Using PU4ii corrosion casts to characterize the tracheal system of the grasshopper leg (879.21)

The lightweight, air‐filled tracheal system has enabled insects to be the most evolutionary successful animals on the planet. While adult Schistocerca americana grasshoppers use abdominal pumping and convection to drive oxygen through their head, thorax, and abdomen, it is less clear how oxygen delivery occurs down the metathoracic jumping leg. We cannulated the tracheal system of an adult grasshopper and injected PU4ii [vasQtec, Switzerland] low viscosity polymer resin, to create a corrosion cast of the tracheal system of the metathoracic leg. After the resin had solidified, tissues were chemically digested, leaving only the tracheal cast. The cast revealed a highly organized system. In the femur, six primary tracheae [0.2‐0.3 mm diameter] run along the proximodistal axis, connected via more than 20 secondary tracheae [0.09‐0.2 mm] running along the dorsoventral axis in a chevron pattern. Secondary tracheae form a network around the femur between the dorsal and ventral primary tracheae on each face. Many tertiary tracheae [9‐25 µm] descend from the chevrons into the muscle cavity. The lateral face of the femur has an additional central primary tracheae and 40° angled chevrons, while the medial face has only dorsal and ventral primary tracheae and 130° angled chevrons. Air sacs have been observed in multiple locations down the leg: at the junction between the primary and secondary tracheae, in the hip and knee joints, and in the tibial spikes. Results indicate PU4ii resin yields higher resolution casts than alternative methods using Mercox resin. Grant Funding Source : Supported by Union College Undergraduate Research Grants