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We present XMM-Newton X-ray observations of two shell galaxies, NGC 7070A andESO 2400100, and far UV observations obtained with the Optical Monitor forthese and for an additional shell galaxy, NGC 474, for which we also have nearand far UV data from GALEX. We aim at gaining insight on the overall evolutiontraced by their star formation history and by their hot gas content. The X-rayand the far UV data are used to derive their X-ray spatial and spectralcharacteristics and their UV luminosity profiles. We use models developed adhoc to investigate the age of the last episode of star formation from the (UV -optical) colors and line strength indices. The X-ray spatial and spectralanalysis show significant differences in the two objects. A low luminositynuclear source is the dominant component in NGC 7070A log L_X=41.7 erg s^{-1}in the 2-10 keV band. In ESO 2400100, the X-ray emission is due to a lowtemperature plasma with a contribution from the collective emission ofindividual sources. In the Optical Monitor image ESO 2400100 shows a doublenucleus, one bluer than the other. This probably results from a very recentstar formation event in the northern nuclear region. The extension of the UVemission is consistent with the optical extent for all galaxies, at differentdegrees of significance in different filters. The presence of the doublenucleus, corroborated by the (UV - optical) colors and line strength indicesanalysis, suggests that ESO 2400100 is accreting a faint companion. We explorethe evolution of the X-ray luminosity during accretion processes with time. Wediscuss the link between the presence of gas and age, since gas is detectedeither before coalescence or several Gyr (>3) after (Abridged).

XMM-Newton X-ray and Optical Monitor far UV observations of NGC 7070A and ESO 2400100 shell galaxies