Anglerfish: The Deep Sea's Glowing Nightmare

In the pitch-black depths of the ocean — where sunlight never reaches — the anglerfish dangles a glowing lure and waits. Few creatures are as fascinatingly strange as the anglerfish, a deep-sea predator that has evolved some of the most bizarre adaptations in the animal kingdom.

What Is an Anglerfish?

Anglerfish belong to the order Lophiiformes — over 300 species found in oceans worldwide, from shallow coastal waters to depths of over 3,000 feet. The most famous are the deep-sea anglerfish, which live in the mesopelagic and bathypelagic zones where no sunlight penetrates.

How Does the Lure Work?

The anglerfish's most iconic feature is its bioluminescent lure — called an esca — a modified spine that extends from its forehead and glows due to light-producing bacteria living inside it. The fish dangles this lure in the darkness; when a curious fish swims close to investigate, the anglerfish strikes with lightning speed, swallowing prey whole.

How Big Are Anglerfish?

Most deep-sea anglerfish are surprisingly small — females typically grow to 3–18 inches. However, the goosefish (a shallow-water relative) can reach up to 4 feet long and weigh 50 lbs. Their enormous jaws and expandable stomachs allow them to swallow prey up to twice their own size.

The Strangest Mating in the Animal Kingdom

Only female anglerfish have the iconic lure. Male anglerfish are tiny — about the size of a fingertip — and their sole purpose is finding a mate. When a male finds a female, he bites into her body and fuses permanently, his circulatory system connecting to hers. He loses his eyes, internal organs, and eventually everything except his testes. She may carry several males fused to her body at once. It's the most extreme example of sexual parasitism in nature.

Amazing Anglerfish Facts

• Their teeth point inward — prey can enter the mouth but cannot escape.
• Anglerfish can open their jaws so wide they can swallow prey larger than their entire body.
• The glowing bacteria in their lure have a symbiotic relationship with the fish — they get shelter, the fish gets light.
• Deep-sea anglerfish live in near-freezing water under enormous pressure.
• They were almost completely unknown to science until deep-sea submersibles were developed in the 20th century.