for National Geographic News
The number of rorqual whale species swimming in the world's oceans has jumped to eight from six, according to new research by a team of Japanese scientists published in tomorrow's issue of the science journal Nature. The research shows that rorquals commonly referred to as Bryde's whales actually represent three distinct species.
Rorqual whales (Balaenoptera) do not have teeth. Instead they have baleen, a horny substance found in rows of plates along their upper jaws, and they are thus classified as baleen whales. They range from about 26 to 92 feet (8 to 28 meters) in length and weigh upwards of 220,000 pounds (100,000 kilograms).
Rorquals are found throughout the world's oceans and are distinguished by their long bodies and pleated throats. Their most familiar species are the common minke whale (B. acutorostrata) and the blue whale (B. musculus).
The Japanese scientists identified a new species of rorqual, Balaenoptera omurai, and resolved a long-standing debate by showing that other whales previously referred to as Bryde's whale are indeed distinct species: (B. brydei) and (B. edeni).
"It was not a big surprise to me that we encountered the species we described," said Tadasu Yamada, a biologist at the National Science Museum in Tokyo and co-author of the research describing the species.
Scott Baker, an associate professor of population genetics and evolution at the University of Auckland in New Zealand, said limited access to the holotype of B. edeni (a holotype is the museum specimen that represents the species for taxonomic purposes) and to other specimens of the rarer B. omurai had previously prevented the scientific community from closely studying the various Balaenoptera species.
Yamada and colleagues Shiro Wada of the National Research Institute of Fisheries Science in Yokohama and Masayuki Oishi of the Iwate Prefectural Museum in Morioka, gained access to the specimens and based their conclusions on a comparison of the species' morphology (body form), bone structure, and DNA.
"Scientists, noted Yamada, rely on access to museum specimens—many of them more than 100 years old—to do their work. By applying improved techniques to these specimens, the researchers can mine new knowledge—in this case an improved understanding of taxonomy.
"The basic conclusion that there are a number of taxa from a single group is sound," said Baker. "But there will be some skepticism about how they were able to resolve the previous taxonomy because of the nature of the holotype specimens."
Bryde/Sei Complex
Since Wada noted a distinct Bryde's whale in a 1991 study and Baker and his colleagues found B. edeni in Korean markets in 1994, there have been scientific murmurings that there could be "more than one species in the group of whales known as Bryde's whale," said Yamada.
The confusion over the Balaenoptera species dates back to the original description in 1878 of a specimen stranded in Burma and now located in a museum in Calcutta, India, as B. edeni. A second species found in 1913 off the coast of South Africa was informally described as B. brydei.
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