  We study the interplay between gas phase metallicity (Z), specific star
formation rate (SSFR) and neutral hydrogen gas (HI) for galaxies of different
stellar masses. Our study uses spectroscopic data from GAMA and SDSS star
forming galaxies, as well as HI-detection from the ALFALFA and GASS public
catalogues. We present a model based on the Z-SSFR relation that shows that at
a given stellar mass, depending on the amount of gas, galaxies will follow
opposite behaviours. Low-mass galaxies with a large amount of gas will show
high SSFR and low metallicities, while low-mass galaxies with small amounts of
gas will show lower SSFR and high metallicities. In contrast, massive galaxies
with a large amount of gas will show moderate SSFR and high metallicities,
while massive galaxies with small amounts of gas will show low SSFR and low
metallicities. Using ALFALFA and GASS counterparts, we find that the amount of
gas is related to those drastic differences in Z and SSFR for galaxies of a
similar stellar mass.
