Rajabi, H. | bioRxiv Science

bioRxiv2020

Hunting with catapults: the predatory strike of the dragonfly larva

Dragonfly larvae capture their prey with a strongly modified -extensible- mouthpart using a biomechanically unique but not yet understood mechanism. The current opinion of hydraulic pressure being the driving force of the predatory strike can be refuted by our manipulation experiments and reinterpretation of former studies. On this fact, we present evidence for a synchronized dual-catapult system powered by two spring-loaded catapults. The power output of the system exceeds generally the maximum power achievable by musculature. Energy for the movement is stored by straining a resilin-containing structure at each joint and possibly the surrounding cuticle which is preloaded by muscle contraction. To achieve the precise timing required to catch fast-moving prey, accessory structures are used to lock and actively trigger the system, ensuring the synchronisation of both catapults. As a proof of concept, we developed a bio-inspired robotic arm resembling the morphology and functional principle of the extensible mouthpart. Our study elucidates the predatory strike of dragonfly larvae by proposing a novel mechanism, where two synchronized catapults power the ballistic movement of prey capturing in dragonfly larvae – a so-called synchronized dual-catapult system. Understanding this complex biomechanical system may further our understanding in related fields of bio inspired robotics and biomimetics.One Sentence Summary The synchronized dual-catapult, a biomechanically novel mechanism for the ballistic movement of prey capturing in dragonfly larvaeCompeting Interest StatementThe authors have declared no competing interest.View Full Text

zoology↗

bioRxiv2020

A ballistic pollen dispersal strategy hidden in stylar oscillation

Asteraceae, the most successful flowering plant family, is adapted to the vast range of ecological niches. Their adaptability is partially based on their strong ability of reproduction. The initial, yet challenging, step for plant reproduction is to transport pollen to flower-visiting pollinators. Using quantitative experiments and numerical simulations, here we show that the common floral feature of Asteraceae, a pollen-bearing style, serves as a ballistic lever for catapulting pollen grains to pollinators. This is likely to be a pollination strategy to propel pollen to blind spots of pollinators bodies, which are beyond the physical reach of the styles. Our results suggest that the specific morphology and length of the floret, as well as the pollen adhesion, avoid pollen waste by catapulting pollen within a certain range equal to the size of a flowerhead. The insights into the functional floral oscillation may shed light on the superficially unremarkable, but ubiquitous functional floral design of Asteraceae.

plant biology↗