Octopus There are about 300 species of octopus, ranging in size from about half an inch (1 cm) to more than 16 feet (5 m) long. Octopi are divided into two groups, cirrata (fi nned octopi) and incirrata (fi nless). Most octopi (85 percent) belong to the incirrata group; these animals have no fi ns, and they are found in shallow water and live in caves or crevices. The cirrata group has two fi ns and an internal shell. They are found in the deep sea, at depths of between 1,000 (304 m) and 24,000 feet (7,315 m). Octopi have soft bodies, large heads and eight arms. The arms have suction cups that help grab and hold prey. The tentacles also have taste sensors that help identify food. Octupus eat bottom-dwelling crustaceans (crabs, crayfi sh and mollusks). The mouth of the octopus has a sharp beak (shaped like a parrot’s) well suited to cracking shells. Octopi are considered to be the most intelligent of all invertebrates (animals without backbones). Studies show that octopi have both short- and long-term memories and superior problem-solving skills. All species are venomous, and some subdue prey with toxic saliva, but only one – the blue-ringed ocutopus – is deadly to humans. The main predators of octopi are moray and conger eels, dolphins and sharks. Hiding is the octopus’ main defense, but if spotted by an enemy, it emits ink clouds or uses camoufl age. Some species have automated limbs (the ability to detach and regrow an arm).Octopi are solitary animals and always live alone. Depending on the species, they live six months to fi ve years.
Squid
There are about 375 species of squid that range in size from about 1 inch (2.5 cm) to more than 60 feet (18 m) in length. The Giant Squid (Architeuthis) can weigh more than 1,000 pounds. Unlike their cousin the octopus (a solitary creature found only in shallow saltwater), squids often travel in groups and prefer open oceans — some live in freshwater.Squids have soft bodies, a mantle/head (with a large brain), a beak, two fi ns, eight arms and two long, muscular tentacles. Their powerful suckers have an extra ring of hooks that provide superior grasp of prey. (If severed, their tentacles do not grow back.) They breathe using gills. Some deep-sea squid are bioluminescent and can produce a form of light.Squids are carnivores (meat eaters) feeding on a variety of fi sh and shrimps; larger species eat larger prey.These invertabrate are fast and agile swimmers, and use a kind of jet propulsion to move. Some species will jump out of the water and “fl y” for short distances. Squids are intelligent (like the octopus) and have the ability to change color to mimic their environment and hide from predators.Squid reproduce by releasing eggs into the water. Some squid eggs are free-fl oating; others are attached to seaweed or to the ocean fl oor. Squids play an important role in marine food chains; they are eaten by fi sh, sharks, other squid, whales and people.Depending on the species, the life span of a squid ranges from nine months to fi ve years.