Attachment discs of the diving bell spider Argyroneta aquatica

To adhere their silk threads for the construction of webs and to fix the dragline, spiders produce attachment discs of piriform silk. Uniquely, the aquatic spider Argyroneta aquatica spends its entire life cycle underwater. Therefore, it has to glue its attachment discs to substrates underwater. Here we show that Argyroneta aquatica applies its thread anchors within an air layer around the spinnerets maintained by superhydrophobic setae. During spinning, symmetric movements of the spinnerets ensure retaining air in the contact area. The flat structure of the attachment discs is thought to facilitate fast curing of the piriform adhesive cement and improves the resistance against drag forces. Pull-off tests on draglines connected with attachment discs on different hydrophilic substrates point to dragline rupture as the failure mode. The Young's modulus of the dragline (8.3 GPa) is within the range as in terrestrial spiders. The shown structural and behavioral adaptations can be the model for new artificial underwater gluing devices.

Automated summary

The aquatic spider Artyroneta aquatica uses piriform silk and attachment discs to fix draglines underwater, and maintains the attachment discs by retaining air in the area around the spinnerets. The flat structure of the attachment discs facilitates fast curing of the adhesive and enhances resistance against pulling forces.