In this dissertation, we examine mechanics of rhythmic tracheal compression (RTC) in the darkling beetle, Zophobas morio. In Chapter 2, we studied the relationship between hemolymph pressure and tracheal collapse to test the hypothesis that pressure is a driving mechanism for RTC. We found that tracheae collapse as pressure increases, but other physiological factors in the body may be affecting tracheal compression in live beetles. Additionally, as the tracheae compress, they do so in varying spatial patterns across the insect body. In chapter 3, we examined spatial variations in the taenidial spacing, stiffness, and tracheal thickness along the length of the tracheae. We related variations in Young's modulus and taenidial spacing with measurements of collapse dimples and found that spatial patterns of Young's modulus correlate with dimensions of collapse dimples. This correlation suggests an intuitive link between tracheal stiffness variations and the unique patterns observed in compressing tracheae. Lastly, in chapter 4, we studied the non-uniform collapse patterns in 3-D. By manually pressurizing the hemocoel and imaging using synchrotron microcomputed tomography (SR-µCT), we reconstructed the tracheal system in its compressed state. While previous studies used 2-D x-ray images to examine collapse morphology, ours is the first to quantify collapse patterns in 3-D and compare with previous 2-D quantification methods. Our method is also the first to make a direct measure of tracheal volume as the tracheal system compresses, similar to the phenomenon that occurs during rhythmic tracheal compression. / Doctor of Philosophy / Insects have long been a source of curiosity and inspiration for scientists and engineers. The insect respiratory system stands as an example of a seemingly complex oxygen delivery system that operates with relative simplicity. As opposed to mammals and other vertebrates, the insect respiratory system does not deliver oxygen using blood. Instead, insects possess a massive network of hollow tracheal tubes that are distributed throughout the body. Air enters spiracular valves along the length of the insect body, travels through the tracheal tube network, and is delivered directly to the tissues. In some insects, the tracheae compress and expand, driving flow of respiratory gasses. However, unlike vertebrate lungs, there are no muscles directly associated with the tracheal system that would drive this tracheal compression, and exactly how this behavior occurs is not fully understood. In this dissertation, we examined pulsatory increases in blood pressure as a possible mechanism that underlies these tracheal compressions in the darkling beetle, Zophobas morio. Additionally, as the tracheae compress, they do so with varying spatial patterns across the insect body. Because tracheae are complex and non-uniform composite tubes, we examined spatial variations in the microstructure, stiffness, and tracheal thickness along the length of the trachea. Lastly, we visualized the variable collapse patterns in three dimensions using synchrotron micro-computed tomography combined with manual pressurization of the hemocoel. While previous studies used two-dimensional x-ray images to quantify tracheal collapse patterns, this work represents the first three-dimensional study. Understanding tracheal collapse mechanics, material properties, and their relationships with the circulatory system can help to gain an understanding of how insects create complex fluid flows within the body using relatively simple mechanisms.

