Octopuses: They have nine brains in total. There is one central brain in their head that governs overall behavior, and eight smaller "mini-brains" (ganglia) located in each of their arms. These mini-brains allow individual arms to taste, touch, and make movement decisions independently from the main brain. [1, 2]
Cockroaches: They have two brains. One is located in the head, and a second primitive cluster of nerve cells sits in the abdomen. This dual setup explains why a cockroach can survive for several days even if its head is removed, as the abdominal brain continues to control its basic reflexes and movements. [1, 2, 3]
Squids: They have three brains. They possess one main brain that controls their body, and two large optic lobes that are dedicated solely to processing information from their highly advanced eyes.