Gar

Gars are very old fish.

Their bodies are long. They have hard skin. This skin acts like armor.

Gars have long jaws. They have sharp teeth. These teeth help them catch food.

Most gars swim to the top. They take a gulp of air. This helps them breathe.

Some gars are very big. The alligator gar is the largest. It can grow very long.

Gars are very old fish. They belong to a group called Ginglymodi. This group first appeared over 240 million years ago. Gars are the only members of this group still alive today.

Gars have long bodies. They are covered in ganoid scales. These are hard parts that act like armor. Their long jaws are filled with sharp teeth. These teeth help them catch prey like small fish and crabs.

The alligator gar is the largest species. It can grow to over 3 meters long. It can also weigh over 113 kilograms.

Gars have a special way to breathe. They have a swim bladder, which is a gas-filled part of their body. This part can work like lungs. Most gars swim to the surface to take a gulp of air. They do this more often when the water is warm. This helps them live in water with very little oxygen.

Today, living gars are found in North America. They live in rivers, lakes, and some sea water.

Gars are a fascinating group of ancient fish. They belong to a family called Lepisosteidae. These fish live in fresh water, brackish water, and sometimes the sea. Most living gars stay in eastern North America. They can be found in rivers, lakes, and bayous. They like to hide in shallow, weedy areas.

Gars have a very unique way of working. Their bodies are long and covered in ganoid scales. These scales act like a heavy suit of armor. They also have long jaws filled with sharp teeth. Some teeth are long fangs, while others are short and conical. These teeth help them catch prey like small fish and crabs. They use a quick sideways strike of the head to grab food.

These fish have a very long history. They are the only living members of a group called Ginglymodi. This group first appeared during the Triassic period, over 240 million years ago. Gars evolve very slowly. Their DNA changes up to a thousand times slower than other animals. This slow change is why some call them living fossils. The oldest modern gar fossil is from Mexico and is 157 million years old.

There are seven living species of gars today. The alligator gar, or Atractosteus spatula, is the biggest. It can grow to be over 3 meters long. It can also weigh more than 113 kilograms. Some reports say they can even be larger. Other species, like the spotted gar, still reach lengths over 60 centimeters.

Gars can survive in places where other fish might struggle. They have a special swim bladder that works like lungs. This organ lets them gulp air from the surface. They do this more often when the water is warm or has low oxygen. This makes them very resilient in many environments. Even though they are fierce hunters, humans can eat their flesh. However, you must be careful because gar eggs are highly toxic.

Gars are a unique group of ray-finned fish within the family Lepisosteidae. They are the only living members of the clade Ginglymodi, a group of bony fish that flourished during the Mesozoic era. While many fish groups have changed drastically over millions of years, gars are known for their incredible stability. They inhabit various environments, including fresh, brackish, and occasionally marine waters. Today, most living gars are found in eastern North America, though their ancestors once lived across the globe.

The anatomy of a gar is built for survival and ambush hunting. Their bodies are elongated and covered in ganoid scales, which act as a heavy suit of armor. Their most striking feature is the elongated jaw, which is supported by bones called the premaxilla, vomer, and dentary. These bones are almost fully ossified, or hardened, before the fish even hatches. This means the shape of the snout is established very early in life. The jaws are filled with diverse teeth, including long, sharp fangs and shorter, conical teeth.

One of the most remarkable biological mechanisms in a gar is its respiratory system. Most fish rely solely on gills to extract oxygen from the water. However, gars possess a vascularised swim bladder, which is an internal organ used for buoyancy. In gars, this organ can also function like a lung. This allows them to surface periodically to gulp air from the atmosphere. This adaptation is especially useful in warm or stagnant water where oxygen levels are low. Because they can breathe air, gars are extremely resilient and can survive in conditions that would kill most other fish.

There are currently seven living species of gars divided into two genera: Atractosteus and Lepisosteus. The largest species is the alligator gar, Atractosteus spatula. It is named for its wide, stocky snout, which often leads locals to mistake it for an alligator. This massive fish can grow to lengths over 3 meters and weigh more than 113 kilograms. Some reports even suggest specimens have reached much larger sizes. Other species, such as the spotted gar, Lepisosteus oculatus, are smaller but still reach lengths over 60 centimeters.

The evolutionary history of the gar is a study in extreme patience. The Ginglymodi first appeared during the Middle Triassic period, more than 240 million years ago. They exhibit the slowest known rate of molecular evolution among all jawed vertebrates. Their DNA evolves up to a thousand times more slowly than in other groups. This slow rate of change has resulted in a very low rate of speciation. The oldest anatomically modern gar fossil, Nhanulepisosteus, dates back approximately 157 million years to the Upper Jurassic of Mexico.

Fossil evidence shows that gars were once much more widespread than they are today. In the past, they were found on every continent except Australia and Antarctica. During the Cretaceous period, gars dispersed from western North America to regions like Africa, India, South America, and Europe. After the Cretaceous–Paleogene extinction event, their range contracted. They became restricted to North America and Europe. Eventually, they moved into eastern North America, which has served as a vital refugium, or a place of safety, for the group to diversify.

Understanding gars helps scientists learn about the history of life on Earth. Because they have changed so little over millions of years, they are often called "living fossils." Their ability to survive massive extinction events and low-oxygen environments shows how specialized their biology is. While their flesh is edible for humans, it is important to note that gar eggs are highly toxic. Studying their slow molecular evolution may even provide insights into human health and how DNA changes over time.