No, a salamander is not a fish. The answer to this common question lies in the fundamental biological classification of these two animals. While both salamanders and fish are vertebrates, they belong to entirely separate classes within the animal kingdom. Fish are categorized in classes like Osteichthyes (bony fish) or Chondrichthyes (cartilaginous fish), while a salamander is firmly placed in the class Amphibia. This distinction reflects profound differences in their anatomy, life cycle, and physiology.
Salamanders Are Amphibians
Salamanders are members of the order Urodela and are classified under the Class Amphibia, alongside frogs and caecilians. The term “amphibian” means “double life,” referring to the typical transitional existence of these creatures. Most salamanders begin life as aquatic larvae, possessing external gills and a tail fin.
The defining characteristic of amphibians is metamorphosis, where the aquatic larva transforms into a terrestrial or semi-terrestrial adult. This process typically involves the absorption of gills, the development of lungs for air breathing, and the growth of four limbs. Adult salamander skin is smooth, moist, and permeable, allowing for cutaneous respiration (oxygen absorption directly through the skin). This reliance on permeable skin necessitates that salamanders remain in damp environments to prevent desiccation.
Key Biological Differences Between Fish and Salamanders
The primary differences between fish and salamanders relate to their evolutionary adaptation to different environments.
Respiration
Fish exclusively use internal gills to extract dissolved oxygen from water, a system that must be constantly irrigated. Adult salamanders, in contrast, primarily use lungs and their permeable skin for gas exchange, a respiratory strategy adapted for life on land or at the water’s surface.
Skin and Covering
Fish bodies are typically covered in overlapping scales, which provide protection and reduce friction in the water. These scales are not permeable for breathing. Salamanders lack scales entirely, possessing thin, smooth skin rich in mucous glands to keep it moist for breathing and to secrete defensive compounds.
Locomotion and Reproduction
Fish rely on fins (dorsal, caudal, and pectoral) for propulsion, steering, and balance in water. Salamanders, as tetrapods, possess four distinct limbs with digits, allowing them to walk and climb on land. Reproduction also differs: most fish engage in external fertilization of eggs, while the majority of salamanders utilize internal fertilization.
Why Aquatic Salamanders Cause Confusion
Confusion often arises because some salamander species are fully aquatic and retain features that look fish-like. Certain species, such as the Axolotl and the Mudpuppy, exhibit a phenomenon called neoteny. They keep their feathery, external gills and remain entirely aquatic, never completing a full metamorphosis. The Mudpuppy’s slimy skin texture also contributes to the visual mix-up with certain fish.
Other aquatic salamanders, like the Amphiuma, are long and eel-like, leading to common names such as “Congo eel” that further obscure their true identity. Even these perennially aquatic salamanders possess the four-limbed body plan, albeit sometimes in a reduced or vestigial form. Their classification as amphibians remains unchanged because they share a common evolutionary lineage and fundamental anatomical traits with their terrestrial relatives, including characteristic smooth, scaleless skin.