Do Lizards Have Lungs? A Detailed Look At Lizard Respiration

Lizards are fascinating reptiles that have roamed the Earth for over 200 million years. If you’ve ever handled a lizard or peeked into a lizard terrarium, you may have wondered: do lizards have lungs? Read on to learn the answer.

If you’re short on time, here’s a quick answer: Yes, lizards do have lungs. Lizards are air-breathing reptiles that use lungs to breathe. Their lung structure and breathing methods differ from mammals, but they still rely on lungs to intake oxygen and release carbon dioxide.

The Respiratory System of Lizards

Lizards Have Two Lungs

Just like humans and other mammals, lizards have two lungs located in their chest cavity. The lungs are spongy and full of air pockets known as alveoli. When the lizard inhales, air flows into the trachea (windpipe) and down into the lungs, filling the alveoli with oxygen.

The alveoli provide a large surface area for gas exchange to occur. As the lizard exhales, carbon dioxide leaves the body.

Lizard Lungs are Simple but Effective

While lizard lungs get the job done, they lack some of the complexity seen in mammalian lungs. For example, lizard lungs do not contain respiratory bronchioles or alveolar ducts. Their lungs are more sac-like in structure. Additionally, lizards do not have a diaphragm to facilitate breathing.

However, their lightweight and spongy lungs allow for adequate oxygen absorption and carbon dioxide expulsion.

An interesting feature of some lizards is that they have multichambered lungs. Monitor lizards have this adaptation, with as many as 12 chambers per lung! The chambers likely act as bellows to move air through the lungs when the lizard inhales and exhales.

Lizards Use a Combination of Lungs, Ribs, and Throat to Breathe

A lizard’s ribs play an important role in moving air in and out of the lungs. When the lizard inhales, specialized muscles pull the ribs upward and outward, expanding the chest cavity and drawing air into the lungs. As the ribs return to their normal position, the lizard exhales.

Additionally, some lizards rely on buccal pumping to help them breathe. This means they rhythmically contract and expand their throat muscles to pull air into the lungs. Species like bearded dragons are known to employ buccal pumping regularly.

Lizards also have air sacs connected to their lungs that can store oxygen. The air sacs give lizards an extra buffer when holding their breath underwater or engaging in strenuous activity. Some species even have a glowing pigment called fluorescent erythrophores in the air sacs to help absorb heat from the sun!

How Do Lizards Breathe?

Lizards Mostly Use Their Ribs to Inhale and Exhale

The primary way lizards breathe is by using their ribs. When a lizard inhales, the rib muscles contract and pull the ribs forward and outward, expanding the chest cavity and drawing air into the lungs.

As the ribs swing outwards, they also pull the vertebrae in the spine back, further expanding the body cavity (1). During exhalation, the ribs swing back inward, reducing the chest cavity volume and forcing air out of the lungs. This method of breathing is known as costal ventilation.

The intercostal muscles between the ribs also assist with breathing. When the intercostal muscles contract, they pull the ribs upward to open up the chest cavity. Relaxing the intercostal muscles allows the ribs to move back down, expelling air from the lungs (2).

Having ribs allows for more efficient breathing than relying solely on throat or mouth movements. The increase in chest volume creates a greater change in thoracic pressure, pulling more air into the lungs.

Lizards generally take shallow rapid breaths compared to mammals, but their ribcage anatomy optimizes airflow.

Some Lizards Supplement Breathing with Their Throat

While most lizards use ribs as their primary breathing mechanism, some species also use throat or mouth movements to supplement costal ventilation. This is known as buccal pumping. When a lizard expands its throat, it increases the space for air to enter the lungs.

Closing the mouth and throat forces air back out (3).

Buccal pumping may allow for deeper, slower breaths compared to only using the ribs. Species like bearded dragons often use buccal pumping when at rest to fully inflate their lungs. However, this breathing method requires considerable mouth and throat muscle strength.

Smaller lizards generally rely entirely on their ribs for breathing due to having less developed buccal muscles.

Breathing Frequency Varies Among Lizards

Breathing frequency can differ substantially between lizard species depending on their size, activity level, and habitat temperature:

Smaller lizards tend to breathe more rapidly than larger species. Their higher surface area to volume ratio means they lose heat quicker and require faster oxygen circulation (4). Lizards also breathe faster when active versus resting.

Higher body temperatures raise their metabolism, necessitating additional oxygen.

Environmental temperatures further influence breathing rates. Lizards often pant to dissipate heat through evaporation. Breathing frequencies may double or even triple on hot days to maximize heat loss.

Lung ventilation allows lizards to thrive in diverse environments despite their lack of sweat glands.

Unique Breathing Adaptations in Certain Lizards

Chameleons Have Specialized Lungs

Chameleons have a very unique lung structure that allows them to breathe more efficiently. Their lungs are attached to the inside of their ribcage in a sponge-like way, which increases the surface area for gas exchange.

When the chameleon inhales, the pressure differences cause the lung tissue to expand like a balloon, filling up more space in the chest cavity. On exhalation, the elastic tissue compresses down again. This allows chameleons to take bigger breaths than other lizards of similar size, which helps provide the oxygen needed to support their highly active lifestyle.

