A team of scientists from Brazil and Scotland have discovered a new species of river dolphin, the first described in nearly 100 years. The study, published in PLoS One last week, used both molecular and anatomical evidence to identify the new species. The new dolphin species is named Inia araguaiaensis after the region in which it lives – the Araguaia River basin of Brazil.
The team, consisting of researchers from Federal University of Amazonas (UFAM), National Research Institute of the Amazon (INPA) and the University of Dundee, sampled 30-40 individuals from two known species and from the new candidate species. They looked at a variety of DNA including microsatellites – small sections of DNA that act as markers for genes- and mitochondrial DNA, which is inherited directly along the maternal line, allowing the tracking of genetic changes over many generations. Skull measurements were also taken to compare any anatomical changes that might differentiate the two dolphin populations.
These techniques found clear differences in both the genes and anatomy of Inia araguaiaensis and the other dolphin species measured. The authors of the paper acknowledge that critics may argue that this new dolphin is a subspecies rather than an entirely new species, despite their findings showing clear differences between the groups. More work to further identify and characterise this dolphin population may reduce this criticism.
The researchers estimate that this species diverged from it’s closest relative 2.08 million years ago. This is interesting because this is the period of time that the Araguiaia basin separated from the Amazon, leading the authors to suggest that the two events could be linked. It may be that this was not the only speciation event occurring during this river separation. Future studies could investigate other organisms to see if there are more undiscovered species lurking in the basins of Brazil.