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The basic
body structure consists of two body parts. They are the cephalothorax
and the abdomen.2
CEPHALOTHORAX
The
cephalothorax consists of the external body parts. In short, it is
basically the head of the spider.
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It has a face that consists of a tiny mouth with no teeth.
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It has fangs, or chelicerae, that is used to seize
prey. They resemble a hollow claw that if looked at with a microscope,
will show that they point in a downward position. Located at the base
of these fangs are the poison glands. When the spider is pursuing the
victim, it will pierce it with the fangs. Venom, which varies with
different spiders, is injected. The venom will only paralyze the
victim because a spider will not eat dead prey. Since the spider
cannot actually chew, a digestive juice is injected. This breaks down
the nutrients of the victim so that the spider may feed. It is kind of
like sucking through a straw. This process is known as suctorial
feeding.3
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Another feature on the head are a pair of pedipalp.
"The pedipalps are either the second pair of appendages of spiders, and
other arachnids, variously developed for grasping, sensing, fertilizing,
etc." as defined by Webster's New World Dictionary4.
Basically, if you look really close, these pedipalp look like a tiny pair of
legs that have six segments (our fingers only have three). The
segments closest to the head are used for crushing food.5
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What would a face be without those beautiful eyes?! We
have two. A common number for a spider is eight, placed on their face in two
rows of four. Depending on the spider, six, four, two, or zero (in the
case of a cave spider this is literally blind.) Spiders' eyes are
simple. This means that they are not divided into pieces like a
compound eye. Some spiders that live in dark places or hunt at night
have nocturnal eyes. These eyes are whitish in color and have a pearly
luster. The rest of the spiders have diurnal eyes. These eyes
vary in color.
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These previous sections make up their face.6
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The last major component of the cephalothorax, and one of the
intimidating components to some is the legs. ALL spiders have eight
legs. Each leg has seven segments. Most spiders have a tiny claw
at the end of each leg and a little pad of hair around this claw to assist
the spider in climbing.
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ABDOMEN
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The abdomen is the larger of the two body parts. It
consists of all the internal body parts of the spider.
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The nervous system has a brain acts as the control system
for all the other parts of the spider. A spider does not "think" like
a mammal does. Instead, it gains its knowledge of its surroundings by
sense organs. Each hair on the spiders body contains a nerve.
When touched, these nerves tell the spider how to respond.7
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The circulatory system transfers blood throughout the
spiders' body. Spiders have transparent blood. The circulatory
systems includes a long, slender heart. If the spiders' body is broken
or punctured, its blood will drain and the spider will die.
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There are muscles in a spiders' body but the blood is
necessary for the legs to extend. Low blood pressure would make the
spider's legs curl up and make it unable to walk.8
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The digestive extends through the length of the body.
The stomach pulls the food, or nutrient broth, through special digestive
juices. The food is then distributed though the blood. Because
of this unique process, there is no need for an excretory system.
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At the base of the abdomen, there are fingerlike spinnerets.
Most spiders have six, but some have four or two. At the tip of the
spinnerets closest to the body, there is a spinning field. It is
covered by as many as one hundred spinning tubes. Silk flows through
these tubes from a silk gland inside.9
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We have a nose, spiders have a spiracle. It is located
on the tip of the rear of the abdomen. It is located just in front of
the spinneretts. A spider has two breathing organs, trachae and
booklungs. Almost all trachae tubes carry air throughout the
body. The air enters tubes through the spiracle. The book lungs
consist of 15 or more folds. The air enters here and is passed through
to go to the blood.10
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