O colapso traqueal é uma obstrução parcial ou total da traqueia caracterizado pelo achatamento dorsoventral dos anéis cartilaginosos e pela frouxidão da membrana traqueal dorsal. Acomete principalmente cães de raças pequenas, de meia idade a idosos, embora também possa ocorrer em cães jovens. O diagnóstico é feito com base nos sinais clínicos e exames complementares. A traqueobroncoscopia permite avaliar o diâmetro da traqueia e dos segmentos brônquicos, principalmente quando as radiografias e fluoroscopia não forem conclusivas e ainda permite a coleta de amostras para citologia, histopatologia e culturas. O objetivo deste estudo foi correlacionar a infecção traqueal com a inflamação da traqueia em cães com colapso de traqueia. A pesquisa foi realizada no HOVET da FMVZ-USP e no Hospital Veterinário Clinivet em Curitiba. A amostra foi constituída por 28 cães, sendo 12 com colapso de traqueia e 16 hígidos para o grupo controle, que propiciou parâmetros de normalidade em relação ao grupo colapso traqueal. Para a coleta de dados utilizou-se a traqueobroncoscopia, com a qual visualizamos a traqueia e graduamos o colapso, colhemos material para cultura bacteriana e citologia. Após a análise dos resultados foi observado diferença estatística significativa nos cães com inflamação e colapso de traqueia. Não foi observado correlação entre a infecção bacteriana e a inflamação na traqueia. Com um teste de dissimilaridade verificou-se que a população bacteriana da orofaringe foi semelhante a da traqueia nos cães do mesmo grupo. Portanto, concluímos que cães com colapso de traqueia tendem a ter a traqueia inflamada, porém não apresentam infecção bacteriana. A composição das bactérias na traqueia pode ser devido à aspiração do conteúdo da orofaringe. / The Tracheal collapse is a partial or total obstruction of the trachea, featured by dorsoventral flattening of the cartilaginous rings and by the laxity of the dorsal tracheal membrane. It mainly affects small breeds, middle-aged and older dogs, although it can also occur in young dogs. The diagnosis is made based on clinical signs and additional exams. The trachealbronchoscopy allows evaluating the trachea diameter and bronchial segments, especially when radiographic and fluoroscopy is not conclusive and still allows the collection of samples for cytology, histopathology and cultures. The objective of this study was correlating the tracheal infection with the tracheal inflammation in dogs with tracheal collapse. The research was conducted in the HOVET FMVZ-USP and Clinivet Veterinary Hospital in Curitiba. The sample consisted of 28 dogs, including 12 with collapsing trachea and 16 healthy subjects in the control group, which allowed normal parameters in relation to the group tracheal collapse. For data collection was used the trachealbronchoscopy, in which was visualized the trachea and the grade of the tracheal collapse was recorded. We also collected samples for cytology and bacterial culture. After analyzing the results we found statistically significant difference in dogs with tracheal collapse and inflammation of the trachea. There was no correlation between bacterial infection and inflammation in the trachea. With dissimilarity test was observed that the bacterial population of the pharynx was similar to the trachea in dogs of the same group. n this study, therefore, concluded that dogs with collapsing trachea tend to have the inflamed trachea, but it does not have bacterial infection. The composition of the bacteria in the trachea may be due to aspiration of pharynx\'s contents.

O colapso traqueal é uma obstrução parcial ou total da traqueia caracterizado pelo achatamento dorsoventral dos anéis cartilaginosos e pela frouxidão da membrana traqueal dorsal. Acomete principalmente cães de raças pequenas, de meia idade a idosos, embora também possa ocorrer em cães jovens. O diagnóstico é feito com base nos sinais clínicos e exames complementares. A traqueobroncoscopia permite avaliar o diâmetro da traqueia e dos segmentos brônquicos, principalmente quando as radiografias e fluoroscopia não forem conclusivas e ainda permite a coleta de amostras para citologia, histopatologia e culturas. O objetivo deste estudo foi correlacionar a infecção traqueal com a inflamação da traqueia em cães com colapso de traqueia. A pesquisa foi realizada no HOVET da FMVZ-USP e no Hospital Veterinário Clinivet em Curitiba. A amostra foi constituída por 28 cães, sendo 12 com colapso de traqueia e 16 hígidos para o grupo controle, que propiciou parâmetros de normalidade em relação ao grupo colapso traqueal. Para a coleta de dados utilizou-se a traqueobroncoscopia, com a qual visualizamos a traqueia e graduamos o colapso, colhemos material para cultura bacteriana e citologia. Após a análise dos resultados foi observado diferença estatística significativa nos cães com inflamação e colapso de traqueia. Não foi observado correlação entre a infecção bacteriana e a inflamação na traqueia. Com um teste de dissimilaridade