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Now that we have landed in our new home in Nahant, we are learning a bit about our new colleagues and the research that they are doing here at the Marine Science Center-- and sharing what we learn with you. In this issue, we talk to Dr. Bill Detrich and learn about icefish. Read on to see how the Detrich lab is using genomics to understand how these "white-blooded" fish evolved and the potential applications they may have for human blood and bone diseases.
And, as always, follow our expeditions and other news from the marine world on our Facebook and Twitter pages!
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Antarctic icefish genomic research
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The Research Vessel Icebreaker Nathaniel B. Palmer at Grytviken, South Georgia during the ICEFISH 2004 Cruise, organized and led by Dr. H. William Detrich
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Nearly all vertebrate species, from fishes to humans, use red blood cells, full of the red protein hemoglobin, to carry oxygen to their tissues and cells. Yet Antarctic icefishes (family Channichthyidae, suborder Notothenioidei) have lost the capacity to make red blood, presumably because many of the genes necessary for red blood cell formation have been lost or mutated. So why don't they make red blood cells? And how do they get the oxygen they need?
Bloodthirsty...
The Detrich lab is using a comparative approach to learn how Antarctic icefish lost their red-blood cells. By comparing the genes of "white-blooded" and closely related red-blooded species, they look for genetic differences that might be involved in red cell formation.
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The icefish Pagetopsis macropterus. This fish is one of the 16 species of icefish, all of which fail to make red blood cells or produce the oxygen transporter hemoglobin.
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The lab has already identified two genes necessary to make red blood cells-- hemogen (also known from the mouse and human genome projects) and a second previously undiscovered gene that they've dubbed "bloodthirsty." The surprising similarity of these genes to the corresponding human genes highlights the potential value of Detrich's results for human disease research. For example, people with a variety of different diseases require dialysis treatments to "clean" their blood when their own kidneys can't. Unfortunately, dialysis tends to destroy red blood cells, and so doctors administer drugs to stimulate red cell development. Detrich's research may point toward new ways to stimulate red cell production.
White-blooded...
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Red-blood vs. white-blood: The red blood is from the Marbled Notothen (Notothenia rossii). The white blood is from the Blackfin Icefish (Chaenocephalus aceratus).
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So how do icefishes function without red blood cells? It turns out they have some distinctive traits compared to closely-related red-blooded species. The icefishes' hearts are four times larger, their blood vessels carry 4-5 times more blood, and their gills are much larger than their red-blooded cousins. In addition, they can "breath" through their scaleless skins!
The icy cold water of their Antarctic home also contributes to the icefishes' "alternative lifestyle." Cold water holds more oxygen than warmer water and frequent Antarctic storms and strong currents help to keep the cold water "well-mixed" and full of oxygen. It's unlikely that the icefishes' unique physiology could have evolved in warmer, oxygen-poor temperate or tropical waters.
The history of the Southern Ocean is also relevant to icefish evolution. The Southern Ocean cooled substantially during the Miocene epoch (23-5 million years ago), effectively chasing away temperate fish species. The notothenioids, able to tolerate cooler temperatures, remained and diversified without competition from their heat-seeking brethren. This "species radiation" led to one of the best-known examples of a marine species "flock," or a group of closely related species that evolved rapidly in an isolated area.
Marine comparative genomics and OGL...
Dr. Detrich is planning his 20th expedition to Antarctica in April 2014. Supported by the National Science Foundation, he's been working at Palmer Station, located almost 1,000 nautical miles below the tip of South America, since 1983. Detrich uses a small scientific trawl to capture his targets while minimizing disturbance to the ocean floor. Luckily for OGL, he's planning to bring back many samples for the Ocean Genome Resource collection to share with other researchers and to preserve for the future. In addition, he hopes to use some of the diverse fish genomes already archived at OGL to expand his research program and to look at other major events in the evolution of fish and other vertebrates.
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Dr. Detrich and Corey Allard at Palmer Station, Antarctica. Corey was Northeastern University's first undergraduate to have a co-op experience in Antarctica!
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Coming Soon... More MSC Research Highlights
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We'll highlight more of the exciting research going on at Northeastern's Marine Science Center and focus on the ways OGL can contribute to its new community.
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DONATE TO OGL
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Want to help OGL document and preserve the spectacular genetic diversity of our world's oceans? Visit
www.northeastern.edu/marinescience/support-the-msc/
and specify "OGL" in your gift.
Thanks for your continued support!
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