  Recently, we have predicted that the modulation instability of optical vortex
solitons propagating in nonlinear colloidal suspensions with exponential
saturable nonlinearity leads to formation of necklace beams (NBs)
[S.~Z.~Silahli, W.~Walasik and N.~M.~Litchinitser, Opt.~Lett., \textbf{40},
5714 (2015)]. Here, we investigate the dynamics of NB formation and
propagation, and show that the distance at which the NB is formed depends on
the input power of the vortex beam. Moreover, we show that the NB trajectories
are not necessarily tangent to the initial vortex ring, and that their
velocities have components stemming both from the beam diffraction and from the
beam orbital angular momentum. We also demonstrate the generation of twisted
solitons and analyze the influence of losses on their propagation. Finally, we
investigate the conservation of the orbital angular momentum in necklace and
twisted beams. Our studies, performed in ideal lossless media and in realistic
colloidal suspensions with losses, provide a detailed description of NB
dynamics and may be useful in studies of light propagation in highly scattering
colloids and biological samples.
