London: Marine scientists have discovered that two species of dolphin in the waters off Bangladesh are genetically distinct from those in other regions of the Indian and western Pacific Oceans.

The finding supports a growing body of evidence that the Bay of Bengal harbours conditions that drive the evolution of new life forms.

In the comparative study using DNA collected from both Indo-Pacific humpback dolphins (Sousa chinensis) and Indo-Pacific bottlenose dolphins (Tursiops aduncus) and data from previous genetic studies, the researchers found that both populations of both species are distinct from populations in other parts of the Indian Ocean and western Pacific.

This discovery follows the recent description of a possible new species of ‘river shark’ in the same waters.

‘Our findings indicate that there is a connection between the presence of these distinct populations of dolphins and the unique oceanic habitat that is found in the Bay of Bengal,’ said lead author of the study Ana Amaral of the Centre for Ecology, Evolution and Environmental Changes, Universidade de Lisboa, Portugal.

‘The combination of a biologically rich yet isolated seascape could be driving speciation, or the emergence of new species,’ Amaral noted.

Located in the northern Indian Ocean, the Bay of Bengal receives vast amounts of freshwater and organic matter from the Meghna, Brahmaputra, and the Ganges Rivers. The confluence also supports the world’s largest mangrove forest.

During the study, researchers collected skin samples from 32 coastal Indo-Pacific and humpback dolphins.

The study published in the journal Conservation Genetics showed that two species of dolphin in the waters off Bangladesh are genetically different from neighbouring populations, a tantalising result that the authors say merits further investigation.

‘The discovery of genetically distinct dolphin populations helps us to expand the body of knowledge of how these dolphin species have changed over time,’ said Howard Rosenbaum, Director of Wildlife Conservation Society’s Ocean Giants Programme.