Genomic Analysis Indicates Mulitples Species of Killer Whale

April 22, 2010
Type-B “pack ice killer whale” from the Antarctic. Note the large eye-patch and two-tone gray color pattern. This type specializes in hunting seals, which are often on the ice and need to be knocked off the ice by the whales before they can be caught. Photo Credit: Bob Pitman, NOAA Southwest Fisheries Science Center

In a report published today in the journal Genome Research, scientists report finding strong genetic evidence supporting the theory there are several species of killer whales (Orcinus orca, also known as orcas) throughout the world's oceans.

Scientists have suspected for some time that there was more than one species of because of differences in behavior, feeding preferences and subtle physical features. But until now analysis has been inconclusive because of the inability to map the entire genetic picture, or genome, of the whales' mitochondria, an organelle within the cell inherited from the mother.

"The 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," said Phillip Morin, lead author and geneticist at NOAA's Southwest Fisheries Science Center in La Jolla, Calif. "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."

In all, tissue samples from 139 killer whales were analyzed. Samples came from killer whales found in the North Pacific, the North Atlantic and oceans surrounding Antarctica. As a result of the study, two types of killer whales in the Antarctic that eat fish and seals, respectively, are suggested as separate species, along with mammal-eating "transient" killer whales in the North Pacific. Several other types of killer whales may also be separate species or subspecies, but additional analysis is required.

Highly parallel sequencing of DNA is far faster and less costly than historical methods of analysis. For instance, the examination of genome in one sample could have taken as long as several months. But with the use of high throughput sequencing, researchers can complete the same analysis for 50 or more samples in just a few weeks, and technology to sequence larger parts of the and more individuals continues to improve rapidly.

Determining how many of killer whales there are is critically important for resource managers to establish conservation priorities and to better understand the ecological role of this large and widespread predator in the world's oceans.

Explore further: Whales die in Tasmanian stranding

More information: Morin PA, Archer FI, Foote AD, Vilstrup J, Allen EE, Wade P, Durban J, Parsons K, Pitman R, Li L, Bouffard P, Abel Nielsen SC, Rasmussen M, Willerslev E, Gilbert MTP, Harkins T. Complete mitochondrial genome phylogeographic analysis of killer whales (Orcinus orca) indicates multiple species. Genome Res, doi:10.1101/gr.102954.109

Related Stories

Orcas most polluted Arctic mammal

December 12, 2005

Orcas, or killer whales, reportedly have passed the polar bear to become the most contaminated mammal in the Arctic.

Older killer whales make the best mothers

February 3, 2009

Killer whales (Orcinus orca) nearing the menopause may be more successful in rearing their young. New research published in BioMed Central's open access journal Frontiers in Zoology shows that estimated survival rates for ...

Zoning the ocean may help endangered whales to recover

December 16, 2009

Scientists in Scotland, Canada and the US have proposed a new method to identify priority areas for whale conservation. The team's findings, published in Animal Conservation, suggest that even small protected areas, identified ...

Recommended for you

New insights into the production of antibiotics by bacteria

July 31, 2015

Bacteria use antibiotics as a weapon and even produce more antibiotics if there are competing strains nearby. This is a fundamental insight that can help find new antibiotics. Leiden scientists Daniel Rozen and Gilles van ...

Out of the lamplight

July 31, 2015

The human body is governed by complex biochemical circuits. Chemical inputs spur chain reactions that generate new outputs. Understanding how these circuits work—how their components interact to enable life—is critical ...

Cell aging slowed by putting brakes on noisy transcription

July 30, 2015

Working with yeast and worms, researchers found that incorrect gene expression is a hallmark of aged cells and that reducing such "noise" extends lifespan in these organisms. The team published their findings this month in ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.