The ways of an octopus
Octopuses have always amazed the world with their intelligent behavior, unique colorations to adapt to the background, and the way they manage their flexible arms without getting them entangled. The octopus is an example of advanced cognitive adaptation, but how its brain (see yellow part in picture) works still remains a mystery. The octopus brain does not look at all like brains of other animals. Is has a huge optic lobe underneath their eyes and a highly developed touch system which explains their excellent eye sight and sense of touch*. It has two memory systems that follow these two sensory systems. A visual and a tactile memory used to identify signals in the environment for attack or retreat. But also to explore novel situations. But most amazing is how the octopus controls its eight arms. Two-thirds of the nerve cells in the nervous system are located in the nerve cords of its arms (see yellow extensions in picture), which makes the eight tentacles function as an extended brain. The central brain only has to trigger a command to the arms, which then carry out the full action sequence. Suggesting that the entire movement plan is embedded in the arm itself and not in the central brain like in mammals. There is no propriocepsis, that is neural feedback paths of their movements to the brain, so movements must be monitored by 'seeing what happens'. Octopuses are also known to use their arms in battles, by hurling sand and debris to its rivals**. Getting to know the octopus makes it hard to accept that this superb creature is still hunted down to end up in sea food dishes all over the world.
J. Z. Young's "The Anatomy of the Nervous System of Octopus Vulgaris" (1971)