Introduction to the Arthropoda
. . . the REAL rulers of the Earth. . .
By nearly any measure, the most successful animals on the planet
are the arthropods.
They have conquered land, sea and air, and make up
over three-fourths of all currently known living and
fossil organisms, or over one
million species in all. Since many arthropod species remain
undocumented or undiscovered, especially in tropical
rain forests, the true number of
living arthropod species is probably in the tens of millions.
One recent conservative estimate puts the number of arthropod species
in tropical forests at 6 to 9 million species (Thomas, 1990).
Arthropods range in distribution from the deep sea to mountain peaks,
in size from the
king crab with its 12-foot armspan to microscopic insects and
crustaceans, and in taste from chocolate covered ants to crawfish
jambalaya and lobster Newburg. Despite this unbelievable diversity,
the basic body plan of arthropods is fairly constant. Arthropods
have a stiff cuticle made largely of chitin and proteins, forming
an exoskeleton that may or may not be further stiffened with
calcium carbonate. They have segmented bodies and show various patterns
of segment fusion (tagmosis) to form integrated units (heads, abdomens,
and so on). The phylum takes its name from its distinctive jointed
appendages, which may be modified in a number of ways to
form antennae, mouthparts, and reproductive organs.
Source:
Thomas, C. D. 1990. Fewer species. Nature 347: 237.
Click on the buttons below to learn more about Arthropoda.
Information and images of living California arthropods, mostly
crustaceans, are available from the
DELTA
Project at the California State University system. The
Tree
of Life at the University of Arizona also contains information on
the systematics of the Arthropoda. Links to more specialized
servers may be found within this exhibit.
