Many advances in the study of touch sensation have benefitted from Caenorhabditis elegans and its skin and sensory neurons as a model. As in mammals, C. elegans skin is a layered structure consisting of both an acellular layer (cuticle) and cellular layer (hypodermis) that harbors touch receptor neurons (TRNs). Understanding how forces applied to the skin surface are transferred to the TRNs requires proper analysis of the structure and mechanics of the layers in between. Collagen is a major component of the cuticle, and cuticle collagens are encoded by more than 150 genes in the genome. Cuticle collagen genes are required for normal body size and can act as negative or positive regulators of body size. In this study, we seek to examine cuticle structure of intact adult animals and to determine how the structure and mechanics differ in genotypes with cuticle collagen mutations. Using Atomic Force Microscopy (AFM), we reveal the topography of the adult C. elegans cuticle with nanometer resolution and investigate the correlation of the cuticle feature size with its mechanical properties. We started by examining three genotypes: N2,
dpy-5(
e61), and
rol-6(
e187n1270). The
rol-6 and
dpy-5 genes encode cuticle collagens and both genes can mutate to alter body size and shape.
dpy-5(
e61) animals are shorter and wider than wild-type, whereas
rol-6(
e187n1270) mutants are similar to wild-type. [SC1] We analyzed the microtopography of the cuticle from head to tail in at least 20 individual worms for each genotype. For each of them we tried to scan four location along the 15%, 40%, 60%, and 85% of the body length. The results reveal the topography of the annuli and the furrows, from which the width of the annuli and the depth of the furrows can be measured and analyzed in the mutants. The average measured annuli width of all locations along the body are 1.61 ( plus or minus 0.44) um, 1.16 ( plus or minus 0.32) um, and 1.4 ( plus or minus 0.43) um for wild type,
dpy-5, and
rol-6, respectively. Normalizing annulus width to body length, we find that the annuli of
dpy-5 and
rol-6 are larger than the wild type. Assuming Derjaguin-Muller-Toporov (DMT) model of elastic contact of the AFM probe tip-sample, the average values of the cuticle stiffness are 0.73 MPa, 0.56 MPa, and 0.47 MPa for wild type,
dpy-5, and
rol-6, respectively. The
dpy-5 and
rol-6 cuticles are 23% and 35% softer than those of wild type animals, respectively. Our initial results indicate that the wider the annulus (relative to body length), the less stiff the cuticle. These measurements provide insight into the mechanical properties and microstructure of the cuticle and enable future studies of force transmission across the skin during touch and the interplay of collagen expression, body shape, and body mechanics.