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Invertebrates constitute the majority of all living
animals. The number of species go well into the millions with many still
waiting to be classified. Whereas the well studied vertebrate
animals, like mammals, birds,
etc.... only comprise 1% of all animal species.
In a tropical country like Ecuador that holds true as well and
the numbers of insects for e.g. in the tropical rainforests or
mollusks in the oceans are unknown.
We will be dealing here mainly with the
Arthropods
which are spiders, insects and crustaceans and
a little bit with
mollusks, which are bivalves and squids and also introduce
corals.
The number of insects, like beetles,
which are the world's most numerous in species,
butterflies,
ants, grasshoppers, mantis and stick insects and so on are
unknown and very high in the tropical forests. Studies of
insect population in the tree crowns of tall tropical trees
showed an amazing count of unknown species. But insects can also be found right up to the glacier of 5000m,
where they fulfill an important role in
this high altitude ecology.
Spiders
also are very numerous and found in all ecosystems. You
encounter the smaller web building ones and the larger
hunting spiders, with the tarantula being the largest.
Crustaceans are mostly found in and near waters and have
some important economic species in Ecuador present as is the
case of the shrimps and in a lesser degree crabs.
Mollusks are the second largest animal phylum after the
before mentioned arthropods with over 50 000 species.
They are highly adaptable and found in many ecosystems but
their largest numbers are in the oceans of the world.
They also have the largest invertebrate of the world in their
group, the giant squid, which can weigh up to 2000 kg. Other
important members are clams, oysters, snails, slugs and
octopuses.
Corals are marine invertebrates with a horny skeleton of
protective calcium carbonate. The best known are the corals
which build reefs and are found in the shallow and warm ocean
waters of the world. They live together in a symbiotic
relationship with an algae and therefore need light for
photosynthesis by the algae. There exist colonial corals which can be found in the deep
waters.
There are 30 or so more phyla of invertebrates, most
of them marine dwelling animals, which we will not discuss
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