[Introduction] A recent high-resolution α , X -ray, and γ -ray coincidence-spectroscopy experiment offered the first glimpse of excitation schemes of isotopes along α -decay chains of Z = 115. To understand these observations and to make predictions about shell structure of superheavy nuclei below 288 115, we employ two complementary mean-field models: the self-consistent Skyrme energy density functional approach and the macroscopic-microscopic Nilsson model. We discuss the spectroscopic information carried by the new data. In particular, candidates for the experimentally observed E 1 transitions in 276 Mt are proposed. We find that the presence and nature of low-energy E 1 transitions in well-deformed nuclei around Z = 110 ,N = 168 strongly depends on the strength of the spin-orbit coupling; hence, it provides an excellent constraint on theoretical models of superheavy nuclei. To clarify competing theoretical scenarios, an experimental search for E 1 transitions in odd- A systems 275 , 277 Mt, 275 Hs, and 277 Ds is strongly recommended.