Anglerfish: Two Become One

Male anglerfish fuses with larger female (scitechdaily)

We can't avoid lingering on the sensational aspect of anglerfish reproduction before getting serious: [bold added]

These anglerfishes, called ceratioids, reproduce through sexual parasitism, in which the tiny males attach to their much larger female counterparts to mate. In some species, the males bite the females and then release once the mating process is complete. In others, the male permanently fuses to the female. In a process called obligate parasitism, the male’s head dissolves into the female and their circulatory systems merge. He transforms into a permanent sperm-producing sexual organ.

The theory is that it is so difficult to find a mate at the bottom of the ocean that the male latches onto the female and becomes a "permanent sperm-producing sexual organ." (Insert jokes here.)

Somehow the female's immune system does not reject the male's foreign tissue, as it would in every other species. Despite her absence of protective "killer T" cells, the female is able to stave off infection by other means. Research into the anglerfish mechanisms could have profound implications for human health, where foreign tissue rejection is a major problem for transplant surgery.

“Better understanding how deep-sea anglerfishes lost adaptive immunity could one day contribute to advances in medical procedures, such as organ transplants and skin grafting, where suppressing immunity is crucially important,” [Yale Professor Thomas Near] said. “It’s an interesting area for future medical research.”

The science is interesting and important, but my takeaway is that the next time your friend says he's lost his mind over a woman, tell him that's nothing compared to the male anglerfish.