Newt
Newts, as with salamanders in general and other amphibians, serve as bioindicators because of their thin, sensitive skin and evidence of their presence (or absence) can serve as an indicator of the health of the environment. Most species are highly sensitive to subtle changes in the pH level of the streams and lakes where they live. Because their skin is permeable to water, they absorb oxygen and other substances they need through their skin. Scientists study the stability of the amphibian population when studying the water quality of a particular body of water.
Neoteny
Many species of salamander, and amphibians in general, are known to have neotenized characteristics because of the environment they live in. Axolotl and olm are species of salamander that retains their juvenile aquatic form throughout adulthood, examples of full neoteny. Gills are a common juvenile characteristic in amphibians that are kept after maturation; an example of this would be a comparison of the tiger salamander and the rough-skinned newt, both of which retain gills into adulthood.