  The Early Universe, together with many nearby dwarf galaxies, is deficient in
heavy elements. The evolution of massive stars in such environments is thought
to be affected by rotation. Extreme rotators amongst them tend to form
decretion disks and manifest themselves as OBe stars. We use a combination of U
B, GAIA, Spitzer, and Hubble Space Telescope photometry to identify the
complete populations of massive OBe stars - one hundred to thousands in number
- in five nearby dwarf galaxies. This allows us to derive the galaxy-wide
fractions of main sequence stars that are OBe stars (f_OBe), and how it depends
on absolute magnitude, mass, and metallicity (Z). We find f_OBe = 0.22 in the
Large Magellanic Cloud (0.5 Z_Sun), increasing to f_OBe = 0.31 in the Small
Magellanic Cloud (0.2 Z_Sun). In the so far unexplored metallicity regime below
0.2 Z_Sun, in Holmberg I, Holmberg II, and Sextans A, we also obtain high OBe
star fractions of 0.27, 0.27, and 0.27, respectively. These high OBe star
fractions, and the strong contribution in the stellar mass range which
dominates the production of supernovae, shed new light on the formation channel
of OBe stars, as well as on the preference of long-duration gamma-ray bursts
and superluminous supernovae to occur in metal-poor galaxies.
