DISSERTATION RESEARCH: Does Hormone Provisioning Link Maternal Social Environment and Offspring Phenotype?

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In animals, when ones' body and behavior are matched to the environment success is maximized. Animals often rely on steroid hormones to adapt to the environments they are in. But in young individuals small differences in the concentration of hormones during development can profoundly alter later survival and behavior. During development a mother's hormone levels impact her developing offspring, and therefore impact more than her own immediate survival but also that of the young she produces. Many studies have tested the idea that steroid hormones provided by mothers to their offspring could help offspring exploit their later adult environment. However, these studies have used animals that take care of their offspring after birth. Can mothers use steroid hormones alone to optimize offspring, or is parenting behavior also necessary? This project will investigate that question by measuring the effects of a steroid hormone on offspring development and survival in an insect species that provides no parental care to its offspring. The results will show whether mothers can use steroid hormones to prime their offspring for future behavioral environments without relying on parental care. Because every mother transmits hormones to her offspring regardless of species, the results of this study will amplify our general understanding of how hormones function across generations. As such, it will likely be especially relevant to conservation of endangered species and environments, and individualized medicine. This broad applicability will also facilitate outreach to local K-12 students and findings will be presented to the scientific community through publications and presentations. This study will investigate maternal effects and aggressive behavior in an invertebrate (Acheta domesticus, the house cricket) that provides no care to offspring, but which naturally experiences variable social environments. Previous data shows that higher levels of ecdysteroid hormones (ESH) in eggs are associated with increased fitness for hatchlings. Proposed research addresses the question of whether and to what extent parents that have no later contact with their offspring can alter the development and behavioral phenotype of said offspring in response to social environment and through endocrine maternal effects alone. Female house crickets will be raised in four social environments (high and low total density, high female density and high male density), and their egg ESH deposition and total reproductive output will be measured, also. Research proposed here will disentangle the effects of maternal hormone provisioning and parental care on offspring life history by measuring hormone provisioning in a system without parental care. This work will also provide more information about ecological and evolutionary functions of ecdysteroid hormones (ESH), which have until now been studied primarily in the context of embryogenesis and molting and are generally underappreciated as mediators of long-term 'organizational' effects. Finally, this research tests the current behavioral endocrinology framework established using vertebrate study systems by considering hypotheses in the independently evolved insect endocrine system.