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- All Subjects: Entomology
- Creators: Huijben, Silvie
Description
A notable feature of advanced eusocial insect groups is a division of labor within the sterile worker caste. However, the physiological aspects underlying the differentiation of behavioral phenotypes are poorly understood in one of the most successful social taxa, the ants. By starting to understand the foundations on which social behaviors are built, it also becomes possible to better evaluate hypothetical explanations regarding the mechanisms behind the evolution of insect eusociality, such as the argument that the reproductive regulatory infrastructure of solitary ancestors was co-opted and modified to produce distinct castes. This dissertation provides new information regarding the internal factors that could underlie the division of labor observed in both founding queens and workers of Pogonomyrmex californicus ants, and shows that changes in task performance are correlated with differences in reproductive physiology in both castes. In queens and workers, foraging behavior is linked to elevated levels of the reproductively-associated juvenile hormone (JH), and, in workers, this behavioral change is accompanied by depressed levels of ecdysteroid hormones. In both castes, the transition to foraging is also associated with reduced ovarian activity. Further investigation shows that queens remain behaviorally plastic, even after worker emergence, but the association between JH and behavioral bias remains the same, suggesting that this hormone is an important component of behavioral development in these ants. In addition to these reproductive factors, treatment with an inhibitor of the nutrient-sensing pathway Target of Rapamycin (TOR) also causes queens to become biased towards foraging, suggesting an additional sensory component that could play an important role in division of labor. Overall, this work provides novel identification of the possible regulators behind ant division of labor, and suggests how reproductive physiology could play an important role in the evolution and regulation of non-reproductive social behaviors.
ContributorsDolezal, Adam G (Author) / Amdam, Gro V (Thesis advisor) / Brent, Colin S. (Committee member) / Gadau, Juergen (Committee member) / Hoelldobler, Bert (Committee member) / Liebig, Juergen (Committee member) / Arizona State University (Publisher)
Created2012
Description
Insecticide resistance is a continuing issue that negatively affects both public health and agriculture and allows vector-borne diseases to spread throughout the globe. To improve resistance management strategies (RMS), robust susceptibility bioassays need to be performed in order to fill the gap of the relationship between resistant and susceptible genotype and phenotype, and a deeper knowledge of how bioassay data relates to vector control success or failure is imperative. A bioassay method that is infrequently used but yields robust results is the topical application bioassay, where the insect is directly treated with a constant volume and concentration of an insecticide via a syringe. To bring more attention to this method, my colleagues and I published a paper in the Journal of Visualized Experiments where the optimized protocol of the topical application bioassay for mosquitoes and fruit flies is described, and the strengths and limitations to the method are explained. To further investigate insecticide susceptibility tests, I set up my individual project where I used Aedes aegypti mosquitoes to compare the topical application bioassay to the commonly used Centers for Disease Control and Prevention (CDC) bottle bioassay and World Health Organization (WHO) tube test. The objective of this study was to test which method exhibited the most variability in mortality results, which would guide the choice of assay to determine the link between resistant and susceptible genotype and phenotype. The results showed that the topical application method did indeed exhibit the least amount of variation, followed by the CDC bottle bioassay (WHO data is currently being collected). This suggests that the topical application bioassay could be a useful tool in insecticide resistance surveillance studies, and, depending on the goal, may be better than the CDC and WHO tube tests for assessing resistance levels at a given site. This study challenges the value of the widely used CDC and WHO assays and provides a discussion on the importance of technical and practical resistance assays. This will help vector control specialists to collect accurate surveillance data that will inform effective RMS.
ContributorsAlthoff, Rachel (Author) / Huijben, Silvie (Thesis advisor) / Harris, Robin (Committee member) / Collins, James (Committee member) / Arizona State University (Publisher)
Created2022
Description
Vector control plays an important role in the prevention and control of mosquito-borne diseases (MBDs). As there are no (prophylactic) drugs and/or vaccines available for many arboviral diseases (such as zika, chikungunya, Saint Louis encephalitis, Ross River virus), the frontline approach to prevent or reduce disease morbidity and mortality is through the reduction of the mosquito vector population size and/or reducing vector-human contact using insecticides. Frontline tools in malaria (an MBD caused by a parasite) control and elimination have been drugs (targeting the malaria parasite) and insecticides (targeting the vectors) through indoor residual spraying (IRS) (spraying the internal walls and sometimes the roofs of dwellings with residual insecticides to kill adult mosquito vectors), and long-lasting insecticidal nets (LLINs), while arboviral vectors are frequently targeted using outdoor fogging and space spraying (indoor or outdoor spraying of insecticides to kill adult mosquito vectors). Integrative and novel vector control efforts are urgently needed since the aforementioned tools may not be as effective against those mosquito species that are resistant to insecticides and/or have a different (or changed) behavior allowing them to avoid existing tools. In Chapters 2 and 3, I investigate mosquito vector surveillance in Arizona by (i) discussing the species composition and public health implications of the State’s mosquito fauna, and (ii) comparing the effectiveness of 4 different carbon dioxide (CO2) sources in attracting different mosquito species on the Arizona State University Tempe Campus. In Chapters 4 and 5, I investigate a novel vector control tool by (i) completing a literature review on using electric fields (EFs) to control insects, and (ii) presenting novel data on using Insulated Conductor Wires (ICWs) to generate EFs that prevent host-seeking female Aedes aegypti from entering spaces. In Chapter 6, I discuss the non-target effects of chemical malaria control on other arthropods, including other biological and mechanical infectious disease vectors. Overall, this dissertation highlights the important role that the development of novel surveillance and vector control tools could play in improved mosquito control, which ultimately will reduce disease morbidity and mortality.
ContributorsJobe, Ndey Bassin (Author) / Paaijmans, Krijn (Thesis advisor) / Cease, Arianne (Committee member) / Hall, Sharon (Committee member) / Huijben, Silvie (Committee member) / Arizona State University (Publisher)
Created2024