Meeting Abstract
Trap-jaw spiders (Mecysmaucheniidae) have been shown to have ballistic, high-speed “jaw” movements that are the fastest known arachnid movements to date. Within the family there is considerable interspecific functional diversity, with the fastest species moving their “jaws” two orders of magnitude faster than the slowest species. Phylogenetic analysis has revealed that the four fastest lineages do not form a monophyletic group but instead have evolved in parallel. The tiny size of these spiders (carapace length ranges from 0.8 – 3.0 mm) precludes in vivo manipulations. Instead, I use micro-CT scanning techniques, histology, and high-speed videography to reverse engineer the trap-jaw mechanism. I compare and contrast the functional morphology of two different mecysmaucheniid lineages, both from New Zealand, that are each other’s closest relative, with one lineage capable of ballistic, high-speed “jaw” movements and the other with slower movements. Based on differences in muscle morphology and anatomical shapes between the two sister-lineages, I develop a hypothesized mechanism for the trap-jaw strike. Finally, I test this mechanism by 3D printing a scaled-up model of different structures and use string and elastics to replicate “jaw” function, thereby demonstrating proof of mechanical concept. This research highlights the morphological steps that were taken to evolve a ballistic, complex, structural mechanism.
