Mexican Cavefish Living in Hypoxic Environments Exhibit Changes in Expression of Oxygen-transporters

Abstract

Record ID: 135

Award(s): Excellence in Research Mentoring

Student Major: Biochemistry; German Studies

Project Advisor: Joshua Gross

Abstract: In order to survive, animals living amidst extreme environmental pressures tend to evolve unusual adaptive features. This principal is well illustrated by differences between the differing morphotypes of Astyanax mexicanus, a freshwater fish species. These fish, from the El Abra region of Mexico, includes surface fish residing in streams and rivers of this region marked by lush vegetation and well-oxygenated water. Cavefish, however, live in underground caves with limited nutrition and detrimentally low-oxygen water. I examined how cave morphs have evolved to survive this extreme environmental pressure. Specifically, I investigated how altered hemoglobin expression in cavefish enable them to thrive despite their low-oxygen environment. This project began with a literature search to identify primary studies measuring gene expression using RNA-sequencing in various Astyanax populations. I examined studies published between 2013 and 2021, alongside one study in preparation for publication. These studies were diverse, including specimens of varying ages (ranging from 24 h post-fertilization through adulthood) and populations (including the Tinaja, Pachón, Chica, and Molino cavefish; and Río Choy surface fish). These studies involved different experimental conditions examining features like sleep loss, dark-rearing, and comparisons between captive and wild-caught fish. My results suggest hemoglobin expression is highly influenced by life history and experimental conditions. The outcome highlights the importance of hemoglobin research in Astyanax mexicanus and informs certain molecular mechanisms of adaptation to extreme environments. This work showcases the nature of cavefish adaptation to low-oxygen environments, and furthers our understanding of how animals assimilate to diverse ecological pressures.