Killer whales, researchers have noticed for some time by different behaviors. Photo: Robert Pittman, public domain
Read aloud The killer whales living in the oceans around the world do not belong? as previously thought? all of the same kind. There seems to be at least three distinct species of this orca, also known as orca, and a whole range of subspecies, Danish and American researchers have now discovered in a genetic analysis of 139 tissue samples from different regions. Since orcas live in isolated groups, some of which have very different dietary preferences and behaviors, the findings support the earlier assumptions that they may be different species, according to Phillip Morin of the Scripps Institute of Oceanography at La Jolla and his colleagues. Although killer whales from different regions are relatively similar visually except for slight differences in body size and pattern, they differ in some ways significantly in their way of life. For example, some prefer coastal areas as a habitat while others live in open water. Some are more sedentary, others are roaming around. Her songs and other behavior are not completely consistent either. The most notable, however, are the differences in diet: some groups eat exclusively fish, others prefer a mixed diet of fish and mammals, such as seals, and still others feed exclusively on mammals.

Nevertheless, so far all animals were considered as a single species. The different groups were indeed considered as different types, of which interestingly, in part, several lived in the same habitat. However, a more detailed classification was difficult, as little was known about the hereditary composition of the animals. The few areas that had already been sequenced also provided only incomplete information? among other things, because the rate of change of DNA over time is extremely low in whales. To get around this problem, Morin and his colleagues have now used modern sequencing methods that allow much more samples to be analyzed in less time than before. They focused on the genome of the mitochondria, the small power plants within the cells that are always transmitted through the maternal lineage and are therefore often used for the elucidation of lineages.

The building block sequence showed three distinctly different groups that corresponded to three types already known and, according to the researchers, should be classified as distinct species. The lineage of one of these species, which lives in the eastern North Pacific, has already separated from the other killer whale groups about 700, 000 years ago, much earlier than previously thought. The other two newly identified species live in the southern oceans around the Antarctic and have been developing independently for about 150, 000 years. For the other groups, the data is currently not enough to be able to clearly integrate them, write the scientists. The more detailed knowledge of the Orca family tree is important because it can help to better understand the individual variants? and to better protect them as well.

Phillip Morin (Scripps Institute of Oceanography, La Jolla) et al .: Genome Research, doi: 10.1101 / gr.102954.109 ddp / wde? Ilka Lehnen-Beyel advertisement

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