Though it breathes through gills, the octopus is not a fish but a cephalopod marine mollusk. Also, unlike a fish, an octopus is an invertebrate, which means it doesn't have a backbone. It also has three hearts. More »

Octopuses are not mammals. They are classified as cephalopods, a class of mollusk. Octopuses are invertebrates, meaning that they do not have a backbone; on the other hand, mammals are vertebrates. More »

There are many different oceanic mollusks, such as clams, octopus and oysters, but there are also mollusks that live on land, such as snails and slugs. Mollusks are the second largest group of invertebrates in the world,... More »

The octopus mainly eats crabs and other shelled invertebrates, though they do eat fish and small sharks as well. The fact that they eat crabs primarily is the reason why an octopus has a beak. More »

A live octopus can be bought both in aquarium stores and ordered online to be delivered through the mail. Depending on whether you are hobbyist or a scientist, you can buy an octopus from various suppliers. Certain selle... More »

www.reference.com Pets & Animals Marine Life Octopi

The octopus belongs to the phylum Mollusca in the Animalia kingdom. The phylum contains a large number of aquatic life forms in addition to the octopus, such as squid, mussels and oysters. More »

Some enemies of the octopus include eels, sharks, halibut, ling cod and dolphins. The octopus uses camouflage to protect itself from predators, which allows it to hide in plain sight. It also releases a cloud of black sm... More »