Meeting Abstract
P2.75 Wednesday, Jan. 5 3D Reconstruction of Tracheal Systems in One-eared and Two-eared Praying Mantises. JAMIL, A.; SOCHA, J.J.; YAGER, D.D.*; Univ. Maryland, College Park; Virginia Tech, Blacksburg; Univ. Maryland, College Park ddyager@umd.edu
Most mantises have an ultrasound-sensitive ear in the ventral midline of the metathorax (MT), and a few lineages have additionally evolved a second, serially homologous ear tuned to 2-4 kHz in the mesothorax (MS). We hypothesize that modifications of tracheal structures necessary for impedance matching may play a key role in the evolution of praying mantis hearing. We used synchrotron x-ray tomography (3-6 µm resolution) to create 3D reconstructions of the MS and MT tracheal systems of nymphs (earless) and adults from three genera: Creobroter (two ears), Pseudocreobotra (two ears) and Parasphendale (one ear). The ca. 30 reconstructions show patterns of trachea development and provide quantitative data on the dimensions, volumes, and locations of tracheae and air sacs. The data show that: 1) the high-level pattern of tracheae in the thorax is the same for all genera and ages; 2) the ventral midline tracheal patterns always differ between the thoracic segments; 3) the MT tympanal sacs have the same relative sizes, shapes, and location apposed to the tympanum in all adults; 4) the MT tracheal sacs develop from lateral tracheal tubes. They gradually enlarge, change shape, and move to the midline; 5) surprisingly, even in hearing adults, the MS segment has no midline air sacs comparable to those in the MT. In hearing adults (not nymphs or earless adults), there is simply an expansion of a trachea that lies close to, but not apposed to each tympanum. However, there are many large tracheal tubes nearby so that the internal volume surrounding the MS ear is mostly air. Although built of homologous components, the MS and MT ears have solved the impedance-matching problem through different strategies related to the bioacoustics of hearing at such different frequencies.
