The body of tiny spiders is so small, that its brain does not fit in the body cavity. According to researchers, the brain of spiders is also distributed among their legs which make us to say that spiders are partially thinking with their legs. A research was made on nine different species of spiders, including large spiders from the rainforest and ending with the microscopic spiders. As spider’s size gets smaller, its brain occupies more space proportionally to the whole body sizes. Since the tiny body is unable to fit even minimal brain sizes, it is getting split into the legs of the spider. It is no matter whether the spider is small or large – they all have ability to survive, weave a web and perform other spider specific actions.
This means that independent on the sizes of the spider its brain should be of an optimal size to handle the common behavior. For tiny spiders, central nervous system occupies almost 80% of the body, including 25% of the legs. Some tiniest immature spider species have even deformed their bodies to fit the excess of the brain in the bulge. However, once they get adult, the bulge disappears. Spider brain cells cannot decrease in size for smallest species because most cells have a nucleus that contains the whole set of spider’s genes, and that takes up space. The diameter of the nerve fibers or axons also can’t be made smaller because if they are too thin, the flow of ions that carry nerve signals is disrupted, and the signals are not transferred properly. Spider brain cells use huge energy to transfer nervous signals, which means that spiders should take a lot of food to process the brain.