Hapalochlaena - The Blue Ringed Octopus
The Hapalochlaena, or Blue Ringed Octopus, has no internal skeleton. It is almost entirely soft, except for its beak in which it ingests food. The beak is made of chitin, which also makes up insect exoskeletons and bird beaks. Octopus, squid and cuttlefish have developed sophisticated skins so they can hide in an ocean full of hungry predators. They are completely loose from the rest of the body, except for thin tendons and ligaments that connect it to their organs. This enables octopi to squeeze into thin cracks in coral reefs and holes in the sea floor. Octopi skins also contain a protein made of cells called leucophores. A common misconception is that octopi can change colors and almost perfectly match their environment. However, that is not true. In a completely isolated habitat, with perfect water temperature and light distribution, the Hapalochlaena will have blue spots on an orange skin. If the temperature is not correct, they will change color. Usually, when an octopus retreats into a hole in the coral, the light striking the leucophores will decrease. This will cause the leucophores to reflect the most common color around them. That will be whatever the coral color inside the crack is.