New species of river dolphin identified in Brazil

Published January 24, 2014
 Species spotlight

A new species of river dolphin has been discovered in the Araguaia River basin of Brazil, the first new river dolphin to be described since 1918. The new species is called Inia araguaiaensis and the proposed common name is  “Araguaian boto” and “Boto-do-Araguaia”. Boto is the common regional and international name of species of Inia, and Araguaia refers to the geographic distribution of this species. Through DNA analysis, Tomas Hrbek of the Federal University of Amazonas in Manaus, Brazil, and colleagues found that Inia araguaiaensis differ from all other species in Brazil. The new species is also different in that it generally has a wider skull and fewer teeth. At a mitochondrial DNA level there is no evidence of the new species sharing lineages with other Inia species such as Inia boliviensis or Inia geoffrensis humboldtiana.

Distribution map of all known species and subspecies of Inia. (Hrbek et. al.)

Distribution map of all known species and subspecies of Inia. (Hrbek et. al.)

It is speculated that the new species formed 2.08 million years ago, when the Araguaia-Tocantins basin was cut off from the rest of the Amazon river system by huge rapids and waterfalls. It is possible that the shifting landscape isolated the dolphins from their fellows, because river dolphins are slow swimmers that rarely leap.

River dolphins are endangered and extremely rare, with three of the four known species listed by the IUCN’s as Vulnerable. Hrbek explains that the Araguaia river basin has been experiencing “significant anthropogenic pressure via agricultural and ranching activities, and the construction of hydroelectric dams” and that Inia araguaiaensis will most probably be classified as Vulnerable as well.

The discovery highlights the deficit in our knowledge of biodiversity and the potential impact of human actions on biodiversity.

 

Image by Nicole Dutra

Image by Nicole Dutra

Source: Hrbek T, da Silva VMF, Dutra N, Gravena W, Martin AR, et al. (2014) A New Species of River Dolphin from Brazil or: How Little Do We Know Our Biodiversity. PLoS ONE 9(1): e83623. doi:10.1371/journal.pone.0083623

 

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