Snails' Slime: From Slippery to Sticky Engineering

How do snails make "slime" (mucus) that can do so many jobs, from helping snails slide to helping them stick, to serving as a defense mechanism? A new study reports that collagen and calcium work together to fine-tune snail mucus's mechanical properties for each task, offering inspiration for adhesives and other novel materials that could benefit humans. "Snail mucus has a high potential to serve as inspiration for various sustainable applications such as in wound healing and drug delivery, and is currently of great commercial interest," say the authors. Mucus is widespread across animals, where it typically lubricates and protects tissues while helping defend against pathogens. However, in some species, mucus serves as a specialized material outside the body, forming cohesive slimes or adhesives used for prey capture, defense, or attachment. Terrestrial snails such as Cepaea nemoralis are particularly useful for studying these materials because they produce several types of mucus for different purposes. Snail mucus consists largely of water along with glycoproteins (mucins) and complex carbohydrates. However, little is known about the molecular and structural mechanisms that allow a single organism to produce materials with such contrasting properties using a limited selection of biological materials. Here, Mariella Gabler and colleagues examined five distinct C. nemoralis secretions, each adapted to a different function: a lubricant mucus that allows the snail to move, an adhesive mucus that anchors the shell to surfaces, a calcite-containing protective mucus, a highly sticky yellow mucus that is exceptionally extensible and resistant to tearing, and a bubbly mucus thought to deter predators. Using proteomic and materials analysis and imaging, Gabler et al. found that the different mucus types share a similar protein composition, with collagen VI serving as the primary structural component, while differences in collagen content and the addition of amorphous calcium carbonate (ACC) determine each mucus's unique properties. Calcium acts as an ion source for cross-linking in wet mucus and as a mineral precursor in dry mucus, enabling the mucus to switch between distinct mechanical functions.