Presenter: Nathaniel Earp
Mentor: William Cresko
Poster: 37
Major: Human Physiology
Perchlorate is a widespread contaminant in the environment. We have found that perchlorate has masculinizing effects on threespine stickleback, Gasterosteus aculeatus. The mechanism of this masculinization is unknown. Our previous studies found that during development female stickleback show increased proliferation of undifferentiated primordial germ cells (PGC) followed by a larger wave of apoptosis compared to male stickleback. We hypothesize that perchlorate treated stickleback will show a decrease in total number of PGCs compared to control fish. To test our hypothesis, stickleback of 15 and 20 days post fertilization (dpf) – a critical time for primary sexual differentiation– were grown from fertilization to the end of the experiment in 10 or 100 ppm perchlorate treated medium or control medium with no perchlorate. Stickleback were sectioned and stained with hematoxylin and eosin, and visualized by light microscope. Total number of PGCs were counted and characterized as either pre-meiotic or meiotic based on morphology of the PGC and nucleus. Perchlorate treated fish show a significant decrease (27.6%) in total number of PGCs compared to controls. Furthermore, control stickleback showed a decrease in total number of PGCs from 15 dpf to 20 dpf, presumably due to female germ cell apoptosis, while perchlorate treated stickleback did not show this decrease. These findings are consistent with perchlorate’s masculinizing effect. We are further investigating the effects of perchlorate on total PGC count in zebrafish, Danio rerio, as perchlorate has been shown to have a feminizing effect on zebrafish, giving us an opportunity to explore the basic mechanisms underlying the reproductive abnormalities caused by perchlorate. Our findings contribute to understanding mechanisms of perchlorate induced reproductive abnormalities in vertebrates, and to better understand the underlying process of sex determination in two divergent teleosts.