Researchers have investigated the phenomenon of sexual parasitism in deep-sea anglerfish. The scientists show that this very rare mode of reproduction is associated with the loss of adaptive immunity. In the course of evolution, however, the animals have reorganized their immune systems and only survive with the help of their innate immunity. 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 her mother or a donor organ in a transplant patient. In anglerfishes, this unusual phenomenon is referred to as sexual parasitism and contributes to the reproductive success for these animals living in the vast space of the deep sea, where females and males otherwise rarely meet.

Interestingly, the researchers found that anglerfishes that utilize permanent attachment are largely depauperate in genes that encode these MHC molecules, as if they had done away with immune recognition in favor of tissue fusion. "Apart from this unusual constellation of MHC genes, we discovered that the function of killer T cells, which normally actively eliminate infected cells or attack foreign tissues during the organ rejection process, was also severely blunted if not lost entirely.

These findings hinted at the possibility that the immune system of anglerfishes was very unusual among the tens of thousands of vertebrate species," says Jeremy Swann from the MPI of Immunobiology and Epigenetics and first author of the study.

Regards

John
Editorial Assistant
Immunogenetics Open Access