In this post, we will describe and discuss the Anglerfish adaptations to the depths. We will also outline evolutionary Anglerfish characteristics and their biology.
What are the Anglerfish adaptations?
The Anglerfish have many anatomical, behavioural, and physiological adaptations to the depths. These adaptations are:
- Large mouth and teeth;
- Expandible stomach;
- Bioluminescent lure;
- Discrete non reflective skin colour;
- Male parasitic specificities for breeding
- Strong olfactory system;
- Ambushing strategy for hunting;
- Low-energy input for swimming and breeding;
- Reduced amount of air cavities in the body.
Anglerfish are fish that inhabit one of the most inhospitable environments in the world, the deep sea. Many people consider Anglerfish to be the Earth’s ugliest beings. Anglerfish are classified as a cosmopolitan species, as they can be found in all the oceans. There are around two hundred species for the group (genera Lophius). However, only a few of them occupy the deep sea.
Pressure in the deep sea intensifies as the depth increases. Although, these organisms face several other conditions, such as extremely low temperatures, reduced oxygenation, lack of light, etc.
To inhabit the deep sea, the Anglerfish had to evolve, developing many characteristics that provided them adaptations to survive the harsh conditions of the deep sea. These adaptations can occur in many systems and structures of their bodies, as listed below:
– Anatomical adaptations;
– Behavioural adaptations;
– Physiological adaptations.
Anatomical adaptations
One of the most remarkable adaptations to live in the deep is the modified dorsal fin spine with a bioluminescent lure, or photophore. This muscular structure hangs at its end a bacteria agglomerate, similar to a fishing pole with an esca. These bacteria produce light by chemical reactions, this light production is called bioluminescence.
This lure is used to attract prey, crustaceans and fish, mainly. The prey is attracted by the pulsing lure and swims towards the Anglerfish’s mouth. Once the prey is close enough they use other adapted structures to capture and quickly take the prey down.
Anglerfish also own very large teeth. Associated with this, they also have huge mouths and stomachs. These characteristics allow them to capture and feed without spending too much energy on ambush hunting.
The bright lure is also used for breeding purposes. Only females own lures. The males are tiny and not predatory. The males usually are 3 centimetres long. Typically, males spend their entire energy searching for females, from the moment they hatch.
Sometimes, the males can even become female parasites, until they mate again. However, the majority of species with the parasitic male are not inhabitants of the deep sea. In the depths, usually, the males keep seeking another mate right after spawning. They form very short reproductive bonds, to improve the chances of the eggs getting fertilized. Their reproduction occurs via external fertilization.
Due to the poor visibility, male Anglerfish developed a very strong olfactory sensor that is capable of detecting the female’s pheromone from enormous distances.
Anglerfish also have adaptations related to their colour. Aiming to avoid predators and to be seen by prey, they have a very particular skin colour. A dark-brown-greyish tone. This colour allows them to swim around without dragging too much attention. In addition, as the colour emitted by the bacteria is typically blue, Anglerfish tend to have skin that is capable of reflecting specific light colours. Thus, they are not li by their light.
About swimming behaviour, their globular bodies are very suitable for floating, not for swimming, as we will see the reason below, they use water currents to float around.
Behavioural adaptations
As prey are not easy to find and capture in the deep sea, Anglerfish developed a low-energy input hunting style. They ambush the prey by using the pulsing lure. Thus, they use only about 2% of their energy in swimming. In addition to the ambushing strategy, they also use water current to float around, only making some adjustments in direction.
Also, a minimal amount of energy and time is spent to kill the prey. Their large teeth, mouth and expansible stomach allow them to preserve these low-energy input behaviours.
Physiological adaptations
To resist the high pressure of the depths, the Anglerfish have a very little amount of body cavities. Thus, they do not have air concentrations inside their bodies to collapse, which reduces the effect of high pressures.
Are Anglerfish pets?
If you own a saltwater fish tank, you can keep an Anglerfish on it. Some species of Anglerfish occupy coastal shallow waters, so they are fine to be kept in a fish tank.
Anglerfish can be very large, reaching up to 4 feet and weight almost 200 pounds. Thus, choosing the species and tank size properly is highly recommended.
