Earthworms- Five Hearts, But Not Much Of A Brain

With all the talk about earthworms on this site, you might be interested in knowing a little bit about them. Here for your perusal are some interesting and little known facts about earthworms.

Earthworms have five hearts! In close proximity to those hearts, they also possess what are known as calciferous glands, which allow them to process the large amount of calcium contained in a diet that consists largely of soil.

Five hearts but no lungs. That's right, worms breathe directly through their skin. This works fine as long as the worms do not become dried out, as the skin must stay damp in order for oxygen to pass through the skin and be deposited directly into the bloodstream.

Earthworms have brains, in a manner of speaking. The brain is extremely simple, however, and when the brain is removed, the worms appear to behave pretty much the same as they did when they had the brain.

Earthworms cannot see, as they don't have eyes. That simple brain works in combination with sensitive cells located in their skin to help them ascertain changes in ambient light.

Earthworms are 'hermaphroditic', which means they have both male and female sexual organs. Be that as it may, they still apparently do engage in mating, in a very complex scenario too involved to relate here.

Earthworms move through the ground by using their setae, the hairy bristles that emanate from their body. First, they will stretch their body to be long and skinny, stick out their front setae and plant them in the ground. They then scrunch themselves up to be short and fat, pull in the front setae, plant their rear setae in the dirt and push themselves forward, once again becoming long and skinny, and continue on like that. This motion one of the ways that they condition the soil, creating little tunnels where air and moisture can circulate.

It's pretty hard to tell one end of an earthworm from another if you're not familiar with them, but they do have a mouth on one end, located under a flap of skin called the prostomium. The mouth end is called the anterior, and the rear end - you got it- the posterior. As you might expect, worms don't have teeth. They have gizzards, somewhat like poultry. The gizzard helps to grind up whatever the worm eats and send it to the intestine.

You may have heard that you can cut an earthworm in half and both halves will grow back. That's not true. If an earthworm is cut in half, it will usually die. However, it is true that if a third or less of the posterior portion of the worm gets chopped off, the earthworm can usually regrow that portion - but the chopped off posterior will not grow a new head.

You would think earthworms would have been hanging around in the soil since prehistoric times, but earthworms are actually an invasive species in the US. Near as we can tell, they came over from Europe in plants brought by some early settlers in the 1600's. Good thing for our soil that they did!

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