Their specialized lung anatomy also enables chameleons to breathe while running, climbing, eating, and even changing colors.

Aquatic Lizards Can Extract Oxygen from Water

Certain lizards have adapted the ability to draw oxygen from the water around them, allowing them to stay submerged for long periods of time. Aquatic lizards like marine iguanas have vascularised mouth tissues that act as primitive gills.

When they submerge, seawater flows into their mouths and dissolved oxygen gets absorbed directly via the mouth tissue capillaries. Their throats can rhythmically pump water over the gills, enabling a constant flow of oxygen.

Some lizards also have skin flaps or fringes that increase the surface area for cutaneous respiration. By using dissolved oxygen in water, these lizards can minimise the need to surface for air.

Monitors Have a Unidirectional Lung

Monitor lizards have a very unique lung anatomy that allows for unidirectional airflow. Their lungs contain septa and connective tissue that direct airflow in one direction, through saccular outpoaches called faveoli.

When the monitor inhales, air enters the posterior end of the lung and travels anteriorly through the faveoli, which extract oxygen. Upon exhalation, air exits through distinct anterior bronchi. This unidirectional flow allows for complete filling and emptying of the lung with each breath.

The faveolar structure also provides a very large surface area for gas exchange. This special lung design powers monitors’ incredible athletic abilities, allowing them to run rapidly for miles in pursuit of prey while still breathing hard.

Why Do Lizards Need Lungs?

Lungs Allow for Internal Gas Exchange

Lizards, like all terrestrial vertebrates, require oxygen to power cellular respiration and carbon dioxide removal as a byproduct of this process. Lungs provide a highly efficient means of facilitating gas exchange – the intake of oxygen and removal of carbon dioxide – internally rather than relying solely on external respiration through the skin.

With increased body size and activity levels, lungs become essential, as the skin surface area is insufficient for the scale of respiration required. Studies show that for lizards above 10 grams in mass, lungs begin playing a major role in gas exchange.

Lizards Are Too Large to Breathe Through Their Skin

Smaller reptiles like salamanders have sufficient skin surface area relative to their oxygen needs for cutaneous (through the skin) respiration. But most lizards are too large relative to their skin area to meet their respiratory needs this way.

Larger lizards like monitor lizards and iguanas have high oxygen demands from their sheer bulk that requires the enhanced respiratory capacity lungs provide.

Lungs Suit Lizards’ High Activity Levels

Most lizards are very active reptiles. They use burst speed running to catch prey and evade predators. Some species like monitor lizards sustain activity over longer durations. This requires elevated levels of gas exchange compared to their more sedentary turtle cousins.

Additionally, most lizards are ectothermic – relying on external heat sources to power their metabolism. As external temperatures rise, so does a lizard’s internal temperature and concomitant increase in oxygen uptake and carbon dioxide release.

Lungs provide the increased capacity ectotherms need to meet respiratory demands across varying environmental temperatures.

Lizard Lung Health and Potential Problems

Signs of Healthy Lizard Lung Function

There are a few key signs that indicate a lizard’s lungs are functioning properly. Healthy lungs will allow the lizard to be active and move around without appearing short of breath. A healthy lizard will not make wheezing sounds or have an open-mouthed breathing pattern.

Clear nasal discharge is also a good sign. Good appetite and steady weight are further indicators that the respiratory system is working as it should.

Issues that Can Affect Lizard Lung Health

There are various issues that can negatively impact a lizard’s respiratory health, including:

• Respiratory infections – These are typically caused by bacteria, fungi or parasites invading the lungs. Symptoms include wheezing, nasal discharge and lethargy.
• Pneumonia – An infection of the lungs that causes inflammation. Lizards with pneumonia often have labored breathing and lack energy or appetite.
• Abscesses – Pockets of pus that form in the lungs, usually due to chronic infection. Can obstruct breathing.

Other problems like inhaling foreign objects, trauma resulting in collapsed lungs, lung cancer or exposure to toxins can also affect lizards’ respiration.

Caring for a Lizard with Respiratory Illness

If a lizard develops respiratory problems, the first step is to take it to a qualified reptile veterinarian for an accurate diagnosis and treatment plan. Treatment depends on the specific illness but may include:

• Antibiotics for infections
• Anti-inflammatory medication
• Breathing treatments with a nebulizer
• Surgery to remove obstructions or abscesses

At-home care for a lizard with lung problems involves keeping its habitat very clean, warm and stress-free. Extra heat is often needed to maintain ideal body temperature. Nutritional support is also important, and the lizard’s preferred food should be offered frequently.

With prompt veterinary attention and good at-home nursing care, many lizards can recover fully from respiratory illness. But prevention is ideal – maintaining proper husbandry and habitat hygiene keeps lizards’ lungs functioning at their best.

Conclusion

In the end, lizards may seem quite alien, but their need to breathe links them to all air-breathing creatures on Earth. Their lungs allow these cold-blooded creatures to access the oxygen they require to scamper, bask, hunt, and carry out all their lizard activities.

Understanding the lizard respiratory system provides insight into how these remarkable reptiles function and thrive.