Feather stars - a distinctive reef invertebrate
All others, constituting 95 per cent of the animal kingdom, are invertebrates.
On the Great Barrier Reef, animals without backbones outnumber vertebrates by 20 to one, and new species are discovered every month.
Invertebrates come in a myriad of colours, shapes and sizes, from clams to cuttlefish and corals to crabs.
Some, like the octopus are among the most intelligent animals in the ocean. Others have no brain at all.
Invertebrates are the foundation of the Great Barrier Reef, and lead an astonishingly diverse range of lifestyles. Without them, the Reef could not exist.