Arthropods
Author: Ray Bowers
| Phylum: Arthropoda |
Description:
The phylum Arthropoda includes three subphyla the Chelicerata, the
Crustacea, and the Atelocerata, The Crustacia are primarily found in aquatic environments. The Crustacia
will be discussed with the playa sub-community, which is a temporary pond or lake.
The phylum Arthropoda is characterized by having paired jointed appendages, which is what the name
arthropod means. The arthropods jointed appendages and bilateral segmented body is covered by an
exoskeleton made of chitin. Chitin is a carbohydrate that is so resistant to being decomposed that the
exoskeletons of dead arthropods can lay around the desert for months. Internally, arthropods have an open
circulatory system, consisting of a heart with valved openings and tubes emptiing into the body cavity.
They have a complete tubular digestive system, with a mouth and an anus. The nervous system consists of a
brain, a pair of nerve cords that go around the digestive system to meet below the digestive system, and
paired nerve cords extending along the ventral side of the body. The respiratory and excretory systems
vary with arthropods.
Arthropods are the largest phylum in the animal kingdom; there are more types of arthropods than all
other types of animals combined. They can vary in size from microscopic to larger than an adult human.
Land arthropods are usually less than 15cm (approximately 5 inches).
Geographic Range:
Arthropods are found worldwide.
Habitat:
The diversity of the arthropods has allowed them to occupy every habitaton Earth, including the deepest parts of the ocean.
Reproduction and Development:
Almost all arthropods are dioecious. The eggs may be
released by the female into the environment, carried by the female, placed in a sac and guarded by the
female, or develop inside of the female.
As arthropods grow their exoskeleton must be replaced to accommodate their increased size. This replacement
of the exoskeleton is called molting.
Behavior:
Because of the great diversity of arthropods there is a great diversity in
their behaviors.
Ecosystem Roles:
Arthropods are found in all consumers' roles of an ecosystem,
whether they eat plants or animals, and some are important decomposers. They are important in the
pollination of flowering plants. Some play an important role in soil aeration and water infiltration.
Conservation:
Some arthropods are considered pest and substantial sums of money are
spent to control or eradicate them with varying degrees of success. Other arthropods have become endangered or extinct primarily due to habitat destruction, although in some cases it is due to collection of a
particular Species.
Taxonomy:
Kingdom:Animalia
Phylum:Arthropoda
Subphylum:Trilobita (fossil only)
Subphylum:Chelicerata
Subphylum:Crustacia; most are aquatic
Subphylum: Atelocerata
The 14 living classes of arthropods are:
Class: Merostomata: horseshoe crabs (marine only, not in New Mexico)
Class: Arachnida: scorpions, spiders, ticks and others
Class: Pycnogonida: sea spiders (marine only, not in New Mexico)
Class: Branchiopoda: fairy shrimp, tadpole shrimp, clam shrimp, and cladocera
or water fleas
Class: Cephalocardia: (marine only, not in New Mexico)
Class: Ostracoda:
Class: Copepooda:
Class: Mystacocarida: (marine only, not in New Mexico)
Class: Branchiura; aquatic bloodsucking ectoparasites
Class: Cirripedia; barnacles (marine only, not in New Mexico)
Class: Malacosta: isopodes or pillbugs, crayfish, crabs, and shrimp
Class: Diploda; millipedes
Class: Chilopoda; centipedes
Class: Hexapoda; insects
References:
Borror, Donald J. and Richard E. White. 1970. A Field Guide to the
Insects of America North of Mexico.
Boston: Houghton Mifflin Co.
Barnes, Robert D. 1980. Invertebrate Zoology. Philadelphia: W. B. Saunders Co.
Borror, Donald J., Charles A. Triplehorn, and Norman F. Johnson. 1989. An Introduction to the Study of
Insects. Philadelphia: W. B. Saunders Co.
Related Terms: Arthropoda