photo: j.p. Sylvestre
A new type of orca has made its debut in Drake Strait. It lives off the waters of Antarctica.
They are being preliminarily identified as Type D orcas, and they seem to be a divergence in species that might have occurred 400,000 years ago. This finding points to the possible continuing evolution of the species in the future, and that further species may evolve from present ones.
Type D orcas only live in frigid waters or sub-Antarctic waters.
The reason why people believe this species might not have been identified before is because they live in such treacherous waters that no one was able to observe them before.
The first Type D orca was thought to have been sighted in 1955, when a pod of the orcas became stranded off the New Zealand coast. They differ in body from the orcas widely known for having a shorter and sturdier body. Their dorsal fins are also quite different.
A skeleton from one of the marooned orcas was preserved in the Museum of New Zealand Te Papa Tongarewa.
For a long time, scientists did not know if this was an infraspecies mutation or a single species onto itself.
The cetaceans were spotted again in 2004, when the first pictures of the orcas at large were taken.
This prompted scientists to extract DNA from the skeleton preserved in the New Zealand. The sequencing revealed that the species is extremely different from the other orcas. They are so different, that the divergence in the species could go back almost half a million years.
Although this is recent in evolutionary terms, it is long enough to have caused significant genetic mutations in the genome. These are believed to be adaptive differences.
Source : Wired./ 7.1.13
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