Anglerfish

Deep-sea anglerfish The glowing rod dangling over a female anglerfish's head, as on the humpback anglerfish pictured, is a fishing lure. It hangs just in front of her mouth, enticing smaller fish in the dark, and its tip glows thanks to bioluminescent bacteria that it gathers from the water as she ages. The stranger body plan belongs to the males. They are far smaller than females, usually have no lure, and in some species a male fuses into the female's body until he is little more than a sausage-like attachment. In a vast, empty ocean, holding on to the one mate you found makes a kind of sense.