Deep-sea anglerfish deleted part of immune system to fuse with its mate: Study

Some male deep-sea anglerfish permanently "fuse" their tissues with a larger female partner while mating. With this "sexual parasitism", the two share the same blood circulation system. A study has found that anglerfish have evolved over time to lose genes that control their adaptive immune system, allowing their bodies to fuse without triggering an immune response and attacking foreign tissue.