Taxonomy
Nomenclature
The genus name, Balaenoptera, means winged whale,[6] while the species name, musculus, could mean "muscle" or a diminutive form of "mouse", possibly a pun by Carl Linnaeus[6][7] when he named the species in Systema Naturae.[8] One of the first published descriptions of a blue whale comes from Robert Sibbald's Phalainologia Nova,[9] after Sibbald found a stranded whale in the estuary of the Firth of Forth, Scotland, in 1692. The name "blue whale" was derived from the Norwegian blåhval, coined by Svend Foyn shortly after he had perfected the harpoon gun. The Norwegian scientist G. O. Sars adopted it as the common name in 1874.[10]
Blue whales were referred to as "Sibbald's rorqual", after Robert Sibbald, who first described the species.[9] Whalers sometimes referred to them as "sulphur bottom" whales, as the bellies of some individuals are tinged with yellow.[11] This tinge is due to a coating of huge numbers of diatoms.[11] (Herman Melville briefly refers to "sulphur bottom" whales in his novel Moby-Dick.[12])
Evolution
| A phylogenetic tree of six baleen whale species[13] |
Blue whales are rorquals in the family Balaenopteridae. A 2018 analysis estimates that the Balaenopteridae family diverged from other families in between 10.48 and 4.98 million years ago during the late Miocene.[13] The earliest discovered anatomically modern blue whale is a partial skull fossil from southern Italy identified as B. cf. musculus, dating to the Early Pleistocene, roughly 1.5–1.25 million years ago.[14] The Australian pygmy blue whale diverged during the Last Glacial Maximum. Their more recent divergence has resulted in the subspecies having a relatively low genetic diversity,[15] and New Zealand blue whales have an even lower genetic diversity.[16]
Whole genome sequencing suggests that blue whales are most closely related to sei whales with gray whales as a sister group. This study also found significant gene flow between minke whales and the ancestors of the blue and sei whale. Blue whales also displayed high genetic diversity.[13]
Hybridization
Blue whales are known to interbreed with fin whales.[17] The earliest description of a possible hybrid between a blue whale and a fin whale was a 20 m (66 ft) anomalous female whale with the features of both the blue and the fin whales taken in the North Pacific.[18] A whale captured off northwestern Spain in 1984, was found to have been the product of a blue whale mother and a fin whale father.[19]