2025 Research Results
What have we been up to this year? – Let's take a deep dive!







 

​Bottlenose dolphin biopsy locations were arranged by sex and three ecotypes along the U.S. Southeastern shore: inshore, shelf, and offshore. Each of these dolphin ecotypes were distinguished by their varying adaptations to hypoxic environments. 

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Based on dolphin ecotypes, we created a workflow to identify candidate genes linked to hypoxia tolerance, using RADSeq outlier SNPs and functional gene sets.

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Using a Seahorse Mito-Stress Assay, we measured the oxygen consumption rates of a variety of skin fibroblasts–including humans and deep-diving goose-beaked whales–grown in low-oxygen and normal-oxygen conditions. Analysis shows that when oxygen levels are lowered to 1%, most species like humans lower their oxygen consumption rate. In contrast, goose-beaked whale cells maintain a high oxygen consumption rate regardless of oxygen levels. These results suggest that deep-diving goose-beaked whales have adapted cellular metabolic pathways for hypoxia.

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The previous findings prompted us to investigate these underlying adaptive cellular pathways and mechanisms. One approach involved examining the relative expression of frataxin–a gene involved in building and maintaining mitochondrial function– across various mammalian fibroblast lines. By performing a Quantitative Polymerase Chain Reaction (qPCR), we uncovered that frataxin is expressed at a higher level in goose-beaked whales relative to humans under both normoxia and hypoxia. These results indicate that frataxin may be playing a role in goose-beaked whale’s distinctly elevated oxygen consumption rates.

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To further understand alternative cellular adaptations, we examined lipid metabolism. This approach was inspired by metabolomics data showing that deep-diving marine mammals have naturally elevated carnitine levels compared to shallow-diving and terrestrial mammals. Carnitine is essential for transporting lipids to mitochondria for oxidation. So, these results may suggest that deep-diving whales may rely more heavily on lipid metabolism than other mammals as an adaptation to hypoxia.

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To investigate this lipid metabolism hypothesis, we exposed human and goose-beaked whale fibroblasts to hypoxia for twenty-four hours and then stained cells with a fluorescent lipid droplet marker. Immunofluorescence analysis revealed that goose-beaked whales had much less lipid droplet accumulation than humans. These results support our hypothesis that these deep-diving marine mammals may be using upregulated lipid metabolism as an adaptation to hypoxia.

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We next assessed carnitine’s impact on oxygen consumption in mammalian fibroblasts using the Seahorse XF Palmitate Oxidation Stress Assay. This allowed us to measure oxygen consumption in human and goose-beaked whale cells, with and without carnitine, under normoxic and hypoxic conditions. Goose-beaked whale fibroblasts showed increased oxygen consumption with carnitine under both conditions, while human fibroblasts showed no change. These results further support our hypothesis that these deep-diving marine whales may be using an upregulated lipid metabolism pathway as an adaptation to hypoxia.