While they may look related, amphibians and reptiles are very different creatures! Each with its distinctive characteristics and adaptations to their environments. From slippery salamanders to color-changing chameleons, here’s a look at some of the differences between amphibians and reptiles!
Differences Between Amphibians and Reptiles
Amphibians and reptiles are both cold-blooded vertebrates that make up the herpetofauna group. Currently, there are 11,940 reptiles and 8,579 amphibians in known existence around the world. From tropical rainforests to dry sandy deserts and mountain streams to swamps, these unique creatures inhabit all sorts of environments.
The most common reptiles include lizards, snakes, turtles, and crocodiles. Well-known amphibians include frogs, toads, and salamanders. Each of these groups has several species and subspecies within them.
Reptiles and amphibians may look similar, but they are in fact very different from their lifecycles to their habitats and physical characteristics.
Lifecycles of Amphibians and Reptiles
One of the significant differences between amphibians and reptiles is their lifecycles. More specifically, how their lifecycles relate to water and whether their stages into adulthood include metamorphosis. Another difference is how and where they lay their eggs as well as the eventual physiological traits of their offspring when they are born.
Amphibians have a unique lifecycle that begins in water. They lay their soft eggs in jelly-like masses in or around the water's surface or attached to floating vegetation. When these eggs hatch, they enter what is known as the larval stage. These larvae are born with gills and a tail and will eventually go through several stages of metamorphosis before adulthood.
The most known example is the transformation of tadpoles into frogs. Tadpoles are strictly aquatic, meaning they only live in the water. They will however undergo metamorphosis to become terrestrial.
Reptiles on the other hand, are born on land and hatch via hardshell eggs. Certain reptiles such as turtles or crocodiles lay their eggs near the water, on sandy beaches or in mounds of dried vegetation. Their hatchlings will head to the water quickly after birth but are not born with gills. Instead, they have lungs. Other reptiles like snakes and lizards, may lay their eggs anywhere and not necessarily near water, and their hatchings will exclusively live on land.
Reptiles do not undergo a metamorphosis and are born with the same characteristics as the adults of their species. Newborn turtles, crocodiles, or lizards will all look reasonably identifiable, whereas tadpoles from frogs, toads, or salamanders look very much the same to the untrained eye.
Differences in Characteristics
Most amphibians have smooth aqueous skin that is covered with a thin layer of mucus for protection. While they will spend time on land, amphibians must stay near the water and keep their skin hydrated. Their skin helps them absorb oxygen. This is known as cutaneous respiration.
Desert-dwelling amphibians have unique adaptations to survive in their dry environment by digging holes where they’ll spend most of their time preserving water. They will also use temporary rain pools from summer storms to lay their eggs in.
While some reptiles live in or around water, they don’t need to keep their skin hydrated in the same way amphibians do. Reptiles have dry, scaly skin. Some also have spikes like bearded dragons or bony plates like crocodiles. This helps protect them like a suit of armor.
There are different variations of scales across the reptile world. Lizards like chameleons or iguanas have very bumpy textured skin while snakes are surprisingly smooth scaled.
Reptilian skin is high in keratin which contributes to its overall hardiness. It’s also constantly undergoing cell renewal, so reptiles are notorious for shedding skin. Snakes have a unique ability to shed their entire skin at once, resulting in a long sleeve-like piece they will eventually slither right out of.
Distribution and Habitat
Amphibians and reptiles are widely distributed in various habitats across every continent except Antarctica. The greatest diversity of species remains in warmer climates where these cold-blooded creatures tend to thrive.
In tropical and subtropical areas, a wide variety of lizards, crocodilians, turtles, tortoises, frogs, and snakes can be found. In arid and semi-arid regions, snakes, salamanders, lizards, and frogs can all be found.
Some of the most biodiverse places on the planet also have high concentrations of reptile and amphibian life. This includes areas like the Amazon Rainforest, Galapagos Islands, Monteverde Cloud Forest, Caribbean Islands, Forests of East Australia, Indonesian Islands, and Madagascar.
Unique Adaptations of Amphibians and Reptiles
While each amphibian and reptile is unique in its own right, there are a few that stand above the crowd with special adaptations. Chameleons are just one example of extraordinary reptiles. Experts at camouflage, chameleons can change colors and even in some cases shapes to blend with their environment.
The Galapagos marine iguana is another standout species among reptiles. These fascinating creatures have evolved to develop salt glands and spend much of their time underwater. They are the only known marine iguanas in existence.
The first known turtle species to exist did not have shells, rather they had rigid and elongated spines. Turtles evolved over millions of years to develop the unique shells they have today that serve as protection.
Uniquely adapted amphibians include the olm, a cave-dwelling salamander that is so uniquely adapted to its environment it can go up to 10 years without eating! Wood frogs, which can be found throughout the US, including Alaska, are uniquely adapted to cold weather. When temperatures drop, they can quite literally enter a “freezing” stage where their heart and respiration stops. Their bodies produce a specialized anti-freeze-like substance to prevent their cells from freezing.
Other unique amphibians include the Mount Lyell Salamander, which lives in the Sierra Nevada Mountains. This stealthy little salamander has the unique ability to curl itself into a ball and roll down hillsides when threatened.
While most frogs are born with gills and later develop lungs, the Bornean flat-headed frog of Indonesia is the world’s first known lungless frog. They breathe solely through cutaneous respiration. Scientists speculate they may have evolved this way to be able to sink to the bottom of freezing waters.
These are just a few of the world’s most uniquely adapted reptiles and amphibians. With ever-changing landscapes and environmental threats, it’s possible more are to be discovered someday!