aquatic animals, such as fish, use a countercurrent exchange system, where blood flows in the opposite direction to the water, further enhancing oxygen uptake. Gills are common in fish, some amphibians during their larval stages like tadpoles, and various invertebrates such as crabs and mollusks.
Why Lizards Do Not Have Gills
Lizards do not possess gills because these organs are adapted for respiration in water and are ineffective in air. Gills rely on the buoyancy of water to keep their delicate, feathery filaments separated, allowing for a large surface area necessary for gas exchange. When removed from water, the gill filaments collapse and stick together, drastically reducing the surface area exposed to the respiratory medium.
The thin, moist membranes of gills are susceptible to drying out in air, which would impair their function. Lizards are terrestrial animals, and their evolutionary path has equipped them with lungs that are suited for extracting oxygen from the atmosphere. The development of lungs was an adaptation that allowed vertebrates to transition from aquatic to terrestrial environments.