From Microcosm Aquarium Explorer
- Crustaceans. Exotic Sea Life, Japanese illustrations, 1931.
- Anemones (detail). Ernst Haeckel, Kunstformen der Natur, 1899.
- Echinoderms. Exotic Sea Life, Japanese illustrations, 1931.
- Slipper Lobster. Histoire Naturelle, Lamarck, 1782.
- Mollusks. Exotic Sea Life, Japanese illustrations, 1931.
Invertebrates: A Definition
An invertebrate is an animal without a spinal column.
Invertebrates account for some 97% of all known animal species. (Vertebrates that fall within the subphylum Vertebrata include the fishes, reptiles, amphibians, birds and mammals.)
There are more than 30 invertebrate phyla, with an incredible diversity of life forms, ranging from rudimentary sponges to dazzlingly beautiful and anatomically sophisticated crustaceans.
With the exception of insects and spiders, members of all of these invertebrate phyla routinely make their way into home aquariums.
- Sea Anemones
- Comb Jellies
- Ribbon Worms
- Segmented Worms (Fireworms, Fan Worms)
- Arachnids (Spiders)
- Crustaceans (Shrimps, Lobsters, Crabs, Barnacles)
- Sea Urchins
- Sea Cucumbers
- Bivalves (Clams, Mussels, Oysters)
- Sea Slugs
- Moss Animals or Sea Mats
Need help? Read the Species Profiles instructions for Invertebrates.
World's Largest Invertebrate Giant squid, with the larger females reaching lengths of 43 feet, are the largest invertebrates. There are eight species of giant squid, Genus Architeuthis. They have the largest eyes in the animal kingdom, roughly the size of a human head. The largest giant squid ever measured was 59 feet long.
Largest Invertebrate (land) The coconut crab has a legspan of up to two and a half feet and weighs about 6.6 pounds. Native to tropical Indo-Pacific islands, this hermit crab species has muscular claws capable of punching holes into coconuts so that it can scoop out the flesh.
Most Venomous Animal A single sea wasp (a kind of jellyfish with 60 tentacles, each 15 feet long) has enough venom to kill 60 adult humans.