Angelfish are one of the most beautiful reef fish due to their elegant shape and diverse coloring. However, an angelfish’s form and behavior have more to do with survival than cosmetics. From wild saltwater kinds to freshwater angels, these species have changed to suit their environment. This adaptability shows in their colors, shape, and aggressive nature.
Angelfish have adapted to their environment over millions of years. They have developed extended jaws and sharp teeth to get more food. Their bodies have become slim and striped to avoid predators and chase down prey. Their colors will slightly change to help them blend during vulnerable times. They can even breathe without swimming to better hide from predators.
From the Terminal Tethyan Event to the closure of the Isthmus of Panama, angelfish were forced to evolve. Even in modern times, angelfish have learned to adapt to tank environments and handle conditions outside of their ideal range. This makes angelfish seem hardy and resilient, both to predators and food shortages. You can match that to their behavioral changes, such as schooling, aggression, and parental behavior.
Angelfish Adaptations for Survival
Angelfish have evolved throughout the last several million years. As they did, they adapted to have several physical and behavioral characteristics, each of which helped them to survive. According to Molecular Phylogenetics and Evolution, angelfish are an ancient species. This was discovered upon studying the fossil record and genic markers between:
- Modern angelfish
- Some related species, such as the butterfly fish
Where did they diverge? What made them diverge? Researchers explored these questions and came upon an answer. Angelfish and close family species were set apart, physically and genetically, after two major events:
- The Terminal Tethyan Event
- The closure of the Isthmus of Panama
The former took place millions of years ago when the African–Arabian plate collided with the Eurasian, according to the Journal of Biogeography. Meanwhile, the Isthmus of Panama closed about 3 million years ago. When it did, it separated countless numbers of fish species.
Of course, this helped land-based creatures to enjoy a new land bridge, which they used to migrate from one continent to another. However, angelfish were removed from their genetic families and thrust into slightly new environments without access to their old ones.
Because of this, angelfish and other species of marine life had to adapt to their new conditions. They were firmly in the presence of new predators, new water conditions, and new competitors. They would either fall behind and slowly die off, or they would pick up new traits that allowed them to thrive.
Modern Vs. Ancient Angelfish
Clearly, angelfish and many others adapted. They changed colors, body types, and even picked up completely new personalities. It took several million years for these changes to become concrete, but modern angelfish are very different from their ancestors.
We have fossil records of early angelfish, imprinted on stone and often sold as high-value decorations on the open market. When we compare modern angelfish to the fossil record, we can see a few different traits.
The angelfish in your tank, for example, is much slimmer and less stocky than ancient angelfish. It’s possible that slimming out was crucial for the fish’s ability to hide and evade its new predators. That’s not to mention the numerous changes to its behavior and habits.
Of course, not all adaptations are a product of some ancient event. Angelfish have also changed their abilities because of human intervention. That’s seen most clearly in domestic angelfish that you keep in your tank.
Are Domestic Angelfish Adaptable?
In today’s world, the most rapid changes in the environment occur when there is human intervention. As such, domestic angelfish are some of the most adaptable. This is seen in the aquarium conditions they can tolerate, which their wild varieties cannot.
Angelfish are considered hardy creatures, suited to domestic life in aquariums. They aren’t picky when it comes to food and can get along with different types of fish when the conditions are right. They can even tolerate a range of water parameters, as seen most commonly with freshwater angelfish.
However, enthusiasts agree that the most attractive angelfish are those that come from a wilder lineage. These are a lot more delicate and suffer greatly if the tank conditions aren’t right. Creatures bred domestically adapt to their new conditions better than wild kinds suddenly thrust into captivity.
Angelfish have been bred for captivity since the late 1920s. Of course, this may not seem like a long time for adaptations to occur. Yet, breeders are already noticing a difference in the physical and behavioral adaptations in the newer generations of pet angelfish. Because of this, knowing how much “wild” blood your angelfish has is paramount if you want it to live comfortably.
The development of long-lasting adaptations takes roughly a million years. However, it is possible to see changes in a species as early as 100 years. That’s especially true if the species is adaptable, as seen with angelfish.
Angelfish Physical Adaptations
Whether it’s from ancient times or the last 100 years to suit your tank, angelfish have adapted. These new physical traits have helped them to survive, and even thrive. They work to:
- Evade predators
- Hide from danger
- Drive off competitors
- Find food
Let’s explore the physical adaptations found in angelfish today:
Slenderness
An angelfish’s iconic diamond shape gives it many advantages in the wild. Their form makes them a lot more hydrodynamic. This allows them to smoothly cut through the water at higher speeds, able to corner at a rapid pace and dart into small spaces.
This feature comes in handy when swimming away from predators. Angelfish use their thin form to stealthily hide from larger creatures or other aggressive angelfish. They can out-swim them and take cover among the plant life in their environment.
Aside from dodging predators, angelfish also eat smaller fish. Their slender form gives them an advantage when chasing their food. If small fish try to hide, angelfish can pull their prey out of the crevices, something that other fish can’t.
Domestic angelfish tend to be a little more robust than those out in the wild. After all, they don’t typically need to be as hydrodynamic and don’t need to hide behind plants as often as their wild counterparts. They devote their energy toward being resilient against illness and unpleasant tank conditions.
