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Student Research Highlight - John Swenson

Meet John Swenson. He took a minute to tell us a little bit about himself and his research.

Q. How did you get started in this field?

John: I have felt magnetized to sharks and rays for a very long time now. When my family and I used to visit the local aquarium, I would plant myself on the ground and watch the single ragged-tooth shark swim in circles around its tank. As an adult, I still find myself spending an inordinate amount of time staring transfixed at the elasmobranchs (sharks and rays) whenever I visit an aquarium or see one in the wild. Manta rays are particularly awe-inspiring: the way they combine size, grace, and curiosity is simply unmatched. Watching them fly through the water with such agility and elegance has touched me in a profound way.


Q. Can you tell us a little about your research? 

John: I am investigating the mechanisms by which manta rays and their relatives have evolved their beautiful diamond-shaped body plan. This unique body plan is shared by other rays of the family Myliobatidae, of which manta rays, devil rays, cownose rays, and bat rays (among others) are members. Part of what makes this body plan unique is the presence of a third set of functional, paired appendages called "cephalic lobes," which are only found in this group. Cephalic lobes are thought to have evolved from the anterior pectoral fins of ancestral stingrays and the feeding benefits they provided may have allowed the myliobatids to transition away from a bottom-dwelling lifestyle. Using an approach rooted in comparative transcriptomics, I aim to identify some of the genetic pathways that have been modified in conjunction with the evolution of the unique cephalic lobes and diamond-shaped pectoral fins that constitute the elegant body plan of the myliobatids.


Q: Explain the relevance of your study system or something interesting about the taxa/taxon of interest? 

John: Healthy ecosystems contain a certain level of genetic diversity both within and across species. In order to accurately assess (and therefore preserve) the genetic diversity present in an ecosystem, we must understand which genetic elements are conserved and which are variable across a wide range of taxa with various adaptive traits. Most of what we know today about the genetic evolution of trait diversity has come from studies focused on model taxa, while the majority of diversity present in nature is harbored by non-model taxa, like stingrays. Myliobatids also occupy an interesting phylogenetic position within the cartilaginous fishes (Class Chondrichthyes), themselves the only extant sister group to all other vertebrates with jaws. Studying the genetic evolution and development of adaptations unique to myliobatids may reveal much about the genetic underpinnings of biodiversity and the generation of phenotypic disparity.  Understanding these issues may ultimately help us to understand and conserve genetic diversity within threatened ecosystems.


Q. What are your other research & career goals?

John: Next-generation sequencing techniques, like those that are being employed in this project, have much potential for applications in conservation biology. The present project will shed light on the long-term adaptive mechanisms that have helped myliobatids adapt to past environments, but we can also use next-generation sequencing to help us understand the short term adaptive mechanisms being employed by sharks and rays in the present as they face climate change, oil spills, over-fishing, and other human-caused disturbances. By looking at how myliobatids have adapted to past and present environmental pressures, we may be able to predict how they will adapt to those that will arise in the future and this information will help us to hone future conservation efforts.

Thanks John and good luck!