As of 2009, the International Union for Conservation of Nature has identified over 1.3 million species of invertebrates. These spineless, cold-blooded animals have little more in common than, well, their lacking backbones and prevalence. This diverse group of animals makes up approximately 75 percent of all known species on Earth.
Crustaceans are a large, diverse group of invertebrates with over 30,000 recognized species. Lobsters, crabs, shrimp, tiny copepods and even barnacles all belong to the crustacean family. Crustaceans have several uniting characteristics: a protective shell made of a substance call “chiton,” jointed legs and two pairs of antennae. They also have the unique ability to break off or drop off their appendages. This is mainly employed to escape natural prey or unnatural dangers like fishing nets. Afterwards, a new appendage easily grows in the old one’s place.
Insects are perhaps the most prevalent invertebrates on earth, or at least it seems that way to humans. From butterflies and ants to honeybees and termites, insects seem to be around every corner. Butterflies are some of the most welcomed and colorful. A subspecies of butterfly, the monarch butterfly, starts out its life as larvae and develops into a caterpillar and eventually the black, orange and white flying beauty found in North American skies. Each winter they migrate, sometimes up to 3,000 miles, to California and Mexico; monarch butterflies are the only butterfly species to make such a long, migratory journey.
Worms, Centipedes and Millipedes
Wiggly, sneaky and close to the ground, worms, centipedes and millipedes are some of the most common invertebrates, especially for gardeners. The common earthworm loves moist soil. This is because he takes in oxygen through his body and needs moisture to facilitate the process; he tends to avoid the warm, dry daytime hours for this very reason. Centipedes are speedy compared to earthworms. Unlike worms, centipedes have pairs of legs that run the length of their bodies, normally around 15-30 total depending on size. A millipede is like a centipede’s larger, older brother. The average millipede has a long, narrow body with 80 to 400 individual legs.
The mollusk group spans over 50,000 known species. They include snails, clams, oysters, mussels, squid and octopods. In general, their bodies include three parts: the head, internal organs and a “foot.". A mollusk’s foot is essentially the muscular, lower part of its body that comes in contact the ground. Most mollusks, like the clam and oyster, have shells but some do not. The octopus is one shell-less mollusk. A member of the subgroup, cephalopod, theses beauties swim the open ocean and have the most developed eye of any mollusk.
Christina Stephens is a writer from Portland, Ore. whose main areas of focus are pets and animals, travel and literature. A veterinary assistant, she taught English in South Korea and holds a BA in English with cum laude honors from Portland State University.