Actinopterygii

Ray-Finned Fish

Ray-finned fish, also called Actinopterygii, are the most common fish in the world. They make up most of the fish species we see today. You can find them in many places — in freshwater like rivers and lakes, in brackish water near the coast, and in the deep oceans.

These fish get their name from their special fins. Their fins have thin, bony spines called lepidotrichia. These spines help them move easily through the water. Unlike some other fish, their fins can change shape and direction quickly, making them great swimmers.

Ray-finned fish come in many sizes. The smallest one is Paedocypris, which is only about 8 millimeters long — that’s smaller than a grain of rice! On the other hand, the giant sunfish and the giant oarfish are huge. The giant sunfish can weigh more than a small car, and the giant oarfish can grow up to 8 meters long, almost as long as a school bus!

One special feature many ray-finned fish have is a swim bladder. This is a tiny air-filled bag that helps them stay afloat in the water. Some fish, like bowfins and gars, can even use their swim bladder to breathe air!

Ray-finned fish live everywhere in the water world. They swim in fast rivers, deep oceans, and even in tiny mountain streams. They come in many shapes and sizes, from speedy tuna to flatfish that can hide on the ocean floor. Their fins and bodies are adapted to help them live in different places and catch their food.

These amazing fish have been around for a very long time. Fossils show that ray-finned fish have existed for over 420 million years! They have evolved into many different types, filling many roles in our oceans, rivers, and lakes.