noun, plural: invertebrates
Invertebrates are multicellular animals that do not have a backbone (vertebral column). This feature separates them from other animals, particularly the vertebrates, with a backbone. These invertebrates include insects, mollusks, crustaceans, corals, arachnids, velvet worms, horseshoe crabs, jellyfish, echinoderms, sponges, other worms, etc. These animals share other common features such as showing symmetry (radial, bilateral, or spherical). Nevertheless, the gastropods, the fiddler crabs, the hermit crabs, and certain sponges are the exceptions since they do not exhibit symmetry. Invertebrates reproduce sexually through specialized reproductive cells although there are also other invertebrates that are capable of asexual reproduction.
As regards taxonomy, the invertebrates may be classified as follows: Porifera (sponges), Cnidaria (stinging jellyfish and corals), Ctenophora (comb jellies), Platyhelminthes (flatworms), Nematoda (roundworms), Annelida (segmented worms), Arthropoda (insects, spiders, crabs, etc.), Mollusca (cuttlefish, snails, mussels, etc.), and Echinodermata (starfish, sea cucumbers, etc.).
The branch of science that deals particularly with the invertebrates is called invertebrate zoology.
- vertebral column
- velvet worm
- horseshoe crab