What is an Arachnid?

Tuesday, April 13, 2021

Characteristics of Arachnids

Humans have 206 bones in their bodies. The average cat has 244 bones in its body. Snakes, the boniest animals, have around 1800 bones! Can you guess how many bones a spider has?

all about arachnids

A spider belongs to the phylum Arthropoda and the class Arachnida
Arthropods are the most abundant category of animals on earth. It is estimated that between 75-84% of all animals on earth belong to this category. What are some traits of arachnids?
First arachnids are arthropods.
All arthropods have several traits in common. Let’s take a look at these common traits.
Exoskeleton: Remember the question from the beginning? The answer to “How many bones does a spider have?” is none! Arthropods do not protect their organs with a skeleton made of bones. Instead, they have a hard outer covering called an exoskeleton. 

Bilateral symmetry: All arthropods have bilateral symmetry. This means that if a line was drawn straight down the middle of their bodies, both sides would be identical to one another. Humans also have bilateral symmetry. 

bilateral symmetry

 Bodies with Regions: If you take a look at a spider or an insect, you will notice that their body is made up of more than one segment. A spider has two segments, and an insect has three: a head, a thorax, and an abdomen.
Segmented appendages: What is an appendage? An appendage is a portion of an arthropod that sticks out from its body and has a function. Examples of appendages include legs, arms, and antennae.
The appendages of arthropods are made of many joints. A joint is a location where two parts meet. 
In addition, arachnids have these traits
Arachnids have two body regions,

spiders have 2 body regions

 Four pairs of legs. 

how many legs does a spider have

Arachnids also have two additional pairs of appendages. The first pair, serve in feeding and defense. The next pair, help the organisms feed, move, and reproduce.

appendages arachnids

No antennae
No wings


Common examples of Arachnids include,

Funnel-web spiders

Black widow
Wolf spider
Banded garden spider

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