Basic AnatomyUnlike it’s mollusca relatives, the giant Pacific octopus lacks a shell covering, instead a sack-like tissue called the mantle cavity contains all of the internal organs. Among these organs are three hearts. There is the main heart, the systemic heart, and two smaller hearts, located near the gills. The branchial hearts pump blood to the gills, dumping waste, and take up oxygen before returning the oxygenated blood to the systemic heart. The systemic heart then pumps the oxygenated blood throughout the body. As well as having three hearts, giant Pacific octopuses also have blue blood due to a protein called hemocyanin rather than hemoglobin, which is found in human blood (Flory 2007).
The only hard part of an octopuses’ body is its beak found in the radula. The beak is made of keratin, the same protein that composes human fingernails and bird beaks. The beak is used to drill holes in shells and crush their prey. Because the beak is the only hard part of an octopus, if an octopus can fit it’s beak into a crevice or crack, the rest of the body will fit (High 1976). |
ChromatophoresAn octopuses best tool of defense is camouflage, which is accomplished by chromatophores, neuromuscular organs that contain pigment granules. Unlike other organisms that control chromatophores through hormones, an octopuses’ chromatophores are controlled by sets of lobes within the brain such as the optic lobe which allows for instantaneous appearance change characteristic of octopuses. While camouflage is the primary purpose of chromatophores, communication is also done through the use of chromatophores. For instance, when mating, a male can produce coloration on the body side facing a potential mate, while at the same time producing a different coloration on the body side warding off other males (Messenger 2001).
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TentaclesTentacles covered in suckers that can move independently in eight different directions are perhaps the most recognizable feature on an octopus. Octopus tentacles can play a role in a vast number of behaviors such as feeding, locomotion, and camouflage. Two-thirds of the neurons in an octopus are dedicated to the arms, which may explain their incredible abilities (Hochner 2010). Researcher found octopuses could not differentiate between the weight of different objects, leading them to believe a low-level motor controller exists that controls the tentacles movements rather than the brain (McMahan et al 2007). Muscles called hydrostats compose octopus tentacles; these muscles retain a constant volume during contractions and will increase in length if the diameter of a tentacle decreases and vice versa allowing for incredible flexibility (Mazzolai et al 2007). In fact, due to the unique and incredible abilities of octopus tentacles, researchers are modeling robotic control manipulators and robot arms after octopuses (McMahan et al 2007; Laschi et al 2012).
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