Anglerfish can also get quite aggressive. Due to their feeding behaviour, they can eat fish that are double their size. Thus, some sponges and corals might be best tank mates for an Anglerfish.
However it might be the unique species in the tank, it is possible to raise male and female together, as usually the male is attached and parasitizes the female.
Nice tank for an Anglerfish
They are not active swimmers. Thus, providing hiding spots and covers are essential to the Anglerfish. Keeping some caves, rocks, corals and sponges may provide a nice hiding colourful environment in your tank.
In addition to this, having a good strong filter is also requested. Anglerfish produce huge amounts of waste, and due to this, routinely changing the water is highly recommended.
Tanks with at least 20-gallons id the minimum request to raise an Anglerfish. Also, temperatures between 72 and 78 degrees Fahrenheit with pH between 8.1 and 8.4 are recommended. Other water parameters, such as salinity, hardness and minerals depend on the species you are raising.
What do Anglerfish eat?
In the wild, Anglerfish eat almost every animal that comes around them. From tiny shrimps to double-its-size fish. Its large teeth and expansible stomach allows it to eat practically any animal.
If you are keeping it in a tank, it is recommended to feed them with live fish at least once a week. This is due to their specific ambush behaviours. However, if you are not comfortable with feeding live fish to your Anglerfish, you could stimulate it using a wiggling structure holding food.
Are Anglerfish dangerous to humans?
Even though they have huge mouths and very large and sharp teeth, Anglerfish do not naturally bite humans. However, if you have one in your fish tank, you should keep your hands in the tank. They can bite if disturbed, which would cause an accident. In addition, wiggling fingers inside the water is also a probable cause for an accident. And this is because the anglerfish would understand your fingers as food.
Conclusion
In this blog post, we described and discussed the adaptations of the Anglerfish. We also outlined evolutionary characteristics and their biology.
If you have any thoughts or doubts, feel free to leave us a comment below!
Frequently Asked Questions (FAQs): What are Anglerfish adaptations?
Can Anglerfish turn its light off?
Female Anglerfish carry a bioluminescent lure hanging from their body, like a fishing pole. However, they are not able to turn the bioluminescence off. They can choose to hide or reveal the esca. Although, the bacteria are always producing chemical light.
What is unique about the Anglerfish?
The most remarkable structure of an Anglerfish is the bright lure. They use it to attract prey for an ambush or attract a male to breed. This light is produced by a bioluminescent bacteria agglomerate hanging from the lure. They also have a very unique type of reproduction, in which the male typically parasites the female by attaching himself to her body. This breeding strategy increases the chances of successfully fertilizing the eggs, as they spawn in the water column and the eggs are fertilized externally.
Do anglerfish eat humans?
No, anglerfish are not able to eat humans. However, in case they are disturbed in the wild, they might bite. In addition, if you have an Anglerfish as a pet, it is recommended not to put hands or fingers inside the tank, as it can see you as food wiggling around the tank.
Are angler fish poisonous?
No. Some Anglerfish may have some spines along their body, however, they are not venomous as some people believe.
Why is the male angler fish so small?
The male Anglerfish is typically small because of their evolutionary adaptation of attaching themselves to the female’s body to improve their sexual success. When they are constantly attached to the female, they are close when the female spawn. Thus, the male can spawn at the same time, to fertilize her eggs in the water column. This is called sexual parasitism and it is very common within the Anglerfish group.
Why do anglerfish glow?
Anglerfish have a structure that hangs from its head, as a bioluminescent lure. This structure holds a bacteria agglomerate that is capable of generating light by chemical reactions. This agglomerate bulb is called esca, and it glows constantly. The Anglerfish can control if they hide or reveal their light. This lure can be used to attract prey and mates and can be in different colours, normally blue, but also can be red, orange, green and yellow. This colour variance relies on the different types of bacteria the Anglerfish can hold in their esca.
References
Deep-Sea Anglerfish, Melanocetus johnsonii. https://oceana.org/marine-life/ocean-fishes/deep-sea-anglerfish
Anglerfish Care – Can You Keep This Fish as a Pet in Your Tank? 2021. https://reefkeepingworld.com/anglerfish-care/
