In the very early stages of human growth, the sexual parasitism and degeneration of the female formed no possible source of social danger.

But among the 160 deep-sea species, only some 25 engage in the aforementioned biting-fusing-mating, what is known as sexual parasitism.

The Anglerfish Deleted Its Immune System to Fuse With Its Mate Underwater " sexual parasitism" between male and female allows two bodies to become one.