Octopods Nautilids Cuttlefishes Squids and Relatives: Cephalopoda

Cephalopods have large brains, well-developed eyes, and complex behaviors. Some species, such as octopuses, lead solitary lives, while others, like cuttlefish, live in small to very large groups called schools. Some cuttlefishes or squids get together only to find a mate and reproduce. Many species live at depths of 1,310 to 3,280 feet (400 to 1,000 meters) during the day and swim closer to the surface at night to feed, but the activity patterns of most are unknown. Most cephalopods do not guard or defend territories. Some species will change their colors as a means of camouflage or to startle predators. Many squids and octopuses have special glands for making a defensive inklike fluid that is squirted in the water to confuse their enemies.

Both males and females are required for reproduction, but the mating behaviors of most cephalopods remain unknown. Although nautiluses reproduce many times throughout their lives, most cephalopods do so only once. The time for reproduction in these species may be either very brief or extended over a long period of time. In some species, the male simply grabs the female and places a packet of sperm in a specific place on or inside her body. Others engage in elaborate courtship behaviors that involve lots of touching just before they mate.

Depending on the species, females produce dozens to hundreds of thousands of eggs at a time. One or more layers of a special, protective coating surround each egg. The eggs are usually laid in masses, either on the ocean bottom, in between rocks, or inside seashells, while others release them into the open water. Only some kinds of octopuses and squids care for their eggs until they hatch.

The eggs take a few days to several months to hatch. The hatchlings of some species look and live like the adults and simply grow larger as they develop. Others look nothing like the adults and spend the early part of their lives as plankton. Planktonic plants, animals, and other organisms live in open water and float about on ocean currents. Eventually, the young planktonic cephalopods settle to the ocean bottom, where they develop to more closely resemble the adults in both form and habit.