Recent reports on the phagotrophic feeding of M. rubrum are based on cultivation experiments with novel isolates of this ciliate species from Gomso Bay, Korea. Photo-adapted cryptophyte(CR-MAL01) cultures at high light of 100 $mu$mol photons m$^{-2}$ s$^{-1}$ (HL) and low light of 10 $mu$mol photons m$^{-2}$ s$^{-1}$ (LL) were fed to M. rubrum (MR-MAL01) cultures under HL and LL conditions, respectively. Absorbance spectrum by LL M. rubrum showed the same peak at wavelengths around 542nm as that by LL cryptophyte prey, which was not showed in HL M. rubrum. This result supports the implication that light utilization and absorption pattern of M. rubrum population must depend on the status of photo-adaptation of the co-existing population of prey cryptophyte. Consequences of the present research results were discussed in relation to the function of the prey cryptophyte and phagotrophic M. rubrum in marine microbial ecosystem.