The living habits and habitats of cephalopods

Cephalopods occur in benthic and pelagic habitats in all of the world’s oceans, from shallow coastal areas to the deep sea, but only a few species of a few genera (especially the Micropteridae and some squids ) can tolerate brackish water.

Of the existing cephalopods , about 35% are planktonic and 16% are benthic .

19% of the species were bottom pelagic organisms, 5% were benthic pelagic organisms and 25% were nematodes.

Some species are extremely abundant. Some estimates suggest that the biomass of octopuses is as high as that of marine fishes, due to the fact that many deep-sea cephalopods are present in vast quantities but cannot be found.

Pelagic cephalopods

Most of the pelagic cephalopods have a vertical distribution habit. Many species migrate up and down the water, moving to deeper waters during the day and to shallower waters at night. Many squids, most cuttlefishes, and many octopuses live in shallow waters in the photic zone.

To avoid being visually spotted by predators, they rely on color changes to protect themselves. Other squids live in extreme environments, such as deep water, hydrothermal vents, or cold seeps. Deep-sea squids are often translucent. Their eyes may be very large, stalked or even unequal, and they often have light organs.

To achieve neutral buoyancy , they typically reduce their body density by storing high concentrations of ammonium ions in their tissues.

A few cephalopods, notably the octopus and the nautilus , can tolerate prolonged periods of oxygen deprivation, an ability that may have helped their ancient ancestors survive some previous extinction events.

The ghost octopus drifts in the oxygen minimum zones of the deep ocean, feeding primarily on detritus that comes into contact with its arms.

Nautilus live in the tropical central Indo-Pacific. During the day, they live in dark, cold, deep water (about 300-650 meters), probably to avoid predation. When feeding at night, they move 300-100 meters below the surface (sometimes as shallow as five meters).