Bacteriocytes have repeatedly evolved in different lineages. Some insects slot them between other cells; others bundle them together into organs called bacteriomes, which branch off from the gut like clusters of grapes. Whatever their origin, their functions are the same: contain and control bacterial symbionts; stop them from spreading into other tissues; and hide them from the immune system. Bacteriocytes are not luxury accommodation. A single one can contain tens of thousands of bacteria, packed so tightly that they make sardine cans look roomy. They are cells in more ways than one.
Bacteriocytes
