Octopodes are the smartest invertebrates. Taken together the arms contain more neural tissue than the brain, allowing each arm can act independently. In males one of the arms is specialized to deliver sperm to the female, after which the male usually dies. The female protects and aerates the eggs until they hatch, then she dies. Octopodes have very short lifespans, dying shortly after mating, because the act of mating triggers a chemical change that permanently turns off the digestive system. It is believed that this change occurs to prevent overpopulation.