eDNA: Understanding life in a water drop!

Sribas Chowdhury, Adamas University, Kolkata

Quest for creatures

A team of wildlife researchers went on an expedition to Amazon forests. The study was carried out by NatureFirm, an eDNA company. It was headed by Kate Bruce who carried out the study for the charity World Wildlife Fund(WWF) The goal was to look for pink river dolphins, native to the Peruvian Amazon. For this, researchers collected the river water, which contained genetic materials. These genetic materials could be body fluids, scales, etc. They were supposed to help in tracking the dolphins. The team did find the things they were looking for with some twists.

Unexpected discoveries

The team got the genetic information of pink river dolphins. What they didn’t expect to find was genetic information of 675+ species in that same sample. The water sample collected contained the genetic material of many species of mammals and bats. This was fascinating, both in the genetic and ecological realms. It was particularly intriguing for people working in the field of eDNA.

Concept of eDNA

eDNA or environmental DNA is DNA collected from natural habitats of species. The sites could be waterbodies, soil, snow, or even air. Every part of the body of any organism contains DNA. So, as these organisms interact with their surrounding environment, they leave traces of their DNA. It could be in the form of much, feces, shed skin, or any other bodily fluid. These traces contain the genetic information of such organisms and can be analyzed through DNA sequencing. This method is especially useful to identify and locate the habitat of the unknown species that exist on Earth. It has been in use for almost 8 decades and recently has been gaining traction. IUCN has announced a $15 billion project called “eBioAtlas” to collect and analyze 30,000 samples of major freshwater river systems. This includes the Amazon, Ganges, and Mekong Delta and spans over 3 years.

Process and observations

The method used is called “tickle the fish”. The process started with collecting samples of river water. This river water contained genetic materials. While the main source is the feces, skin sheds, mucus, and other bodily products are also taken into consideration. The primary requirement of this process is that the scientists have to be clear about what they are looking for. If they are looking for mammals, then they need to do the DNA sequencing for that specific purpose. After the sequencing, the machine gives the information of almost 30 million DNA sequences. After that, the results are tallied with the available information on the species. While the results are believed to be accurate, 100% accuracy can’t be promised. This is mainly due to the lack of a foolproof reference database.

In this particular study,  the eDNA gave information about more than 675 species. This includes dozens of mammals like deer, jaguar, giant anteater, and 25 species of bats. This was a revolutionary discovery as it can help in speeding the process of discovery of rare and unknown species.

Conclusion and Future Prospects

The prospect of eDNA is indeed very promising for the future ecosystem. According to a recent database, only 20% of the species of fish could be identified in the Amazon. With climate change, a lot of unknown species are going extinct before discovery. This category of hidden species is called “dark diversity”. This method can help scientists uncover the dark diversity more and bring forward the vast array of species that dwell on this Earth. The scientists are hopeful that the method of eDNA collection and sequencing can be a “game-changer” in the field of identification and analysis of species diversity. The officials of IUCN are also keen on getting information and putting it in conservation tools such as the Red List of threatened species. This can help us uncover and see more of the vast array of species dwelling and can also aid in conserving them.

Also read: Effect of Hydrogen bonding on mitochondrial mutation

Reference:

1. “The world in a drop of water: DNA tool transforms nature tracking” (2021) https://phys.org/news/2021-09-world-dna-tool-nature-tracking.html

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