Meeting Abstract
P2-211 Saturday, Jan. 5 15:30 - 17:30 Variation of Young’s modulus and taenidial density in the tracheae of a darkling beetle ADJERID, K*; SOOD, N; DE VITA, R; SOCHA, JJ; Virginia Tech; Pulaski High School; Virginia Tech; Virginia Tech adjerid@vt.edu https://sites.google.com/site/kadjerid/
Some insects facilitate active ventilation by rhythmically compressing their tracheal tubes. When collapsed, the tubes take on an uneven pock-mark like appearance, with patterns that vary across tracheae, individuals, and species. We hypothesize that deformation patterns result from variation in material or structural properties of the tubes. The semi-chitinous walls of the tracheae are reinforced with rings of stiffer sclerotized chitin fiber bundles called taenidia, which vary in branching, width, and orientation. To investigate tracheal properties, we first measured Young’s modulus along the lengths of excised sections of tracheae using atomic force microscopy (AFM). We then measured variation in packing density of the taenidia using SEM images of the same tracheal sections. Preliminary results show that the Young’s modulus varied substantially along the length of the excised sections of tracheae (1.67 ± 2.67 GPa; n=7). Moduli were distributed bimodally, with relatively little variation about the low mean (0.66 ± 0.30 GPa) and greater variation about the high mean (7.40 ± 1.27 GPa). The inter-taenidial spacing varied between 1 to 5 µm. In some specimens, the average spacing increased gradually (~0.11 µm per 100 µm of trachea), whereas in others, it changed rapidly (by up to ~1.33 µm per 100 µm). It is possible that regions with low taenidial density or low Young’s modulus may serve as initiation sites for tracheal compression, but this hypothesis remains to be tested. Supported by NSF 1558052 and 1301037.