Earthworms live in rivers, wet soils, swamps, and ditches. So, you would assume that they can also live in water, right?
I did an experiment. I put an adult tiger worm on the ground indoors and let it crawl…and I had unexpected results.
It got much slower after crawling for about 2 meters and it then even stopped moving.
Then, I sprayed water on it with a sprayer for watering flowers, and it resumed its activities again.
After a certain distance, it got slower again, and it became faster again after being sprayed some water once more.
By the way, water worms are also called red nematodes. They are earthworms that live in water. Read this article for more details.
Unlike humans or fish, earthworms do not have lungs and gills.
They are a kind of creature that breathes through their skin.
Specifically, it exchanges oxygen in the air with water, liquid or mucus secreted by skin pores.
After that, the oxygen enters the capillaries on the earthworm’s skin wall and penetrates into the cells. This process is called “diffusion”
With this simple and primitive skin breathing method, earthworms must keep their skin moist at all times.
Therefore, earthworms like to live and do best in soil with enough moisture, especially near water.
In water, as the oxygen content is lower than it is in the air, the oxygen on the skin cannot be converted very efficiently.
If the earthworms are in water for a long time, they will drown.
This may also be one of the main reasons why earthworms have to crawl out of the soil during heavy rain (though this has been debated).
How Long Can an Earthworm Live in Water?
Some people might ask how long the earthworm can live in water.
It depends on the species of the earthworm and the oxygen content of the water.
Scientists have done experiments by passing oxygen-containing water through the soil layer where earthworms are located.
They found that the oxygen content dropped significantly.
Earthworms can stay in water with low oxygen for a period of time until the carbon dioxide in the water rises to a certain level.
In fact, some earthworms can stay in water for several hours or even days.
Some species that are more suitable for water, such as the Indian blue earthworms and local red earthworms, can even live well in an environment with lots of water.
However, night worms, which are larger in size, need more oxygen and usually cannot survive in water for more than 30 minutes.
Can Earthworms Swim?
Yes and no, it is more like struggling and squirming for survival than actual swimming.
How many respiratory organs does an earthworm have?
Earthworms breathe through their skin, and skin is technically one of their organs. Earthworms have one respiratory organ.
Why don’t earthworms get back into the soil after it rains, and wait to get scorched to death under the sun?
Scientists have not been able to find answers to this question.
According to Charles Darwin, those earthworms are already sick, that’s why they do not have energy to crawl back to the soil.
After the rain, hypoxic earthworms (worms low in oxygen) would ideally want to find a suitable place to crawl back into the soil.
The more common argument for worms staying on the surface even after it rains, is that it happens because of ultraviolet light, and there are corresponding studies here (1).
The theory is that Earthworms are usually extremely sensitive to light and avoid them at all costs.
If it rains during the day and the earthworms are exposed to the sun for a long time, the ultraviolet rays paralyze the earthworms and thus they cannot crawl back to the soil, which eventually leads to dehydration and death.