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Worm Facts


Introducing the Worm

Charles Darwin was fascinated by worms. In his book "The Formation of Vegetable Mould by the Action of Worms" (1896), Darwin wrote "Worms have played a more important part in the history of the world than most persons would at first suppose."

One of an earthworm’s most important roles is to recycle organic waste such as food scraps into a high quality soil conditioner. But how do they do it?


Earthworm Biology



An Earthworm's Anatomy

As everyone knows, earthworms usually look red or pink. Their bodies are long, cylindrical, and divided into rings or segments. But when you take a closer look, you’ll see that adults have a clitellum. The clitellum is a thickened area on the upper and side surfaces of the body that is usually paler than the rest of the worm. For this reason it’s often called a saddle.

Unlike humans, earthworms have no special breathing organs. Oxygen is absorbed and waste gases are passed through the skin via a network of fine blood vessels just under the skin surface.


How Earthworms Digest Food

The earthworm’s digestive system is essentially an unbranched tube that runs from its mouth at one end of its body to the anus at the other end. Just inside the mouth the tube expands into a strongly muscular pharynx. The pharynx turns inside out so that it protrudes through the mouth to surround and grasp pieces of food. The food is then pulled back into the mouth and passes back into the worms’ gizzard. The food is ground down by the gizzard before it passes into the worms’ intestines and eventually out through to the anus as castings.

How Earthworms Move

An earthworm moves by bunching up like a spring then using the bristles on its back like an anchor, to push itself forward. Sounds simple? It’s actually quite complex and involves a set of co-ordinated actions and reactions that include the earthworms’ muscles, small bristles on the body wall (called setae), and the fluid filled body cavity.


An Earthworm has a Brain and Several Hearts!

An earthworm has a brain and several hearts!
The earthworm’s brain is a small bundle of nerve tissue located on top of and right at the front of the pharynx. It is connected to a nerve cord that runs along the body cavity under the gut. The nerve cord provides nerves for muscles and other organs in each segment of the earthworm’s body.
 
Blood is pumped throughout a worms’ body by anywhere between 3-5 pairs of hearts! A pair of hearts surrounds the oesophagus in each of several successive segments of the earthworm.


An Earthworm has a Brain and Several Hearts!

An earthworm has a brain and several hearts!
The earthworm’s brain is a small bundle of nerve tissue located on top of and right at the front of the pharynx. It is connected to a nerve cord that runs along the body cavity under the gut. The nerve cord provides nerves for muscles and other organs in each segment of the earthworm’s body.
 
Blood is pumped throughout a worms’ body by anywhere between 3-5 pairs of hearts! A pair of hearts surrounds the oesophagus in each of several successive segments of the earthworm.


Breeding

An earthworm has both male and female reproductive organs. Most species have two pairs of testes (male organs) and one pair of ovaries (female organs).
 
During mating, two worms align themselves in a head to tail position, and touch each other over a length of around 35 front segments. They produce a thick layer of mucus, discharge sperm cells, then separate from each other.
A broad ring forms around each worms’ body. The earthworm works itself back through the ring and in doing so, leaves behind the eggs and sperm cells. Eventually, the ring passes over the worms’ head to form a cocoon, which houses a number of eggs. Baby worms emerge from the cocoon after a period of approximately three weeks.

From: Earthworms for Gardeners and Fisherman. CSIRO 1978. East Melbourne.
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