The differences between fish and reptiles are vast and varied. Despite being both classified as vertebrates – animals with a backbone – these two groups have a number of distinguishing characteristics in their anatomy, physiology and behavior. Fish and reptiles can live out of water, although one lives mainly in aquatic environments while the other lives mainly on land. In this article, we explore the main differences between fish and reptiles.
Anatomy
Fish and reptiles have vastly different anatomies and the major difference between them lies in their external body composition. Fish are typically covered with scales, which are often thicker than those of reptiles and provide more protection for the fish. Furthermore, fish have fins that help them navigate in the water and gills to take in oxygen from the water. Reptiles have no fins or gills and instead have four legs, two arms and a tail. They also have scales that are usually thinner than the scales on fish, but they provide a lesser degree of protection.
Another major difference between fish and reptiles is their internal anatomy. Fish have a swim bladder that helps them maintain buoyancy, while reptiles don’t. Additionally, fish also possess a two-chambered heart while reptiles have four chambers. Reptiles and amphibians also have lungs, which are used to breathe air while fish extract oxygen from the water through their gills.
Physiology
When it comes to physiology, fish and reptiles have distinct differences. Specifically, fish are cold-blooded animals, meaning that their body temperature varies depending on the temperature of the environment. Reptiles are also cold-blooded but are able to regulate their body temperature better than fish, for example by basking in the sun.
Fish also have specific adaptations that allow them to live in aquatic environments. These include specialized organs, such as the swim bladder and fins, as well as the lateral line system which helps them detect vibrations in the water. Reptiles do not have these adaptations as they mainly live on land.
