Are Fish Reptiles? (7 Reasons + Differences)

The question of whether or not fish are reptiles has been on-going for quite some time now with some being for the opinion that they are reptiles and others for the opinion that they are not. One of the main reasons why there’s some sought of confusion when it comes to fish and reptiles is the number of similarities fish has with animals regarded as reptiles.

Add the theory of evolution which basically suggests that evolved into reptiles and this topic becomes really confusing and pro fish are reptiles. So who is right, are fish really reptiles as some claim or are fish far from being reptiles?

Fish, despite the many similarities they have with animals categorized as reptiles, are not reptiles. This post highlights some of the similarities and most important differences between fish and reptiles. 

Are Fish Reptiles?

By simply looking at a fish and an animal that’s categorized or falls under the category of a reptile, chances are you’ll lean towards fish being a reptile. The reason being, fish has several similarities with animals categorized as reptiles. Some of these similarities include;

  • Vertebral Columns – Both the fish and reptiles are vertebrates. Simply put, they all have a series of bones that help protect the spinal cord. They also (fish and reptiles) have the same central nervous system and gills. Worth noting however is that reptiles tend to lose their gills while they are young.  
  • Scale-Covered Integuments – Those who’ve been keen while looking at both reptiles and fish are bound to have noticed the scaly outer covering that both these two types of animals have. While they might look similar in just about every way, they are not the same. Furthermore, the two scales don’t arise from one embryonic tissue.
  • Ectothermic Metabolisms – Another similarity that’s evident with animals categorized as reptiles and fish is that they are all cold-blooded. Simply put, they both have body temperatures that fluctuate depending on the temperature of the environment they are in.  

Differences Between Fish & Reptiles

Looking at the differences between fish and reptiles is one way of determining whether or not fish can be grouped with other reptiles. That said one obvious detail with fish and reptiles is the fact that reptiles can stay or live in both water and land while a fish can only live on land.  Here are some additional differences;

  • Limbs – Reptiles and fish have different types of limbs. Reptiles have small legs that act as limbs while fish on the other hand have fins that are either paired or unpaired (depending on the fish) that act as limbs.
  • Birth Process – How these two go about the birth process is also very different. Unlike oviparous reptiles, in that they lay eggs, fish are known to develop or fertilize their eggs outside their body.  
  • The Heart System – Reptiles, in general, have a three-chambered heart system that’s accompanied by atria, two aortas, and a partitioned ventricle while the fish has a two-chambered organ that basically allows blood to circulate to and from the atrium into the ventricle.
  • Excretory System – Another difference that’s evident between these two is their excretory system. The fish, simply put, uses its gills to diffuse nitrogenous waste. Reptiles on the other hand rely primarily on their two kidneys on matters excretory.

Conclusion for “Are Fish Reptiles”

Fish, despite the similarities with several animals that fall under the reptile category, are not reptiles. These two have a lot of differences many of which haven’t been highlighted in this particular post.

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