What is Invertebrate Zoology?

Invertebrate zoology (IZ) is the study of animal biodiversity. “Invertebrates” include all animals exclusive of vertebrates, in an artificial division set up centuries ago. Of the 34 or so major divisions (phyla) of animal life, 33 and 2/3 are “invertebrate”. Animals come in a bewildering diversity of forms and pursue an amazing breadth of life styles, including:

Sponges live attached to the ocean floor, lack a nervous system, and filter water for food. Except some deep sea species turned to snagging plankton with specialized, hooked spicules.

Corals build reefs visible from space, the largest structures created by living things, including humans. Internal microscopic algae feed them, but they also indulge in carnivorous fare. Corals host countless other species in their complex colonies.

Worms… The word may repulse some, but for a zoologist, it means diversity. Over half of the animal phyla are “worms” – elongate, muscular organisms that swim in the ocean, burrow in the sea floor or reef, live in soil, or crawl inside most plants and animals large enough to host “helminth” parasites. Feather duster worms, pin worms, large flat worms that swim like flying carpets are unrelated “invertebrates” all sporting a “wormy” body plan.

Mollusks, the second largest phylum, are big not only in species diversity but in body form: worms, clams, slugs, flying squid, tusk shells, chitons, limpets, sea butterflies. The Florida Museum hosts about a third of the 100,000 known species.

More species of arthropods are known than of all other animals put together. A better division of the world would be into Arthropods and Unarthropods… Body forms range from parasitic, pulsating blobs, to centipedes, horseshoe crabs, and butterflies.

Echinoderms include the conspicuous sea stars, sea cucumbers, and sea urchins. They are our symmetrical, large, striking, but weird cousins. How many of your other cousins can change the consistency of their body to turn to slime, or to lock their arm in a position so that it will break before unbending?

Chordates are the most familiar animals, as they include fish, frogs, eagles, and humans. But they also include lancelets, salps, larvaceans, and sea squirts. Animals that make mucus houses several times their own size for filter feeding. Bioluminescent colonies 30 feet long that jet propel through the ocean. Brainless, fish-like lancelets that burrow in the ocean floor to filter-feed on plankton.

Welcome to zoodiversity. Hope you enjoy the pictures, stories, and resources about animal diversity that follow.