Humpback anglerfish facts for kids
Quick facts for kids Humpback anglerfish |
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The humpback anglerfish (Melanocetus johnsonii) is a type of deep-sea fish. It belongs to a family called Melanocetidae, which means "black whale" in Greek. This fish got its name from James Yate Johnson, an English scientist who found the first one in 1863. People also call it the anglerfish, viperfish, or fangtoothfish.
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Discovering the Humpback Anglerfish
The first humpback anglerfish was found by James Yate Johnson on December 24, 1863. He found it near Madeira, a group of islands off Africa. The fish was then taken to Albert Günther at the Natural History Museum, London. Günther was a zoologist who studied animals.
Early Discoveries and Names
Günther described the fish as a new type because of its unusual shape. He noticed it had no pelvic fins. He named it after Johnson, who first collected it. Scientists first thought the anglerfish used its special light-up lure to catch food. Christian Frederik Lütken was the first to suggest this.
Understanding Male and Female Anglerfish
For a long time, scientists thought male anglerfish were a different species. This was because males look very different and do not have the light-up lure. In 1924, a British scientist named Charles Tate Regan made an important discovery. He realized a small fish attached to a larger anglerfish was actually a male. This led to the understanding of sexual dimorphism in anglerfish. This means males and females look very different. Some fish once thought to be separate species are now known to be M. johnsonii.
Where Humpback Anglerfish Live
The humpback anglerfish lives in the deep ocean. It is found in the mesopelagic and bathypelagic zones. These are very deep parts of the ocean. They usually live between 200 and 1,500 meters (about 650 to 4,900 feet) deep.
Light and Location in the Deep Sea
At these depths, very little or no sunlight reaches. This area is far below the photic zone, where light can penetrate. Because of the darkness, the humpback anglerfish uses bioluminescence to hunt. This means it can produce its own light.
Global Distribution of the Species
M. johnsonii lives in more places than any other fish in its group. It is found in warm and mild parts of all oceans. It also lives in the South China Sea and East China Sea. In 2014, a humpback anglerfish was found in Antarctic waters. It was in the stomach of an Antarctic toothfish in the Ross Sea. This showed the fish lives even further south than thought. Another one was found near British Columbia, Canada. This shows it lives very far north in the East Pacific too.
What Humpback Anglerfish Look Like
The humpback anglerfish is a soft-bodied fish. It is dark brown or black. Female humpback anglerfish have round bodies and large heads. Their mouths are wide and almost vertical. They have long, sharp teeth. These teeth help them eat prey even bigger than themselves.
Female Features
Females have many small skin spines under their dorsal fin. Compared to other anglerfish, M. johnsonii has a longer illicium. This is a short fin spine on their snout. It also has a bulb-like lure called an esca. The esca has special crests that help tell it apart from other anglerfish. Females have small eyes that are under their skin. This suggests they do not rely on sight for hunting or finding mates.
Male Features and Differences
Humpback anglerfish show extreme sexual dimorphism. This means females are much larger than males. Females can grow up to 153 mm (about 6 inches) long. Males are tiny, only growing between 15.5 and 28 mm (about 0.6 to 1.1 inches). Males do not have the light-up lure. Instead, they have large eyes and nostrils. These might help them find mates that are far away.
Comparing Similar Species
There are many similarities between M. johnsonii and M. rossi. One way to tell them apart is that M. johnsonii has black color on its upper body. M. rossi does not. Because they are so similar, some scientists think M. rossi might actually be the same species as M. johnsonii.
How Humpback Anglerfish Hunt and Eat
Female M. johnsonii have huge mouths with sharp teeth. They also have very stretchy stomachs. This allows them to eat almost anything they find. Their stomachs can expand easily. They can even eat meals that weigh more than they do. One anglerfish weighing 8.8 grams was found with three snipe eels in its stomach. The eels weighed a total of 12.3 grams.
Hunting in the Deep Sea
Not much food is available in the deep ocean. Only about 5% of the food made in the sunlit surface waters reaches the deep sea. Humpback anglerfish are ambush predators. This means they wait quietly for prey to come to them. They do not chase their food.
Low Metabolism and Survival
M. johnsonii has a very slow metabolic rate. This is even slower than other animals living at similar depths. Scientists studied eight anglerfish in a lab. They found that M. johnsonii can control how much oxygen it uses. This helps them survive for a long time in places with little or no oxygen.
The Bioluminescent Lure
Females use their glowing esca as a lure to attract prey. The light comes from special bacteria called Enterovibrio escacola. These bacteria live on the esca. Scientists once thought these bacteria could only live with the anglerfish. But now they know the bacteria and the fish can survive without each other if needed.
Reproduction and Life Cycle
Finding a mate is hard for M. johnsonii. They live alone and far apart in the deep sea. Male anglerfish have very good senses. They can follow the scent of a female. This is easier in the still deep-sea waters.
Unique Mating Strategy
Unlike some other anglerfish, male M. johnsonii do not stay attached to the female forever. They attach to the larger female using special teeth. They then release their sperm. After this, the males detach and go find other mates. Scientists have seen this happen twice. There was no sign that the male and female fish had grown together.
External Fertilization
Black anglerfish reproduce through external fertilization. Females release their eggs into the water. Males then release their sperm right away to fertilize the eggs. This unique way of reproducing might explain why males do not live on females their whole lives. Both male and female M. johnsonii can become ready to reproduce without the other sex being present. In some other anglerfish, males attach to the female before they are fully grown.
Protecting the Humpback Anglerfish
The humpback anglerfish is listed as a "Least Concern" species on the IUCN Red List of Threatened Species. This means it is not currently at high risk of disappearing. People do not eat this fish. So, it is not hunted by humans.
Potential Threats
However, humpback anglerfish can sometimes be caught by accident. This happens when fishing boats use trawls to catch other fish. As commercial fishing moves into deeper waters, this might affect the species more. The small number of recorded individuals might be because they are spread out in the deep sea. It is also hard to collect animals from such deep and wide areas.
Humpback Anglerfish in the Media
In 2014, a video of M. johnsonii was filmed off the coast of California. The Monterey Bay Aquarium Research Institute used a special underwater robot called Doc Ricketts. The video shows a female M. johnsonii swimming slowly. It was about 1,900 feet deep in the Monterey Canyon.
