TRANS-GENERATIONAL AND REPRODUCTIVE IMPACTS OF ACUTE EARLY-LIFE RADIATION ON THE HOUSE CRICKET, ACHETA DOMESTICUS

Stress is ubiquitous for all organisms, however, impacts vary depending on type and strength of the stressor, as well as the organism’s tolerance. Moreover, stress responses can be described by several models; linear, threshold, or hormetic. Generally ionizing radiation has been described by a “linear no threshold” model where all exposure has negative impacts. However, considerable research, both past and present, suggests that a “hormetic” or threshold model may better describe radiation exposure. My research focused on adult male house crickets, (Acheta domesticus), and the effects of early-life radiation on a variety of life history and reproductive traits, molecular biomarkers, and trans-generational impacts. Each life history and reproductive trait was also analyzed for its dose-response relationship.

Males exposed to radiation showed threshold responses in both hatching success (of 200 eggs) as well as mating success. Doses below 7Gy showed no decline in hatching success nor mating success, whereas above this threshold severe declines occurred, with 12Gy males being sterile. Sexual signals, both acoustic and chemical, were also altered by exposure. Life history traits in F0 males included a dose-dependent reduction in growth rate. Hormetic responses emerged in longevity and survivorship in 7Gy and 10Gy males and their offspring. The dose response relationship for most life-history and reproductive traits analyzed were best described by quadratic and non-linear models. Responses to radiation were also reflected by DNA methylation in F0 and F1 offspring. Generally, radiation impacts on life-history and reproductive traits were best described by non-linear modelling. Multiple aspects of sexual signalling were disrupted by radiation, including courtship signalling and pheromone signatures. Finally, radiation impacts emerged in F1 offspring that expressed significantly extended longevity and superior survivorship with no large reduction in growth rate.