Small, Extended Jaws
Angelfish have small, extended jaws and very hard teeth. When it comes to species that inhabit coral reefs, their primary source of food is sponges. This is very uncommon, since sponges have a tough exterior. Not many fish can get their nutrition from them.
However, angelfish have jaws perfectly suited to chewing on sponges. Their powerful teeth can bite into the tough exterior. Their extended jaws allow them to get a better grip on the surface, so they aren’t repelled by its shape.
Angelfish aren’t very big and can only eat what fits into their mouths. Because of this, they don’t have many dining options (not to mention, it takes a lot of energy to hunt). They had to adapt to acquire the most plentiful source of food, seas sponges, which makes up 95% of their diet.
Vertical Stripes
The beautiful vertical stripes (also called tiger stripes) are used to successfully hide among foliage when escaping predators. The stripes allow them to blend in with the plants better and avoid detection. That’s a trait they often need, since they aren’t always the biggest fish in the tank, ocean, or river.
Angelfish that have been bred for tank life have dull stripes, because they don’t need to hide from predators very frequently. Likewise, aquarium plants aren’t usually as vibrant as those found in freshwater rivers and coral reefs. Since angelfish are so adaptive, the domestic breeds have lighter stripes to match the plants they grow up with.
Mucus Production
Angelfish produce mucus to help shield their bodies and protect their stomach. For that purpose, they have developed this mucus in 2 ways:
- Angelfish have a thin layer of mucus that covers their scales
- They also produce mucus in their mouth
When swimming through the water, wild angelfish encounter all types of bacteria and microscopic foreign bodies. The mucus layer helps to protect them from illness, while also shielding them from poor water conditions.
The layer in their mouth helps them to eat sea sponges. This food source often tastes bad and irritates the stomach, but angelfish are able to cover the sponges in mucus before eating them. This helps with the taste and protects their stomach lining from acidity.
Angelfish Behavior Adaptations
Aside from their physical build, angelfish have also updated their behaviors and personality. This helps them to get along with other fish, be cleverer than predators, and also protect their offspring.
After all, being a fast swimmer will only go so far if you don’t update your habits to mirror it. Because of this, some of your angelfish’s behavior may seem strange and unnecessary. Inside a tank, it may be – but in the wild, the innate behavior patterns make sense.
Schooling
Angelfish do well in groups of 5 or more. In the wild, schooling behavior is very important in defending them from predators. Since most hunters are unable to track such a gyrating swarm of colors and movement, angelfish are safer in groups. The schooling pattern confuses predators and makes them less likely to pick off several angelfish during a hunt.
Angelfish have strict social hierarchies, which are established through aggression and fighting. Although it seems unnecessary, this tells each angelfish where it belongs in the school. When it comes time to swim in a carefully ordered pattern, it protects everyone in the group.
Breathing Without Swimming
Unlike most fish species, angelfish are able to breathe without swimming. This allows them to hide among vegetation for longer periods of time.
It also means that if vegetation is scarce, they can just stay still to avoid detection. This is very effective against a predator that relies on its lateral lines to hunt. If you catch your angelfish staying still for a long time, it’s possibly stressed out or frightened.
Color Changes
Angelfish gradually change their color to camouflage and conceal themselves from predators. Avoiding detection is the primary reason for a change in color, but angelfish do this subconsciously too.
Try adjusting the light conditions in the room where the angelfish’s tank is located. You might notice that the fish change their color within a few minutes to a few hours. It’s not as stark as an octopus, for sure, but it is noticeable.
Angelfish also dull in color when they sleep. This helps them blend with their environments, so they’re in less danger when they’re not sharply aware.
Filial Cannibalism
When an angelfish pair mates, there’s a high chance they will eat all or half of the eggs. This is especially true during their first batches, when their parental instincts have yet to kick in.
Instead, a greater instinct drives them to eat, so they can have the energy to care for their future offspring. They would prefer to stay alive for a chance to breed again, instead of starving and leaving their offspring vulnerable. Although it’s a non-issue in a well-fed aquarium, these fish retain the drive just in case.
Aggressiveness
As cichlids, angelfish are known to be aggressive and protective of their territory. They aren’t as vicious as other members of their family, but they’re not afraid to pick a fight. As mentioned, this helps to establish a social hierarchy. It also helps to protect their offspring, their territory, and each other.
A female angelfish can lay anywhere between 100 to 1,000 eggs. While this may seem like a lot, it is a small number compared to fish like the striped bass. They can lay up to 3,000,000 eggs.
Animals that produce less offspring are usually more hostile, since they need to keep as many offspring alive as possible. That’s vital for future reproduction and the continuation of the species. As such, angelfish learned to be bullies in order to keep their next generation safe.
Mating And Parenting
Angelfish are monogamous and make great parents. They feverishly protect each other as mates and spend hours preparing the area where the fry will hatch. Afterward, the pairs will be highly involved and care for their young until they are independent.
This trait is a clear way to keep the species alive. Since fry are vulnerable, they would easily die off without protection from the adults. Although other angelfish may try to eat the fry, the parents keep them at bay. This ensures more of the species survives.
Angelfish are highly adaptable, taking on both physical and behavioral attributes to survive. From their coloring to their aggressive nature, angelfish refuse to die out. That’s kept them alive for millions of years.
