All cephalopods live in the marine environment, where they are carnivores. A shared trait of the group are sucker-bearing tentacles used to seize and hold prey. The tentacles range in number from eight in the octopus to more than ninety in Nautilus. The tentacles surround a powerful beak-like mouth.
Many living cephalopods (but not Nautilus ) possess an ink sac capable of ejecting a dark fluid to confound predators. Some octopuses, squids, and Suction cups on tentacles are used to grasp prey and cling to surfaces. The common octopus has approximately 240 suction cups per tentacle. cuttlefish have the remarkable ability to change color and color patterns to better blend in with the surrounding seafloor.
While most other mollusks have hard external shells, most cephalopods do not. Nautilus has a planispherally coiled external shell, while squids and cuttlefish have a smaller internal skeleton, and octopus has no hard skeleton at all. The cephalopods all have two well-developed eyes used in hunting prey. The octopus spends most of its time scurrying along the seafloor, feeding on other bottom dwellers such as crabs. In contrast, Nautilus and squids are active swimmers and also can prey on fish. All cephalopods can move backwards fairly quickly by expelling water in a type of jet propulsion.
Because they are elusive creatures, the habits and ecological details of most species of cephalopods are unknown. Similarly, the population sizes are not well known, making it difficult in many cases to determine if a species is endangered. Overfishing of the most commercially desirable species has occurred in the past. Because of the rapid reproduction of cephalopods, a temporary ban on fishing often is successful in restoring the fishery populations.
Read more: http://www.waterencyclopedia.com/Ce-Cr/Cephalopods.html#ixzz3YisV8XKq
Many living cephalopods (but not Nautilus ) possess an ink sac capable of ejecting a dark fluid to confound predators. Some octopuses, squids, and Suction cups on tentacles are used to grasp prey and cling to surfaces. The common octopus has approximately 240 suction cups per tentacle. cuttlefish have the remarkable ability to change color and color patterns to better blend in with the surrounding seafloor.
While most other mollusks have hard external shells, most cephalopods do not. Nautilus has a planispherally coiled external shell, while squids and cuttlefish have a smaller internal skeleton, and octopus has no hard skeleton at all. The cephalopods all have two well-developed eyes used in hunting prey. The octopus spends most of its time scurrying along the seafloor, feeding on other bottom dwellers such as crabs. In contrast, Nautilus and squids are active swimmers and also can prey on fish. All cephalopods can move backwards fairly quickly by expelling water in a type of jet propulsion.
Because they are elusive creatures, the habits and ecological details of most species of cephalopods are unknown. Similarly, the population sizes are not well known, making it difficult in many cases to determine if a species is endangered. Overfishing of the most commercially desirable species has occurred in the past. Because of the rapid reproduction of cephalopods, a temporary ban on fishing often is successful in restoring the fishery populations.
Read more: http://www.waterencyclopedia.com/Ce-Cr/Cephalopods.html#ixzz3YisV8XKq