S8-2 Wed Jan 6 10:30 – 11:00 Sticky predator-prey interactions: The ecology of adhesive secretions in arachnids Wolff, JO; Macquarie University, Sydney, Australia JONAS.WOLFF@MQ.EDU.AU
The coevolution of predators and prey is one of the most important causes of outstanding biomechanical performance. In small animals, gluing is a common and efficient strategy to capture and immobilize fast and strong prey as it may permit direct action without the involvement of muscles. Here, I will present some intriguing and poorly known examples of adhesive systems that play a role in arachnid predation. Harvestmen (Opiliones) use small amounts of a viscoelastic secretion to capture springtails. Remarkably, this natural ‘pressure sensitive adhesive’ may generate a high contact area on the nano-patterned omniphobic cuticular surface of the collembolan. This is achieved by the unique and complex microstructure of the setae that deliver the secretion. The shear-thickening behaviour of the glue effectively permits the generation of a high tensile strength to withstand the strong impacts elicited by the struggling prey. Ground spiders (Gnaphosidae) subdue hazardous prey, such as ants and other spiders, by applying sticky silk coming from modified so-called piriform glands. This silk exhibits a high toughness and is discharged from special enlarged spigots that are actived by elevated hemolymph pressure. Daddy-longleg spiders (Pholcidae) may even produce two different types of piriform gland adhesives, one of which is a rapidly drying secretion used in wrap attacks and defense, and another one being a permanently tacky secretion used to build silken web traps. This is achieved by the addition of organic salts that bind water and to keep the proteinaceous secretion hydrated. These observations are not only important for our understanding of the evolution of functional biomaterials, but may also be promising candidates for biomimetic approaches towards the design of novel sustainable high-performance adhesives.