A newt is classified as an amphibian, belonging to the class Amphibia alongside frogs, toads, and caecilians. The Greek root of the name, amphibios, translates to “living a double life,” which reflects the newt’s biology and life history. This class contains vertebrates that have adapted to exploit both aquatic and terrestrial habitats. Newts are found across North America, Europe, North Africa, and Asia.
What Defines an Amphibian?
Amphibians are ectothermic, meaning they are cold-blooded and rely on their environment to regulate their body temperature. A defining feature is the presence of smooth, glandular, and highly permeable skin, which lacks the protective scales found on reptiles. This skin is kept moist by mucous glands and allows for cutaneous gas exchange, playing a significant role in respiration.
The moist skin makes amphibians reliant on water or a humid environment to prevent desiccation. For reproduction, most amphibians, including newts, must return to water to lay their eggs. The eggs are typically jelly-like and lack the protective shell needed to survive fully on land. These characteristics of skin, temperature regulation, and reproductive needs unite the diverse species within the class Amphibia.
Newts: Members of the Salamander Order
Newts are a specific grouping of salamanders that belong to the order Urodela, also known as Caudata, which means “tailed ones.” Like all salamanders, newts possess an elongated body, a distinct tail, and four limbs of roughly equal size. This body plan distinguishes them from tailless amphibians, such as frogs and toads.
Newts are generally housed in the family Salamandridae and are informally distinguished by their more aquatic nature as adults. While many salamanders have smooth skin, newts often develop a rougher, warty texture when they are living on land. Newts are definitively salamanders, sharing the fundamental amphibian body structure.
The Newt Life Cycle and Metamorphosis
The newt’s complex life cycle, involving metamorphosis, is key evidence of its amphibian identity. The cycle begins with an aquatic larval stage after the eggs hatch in the water. These larvae are fish-like, possessing external, feathery gills for underwater breathing, and a tail fin for propulsion.
After several months, the larva undergoes its first metamorphosis, absorbing its gills and developing air-breathing lungs and robust limbs. It then emerges from the water as a terrestrial juvenile, often called an “eft.” The eft stage is characterized by a land-dwelling lifestyle, frequently displaying bright colors that serve as a warning of the newt’s toxicity.
This juvenile eft phase can last for two to three years before the newt undergoes a second transformation into an adult. The adult then returns to the water to breed, completing the cycle that requires both aquatic and terrestrial habitats. This sequential shift in habitat and breathing apparatus is a hallmark of amphibian biology.
How Newts Differ from Reptiles
Newts are often mistaken for lizards due to their similar four-limbed, tailed body shape, but they belong to entirely separate classes. The most immediate difference is their skin: reptiles have dry, tough skin covered in protective scales, while a newt’s skin is moist and permeable for respiration.
Reproduction also fundamentally divides the two groups. Reptiles lay amniotic eggs on land that have a protective shell. Newts, like other amphibians, lay soft, jelly-coated eggs in the water, which would quickly dry out on land. Furthermore, reptiles hatch as miniature versions of the adult, while newts must undergo metamorphosis, passing through a distinct larval stage with gills.