Quantum unique ergodicity and the number of nodal domains of eigenfunctions

We prove that the Hecke–Maass eigenforms for a compact arithmetic triangle group have a growing number of nodal domains as the eigenvalue tends to $+\mathrm{\infty }$. More generally the same is proved for eigenfunctions on negatively curved surfaces that are even or odd with respect to a geodesic symmetry and for which Quantum Unique Ergodicity holds.