Ceratioidei

Ceratioidei, the pelagic anglerfishes or deep-sea anglerfishes, is a suborder of marine ray-finned fishes, one of five suborders in the order Lophiiformes, the anglerfishes. These fishes are found in tropical and temperate seas throughout the world, living above the bottom of the deep sea, in the pelagic zone. The esca, the anglerfishes' lure and a defining feature of all anglerfish groups, is bioluminescent in the deep-sea anglerfishes, attracting prey in the vast darkness of the bathypelagic zone which they inhabit. The deep-sea anglerfishes have extreme sexual dimorphism; the males are many times smaller than the females. To reproduce, a male seeks out a female, using his sharp teeth-like denticles to clamp onto the female. The details of this sexual parasitism varies between the species; in some, the male permanently becomes part of the female's body, their tissues fusing with each other. This is the only known natural example of a process called parabiosis occurring in adult vertebrates.