Anglerfish
Lophiiformes
Animal Type: Bony fish
Habitat: Deep ocean
Diet: Carnivore
Special Feature: Bioluminescent lure
Depth: Often hundreds to thousands of meters deep
About Anglerfish
Anglerfish are unusual deep-sea fish best known for the glowing lure that hangs in front of the mouths of many species.
They belong to a large group of fish called Lophiiformes. Some anglerfish live in shallow water, but many of the most famous species live far below the ocean surface where sunlight cannot reach.
Deep-sea anglerfish have bodies adapted for life in darkness, high pressure, cold water, and an environment where food can be difficult to find.
The Glowing Lure
Female deep-sea anglerfish often have a long modified spine extending from their heads. At the end is a structure called an esca.
The esca can glow through bioluminescence. The light acts like a fishing lure, attracting curious animals toward the anglerfish's mouth.
Once prey comes close enough, the anglerfish can suddenly open its large mouth and swallow it.
The glow of many deep-sea anglerfish is produced with the help of bioluminescent bacteria living inside the lure. The fish and bacteria benefit from this relationship.
The Midnight Zone
Many deep-sea anglerfish live in the Midnight Zone, also known as the Bathypelagic Zone.
This zone extends from about 1,000 to 4,000 meters (3,280 to 13,123 feet) beneath the ocean's surface.
No sunlight reaches this depth. The water is completely dark except for light produced by living organisms.
Temperatures are cold, pressure is extremely high, and food can be scarce. Animals living here often have unusual adaptations that help them survive these conditions.
Bioluminescence
Bioluminescence is the ability of a living organism to produce light through a chemical reaction.
In the deep ocean, animals use bioluminescence for many purposes. It can attract prey, confuse predators, communicate with other animals, or help an animal hide.
Because the Midnight Zone receives no sunlight, bioluminescent flashes and glowing organs may be some of the only sources of visible light.
What Do Anglerfish Eat?
Anglerfish are predators. They eat fish, crustaceans, and other deep-sea animals that come close enough to capture.
Their large mouths and expandable stomachs allow some species to swallow prey surprisingly large compared with their own bodies.
This is useful in the deep sea because an anglerfish may not know when its next meal will appear.
Living in Darkness
Deep-sea anglerfish do not rely on bright colors or ordinary vision in the same way many surface animals do.
Their bodies are often dark brown, gray, or black. Dark coloration makes them difficult to see in an environment that is already almost completely black.
Many species also have sensitive eyes that can detect small amounts of light, including bioluminescence produced by other animals.
Male and Female Anglerfish
In some deep-sea anglerfish species, males and females are dramatically different in size.
Females may be much larger and possess the famous glowing lure. Males can be tiny by comparison.
In some species, a male permanently attaches himself to a female. Over time, their tissues and blood circulation can become connected.
This unusual reproductive strategy helps ensure that the two animals remain together in the enormous, sparsely populated deep ocean.
Why Such a Huge Mouth?
Finding food in the deep ocean can be difficult. Animals may go long periods without encountering something they can eat.
Many deep-sea anglerfish have large mouths and long teeth that help prevent prey from escaping.
Their jaws and stomachs may also expand, allowing them to take advantage of a large meal whenever the opportunity appears.
Pressure in the Deep Ocean
Water pressure increases dramatically as ocean depth increases. At depths of thousands of meters, the pressure is hundreds of times greater than it is at the surface.
Deep-sea animals have bodies specially adapted to function under these conditions.
Many have soft tissues and lack large gas-filled spaces that would be difficult to maintain under extreme pressure.
Where Are Anglerfish Found?
Anglerfish can be found in oceans around the world. Different species live at very different depths.
Some live along the seafloor in shallow coastal habitats, while deep-sea species inhabit the open water far below the Sunlight and Twilight Zones.
The strange deep-sea anglerfish seen in photographs and documentaries are especially associated with the dark waters of the deep ocean.
Perfectly Adapted to the Midnight Zone
Anglerfish may look strange compared with animals living near the surface, but their unusual bodies make sense in the environment where they live.
A glowing lure helps attract scarce prey, a large mouth makes it easier to capture food, dark skin provides camouflage, and unusual reproductive strategies help animals find mates in a vast ocean.
Each of these features helps anglerfish survive in one of the darkest and most challenging habitats on Earth.