verificou-se que a população bacteriana da orofaringe foi semelhante a da traqueia nos cães do mesmo grupo. Portanto, concluímos que cães com colapso de traqueia tendem a ter a traqueia inflamada, porém não apresentam infecção bacteriana. A composição das bactérias na traqueia pode ser devido à aspiração do conteúdo da orofaringe. / The Tracheal collapse is a partial or total obstruction of the trachea, featured by dorsoventral flattening of the cartilaginous rings and by the laxity of the dorsal tracheal membrane. It mainly affects small breeds, middle-aged and older dogs, although it can also occur in young dogs. The diagnosis is made based on clinical signs and additional exams. The trachealbronchoscopy allows evaluating the trachea diameter and bronchial segments, especially when radiographic and fluoroscopy is not conclusive and still allows the collection of samples for cytology, histopathology and cultures. The objective of this study was correlating the tracheal infection with the tracheal inflammation in dogs with tracheal collapse. The research was conducted in the HOVET FMVZ-USP and Clinivet Veterinary Hospital in Curitiba. The sample consisted of 28 dogs, including 12 with collapsing trachea and 16 healthy subjects in the control group, which allowed normal parameters in relation to the group tracheal collapse. For data collection was used the trachealbronchoscopy, in which was visualized the trachea and the grade of the tracheal collapse was recorded. We also collected samples for cytology and bacterial culture. After analyzing the results we found statistically significant difference in dogs with tracheal collapse and inflammation of the trachea. There was no correlation between bacterial infection and inflammation in the trachea. With dissimilarity test was observed that the bacterial population of the pharynx was similar to the trachea in dogs of the same group. n this study, therefore, concluded that dogs with collapsing trachea tend to have the inflamed trachea, but it does not have bacterial infection. The composition of the bacteria in the trachea may be due to aspiration of pharynx\'s contents.

Abdominal pumping is a well-known behavior in insects, thought to function largely in respiratory processes. In particular, the abdominal pump is considered to produce ventilation of air in the tracheal system, but the mechanistic link between abdominal movement and flow of air is not well understood. In this thesis, we explore the relationship between the abdominal pump and ventilation of air using pupal and adult forms of the darkling beetle Zophobas morio. First, we investigated the mechanical linkage between abdominal pumping and active ventilation in pupae by simultaneously measuring abdominal movement, hemolymph pressure, CO2 emission, and deformation of tracheal tubes. This study revealed that pupae with low metabolic rates do indeed exhibit tracheal compression, which is coincident with abdominal pumping and pressure pulsation. However, more than 63% of the abdominal pumps and associated pressure pulsations did not lead to tracheal compression. This result can be explained by the status of the spiracles; when the system is closed, little compression in the tracheae can occur. Therefore, we conclude that abdominal pumping in insects does not necessarily lead to ventilation and may serve other functions, such as producing hemolymph flow for circulation. Insects have an open circulatory system, with flow driven largely by the small dorsal vessel. Within the open coelom, hemolymph pressure should be mostly uniform, suggesting that abdominal pumping does not produce hemolymph flows within the main body cavity. We tested this assumption by simultaneously measuring hemolymph pressure in different locations in the coelom. Within the abdomen and thorax, hemolymph pressure is nearly uniform, as expected. However, hemolymph pressures are significantly different between the abdomen and thorax. This suggests that the coelom is compartmentalized, and that abdominal pumping can induce hemolymph flow within the coelom. Throughout these experiments, we faced a common difficulty inherent to flow-through respirometry systems: they are incapable of providing direct, instantaneous measurement of gas concentration. Previous methods are not able to reconstitute the rapid dynamical changes in respiratory signals that are required for precise temporal analysis. Therefore, we developed two new methods to accurately recover instantaneous gas exchange signals, based on new models of the impulse response of the system. These methods enabled us to accurately recover fast- changing respiratory signals with a higher fidelity than previously possible. Using these methods, we demonstrate the synchronization of respiratory data with other physiologically relevant signals, such as pressure and abdominal movement. This research was supported by NSF grant #0938047 and the Virginia Tech Institute for Critical Technology and Applied Science (ICTAS). / Ph. D.