Biologists from the CMU Faculty of Science successfully use environmental DNA (eDNA) to explore rare species in Thailand’s major rivers, which would facilitate an aquatic organisms survey in a non-disruptive manner.
Studying the distribution of aquatic species is vital to the conservation, fertility, evaluation, and monitoring of alien species invasion. However, traditional methods involve capturing target organisms using tools such as fishing nets, seines, and rods, or even electricity. Not only do these approaches pose several limitations depending on the water conditions, they are also incapable of surveying all kinds of species, particularly the rare ones, and disrupt aquatic life.
Environmental DNA is short DNA fragments that organisms release into the environment, including soil, water and air. In addition to being useful in studying organisms living in that environment, this approach is quick, convenient, and highly accurate. Thus, the application of eDNA to the study of aquatic organism distribution, instead of traditional equipment, proves to be significant as it yields high accuracy in detecting organisms, even at small amounts, and is not destructive to the ecosystems in which the organisms live.
A team of biologists from the CMU Faculty of Science, led by Assoc. Prof. Dr. Maslin Osathanunkul, conducted a targeted survey of amphibians and fishes in different water sources using the eDNA from water samples. An example of a local amphibian is the Chiang Mai crocodile newt, Tylototriton uyenoi, a Vulnerable (VU) species whose data on natural distribution is scarce. From the fish species there is the Mekong giant catfish (Pangasianodon gigas), which is in the Critically Endangered (CR) category, and the giant snakehead (Channa micropeltes), which is the main reason for the decline in fish diversity.
Research shows that eDNA, as a method to survey the population and the distribution of aquatic organisms living in the major rivers of Thailand, such as the Chao Phraya and Mekong rivers, as well as in large reservoirs, is quicker, more efficient and more accurate than the traditional methods that are currently employed. Moreover, it is applicable in planning the conservation for endangered species, as well as in raising awareness on aquatic biodiversity.
Dr. Maslin also has collaborated with researchers from Switzerland and the UK to use the eDNA method in combination with next generation sequencing (NGS) to survey and identify fish species found in the Chao Phraya watershed, which includes the Ping, Wang, Yom, Nan and Chao Phraya Rivers, allowing for a comprehensive view of the biodiversity, and quicker and more accurate identification of fish species living in the areas of study.
For future research, Dr. Maslin and her team are interested in expanding the scope of study to the application of eDNA to marine organisms tracking, with the emphasis on assessing the risk of encountering venomous jellyfish found along Thailand’s Andaman and Gulf of Thailand coasts.