text: Biological pigmentation is determined by presentation of specific color-producing cells, called chromatophores, which absorb and/or reflect light in a particular way to then appear as a color. In S. atra, there are different cells present or activated, which yield different colors: melanophores contribute to the dark coloration by producing the dark pigment melanin, while xanthophores produce a yellow pigment, and iridophores are simply light-reflecting. The fully-black phenotype seen in S. a. atra results from the salamanders' melanophores in the dermis and epidermis, producing melanin alone. Xanthophore-iridophore complexes are responsible for production of yellow spotting, which appears bright. In species without yellow patches, it appears that they do not ever develop these cells. In S. a. aurorae or other salamanders with different coloration on different parts of their body, two distinct skin types are present: one that only contains melanophores (black), and one that has melanophores, xanthophores, and iridophores in combination.
  The yellow coloring on some alpine salamanders is thought to be an aposematic strategy to fend off predation. The pure black coloring is also hypothesized to be a form of thermoregulation, though it may also be considered a warning to some predators.
  Taxonomy and subspecies
  S. a. atra is a fully melanistic (black) subspecies from central, eastern and Dinaric Alps. This subspecies is the most widespread.