Anglerfish

The anglerfish is a group of strange, deep-sea fish known for the glowing lure that dangles in front of their mouths. There are more than 200 species of anglerfish. Most live in the deep ocean, thousands of feet below the surface, where sunlight never reaches. Anglerfish get their name from the way they fish for food, just like a person using a fishing rod.

The lure is actually a long, thin piece of the anglerfish's spine that grew forward over millions of years. It sticks out above the mouth like a fishing pole. At the tip is a small bulb that glows in the dark. This glow is made by tiny bacteria that live inside the bulb. The bacteria make light, and the anglerfish gives them a safe home and food. This kind of partnership is called symbiosis.

Small fish and shrimp in the deep sea are drawn to the glowing bulb. When one swims close to investigate, the anglerfish strikes. Its mouth is huge compared to its body, and its teeth curve inward like spikes. Once a meal is inside, it cannot swim back out. Some anglerfish can swallow prey twice their own size by stretching their stomach like a balloon.

The deep sea is a hard place to live. It is pitch black, near freezing, and the water above presses down with enormous weight. At 3,000 feet deep, the pressure is about 90 times greater than at the surface. Food is rare down there, so anglerfish often stay still for hours, saving energy and waiting for the lure to do the work.

Finding a mate in the dark is also hard. In many deep-sea anglerfish species, males solve this problem in a shocking way. The males are tiny, sometimes less than an inch long, while females can be more than three feet. When a male finds a female, he bites onto her body and never lets go. His skin slowly fuses with hers, and their blood vessels connect. He becomes a permanent part of her, feeding from her body and supplying sperm when she is ready to lay eggs. Some females end up carrying several males at once.

Not all anglerfish live in the deep. Shallow-water anglerfish, like the goosefish and frogfish, sit on the seafloor and wiggle their lures to trick small prey. Scientists are still discovering new anglerfish species. The deep ocean is the largest habitat on Earth, and most of it has never been explored.