Are fishes part of the reptilian class? But are they?
What makes the fishes different from the reptiles, even if they both have scaly skin and are cold-blooded animals? They both belong to the Phylum Chordata class.
- Fish are cold-blooded, aquatic vertebrates with gills for breathing, fins for movement, and scales covering their bodies, belonging to the taxonomic group Pisces.
- Reptiles are cold-blooded, terrestrial vertebrates with dry, scaly skin and lay eggs, belonging to the taxonomic class Reptilia, which includes snakes, lizards, turtles, and crocodilians.
- The primary distinctions between fish and reptiles are found in their habitats, body structures, and taxonomic classifications, with fish being aquatic and having gills, while reptiles are land-dwelling with scaly skin and lungs for respiration.
Fish vs. Reptile
Fish breathe through their gills and have a two-chamber heart. They have bony and thin scales found in fresh and salt water. Reptiles have lungs for respiration. Their circulatory system consists of three chambers, and their skin is dry. Some reptiles are found on land, and some in water.
Fish belongs to the largest existing vertebrate 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 structured jaw.
Some common examples of fish 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 various 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 cold-blooded vertebrates that have epidermal glands.
|Parameters of Comparison||Fish||Reptile|
|Excretion of waste||Excretion takes place through the gills||Have a defined excretory system with well-functioning kidneys.|
|Limbs||Their limbs are modified as fins||Some have proper forelimbs and hind limbs, while species like snakes do not have them.|
|Skin||Usually have bony and skinny scales||Rough and dry skin without glands|
|Respiration||Through gills and have 6-7 gill pouches||Through lungs|
|Habitat||Only water, mainly fresh water and rivers||Both 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, and Osteichthyes.
They are categorized based on the difference in the fish’s structure. The agnatha fishes do not have a jaw.
The ancient species were said to have a bony and scaly skin, but this feature is absent nowadays. They do not have a stomach in their digestive system, and the paired fins are also absent.
Chondrichthyes are also known as cartilaginous fish. They mostly consist of 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 have bony skeletons and 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 terrestrial and found in warmer places around the globe.
Their features are dry and rough skin that has 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 (lay 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 fish.
Reptiles have two well-functioning kidneys, but they cannot produce urine.
Main Differences Between Fish and Reptiles
- 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.
- Fishes are known to have a two-chambered heart, while reptiles have a three-chambered heart, two auricles, and one partially divided ventricle. Even though crocodiles are reptiles, they have a four-chambered heart, two auricles, and two ventricles.
- Reptiles have modified limbs or pentadactyl limbs that help in crawling and burrowing. These limbs are modified as fins for the fish. This paper-like structure is what helps the fishes navigate through the water.
- Though reptiles and most fishes have scaley skin, they differ. 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, angelfish, etc., have smooth and slippery skin.
- Fishes, as we know, respire through gills. The gills take in water and filter out oxygen supplied throughout the body. But in the case of reptiles, the land of water-based does not have gills. They respire through their lungs, and their ribs can expand and contract, thus having greater capacity.
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Piyush Yadav has spent the past 25 years working as a physicist in the local community. He is a physicist passionate about making science more accessible to our readers. He holds a BSc in Natural Sciences and Post Graduate Diploma in Environmental Science. You can read more about him on his bio page.