Normalized CO(1–0) luminosity as a function of K-band luminosity. IC 3418 is represented with a red arrow with the head corresponding to the marginally detected (B1) CO luminosity and the upper tail bar to the upper limit for the total luminosity of the disk. IC 3418 is compared with a set of nearby low-mass star-forming galaxies from the HERACLES survey (together with more massive HERACLES galaxies, and other Local Group and nearby galaxies) used by Schruba et al. (2012) (filled circles), and with a sample of compact late-type spiral and irregular galaxies of Leroy et al. (2005) (empty circles), plus few starburst dwarf galaxies from Taylor et al. (1998) (triangles), and DDO154 (Komugi et al. 2011). Upper limits are plotted with symbols with small arrows. Colors represent metallicity 12 + log (O/H). The color of the IC 3418 arrow does not correspond to its metallicity (see Sect. 5.2). Small empty circles show marginal detections of Leroy et al. (2005).