What are Arthropods?
An arthropod is an invertebrate animal that has an exoskeleton and jointed appendages. All arthropods are in the phylum Arthropoda, the largest phylum in the Animal Kingdom, including millions of living species of arachnids, crustaceans, insects, and their kin. These animals are prevalent within the world’s ecosystems, making them excellent sources of information on the status of a particular ecosystem, as well as indicators of ecological changes. Professor Barrows and the members of his lab maintain a database on the biodiversity of the Washington, D.C., area, which catalogs many of the arthropods that have been found in the District. Explore the Biodiversity Database of the Washington, D.C.
Arthropods are a major category of animals, encompassing insects, arachnids, crustaceans, centipedes, and a few others. In Greek, arthropod means “jointed foot,” a reference to one of the defining characteristics of the phylum — a segmented body with appendages. Arthropods are the most successful and diverse of all animal phyla, in terms of their numbers and ubiquity. They make up about 80% of all animal species, and over a million have been given scientific names. All arthropods have a dorsal (on top) heart and a ventral (on bottom) nervous system. They are covered by an exoskeleton made of chitin, a rigid polysaccharide which serves as a sort of armor and protects arthropods from drying out. When an arthropod grows, it must shed its layers. In today’s world, arthropods tend to be relatively small, generally smaller than a half meter in size, although a few, like the Japanese spider crab, have a leg span up to 3.5 m (12 ft). The smallest arthropods are plankton about 300 microns large
Arthropods are invertebrate animals with a hard chitinous exoskeleton, jointed appendages, and a body that is composed of segments. These segments are themselves grouped into major body regions (tagmata), for example the head, thorax, and abdomen of insects. All arthropods undergo periodic molting to grow out of the confines of their rigid exoskeleton.
