NIFS said it sequenced the whole genome of Dokdo sea lion (Zalophus japonicus), commonly referred to as Gangchi in Korea that became extinct in the 1970s, and the article was published in the BMC Biology (Springer), the prominent international scientific journal.

The study team sequenced DNA from a total of 16 Dokdo sea lion bone fragments, excavated from Dokdo and Ulleungdo islands in Korea by applying genome-wide SNP analyses. With the application of the next-generation sequencing (NGS), the team succeeded in the whole genome sequencing within the big data (8.4TB) generated by overcoming physical limitations including a small sample numbers and low sequencing depth largely due to the degraded state of all Z. japonicus bone specimens.

The analysis for the first time validated Z. japonicus evolved as a completely independent separate species from California sea lion (Z. californianus) approximately two million years ago. Also, their findings raised the possibility of interspecific gene flow between other marine species including Northern fur seal, Stella sea lion, etc., providing new clues to the study on evolution of marine mammals inhabitating the Northern Pacific Ocean.

In particular, the study shed light on Z. japonicus maintained its genetic diversity before extinction, which represents the possibility that its extinction was influenced more by anthropogenic impacts than by genetic factors alone.

The article: “Dokdo sea lion Zalophus japonicus genome reveals its evolutionary trajectory before extinction” is of great significance in that it underscored national sovereignty over our endemic biological resources and Dokdo by using the name ‘Dokdo sea lion’ as the title of article. In addition, as the achievement of public-private-academia collaborative research* including researchers from in and out Korea, the article served as an opportunity to demonstrate the technical competency for future industry in Korea such as AI-based advanced bioinformatics. 

*NIFS (Cetacean Research Institute, Biotechnology Research Division), Seoul Grand Park, Genome Research Foundation (GRF), UNIST, AgingLab, and Paleogenomics Laboratory (of European University at Saint Petersburg, Russia) 

The Dokdo sea lion (Z. japonicus) is a marine mammal that thrived in the coastal waters of Korea and went extinct between the 1950s and 1970s due to overhunting conducted during the Japanese colonial period. Its closest relatives are California sea lion (Z. californianus) and Galapagos sea lion (Z. wollebaeki). In the mid-eighteenth century, the estimated population 50,000 inhabited along the coast of Northeast Asia. However, by the 1950s, their number plummeted to just 50, leading to their classification as extinct by the international Union for Conservation of Nature (IUCN) in 1990. 

The President of NIFS said, “This international collaborative research set the stage for entrenching geographical and historical traditionality of marine species endemic to Korea by specifying the Dokdo sea lion in international scientific journal as well as revealed the origin of Dokdo sea lion. Going forward, NIFS will make efforts to contribute to securing foothold of future industry while strengthening our biological sovereignty through persistent research on the various genetic characterization of species Korean waters.”