Release Date: May 6, 2013
Robert Meredith, an assistant professor in Montclair State University’s Department of Biology and Molecular Biology wants to know “what makes a whale a whale.”
He is one of the authors of “Rod Monochromacy and the Coevolution of Cetacean Retinal Opsins,” published in the April 18, 2013 issue of PLOS Genetics. (http://www.plosgenetics.org/doi/pgen.1003432) The article’s findings, based on studies conducted when Meredith was a post-doctoral researcher in biology at University of California, Riverside (UCR), focus on the molecular evolution of whale visual pigments.
While whales and other cetaceans evolved from land-dwelling mammals, which had evolved from aquatic ancestors, they ultimately adopted a fully aquatic lifestyle between 40 and 49 million years ago. “This re-invasion of an aquatic habitat resulted in multiple morphological and molecular changes,” says Meredith. The eyes of deep-diving whales such as the giant sperm whale and Sowerby’s beaked whale show anatomical and molecular specializations that enhance their ability to see in the dim, blue light of underwater depths of more than 100 meters.
“Most mammals have a complement of three opsin genes – RH1, LWS and SWS1. In these whales, LWS and SWS1 are inactivated, which results in rod monochromacy since RH1 is the only functional photo pigment,” explains Meredith. This adaptation, which is unique among mammals, increases the whales’ sensitivity to the available blue light of deep waters. Interestingly, LWS was knocked out five times independently in Cetacea, including several times within baleen whales that do not dive as deep as sperm and beaked whales. This could be due to their needing to see bioluminescent schools of tiny prey at night.
Meredith’s UCR colleagues Mark Springer and John Gatesy received a five-year $800,000 award from the National Science Foundation Assembling the Tree of Life Project. Additional support came from a NSF collaborative award to John Gatesy to study the evolution of the feeding apparatus of baleen whales, such as blue, fin, humpback and bowhead whales. Meredith worked with them on an earlier study that offered the first genetic evidence for the evolutionary loss of teeth in baleen whales.
He remains involved in on-going projects with UCR colleagues that deal with whale evolution on a genetic level. “A molecular blue print describes the genetics behind what makes a whale a whale,” states Meredith. “Understanding the blue print is the biggest of big picture questions when it comes to understanding whale genetics.”
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