NATURA

Spiders - Tarantulas
Phylum Arthropoda is a group of invertebrate animals, invertebrate
meaning that they have an external skeleton, named
exoskeleton. Examples of these animals include insects, spiders
and crustaceans. Spiders are often considered the most
successful terrestrial predators on earth. They can be found
all over the globe, on highest mountains as well as on the
shore. There are about 40.000 known species of spiders and
probably many left to discover.
Our focus is on the family Theraphosidae, better known
as tarantulas. They can be found from the southern and
western parts of the United States, in Central America,
and throughout South America. Other species occur
in different areas throughout Africa, much of Asia, and
all of Australia. In Europe, some species can be found
in Spain, Portugal, Turkey, Italy, and Cyprus. They are
found in a wide range of habitats; terrestrially in deserts,
in large open areas of grassland, and in scrub forests,
terrestrially and arboreally and in rain or moist forests
as well. No species has been found as truly aquatic or
marine, even though some choose to live near water.
Tarantulas have in the recent years become popular as
pets, so now they can be found in our homes as well. In
this article our interest is on the behaviour and biology
of tarantulas, and how to keep a tarantula as a pet.
As mentioned earlier, the tarantulas have external skeleton.
The exoskeleton defines the shape of the animal,
is an attach point for the muscles, prevents evaporation
and gives protection. When growing, they need
to expand their former skeleton and make a new one
bigger. This is a complex process called molting. Young
tarantulas may do this several times a year, while fully
grown individuals will only molt once a year or even
less frequently. If a tarantula happens to loose a limb or
urticating hairs (bristles), it may go through molting.
An important thing when keeping tarantulas as pets
is not to handle them while and right after molting,
even not feed them for a few days because they can be
harmed by their prey. Just make sure they have enough
water. Another thing is that having an exoskeleton
makes them fragile, and if dropped on the floor they can
be crushed, possibly to death.
Image 39. The tarantula Avicularia pucallpa.
A spiders body is divided into two parts. The forward
part, the prosoma, has the eyes, mouth fangs, stomach,
brain and the poison glands. The legs are also connected
to this part. The rear part is the opisthosoma, on its
back end are the spinnerets, the silk producing glands.
Between the prosoma and the opisthosoma there is a
narrow part called the pedicel. Tarantulas have eight
pairs of appendages on their bodies. The first one is
chelicerae serving a different purpose in different species.
It is located just below the eyes, directly forward
the mouth.