Friday, February 7, 2014

An old new whale species

Mesoplodon hotaula, Seychelles, 2009
Beaked whales are a widespread but little-known family of toothed whales that are distantly related to sperm whales. They are are found in deep ocean waters beyond the edge of the continental shelf throughout the world's oceans and rarely seen at sea due to their elusive habits, long dive capacity and apparent low abundance for some species. A lot of what we know about the diversity of beaked whales is actually the result of strandings on the world's shores.

On 26 January 1963, a female beaked whale washed ashore at Ratmalana, Sri Lanka. The stranding was reported by the director of the National Museums of Ceylon, P. E. P. Deraniyagala, who described the whale as a new species, Mesoplodon hotaula, deriving the species name from the local Sinhala words for “pointed beak.” Deraniyagala provided no diagnosis by which Mesoplodon hotaula could be differentiated from the other Mesoplodon beaked whales known at that time, except to note that the position of the teeth differed from that of Mesoplodon bidens and Mesoplodon hectori. Two years after it was described, Mesoplodon hotaula, still known only from the holotype, was synonymized with the ginkgo-toothed beaked whale, Mesoplodon ginkgodens. 

Now it turns out that Deraniyagala was right regarding the uniqueness of the whale he described. While the specimen is closely related to the ginkgo-toothed beaked whale, it is actually a representative of a distinct species. An international group of researchers provided genetic and morphological evidence for the distinctiveness of Mesoplodon hotaula, now known from at least seven specimens. The new specimens are held by various institutions and groups, including the US Smithsonian National Museum in Washington DC, the Island Conservation Society in the Seychelles, and the University of Auckland, New Zealand. 

The researchers were able to get good quality DNA from tissue samples from only one specimen. For the remaining ones, they drilled into the bones of the whales in order to analyse short fragments of 'ancient DNA' relying on techniques commonly used with old sub-fossil material from extinct species. The colleagues were able to show that both lineages can be differentiated by maternally (DNA Barcodes), biparentally (autosomal nuclear introns), and paternally (Y-chromosome intron, DBY7) inherited DNA sequences, as well as by morphological features (Cranial and mandibular measurements). The analysis also included all other known beaked whale species to confirm the distinctiveness of Mesoplodon hotaula, including six specimens of the closely related, gingko-toothed beaked whale. The latter is only known from about 30 strandings and has never been seen alive at sea with any certainty.

Wow - it took us 50 years to collect enough evidence to resurrect a species. It is so little we know about life in the ocean despite all the hard work put in so far. That reminds me of a quote from the book "Half Mile down" by William Beebe (1934):

"... the only other place comparable to these marvelous nether regions, must surely be naked space itself, out far beyond atmosphere, between the stars, where sunlight has no grip upon the dust and rubbish of planetary air, where the blackness of space, the shining planets, comets, suns, and stars must really be closely akin to the world of life as it appears to the eyes of an awed human being, in the open ocean, one half mile down." 

1 comment:

  1. Scott Baker one of the authors of the study tried to post in the comments. Apparently that didn't work. I thought I do it for him:
    Thanks for the quote from William Beebe, describing the domain of beaked whales, species which regularly dive to depths greater than 'one half mile down'.

    Readers might also be interested in evidence that the newly re-discoverd beaked whale, Mesoplodon hotaula, is occasionally consumed by people of the Gilbert Islands in Kiribati

    Baker, C.S., A. Hutt, K. Thompson, M.L. Dalebout, J. Robins, R.L. Brownell and G.S. Stone. 2013. Species identity and human consumption of beaked whales in the Gilbert Islands, Republic of Kiribati. Animal Conservation 16:641-647.