Doctor of Philosophy, Miami University, 2024, Biology

This dissertation investigates the sexually dimorphic expression of the nos gene, which encodes for the enzyme Nitric oxide synthase (NOS). NOS activation produces the gaseous signaling molecule nitric oxide (NO), which can impact immune function and behavior. Despite the crucial role of NO in insect physiology, the mechanisms underlying nos expression in both sexes and in different social environments remain poorly understood. Our primary aim was to elucidate the impact that a lack of social interaction can have on nos expression and immune function, providing new insights into insect physiology and behavior. We cloned and characterized the Ad-nos gene, revealing a close phylogenetic relationship with other orthopteran insects. Quantitative PCR analysis showed that early adult females exhibited significantly higher Ad-nos expression in nervous and thoracic fat body tissues than males, while males had higher expression in hemolymph. Following lipopolysaccharide (LPS) injection, males showed increased Ad-nos expression in brain and hemolymph, whereas females showed elevated expression in fat bodies and hemolymph. These findings suggest sex-specific immune strategies, with males prioritizing cellular immunity and females employing both humoral and cellular responses. We also examined the effects of social interaction during different developmental stages on NO levels and immune function. Comparing adult-isolated and nymph-isolated crickets, we found significant sex-dependent differences in Ad-nos expression. Nymph-isolated females had higher Ad-nos expression in brain and hemolymph, while nymph-isolated males showed higher expression in brain fat body and thoracic fat body tissues. NO activity assays indicated lower activity in nymph-isolated crickets compared to adult-isolated crickets. In addition, nymph-isolated females had fewer circulating hemocyte than males, while males had higher hemolymph protein content. Survival analysis post-LPS injection showed that adult (open full item for complete abstract)

Committee: Kathleen Killian (Advisor); Dawn Blitz (Committee Member); Jennifer Quinn (Committee Chair); Yoshinori Tomoyasu (Committee Member); Paul James (Committee Member) Subjects: Biology; Immunology; Molecular Biology; Neurosciences

Doctor of Philosophy, Miami University, 2019, Biology

Fragile X syndrome (FXS) is the most common form of inherited mental retardation and is the primary monogenetic cause of autism spectrum disorders. FXS is caused by a mutation in the regulatory region of the Fragile X Mental Retardation 1 (FMR1) gene, that ultimately leads to loss of the gene product Fragile X Mental Retardation Protein (FMRP). As FXS is a neurodevelopmental disorder, most studies have focused on the role of FMRP during development. However, a few studies have shown that the loss of FMRP during adulthood can impact learning, cognition, and behavior. The primary goal of this study was to decrease FMRP during adulthood and examine the impacts on immune function and social behavior using the cricket Acheta domesticus as a novel insect model. We examined immune function in males and females by assessing several important immune parameters including: the total number of circulating hemocytes in the hemolymph, the total hemolymph protein content, total phenoloxidase enzyme activity, and fat body lysozyme expression. We found that males and females exhibited similar changes in these immune parameters as a result of decreased Fmr1, but males were less likely to survive an immune challenge with an injection of lipopolysaccharide (LPS) from Serratia marcescens. This is the first study to demonstrate that decreased FMRP during adulthood causes sex-specific effects on the immune system. We also examined the effects of decreased Fmr1 on the agonistic behavior of adult male crickets. We observed that the average time to first physical contact during an agonistic interaction was significantly increased in fights between a control male and Fmr1 knockdown male and that Fmr1 knockdown males were less likely to initiate an aggressive interaction than control males. Despite initiating interactions less often, these males fought just as aggressively and won as often as controls. In this study, we also evaluated the parameters required to generate a successful parental R (open full item for complete abstract)

Committee: Kathleen Killian Dr. (Advisor) Subjects: Biology; Entomology; Genetics

Doctor of Philosophy, Miami University, 2007, Zoology

I examined the role of agonistic behavior and social status on neurogenesis in the brain and the terminal abdominal ganglion of the adult male cricket. We also tested whether male crickets maintain a memory of their social rank or of their opponent during agonistic encounters. Using immunohistochemistry and confocal microscopy, we found that adult neurogenesis takes place in neurogenic and non-neurogenic regions of the cricket brain. In the neurogenic mushroom body clusters, fought males had more cell proliferation and neurogenesis than un-fought control males. Dominant males had significantly more new neurons than subordinate males, which in turn had more new neurons than control males. Neurogenesis in non-neurogenic brain regions was not different between control, dominant and subordinates males. Behavioral results prompted us to examine if males form a memory of their social rank or of their opponent during agonistic encounters. Behavioral experiments, in which males were either paired with the same opponent or with a different opponent of opposite rank, indicated that in the trials where dominance relationship was maintained, second trials were less aggressive and had more pre-establishment. Also, subordinate males showed fewer agonistic approaches during their second trials irrespective of the individual identity of the opponent. In trials where males were paired with a different opponent of the same rank, fights between two dominant males were more aggressive that those between two subordinate male, further supporting the notion that a memory of social rank was maintained in these males. We also found that neurogenesis persists in the terminal abdominal ganglion of the cricket and that agonistic interaction could increase neurogenesis in fought males compared to control males in a manner that was not rank-specific. These results indicate that male crickets may form a memory of their social rank during agonistic interactions and that these interactions increase (open full item for complete abstract)

Committee: KATHLEEN KILLIAN (Advisor) Subjects: Biology, Neuroscience

Master of Science (MS), Bowling Green State University, 2013, Biological Sciences

Agonistic behavior is an important social aspect of animal behavior, and the outcome of agonistic interactions is critical to the acquisition of resources such as food, shelter, and mating opportunities. During agonistic interactions, individual participants make behavioral decisions based on energy and time investment such as escalating the intensity of the interaction and whether to end the interaction by retreating. Each of these decisions can be informed through self-assessment (e.g. energy reserves) cumulative assessment (e.g. components of self-assessment in addition to the effects of opponent-inflicted injury) or through some form of mutual assessment (e.g. size differential). Crayfish are ideal model organisms for the study of such behavior because they engage in ritualized fighting, and have a well-established ethogram and well-studied chemosensory organs. In this study, I examine the assessment strategies that crayfish employ during same and mixed sex fights. After a brief acclimation, two individuals (male-male, female-female, or male-female) were allowed to interact for 15 minutes. Video analysis was used to calculate fight duration and times spent at various intensity levels. Analysis indicates that crayfish do not utilize a mutual assessment strategy as hypothesized. Furthermore, males and females appear to be using two different types of assessment strategies.

Committee: Paul Moore Dr. (Committee Chair); Ryan Earley Dr. (Committee Member); Karen Root Dr. (Committee Member) Subjects: Behavioral Sciences; Biology