Blue Ringed Octopus -
Cephalopod - means 'head and foot' animal.
The cephalopod group includes octopus, cuttlefish, squid and the nautilus. In cuttlefish, squid and octopus, the 'foot' has become tentacles. All cephalopods live in salt water and all are carivorous.
Special features of cephalopods include:
- soft-bodied marine animals with a large head and a ring of sucker-bearing tentacles.
- have the most advanced nervous systems of all invertebrates.
- efficient blood systems - 3 hearts, a systematic heart to pump blood throughout the body and 2 brachial hearts that pump blood to the gills.
- eyes are well developed.
- are relatively intelligent.
- react quickly to changes in their surroundings.
- can change skin colours and textures rapidly and dramatically.
- have an ink sac opening off the end of the digestive tract.
- propel themselves through the water by jetting water from the mantle through the siphon.
Cephalopods are believed to be an ancient group that first evolved sometime during the Late Cambrian (over 500 million years ago).
Scientists believe that the ancester of modern cephalopods was a mollusc that developed an air space within it's shell and worked out a method for regulating the air in it. Predators could be avoided by just floating up off the ocean bottom and the cephalopods could transport themselves over large distances without expending too much energy searching for food.