Newts are amphibians, despite their superficial resemblance to some lizards. Their classification is based on fundamental differences in their life cycles, skin, and reproductive strategies compared to reptiles.
Newts: Masters of Two Worlds
Newts are a type of salamander, belonging to the class Amphibia. The name “amphibian” means “double life,” referring to their unique life cycle. This cycle typically involves both aquatic and terrestrial phases. Newts begin as aquatic larvae, often with external gills for underwater breathing, and undergo metamorphosis as they mature.
After metamorphosis, many newts develop into a terrestrial juvenile stage, sometimes called an “eft.” Adult newts possess lungs for air breathing and can live on land, but they depend on water, particularly for reproduction. Their moist, permeable skin allows for gas exchange and water absorption, making them susceptible to dehydration without a damp environment. Newts return to water bodies to breed, laying soft, shell-less eggs directly in the water.
Reptiles: Scales and Dry Skin
Reptiles belong to the class Reptilia and are primarily adapted for a terrestrial existence. Common examples include snakes, lizards, turtles, and crocodiles. A defining characteristic of reptiles is their dry, scaly skin, which is composed of keratin and waxy lipids. This scaly covering provides a protective barrier, significantly reducing water loss and enabling them to thrive in drier environments.
Reptiles breathe exclusively with lungs throughout their lives. Their reproductive strategy highlights their terrestrial adaptation: they typically lay amniotic eggs on land. These eggs feature a protective shell and contain membranes that enclose and nourish the developing embryo, allowing for development away from water. Reptiles are also ectothermic, meaning they rely on external heat sources, such as basking in the sun, to regulate their body temperature.
Amphibian vs. Reptile: The Defining Differences
The distinctions between amphibians and reptiles are evident in several key biological features, primarily their skin, reproduction, and respiration. Amphibians, such as newts, have moist, permeable skin that facilitates gas exchange. This necessitates a humid environment to prevent desiccation. In contrast, reptiles possess dry, scaly skin that acts as a waterproof barrier, allowing them to conserve moisture and inhabit arid landscapes.
Differences in reproduction are also clear. Amphibians generally lay soft, gelatinous eggs in water, and their larval stages are aquatic, typically breathing with gills. The offspring undergo metamorphosis, transforming into their adult form.
Reptiles, however, reproduce via internal fertilization and lay hard-shelled or leathery amniotic eggs on land, which are designed to prevent dehydration. Their young hatch as miniature versions of the adults, without an aquatic larval stage or metamorphosis. Furthermore, while amphibians can utilize their skin and lungs for respiration, reptiles rely solely on well-developed lungs throughout their entire life cycle.