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Thesis
Occurrence of intersex in fishes from the Delaware and Susquehanna River basins: a temporal and interspecific comparison
Master of Science (M.S.), Drexel University
Sep 2017
DOI:
https://doi.org/10.17918/etd-7549
Abstract
Endocrine disruption is an issue of emerging concern in aquatic systems. Endocrine disruption has been documented to result in decreased reproductive success, skewed sex ratios, increased vitellogenin levels, intersex, disease, and death in a variety of freshwater fish species. In this study, intersex or the presence of testicular oocytes in gonochoristic fish species was utilized as an indicator of endocrine disruption. The study design is based on both a temporal and interspecific comparison of intersex occurrence through the use of paired historical and modern fish samples. The historical samples were obtained from the ichthyology collection at the Academy of Natural Sciences of Drexel University and replicate samples were collected in July and August of 2016. Historical samples from the Delaware sites include the oldest available specimens (from as early as 1898). The Susquehanna specimens spanned a longer time gradient with multiple samples (n=4) ranging from 1969 to 2016. Male Cyprinella analostana and C. spiloptera were collected from three sites in the Delaware and one site in the Susquehanna River basins. Twenty male specimens from each sample were analyzed histologically to document the prevalence and severity of intersex. Additionally, several smallmouth bass, Micropterus dolomieu were collected and assessed as a known sensitive species. Four potentially sensitive species were identified and assessed in 2017. These four species were Lepomis auritus, Ambloplites rupestris, Etheostoma zonale, and Notropis hudsonius, and represented additional modern specimens. These species were added in an attempt to gain a better understanding of how endocrine disruption impacts the entire fish community. No specimens analyzed in this study displayed intersex other than eight M. dolomieu collected from the Susquehanna River. Land cover data was used to calculate land cover percentages for each basin. Land cover percentages indicated that the greatest altered land cover type in the Susquehanna River basin was agriculture whereas developed land was the greatest altered land cover type for the three Delaware River basin sites. This study was a first attempt at using historical specimens to understand endocrine disruption prior to the emergence of the field in the late 20th century. Additionally, there is interest in identifying a small-bodied indicator species of endocrine disruption. Although C. analostana, C. spiloptera, L. auritus, A. rupestris, E. zonale, and N. hudsonius did not portray intersex, future efforts should focus on assessing other common, small-bodied species within the Delaware and Susquehanna River basins to identify a small-bodied indicator species that can be used to assess the impact of EDCs across an entire watershed.
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Details
- Title
- Occurrence of intersex in fishes from the Delaware and Susquehanna River basins
- Creators
- Raffaela Marano - DU
- Contributors
- Richard J. Horwitz (Advisor) - Drexel University (1970-)
- Awarding Institution
- Drexel University
- Degree Awarded
- Master of Science (M.S.)
- Publisher
- Drexel University; Philadelphia, Pennsylvania
- Number of pages
- ix, 61 pages
- Resource Type
- Thesis
- Language
- English
- Academic Unit
- Biodiversity, Earth, and Environmental Science (BEES); College of Arts and Sciences; Drexel University
- Other Identifier
- 7549; 991014632253104721