M_HI to M_⋆ ratio as a function of M_⋆. Fornax galaxies (red+blue markers) are compared with non-cluster galaxies from VSG+HRS (grey circles). Red and blue colours show Fornax HI deficient and normal galaxies, respectively. We show Fornax galaxies with a distorted HI morphology with star-shaped markers (see Sect. 3). We show with a black solid line the xGASS scaling relation. The black dashed line is the linear extrapolation of this trend for M_⋆ < 1.4 × 10⁹ M_⊙. The orange dashed line shows the ATCA average sensitivity evaluated as 3 × 2.8 mJy beam⁻¹ with a linewidth of 100 km s⁻¹. The vertical dashed line at 3 × 10⁹ M_⊙ separates low- from high-mass galaxies.