The Atlantic Pygmy Octopus, or the Octopus Joubini, is a very small octopus species that can grow to a maximum of 4.5 cm. Like most cephalopods, the Atlantic Pygmy Octopus has a very weak immune system. However, they do have circulating blood cells called hemocytes. Hemocytes also encapsulate foreign particles and produce immune mediators such as antimicrobial peptides. Immune mediators are the components of the immune system which help in the atherosclerosis process (Example: T-cells). Atherosclerosis is a disease of the arteries characterized by the deposition of plaques of fatty material on their inner walls. Antimicrobial peptides, also known as "host defense peptides", attack germs that invade the body by engulfing them. The hemocytes in the atlantic pygmy octopus act as a police force roaming around the body killing any "trouble making bacteria".