How do lungfish survive without water for months?

In one line

The rule

Estivation is a state of dormancy or inactivity that some animals enter during hot and dry conditions. It helps them conserve energy and water until the environment becomes more favorable.

Let's understand it simply

Imagine it is the peak of summer in Rajasthan. The ponds dry up. If you were a fish, you would have nowhere to swim or breathe. Most fish would die. But the lungfish is different. It has a trick: when water disappears, it digs into the mud and makes a safe, wet shell around itself. Then, it goes to sleep for months—almost like a long nap—until the rains come back. This special sleep is called estivation (a long rest during heat and dryness).

How it works

1. The pond or river dries up in the hot season.
2. The lungfish digs into the soft mud at the bottom.
3. It secretes (lets out) a slimy mucus from its skin, which hardens and forms a cocoon (a protective shell) around its body.
4. Inside the cocoon, the lungfish slows down its breathing and heart rate. It breathes air using its lungs, not gills.
5. The fish's body uses very little water and energy, just enough to stay alive.
6. When the rains return and water fills the pond, the lungfish wakes up, breaks out of the cocoon, and swims away.

The story behind it

Scientists found out about lungfish estivation while studying animals that survive harsh conditions in Africa and South America. The African lungfish is famous for this. People noticed that even when rivers dried up, some fish would reappear after months. In the 1800s, explorers dug up dry riverbeds and found live lungfish inside mud cocoons. The lungfish's ability to survive like this amazed everyone, and scientists studied how it worked.

Where you see it in real life

• African lungfish in dry mud: When rivers dry up, lungfish dig into mud and make a cocoon to estivate.
• Australian lungfish: Some can survive short dry spells by burying themselves, but not as long as African lungfish.
• Snails in Indian gardens: Some snails estivate by sealing themselves to walls during hot, dry months.
• Frogs in Rajasthan: Some frogs burrow underground and estivate until the monsoon returns.
• Earthworms in dry soil: Earthworms go deep into the soil and become inactive when it is too dry.
• Crocodiles in Africa: In extreme drought, some crocodiles estivate in mud to survive.

Why it matters

• Survival in harsh climates: Estivation helps animals live through droughts and heat waves, where others would die.
• Study of adaptation: Shows how animals adjust to extreme environments, a key topic in biology.
• Medical research: Scientists study estivation to learn how to protect human organs during surgery or space travel.
• Biodiversity: Explains why some fish can survive in places with unpredictable rains.

Worked example

Let’s see how long a lungfish can survive:

Given: African lungfish can estivate for up to 4 years without water.
Step 1: Pond dries up. Lungfish buries itself in mud and forms a cocoon.
Step 2: It slows its body functions, breathes air, and uses stored body fat.
Step 3: Rain returns after 2 years. Lungfish breaks out and swims away.
Answer: The lungfish survived 2 years without water by estivating.

Common mistakes

• Thinking lungfish breathe only with gills: They use lungs to breathe air during estivation.
• Mixing up estivation and hibernation: Estivation is for hot, dry times; hibernation is for cold, winter times.
• Believing all fish can do this: Only special fish like lungfish have this adaptation.
• Forgetting the cocoon: The mucus cocoon keeps the lungfish moist and safe underground.

Remember it

Lungfish survive dry months by sleeping in a mud cocoon, breathing air, and waiting for rain.