Essentially earthworms are a digestive tube; surrounded by a body cavity filled with fluid, which acts as part of the circulatory system; and the outer skin of the worm.
The body of the worm is made up of from 200 to 400 muscular rings which assist it to move through the earth like a hydraulic drill, and which also helps its digestive processes.
The earthworms most forward point is the prostomium which both covers the mouth and is used forcefully to burrow. The brain is located just behind the prostomium and just forward of the pharynx or throat.
The earthworms brain does not appear to be extremely important as experiments have shown that by removal of the brain causes little behavioral change in the earthworm. There are many light sensitive cells on the upper front and rear surfaces of earthworms.
- Tip: Light is a powerful aid in worm management. It can be used over the beds of earthworms to prevent night evacuation.
The Digestive System Of Earthworms
Earthworms literally eat there way through the earth or organic material to for burrows. It goes around material to large and hard to swallow. Small particles pass through the mouth and the cavity of the pharynx or throat, along the oesophagus by the calciferous glands, which excrete chalk ( Calcium Carbonate ) thus marginally reducing acidity of the food material eventually assembling in the crop where the enzymes and bacteria controlled by the calcium carbonate solution break it down fine in preparation to be treated in the gizzard, which is a sac surrounded by strong muscles where digestive juices, small grains of stone and mineral particles grind the food to enable it to pass through the intestine.
The smaller particles of food are absorbed through the intestine walls into the blood capillaries and protein and sugars are distributed to body cells while waste matter passes to the outside skin as mucous which lubricates the earthworms progress through the soil.
The undigested and larger particles of food pass through the earthworms intestine to the anus where thet are excreted as nitrogen lading worms castings.
The whole process takes about 24 hours from eating to excretion. Some micro organisms from the worms digestive tract pass out with the castings to continue the digestive process in the soil. Some of this material passes through the worm as it re passes through the soil. The digestive process of earthworms is aided by microbial action in the soil which decays the food in a pre digestion process which is best in slightly acid-but not strong acid-conditions.
- Tip: Healthy earthworms require pH conditions between 6.8 and 7.2 for best digestion of food. Tiger worms will tolerate greater acidity. Earthworms eat their own body weight in a day, so food supply must be reliable.
Earthworms Circulatory/ Respiratory Systems
Earthworms have up to 5 hearts at the anterior end, which pump blood to the posterior end through the main ventral blood vessel beneath the digestive tract. It returns through another large dorsal blood vessel to the hearts.
In the process the blood spreads to and from the organs and the skin through capillaries which exchange nutrient and water for waste matter. The earthworms ventral and dorsal vessels are interconnected in most segments of the worm. The walls of the earthworms capillaries are extremely thin allowing for easy exchange of nutrients and oxygen for waste fluids and gases.
- Tip: The worms circulatory system is extremely fragile so care should be taken in handling them. Never use a spade, and use forks with care.
The earthworms skin is its lungs. The small blood capillary network just beneath its skin exchange oxygen intake into the blood streams for carbon dioxide expelled from the blood. Respiration can only take place if the outside surface is kept moist.
- Tip: Conditions for worms must be kept moist to allow respiration, but not to moist to avoid carbon dioxide build up.
Earthworms Nervous System
Earthworms have no eyes or ears but, in compensation, an extremely sensitive nervous system. They are able to notice a bird walking above them or sunlight on their tender skin. Either of these sensations will send worms diving for cover. They are also able to learn very simple tasks. Because their nerves are so sensitive, and because they respond to stimuli, they probably experience a type of pain-for example, when fish hooks are stuck them.
Contained in the earthworms anterior-the portion in front of the clitellum-are two nerve endings that are extremely sensitive to light. These are called photoreceptor’s, and they are complemented by thousands of lens-like nerve endings, concentrated over the length of the earthworms body. The photoreceptor’s are particularly sensitive to ultraviolet light, which will kill the worm if it fails to burrow for cover quickly enough.
As you can see these are trully complex creatures, but where would we be without earthworms.