Interesting Earthworms

By: Jennifer Lang Vu-Pap Bio-3

Objective

Today, we will learn how to dissect an earthworm. We will learn the internal and external structures of the earthworm and where they are located. We will also see what function each organs have and have a better understanding of the circulatory system of the earthworm.

Lumbricus terrestris

Species: L. terrestris

Genus: Lumbricus

Family: Lumbricidae

Order: Haplotaxida

Class: Clitellata

Phylum: Annelida

Kingdom: Animalia


Earthworms are popular among the groups of decomposers. They live under soils and have really smooth and soft skin. Their body is mostly made up of body fluid so their bodies are so moist. Earthworms can easily adapt to different environments so that's why they could survive for many years.

Dissection Process

First, observe the external structures of the earthworm. Then, use a dissecting pin to pin down the head of the earthworm. It also helps keep it tight if you put the pins at an angle. Then, find the dorsal vein, which is a dark line that goes right across and use a pair of scissors to cut to the side of the dorsal vein. Take your dissecting probe and carefully open up the earthworm and stick in a dissecting pin. Continue to do the other sides with the same process of opening the earthworm and sticking a dissecting pin to the side. You should be able to see the internal structures.
Earthworm Dissection.AVI

Background Information

Earthworms have adapted in many ways over the past generations in order to improve reproduction, to get food and to improve their defenses. Earthworms are hermaphrodites. This means the earthworm contains both male and female reproductive organs. The eggs which contain yolk are buried in the earth in capsules formed from secretions of the clitellum. The clitellum is the thickened section of the body near the front end. The capsules protect the young until they hatch as worms. The fact that the earthworm is a hermaphrodite means the earthworm can easily reproduce which is an excellent adaptation.The earthworm moves by stretching it’s front section through the soil and then pulling its hind section up. Earthworms do not have eyes or ears but they have a mouth and are sensitive to heat, light and touch. This adaptation is important to the survival of the earthworm.

Ecological Niche

Earthworms are the main contributors to enriching and improving soil for plants, animals and even humans. Earthworms create tunnels in the soil by burrowing, which aerates the soil to allow air, water and nutrients to reach deep within the soil. After organic matter is digested, the earthworm releases waste from their bodies called castings. Castings contain many nutrients that the plant can use for themselves.

Body System: Circulatory

Earthworms have closed circulatory systems.Earthworms circulate blood exclusively through vessels. The vessels that provide blood to organs inside the earthworm are the aortic arches, dorsal blood vessels, and ventral blood vessels. The aortic arches acts like a human heart for the earthworm. The five pairs of aortic arches pump blood into the dorsal and ventral blood vessels. The dorsal blood vessels carry blood to the front of the earthworm’s body. The ventral blood vessels carry blood to the back of the earthworm’s body.

Human Impact

Earthworms change the structure of their environments like human engineers. Different types of earthworms can make both horizontal and vertical burrows, some of which can be very deep in soils. Some farmers use them to fertilize their soils. Earthworms eat the soil which has organic matter such as decaying vegetation or leaves. The waste they release is called castings. Castings contain many nutrients that the plant can use. Some people even use earthworm castings as garden fertilizer.

FUN FACTS

There is a species of earthworms in Asia called Amynthas agrestes also known as “crazy snake worm” or “Alabama jumper”. They are starting to cause serious environmental injury to the forests as they eat away leaf litter changing the soil chemistry and causing habit reduction for other creatures. They may have been mistaken by fishermen and causes fishermen to use them as bait and by gardeners who purchased them over the internet for composting. Be very careful when purchasing to get Lumbricus Terrestris L. (night crawlers). It's good that you're worrying about the nutrients your plants are receiving, but when you're ordering something with no idea what bad things might happen because of a wrong purchase you made. The worms you may be feeding your fishes may also be bad and could cause harm for the fish and people who are going to eat it in the future.