Have you ever heard of a fish that breathes air and “hibernates” to survive? The lungfish is an incredibly unique and resilient fish that has developed lungs to extract oxygen from the air. However, like other fish, it still requires water to survive. As you can see in this YouTube video, when their environment becomes too dry for survival, lungfish burrow deep into the ground to estivate—a process similar to hibernation. This behavior keeps them safe and protected during periods without water. But why do lungfish behave this way, and how can they remain dormant for months at a time? Here’s everything you need to know about lungfish.
What Is a Lungfish?
The African lungfish excretes a thick mucus to protect itself during dry periods.
©iStock.com/feathercollector
First evolving nearly 400 million years ago, the lungfish has adapted in remarkable ways, contributing to its impressive survival. The lungfish has powerful jaws and lungs, which require oxygen. According to National Geographic, the lungs are a biological adaptation that developed over time, allowing the fish to extract oxygen from the air, which is why they need to surface frequently. Although lungfish have gills like other fish, their gills are not as well-developed. As a result, most lungfish must rely primarily on their lungs to breathe, especially the African lungfish. When they’re not ‘hibernating,’ these creatures must surface to breathe air through their lungs every few minutes, depending on the species.
Where Are Lungfish Found?
There are six known species of lungfish.
©Galina Savina/Shutterstock.com
Lungfish are found in Africa, South America, and Australia. They most commonly reside in freshwater swamps, slow-moving waters, marshes, backwaters, and small rivers. Specific habitats vary by continent. However, African and South American lungfish are also commonly found underground during dry seasons because they burrow into the mud to survive.
Why Do They Go Underground?
The Australian lungfish does not estivate like other lungfish species.
©paparazzza/Shutterstock.com
During dry seasons, many lungfish—specifically African and South American lungfish—engage in a practice called estivation. Similar to hibernation, which involves a period of dormancy for animals, estivation allows lungfish to encase themselves in mud. The fish does not actually hibernate, but the two processes are often compared.
According to a study published in the journal Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology, “Estivation is a state of aerobic hypometabolism used by organisms to endure seasonally arid conditions, often in desert environments.” As mentioned earlier, lungfish have primitive limbs that allow them to burrow deeply into the mud. They use their mouths to chew through the ground and excrete the mud through their gills.
Once deep enough underground, they secrete a protective mucus cocoon around themselves. This cocoon helps prevent water loss and protects against possible infections during dry seasons. During this dormant period, the lungfish survives by metabolizing its own nutrient-rich muscle tissue. The Australian lungfish, on the other hand, does not estivate like other lungfish species. However, it can survive short periods out of water or in low water, as long as it remains moist.
How Long Do These Fish Hibernate?
Lungfish aren’t the only animals that estivate. In fact, this is a common practice for worms.
©Maryna Pleshkun/Shutterstock.com
Species that estivate, including lungfish, spend significant portions of their lives underground. While estivating, the lungfish undergoes a metabolic slowdown, which helps it conserve energy and survive with little to no food. This period of dormancy is triggered by dry conditions. Lungfish typically remain in their underground cocoons until there is enough water for them to swim again—a period that can last for months or even years, depending on environmental conditions.
What Do Lungfish Eat?
African lungfish will often prey on dwarf frogs.
©Ashley Magyar/iStock via Getty Images
According to National Geographic, African lungfish are omnivores. They typically feed on animals such as frogs, mollusks, and other fish, as well as tree roots and seeds. However, Australian lungfish tend to be mostly carnivorous. According to the California Academy of Sciences, this species feeds on fish, frogs, tadpoles, and freshwater invertebrates. South American lungfish behave similarly, feeding on bony fish, algae, weeds, terrestrial plant stems, shrimp, insects, clams, snails, and other prey.
Lungfish Predators
Young lungfish have various predators, while adult lungfish have few.
©iStock.com/Michel VIARD
Adult lungfish have very few predators, while juvenile lungfish are preyed upon by larger fish, birds, and mammals. Once they reach adulthood, these fish can successfully defend themselves using various adaptations, such as their powerful jaws.
The post This Peculiar Fish ‘Hibernates’ and Actually Needs Air to Live appeared first on A-Z Animals.
