Octopus, also known as octopus (English name octopus), the same marine mollusks. Octopoda (Octopoda) cephalopod mollusks of the common name. But the strict sense only refers to the octopus genus (Octopus) animals, widely distributed in shallow water. The size of octopuses varies greatly. The smallest octopus is the arborescent octopus (O. arborescens), which is about 5 centimeters (2 inches) long, while the largest species can be up to 5.4 meters (18 feet) long, with a carapace spread of up to 9 meters (30 feet). The body of a typical octopus is sac-like; the head is not clearly separated from the carapace, and is surmounted by large compound eyes and eight retractable wrists. Each wrist has two rows of fleshy suckers that provide a strong grip. The base of the carapace is connected to webbed tissue called the skirt, which has a mouth at its center.