Anglerfish

Anglerfish

The Anglerfish is a master of the deep sea, living in the pitch-black "midnight zone" thousands of feet below the surface. Its most famous feature is the bioluminescent lure (esca) that dangles from its head, acting like a fishing rod to attract prey in the darkness.

This hunting tool is only used by females. The male's life is even more bizarre; tiny in comparison, he finds a female, bites onto her, and his body permanently fuses with hers. He connects to her bloodstream, losing his own organs over time, and becoming a lifelong parasitic partner.