Numerical studies of convection driven dynamos in rotating spherical shells exhibit a transition from steady dipolar to reversing multipolar dynamos as the forcing is increased. The dipolar-multipolar transition has so far been characterized using purely hydrodynamic parameters (Christensen and Aubert, Geophys. J. Int. 2006, 166, 97–114, Soderlund et al., Earth Planet. Sci. Lett. 2012, 333–334, 9–20, Oruba and Dormy, Geophys. Res. Lett. 2014, 41, 7115–7120). Motivated by these earlier descriptions, we investigate the hydrodynamic transitions occurring at the critical parameters. We show that the loss of dipolarity in dynamos is associated with a purely hydrodynamic transition, characterized by a breaking of the flow equatorial symmetry. Contrary to earlier expectations, we show by varying the Prandtl number that the transition is not necessarily associated with a degradation of the flow helicity.