How Octopuses Work
The octopus belongs to the phylum mollusca, where you will also find its slimy next of kin, the clams, snails and slugs. But octopuses are separated from the mollusks into the class cephalopoda, which includes the most advanced animals of the phylum. Squid, cuttlefish and nautilus belong to this class as well. The octopus has evolved most since the cephalopods originated more than 600 million years ago. While the other cephalopods sport some form of inner or outer shell like their relatives the mollusks, the octopus has none.
The word cephalopod literally means “head-footed” and refers to the fact that these animals’ arms branch directly off of their heads. Some cephalopods have tentacles as well as arms, but the octopus manages just fine with the eight arms it uses for practically everything: eating, moving, hunting, tasting and mating.
Behind the octopus’s head, directly opposite the arms, is its mantle. The mantle is a highly muscled structure that houses all of the animal’s organs. Its gills, hearts, digestive system and reproductive glands are all crammed into this one space. The strong muscles in the mantle protect the organs and help with respiration and contraction. The octopus also has a funnel, sometimes called a siphon, which is a tubular opening that serves as a pathway for water.
Although the octopus does not have any teeth in the standard sense, it has several other just as effective methods of cracking into crustaceans and mollusks. The octopus has a veritable Swiss Army knife of tools located inside its mouth to pry open the shells it can’t open with its tentacles. Directly inside its mouth, it has a hard retractable beak similar to a parrot’s. This beak is useful for breaking open clam shells and tearing apart flesh. Next to the beak is the radula, a barbed tongue the octopus uses to scrape an animal out of its shell once the shell is opened. And if these tools don’t do the trick, it also has a tooth-covered organ called the salivary papilla that it can use to drill into shells. The papilla’s bodily secretion also erodes the shell and then weakens the prey so it can be consumed.