Date of Award

Spring 4-29-2024

Document Type

Honors Thesis



First Advisor

Jacob Kerby

Second Advisor

Jeff Wesner

Third Advisor

David Swanson


False Map Turtle, Selenium, Selenosis, Selenomethionine

Subject Categories

Biology | Terrestrial and Aquatic Ecology


Selenium is an element that becomes bioactivated in aquatic environments. Selenium bioaccumulation may threaten a South Dakota state-threatened species, the False Map Turtle (Graptemys pseudogeographica). Invertebrate filter feeder species like zebra mussels (Dreissena polymorpha) uptake selenium via exposure. Previous laboratory work has found that False Map Turtles consume large amounts of zebra mussels throughout the summer, leading to selenium bioaccumulation from selenium transfer from prey to predator. A myriad of adverse effects, like selenosis, reproductive infertility, and death, are associated with high selenium concentrations. Sampling was completed on False Map Turtles in the summer of 2022. Samples were taken once a month from July to September. A blood sample and several morphometric measurements were collected from each turtle. Data were collected from 15 male and 38 female False Map Turtles. The average selenium concentration present during each month appeared to peak in July with an average concentration of 0.94 ug/g and a maximum concentration of 6.24 ug/g. The relationship between sex and the average selenium concentration per month showed relatively equal concentrations among males and females, with similar concentrations during August and September. Yet, during the peak month of July, male turtles had a much higher selenium concentration (1.37 ug/g) than their female counterparts (0.73 ug/g). Further work needs to be done to determine why this difference exists. Differences in overall size might alter prey selection, where males are more likely to consume the smaller zebra mussels. Additionally, detoxification systems in the turtles themselves might differ between the sexes. Regardless, these findings highlight the importance of understanding the role of invasive zebra mussels in contaminant distribution in aquatic ecosystems.



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