We find the group of symmetry transformations generated by interacting fluids
in spatially flat Friedmann-Robertson-Walker (FRW) spacetime which links
cosmologies with the same scale factor {\it (identity)} or with scale factors
a and a−1 {\it (duality)}. There exists a duality between contracting
and superaccelerated expanding scenarios associated with {\it (phantom)}
cosmologies. We investigate the action of this symmetry group on
self-interacting minimally(conformally) coupled quintessence and k-essence
cosmologies.Comment: 5 pages, revised version accepted for publication in PL