Japanese scientists say they have identified a new species of whale, a remarkable discovery if confirmed.
The animal is a type of baleen, the family of whales that strain tiny plankton and other food from seawater, the researchers say.
"Can you imagine? An animal of more than 10 meters was unknown to us even in the 21st century," said Tadasu Yamada of Tokyo's National Science Museum, the senior author of the study that appears in this week's issue of the journal Nature.
Most baleens grow to enormous proportions. The blue whale, for instance, at 75 feet long and more than 100 tons, is believed to be the largest animal that has ever lived.
By comparison, the new species is on the small side at about 30 feet long – about the size of a motor home – and slender.
While new species of smaller creatures such as insects, birds and amphibians are discovered every year, it is very unusual for scientists to identify a new mammal, particularly one so large. Most whale species were described during the 18th and 19th centuries when commercial whaling drove many to the brink of extinction.
Scientists currently recognize 70 whale species, including as many as 12 types of baleen whales. But little is known about the subtle differences among many types of whales that are seldom seen by humans.
The Japanese researchers made their discovery through DNA analysis of nine adult whale carcasses. Eight – five females and three males – were killed in 1970 for research in the eastern Indian Ocean and the Solomon Sea. At the time, scientists assumed they were undersized fin whales.
A ninth whale – a female – was killed accidentally in the Sea of Japan in 1998. Fisherman towed it to Tsunoshima Island, where Yamada examined it. Later, he began comparing it to preserved samples of the eight whales in his nation's fisheries research collection. The anatomical and molecular comparison took several years to complete.
Nearly every whale carcass raises new possibilities. It could take additional studies over several years before other biologists accept the new whale species.
According to the Nature study, the new species shows several differences from fin whales, including external features, bone structure and DNA. The researchers named the new species Balaenoptera omurai in honor of the late Japanese whale researcher, Dr. Hideo Omura.
Besides being smaller than fin whales, the new species has fewer baleen plates in its mouth, Yamada says. Baleen is a hornlike substance that forms filaments that hang down from the roof of the mouth to strain food from seawater.
DNA analysis performed on samples from three of the whales showed they differ from fin whales by five nucleotides, or base pairs of amino acids, in sections of the whale genome used for comparison.
Some U.S. researchers are skeptical of the Nature report.
James Mead, curator of marine mammals at the National Museum of Natural History at the Smithsonian Institution in Washington, D.C., said there are at least seven other whale species that share the same traits, and a more careful comparison is needed before a new species is accepted.
"I am disappointed in the lack of thorough comparison with other species of allied whales," Mead said.
Harvard University whale researcher Joe Roman said the evidence for classifying them as a new species was "compelling and certainly warrants further study."
Researchers on both sides of the Pacific said the questions surrounding the nine whales demonstrate how little is known about the mammals. They condemned whale hunting, even for scientific purposes.
In 1986, the International Whaling Commission imposed a moratorium on commercial whaling. Japan, however, takes hundreds of whales a year under a scientific exemption, usually selling them for food and other products after they are studied.
Norway has ignored the ban since 1993 and resumed commercial hunting, while Iceland resumed scientific whaling this year.
Yamada said the new species is a small population, which should be studied more carefully before countries decide to harvest the whales for research.
Roman agreed, saying, "research whaling could actually endanger this exciting discovery."