Science ( IF 41.845 ) Pub Date : 2020-07-30 , DOI: 10.1126/science.aaz9445 Jeremy B. Swann, Stephen J. Holland, Malte Petersen, Theodore W. Pietsch, Thomas Boehm
Sexual parasitism has evolved as a unique mode of reproduction among deep-sea anglerfishes. The permanent attachment of males to host females observed in these species represents a form of anatomical joining, which is otherwise unknown in nature. Striking modifications to immune facilities are associated with this reproductive trait. The genomes of species with temporarily attaching males lack functional aicda genes that underpin affinity maturation of antibodies. Permanent attachment is associated with additional alterations, culminating in the loss of functional rag genes in some species, abolishing somatic diversification of antigen receptor genes, the hallmark of canonical adaptive immunity. In anglerfishes, co-evolution of innate and adaptive immunity has been disentangled, implying that an alternative form of immunity supported the emergence of this evolutionarily successful group of vertebrates.