Deep-sea anglerfishes employ an incredible reproductive strategy. Tiny dwarfed males become permanently attached to relatively gigantic females, fuse their tissues and then establish a common blood circulation. In this way, the male becomes entirely dependent on the female for nutrient supply, like a developing fetus in the womb of a mother or a donated organ in a transplant patient. In anglerfishes, this unusual phenomenon is called “sexual parasitism” and contributes to the reproductive success of these animals living in the vast space of the deep sea, where females and males otherwise rarely meet.