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What happens to a Worm when it breaks in half? Does it die or does it magically grow another head? |
How The Earthworm Moves
The
earthworm has no lungs and takes in oxygen through its moist skin — it is
a skin breather. If the worm’s skin dries out the worm will suffocate. Mucus
secreting cells cover its skin. The mucus, not only serves in respiratory
exchange, but it also lubricates the worm's body and eases passage through
the burrow. The mucus covered skin helps bind soil particles together and
prevents the walls of the burrow from collapsing.
If you watch an earthworm move, you will most likely see it move forward,
with its pointy end in the front. This is its mouth and prostomium (in
front of the mouth). 
There
is a concentration of sensory cells at this anterior end around the prostomium.
And although it has no eyes, the worm possesses light sensitive cells
and can "sense" light. The worm cannot hear, but feels vibrations of animals
moving nearby. The worm's body is divided into 100 or more body segments.
As the worm works its way forward, successive peristaltic or contracting
waves of thickening and thinning (7–10 per minute) pass down the body.
At each place where the body bulges out at a given moment, the bristles,
or “setae”, are extended and grip the burrow walls. Setae, which
are not true legs but pairs of bristles attached to each segment, push
against the ground with each contraction and help the animal move.
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The early European settlers brought earthworms to North America in the 17th and 18th centuries. If earthworms existed in North America prior to this, they were probably wiped out during the last ice age, 10,000 to 50,000 years ago. Some scientists estimate that there are approximately 50,000 earthworms per acre of moist soil. Living in deep, dark, long, and narrow tunnels or burrows under the ground, earthworms cannot tolerate heat or sun, so during the summer they come to the surface only at night.
After a rain have you noticed multitudes of earthworms on the
surface? This happens because the wet surface allows the worm
to move without drying out
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