  We describe two peculiar galaxies falling into the massive galaxy clusters
Abell 1689 (z~0.18) and 2667 (z~0.23) respectively.
  Hubble Space Telescope images show extraordinary trails composed of bright
blue knots (-16.5<M<-11.5 mag) and stellar streams associated with each of
these systems. Combining optical, near and mid-infrared and radio observations
we prove that while both galaxies show similar extended trails of star-forming
knots, their recent star formation histories are different. One (~L*) is
experiencing a strong burst of star formation, appearing as a rare example of a
luminous infrared cluster galaxy. In comparison, the other (~ 0.1 L*) has
recently ceased its star formation activity. Our model suggests that the
morphologies and star formation in these galaxies have been influenced by the
combined action of tidal interaction (likely with the cluster potential) and of
ram pressure with the intracluster medium. These results can be used to gain
more insights to the origin of S0s, dwarf and ultra-compact dwarf (UCD) cluster
galaxies.
