  The morphology and stellar populations of low-luminosity early-type galaxies
in clusters have until now been limited to a few relatively nearby clusters
such as Virgo or Fornax. Scenarii for the formation and evolution of dwarf
galaxies in clusters are therefore not well constrained. We investigate here
the morphology and stellar populations of low-luminosity galaxies in the
relaxed cluster Abell 496 (z=0.0330). Deep multiband imaging obtained with the
CFHT Megacam allowed us to select a sample of faint galaxies (-18.8<M_B<-15.1
mag). We observed 118 galaxies spectroscopically with the ESO VLT
FLAMES/Giraffe spectrograph (R=6300). We present structural analysis and colour
maps for the 48 galaxies belonging to the cluster. We fit the spectra of 46
objects with PEGASE.HR synthetic spectra to estimate the ages, metallicities,
and velocity dispersions. We computed values of $\alpha$/Fe abundance ratios
from the measurements of Lick indices. High-precision estimates of stellar
population properties have been obtained for a large sample of faint galaxies
in a cluster, allowing for the extension of relations between stellar
populations and internal kinematics to the low-velocity dispersion regime. We
have revealed a peculiar population of elliptical galaxies in the core of the
cluster, resembling massive early-type galaxies by their stellar population
properties and velocity dispersions, but having luminosities of about 2 mag
fainter. External mechanisms of gas removal (ram pressure stripping and
gravitational harassment) are more likely to have occurred than internal
mechanisms such as supernova-driven winds. The violent tidal stripping of
intermediate-luminosity, early-type galaxies in the cluster core can explain
the properties of the peculiar elliptical galaxies surrounding the cD galaxy.
