Evolution of Silk Anchor Structure as the Joint Effect of Spinning Behavior and Spinneret Morphology.

Spider web anchors are attachment structures composed of the bi-phasic glue-fiber secretion from the piriform silk glands. The mechanical performance of the anchors strongly correlates with the structural assembly of the silk lines, which makes spider silk anchors an ideal system to study the biomechanical function of extended phenotypes and its evolution. It was proposed that silk anchor function guided the evolution of spider web architectures, but its fine-structural variation and whether its evolution was rather determined by changes of the shape of the spinneret tip or in the innate spinning choreography remained unresolved.

Evolution of aerial spider webs coincided with repeated structural optimization of silk anchorages.

Physical structures built by animals challenge our understanding of biological processes and inspire the development of smart materials and green architecture. It is thus indispensable to understand the drivers, constraints, and dynamics that lead to the emergence and modification of building behavior. Here, we demonstrate that spider web diversification repeatedly followed strikingly similar evolutionary trajectories, guided by physical constraints.