Genetic Sequencing Splits the Orca Family


Sure it's an orca, but what kind of orca is it? Image credit: *christopher*/Flickr

The orca may be a Sea World mainstay, but new research is confirming how little we know about the species. In fact, recent genetic analysis suggests that the widely-distributed Orcinus orca may be made up of several distinct species—a revelation that would have serious implications for conservation efforts around the world.SLIDESHOW: Dolphins, Magnificent Mammals

The research, conducted at the Southwest Fisheries Science Center, used a new method of genetic analysis called "highly parallel sequencing," which yields faster results than traditional methods. Using this method, researchers isolated several "ecotypes" of killer whale.

Phillip Morin, lead author of the study, explained:

The genetic makeup of mitochondria in killer whales, like other cetaceans, changes very little over time, which makes it difficult to detect any differentiation in recently evolved species without looking at the entire genome...but by using a relatively new method called, 'highly parallel sequencing' to map the entire genome of the cell's mitochondria from a worldwide sample of killer whales, we were able to see clear differences among the species.

So far, the following four types have been suggested for separate species status:


Image credit: Bob Pitman, NOAA Southwest Fisheries Science Center

The first new species is the "pack ice killer whale" from the Antarctic. It is distinguished by its large eye-patch and two-tone gray color pattern. This killer whale is a "mammal killer," surviving mostly on a diet of seals.


Image credit: Bob Pitman, NOAA Southwest Fisheries Science Center

The second species is the "Ross Sea killer whale," also from the Antarctic. It is the smallest of the Antarctic types and are distinguished by their narrow angled eye patch. They survive on fish, which they follow deep into the ice as it breaks up in the summer months.


Image credit: Dave Ellifrit, NOAA Alaska Fisheries Science Center

The "North East Pacific Transient killer whale" is found in Alaska. Though its black and white color pattern and eye-patch is very similar to some Antarctic killer whales, it was found to be genetically distinct. The Transients have been observed feeding on all types of marine mammals, including whales, dolphins, and seals, and sea lions.


Image credit: John Durban, NOAA Southwest Fisheries Science Center

Researchers were not able to determine a specific species for the final type, a common Antarctic variety. Found in open water areas, this orca feeds primarily on other cetaceans.

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They pointed out that establishing specific species definitions is critically for developing effective conservation and resource management plans.

The world of the orca, it turns out, is a bit like a black-tie dinner: A lot of variety obscured by the same black-and-white tuxedos.

Read more about killer whales:
Ocean Film Fest 2010: A Killer Whale Takes Down A... Great White Shark?? (Video)
Screaming to be Heard Over Ship Noise is Taking It Out of Killer Whales
Was "Free Willy" Better Off in Captivity?

Tags: Animals | Conservation | Oceans