In 1950, a Norwegian scientist concluded that B. edeni and B. brydei were the same species and per protocol recognized the species as B. edeni since that was how it was first described. Bryde's whale was retained as the common name.
Then, in the 1970s, Japanese researchers killed what they believed were Bryde's whales from ocean waters around Indonesia and the Solomon Islands. In 1991, Wada recognized these eight specimens as distinctive from all other rorquals, including Bryde's whales.
To make things even more confusing, Bryde's whales, from a distance, look a lot like Sei whales (B. borealis), said Baker. The differences are notable only upon close inspection of the morphology.
"We've tended to think of this as the Bryde/Sei whale complex," said Baker. "It is not clear how many species it might include or who is most closely related to whom."
Yamada, Wada, and Oishi compared the morphology, bone structure, and mitochondrial DNA of the eight specimens killed by the Japanese researchers in the 1970s with that of one whale that washed ashore a coastal island in the Sea of Japan in 1998.
As a whole, the researchers determined from outside appearance this group of specimens most closely resemble a smaller version of the fin whale (B. physalus), but owing to differences in skull shape, baleen plates, and DNA they concluded that the group represents a new species of baleen whale, B. omurai.
According to the description in Nature, B. omurai has an adult body length of less than 40 feet (12 meters) long, a relatively broad and flat skull, and a mouth that tapers from its base.
Based on morphological differences, the researchers also concluded that Bryde's whale and Eden's whale are distinct from each other as well as distinct from the new species, B. omurai.
Baker said that analysis of DNA from the B. edeni holotype specimen in Calcutta and morphological examination of additional specimens would be important to confirm the new taxonomy.
Yamada's team was not able to obtain a DNA sample of the B. edeni specimen in Calcutta but instead used DNA from a matching specimen at the National Museum of Natural History, in Leiden, Netherlands.
"They are basically making the argument that the edeni holotype is different from the new species, omurai. If that is right, the proposal to name the new species is valid," said Baker, who added that regardless of the nomenclature, the clarification of the species-level differences is biologically sound and important for conservation.
The next challenge for the Japanese researchers, said Yamada, will be determining the relative abundance and distribution of B. omurai, B. edeni, and B. brydei.
Yamada is currently aware of ten B. omurai specimens stored in museums around the world that were misclassified as Bryde's whales and he expects more to be found in the oceans.
"If we are careful in getting information from stranded animals, we can make some distribution patterns of these three species," he said.
Baker said that understanding the abundance of the various Balaenoptera species is critical because the Japanese have proposed to the International Whaling Commission (IWC) a commercial hunt of Bryde's whales.
"Currently, all baleen whales are protected by an international moratorium on commercial hunting. If this moratorium were to be overturned, however, you need to understand both taxonomic identity and population structure in order to estimate abundance and calculate an appropriate catch limit," he said.
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