Fertilisation in Salamandra salamandra is internal, and the female carries the developing embryos rather than laying eggs. In most populations she then enters shallow running water and releases gilled larvae, typically a few dozen at a time, which complete development in the stream over several months before metamorphosing.
Some populations go further. In parts of the range, notably certain Iberian and mountain subspecies, development continues inside the mother until the young are fully metamorphosed, and she gives birth to small terrestrial salamanders with no free-living larval stage. This viviparity is fed in part by embryos consuming unfertilised eggs and, in some cases, siblings.
The warning colouration is genuine rather than bluff: skin glands, concentrated behind the eyes, secrete samandarin alkaloids that are toxic and irritating. The old belief encoded in the name, that these salamanders are born from or immune to fire, comes from animals fleeing logs brought in for burning.