Difference Between Fish and Reptile

Are fishes part of the reptilian class? But are they?


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What makes the fishes different from the reptiles, even if they both have scaly skin and are both cold-blooded animals. They both belong to the Phylum Chordata class.

Fish vs Reptile

The difference between Fish and Reptiles is that fishes breathe through gills while reptiles do not have gills. They respire through the lungs itself. Their ribs can expand and contract which allows their lungs to have greater capacity than amphibians.

Fish vs Reptile

Fish belongs are the largest existing vertebrates species. They belong to the Gnathostomata class.

This is a subphylum group and a superclass of Chordata. They are all vertebrate species that have a structure jaw.

Some common examples of fishes are clownfish, sharks, etc. They are the species of the animal kingdom that habitat in water.

Reptiles belong to the class known as Reptilian. This class includes a variety are species such as turtles, snakes, lizards, etc.

These animals are categorized under the Reptilian class because of their characteristic features such as cold-blooded, dry skin. They are commonly also known as the cold-blooded vertebrates that have epidermal glands.

Comparison Table

Parameters of ComparisonFishReptile
Excretion of wasteExcretion takes place through the gillsHave a defined excretory system with well-functioning kidneys.
LimbsTheir limbs are modified as finsSome have proper forelimbs and hind limbs while species like snakes do not have them
SkinUsually have bony and skinny scalesRough and dry skin without glands
RespirationThrough gills and have 6-7 gill pouchesThrough lungs
HabitatOnly water, mainly fresh-water and riversBoth land and water


What is Fish?

Fishes are the species that belong to the Phylum Chordata class and the vertebrate species. They are found in freshwaters and rivers and have gills and gill pouches for breathing.

They mostly develop and fertilize eggs outside their bodies. Fishes are further categorized into three: Agnatha, Chondrichthyes, Osteichthyes.

They are categorised based on the difference in the fish’s structure. The agnatha fishes do not have a jaw.

The ancient species were said to have bony and scaly skin but nowadays this feature is absent. They do not have a stomach in their digestive system and the paired fins are also absent in them.

Chondrichthyes are also known as cartilaginous fish. They mostly consist of the predatory and muse eating fishes like sharks.

Osteichthyes have a defined jaw and paired fins, unlike agnatha fishes. They have mucus glands on their skin and these species constitute almost 3000 varieties of fish.

These fishes also a bony skeleton and have numerous vertebrates.

The fishes use their gills itself as their excretory system as well. The nitrogenous waste is diffused into the water through the gills.


What is Reptile?

According to statistics, there are almost 6000 species of reptiles across the globe. These cold-blooded animals are usually terrestrial and are also found in warmer places around the globe.

Their features are dry and rough skin, that have epidermis glands. They also have modified limbs for crawling, except in the case of snakes.

Unlike fishes, reptiles have three-chambered hearts: two auricles and a partly divided ventricle. Reptiles, even though some live-in water do not breathe through gills.

They have lungs and their ribs are capable of expanding. This provides greater capacity than amphibians.

Reptiles are mostly oviparous (lays eggs). They all form the embryonic membrane on the eggs.

Reptiles are also capable of laying eggs on land because they are amniotic. Some say that the different types of reptiles came in due to the evolution of fishes.

Reptiles have two well-functioning kidneys but they cannot produce urine.


Main Differences Between Fish and Reptile

  1. It would be surprising to know that fishes excrete through their gills. The nitrogenous waste from the fish is diffused into the water through their gills. Reptiles have kidneys and a well-functioning excretory system. But since their skin is water-tight, they do not produce urine. They possess a colon for water absorption.
  2. Fishes are known to have a two-chambered heart while reptiles have a three chambered heart, two auricles and one partially divided ventricles. Even though crocodiles are reptiles, they have a four-chambered heart two auricles and two verntricles.
  3. Reptiles have modified limbs or also called pentadacty limbs that help in crawling and burrowing. These limbs are modified as fins for the fishes. This paper -like structure is what helps the fishes navigate through the water.
  4. Through reptiles and most of the fishes have scaley skin, they differ from each other. Reptiles skin is dry,rough and water-tight. Most of the fishes have a boney, scaley structure on their skin. But the species of fishes that do not have scales, like sharks, angel fish, etc have smooth and slippery skin.
  5. Fishes , as we know, respire through gills. The gills take in water and filter out oxyzern that is supplied throughout the body. But in the case of reptiles , land of water – based does not have gills. They respire through lungs and their ribs can expand and contract, thus having greater capacit.
Difference Between Fish and Reptile


  1. https://www.sciencedirect.com/science/article/pii/S0009254101004247
  2. https://eje.bioscientifica.com/view/journals/eje/100/2/acta_100_2_016.xml
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