Earthworms. They are the under-appreciated (no pun intended) workers of the underground world. They do the dirt-y work. They move the earth and oxygenate it as they dig their way through it. They are the great natural compost-ers. They eat decaying leaves, fungi in the soil, and even animal waste, resulting in castings that are full of nutrition that is good for the soil and the things that grow in it.
Some Interesting Facts:
- There are about 2,700 types of earthworms
- They live on (or should we say in) every continent except Antartica
- They do not have eyes or ears
- One end of the body is more sensitive to light than the other, allowing it to know night from day and when it is close to the surface
- They breathe through their skin - once it dries out they cannot breathe, and too much water will suffocate them
- They have no bone structure
- They are both male and female (hermaphrodites)
- Their castings (waste) are full of nutrients, which is why gardeners love their company
- Their bodies have 100-150 segments; each segment is divided inside its body with a septum
- They use the stones they eat to help digest their food
Now, let's look a little closer!
First, we counted the segments. One worm had 120 while the other had 150. When we looked on the underside (ventral) of the worm with a magnifying glass, we could see the setae (see-tay). Setae are stiff bristles that help anchor different parts of the worm in the soil, allowing it to move. The large "band-aide" around the middle of the worm is a clitellum. This is part of its reproductive system.
Next, it was time to see what in side the earthworm! We cut an opening from the mouth to the clitellum, careful not to cut any of the organs.
Next, it was time to see what in side the earthworm! We cut an opening from the mouth to the clitellum, careful not to cut any of the organs.
The worm eats its food, entering the mouth and emptying in to the pharynx, or the throat. It flows down to the esophagus and then into the crop. The crop is where food is stored. Birds also have crops. The crop is large, brown, and round in the image above.
Eventually the food is taken in to the gizzard where it is broken down with the stones that the earthworm has eaten. The gizzard is the white and slightly tan organ below the crop in the image.
Once the food is broken down, it enters the intestine which runs the length of the worm. As the food works its way to the back of the worm, blood vessels that line the intestine absorb the nutrients that the worm needs to grow and function.
Once the food reaches the back of the worm, it is discarded as waste, or castings.
Eventually the food is taken in to the gizzard where it is broken down with the stones that the earthworm has eaten. The gizzard is the white and slightly tan organ below the crop in the image.
Once the food is broken down, it enters the intestine which runs the length of the worm. As the food works its way to the back of the worm, blood vessels that line the intestine absorb the nutrients that the worm needs to grow and function.
Once the food reaches the back of the worm, it is discarded as waste, or castings.
We could also see the worm's aortic arches, four chambers found beneath the esophagus that pump the blood through the worm. We were able to see the worm's tiny brain that is no bigger than a pin head (the teasing pin is pointing to it).
Finally, once all the organs were removed from the posterior section, we could clearly see nerve cord that runs from the front to the back of the worm on its ventral side.
These hidden ground workers are so simple, yet much more complicated than what we initially anticipated. What amazing creations!