As noted above, all the Ganzhorn's in European collections are being managed as distinct from
murinus and no interbreeding has taken place since the original import. They look
very distinct from
murinus - being much smaller and more rufous - and even before the new species was actually described, the newly-imported stock was being treated as something different but of unclear identity by the Czech collections holding the animals in question, and as such wasn't allowed to interbreed with
murinus populations.
For comparison (
ganzhorni above,
murinus below)