Doctor of Philosophy, Miami University, 2017, Cell, Molecular and Structural Biology (CMSB)

Insects rely on their immune system to combat the myriad of pathogens to which they are exposed within their environment. The insect immune system is similar to the innate immune system of vertebrates and consists of cellular and humoral immune responses. These responses are dynamic and under the influence of a variety factors, including pathogenic infection, age/gender, and changes in environmental temperature. The goal of this study was to examine how these factors affect multiple measures of cellular and humoral immune responses including total phenoloxidase activity, number of circulating hemocytes, lysozyme-like activity, and capsule formation in adult male Acheta domesticus crickets. We examined these parameters following immune challenge with one of three different treatments: injection of lipopolysaccharide (LPS) from Serratia. marcescens or Escherichia coli; injection of live S. marcescens; or insertion of a nylon filament. We observed that injection of live S. marcescens induced the strongest and most rapid immune response and that injection of LPS from E. coli induced a more rapid response than LPS from S. marcescens. Inserting a nylon filament induced a rapid immune response that was short-lived. These data suggest that the magnitude of the cricket immune response is dependent on the type of immune challenge and that a more complete view of the true immune response can only be ascertained when measuring multiple immune parameters at multiple time points after a challenge. In this study, we also assessed the effect of age and gender on the cricket immune system. We observed that female crickets had similar measures of immunity across the nymphal and young adult stages we examined. However, sexually mature adult males and females were dimorphic in immunity, causing females to succumb more quickly to a live bacterial challenge. Finally, we assessed how cold stress (CS) at 0°C could impact the immune system. We observed that CS resulted in the translocation (open full item for complete abstract)

Committee: Kathleen Killian Dr. (Advisor); Lori Isaacson Dr. (Committee Chair); Yoshinori Tomoyasu Dr. (Committee Member); Paul James Dr. (Committee Member); Eileen Bridge Dr. (Committee Member) Subjects: Biology; Immunology

Master of Science, Miami University, 2012, Zoology

The immune system is critical to an animal's survival. However, changes in immune function during insect development, and the factors that regulate these changes, are not well understood. Hemocytes carry out cellular defenses such as phagocytosis, nodulation, and encapsulation of pathogens. The enzyme phenoloxidase (PO) plays a key role in this process while the enzyme lysozyme breaks down bacterial cell walls. Total PO (TPA) and lysozyme activities, total blood hemocytes, and encapsulation ability were examined from late nymphal stages through early adulthood in the cricket, Acheta domesticus. TPA increased with age while encapsulation ability tended to decrease. The effects of crowding and light stress during nymphal development on adult immune parameters were determined. Crowding increased TPA in crickets housed in small but not large groups. Light stress negatively impacted survival, but not immune function. Further investigation of the effects of early life stress on adult immune function is thus warranted.

Committee: Kathleen A. Killian PhD (Advisor); Nancy G. Solomon PhD (Committee Member); Ann L. Rypstra PhD (Committee Member) Subjects: