Photo/Illutration A dugong named Serena swims at the Toba Aquarium in Toba, Mie Prefecture, in September 2018. (Takunori Yasuda)

OTSU, Shiga Prefecture--Researchers have developed a new way to locate habitats of the elusive dugong, an endangered type of sea cow, by analyzing DNA left behind in the water from its skin and saliva.

If it proves effective, it could lead to better preservation of a species nearing extinction.

The new technique, created by scientists from the Ryukoku University’s Graduate School of Science and Technology in Otsu and the Toba Aquarium in Toba, Mie Prefecture, is expected to lead to a better understanding of the marine mammal’s ecology and distribution.

“It is really difficult to locate dugongs in the vast expanses of the ocean,” said Yoshihito Wakai, deputy director of the Toba Aquarium. “If their habitats are located with the recently devised method, it will become possible to take focused environment protection measures in specific waters.”

Yumiko Hiraishi, 24, a graduate student at the school, and her colleagues, used polymerase chain reaction (PCR) technology to make copies of their DNA sequences for analysis. The researchers isolated a DNA arrangement unique to dugongs from available sequences of the marine creature, allowing them to produce an artificial copy of its DNA.

The Toba Aquarium, the only facility in Japan with a dugong, named Serena, provided water samples collected from Serena’s tank. The new method was also successfully tested using a DNA sample from a dead dugong found in March 2019 in Okinawa.

Manatees are a species closely related to dugongs, but manatee DNA copies cannot be made using this technique. That makes it unlikely that the DNA sequences of other animals can be mistaken with those of dugongs when using this method.

Currently, scouting for dugong habitats requires a lot of work and money for aerial location or diving surveys.

But the new discovery is expected to lead to discovering where they live much more easily through lab examinations of seawater samples from many different locations--specifically, by identifying environmental DNA discharged from debris the animals leave behind floating in the water, like saliva and peeled skin fragments. 

That would eliminate the need for experts to travel to research sites.

Dugongs used to inhabit a wide range of areas from the Yaeyama island archipelago to Okinawa's main island. But their numbers plummeted after many were caught in fishing operations.

Only a few of dugongs are said to now live in waters off Okinawa’s main island.

For that reason, the dugong is listed by the Environment Ministry in the “Endangered Class IA” category, meaning the species has a high likelihood of going extinct in the wild in the very near future.

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