- Publication of the gangchi’s complete mitochondrial genome in an international journal (SCI) will promote public interest in and education on the sea lion -

 

The Ministry of Oceans and Fisheries (Minister MOON, Seong-Hyeok) announced last October 14^th the publication of the research on the complete mitochondrial genome of the gangchi (Dokdo sea lion, Zalophus japonicus), which was extracted from skeletal remains excavated from Ulleungdo. The research result was published in an international journal^*, Mitochondrial DNA Part B(UK journal, SCI).

 

* Paper title: The complete mitochondrial genome of Japanese sea lion, Zalophus japonicus (Carnivora: Otariidae) analyzed using the excavated skeletal remains from Ulleungdo, South Korea

 

In September 2020, the Korea Marine Environment Management Corporation (Han Ki-Jun, CEO), Pusan National University (Prof. Lee Sang-Heon) and Pukyong National University (Prof. Kim Hyun-Woo) conducted the first excavation of around 40 skeletal remains of gangchi on Ulleungdo.

 

They then mapped the complete, 16,698bp-long mitochondrial genome^* of the Do gangchi using the long-range PCR technique. This genetic information is highly valuable in not only phylogeny and evolutionary relationship interpretation but also the study of environmental DNA (eDNA).

 

* 13 gene-encoded proteins, 22 transfer RNAs, 2 ribosomal RNAs, origin of replication, and non-coding D-loop

 

 

Gangchi inhabited a wide area encompassing coastal areas of Korea, Japan, and Russia. Especially, Ulleungdo and Dokdo in South Korea were its biggest habitats and breeding grounds. In the early 20th century, the population of gangchi declined dramatically due to overhunting,^* leading it to be classified as an extinct species by the International Union for Conservation of Nature (IUCN) in the mid-1990s.

 

* The Gangchi Fishing Corporation (Japanese) killed about 16,500 sea lions between 1904 and 1941. In 1915, it was reported that the sea lion’s population had rapidly decreased and that only 300 were caught due to such overhunting (History of the Extinction of the Dokdo Gangchi).

 

MOF designated the gangchi as a protected marine species in 2007 and has continuously searched for traces of its existence by investigating domestic and foreign habitats of pinnipeds (six species^*), including those of the gangchi, since 2020.

 

* Pinnipeds designated as protected marine species: Northern fur seal, Steller sea lion, gangchi (dokdo sea lion), spotted seal, ringed seal, and ribbon seal

 

In line with these efforts, the Korea Marine Environment Management Corporation constructed a diorama using 3D models of the actual skeletal remains of the gangchi. The diorama is a realistic reproduction of the excavation site at the time. The exhibition of the diorama started this August at the Ulleungdo-Dokdo Ocean Science Station of the Korea Institute of Ocean Science and Technology. Also, the 3D images of the skeletal remains is accessible through the Marine Environment Information System (MEIS) website.

 

In September, information on the past habitats and ecological characteristics of the gangchi was provided through the corporation’s National Marine Environmental Education Center, and educational materials on gangchi was be produced and distributed widely to related educational institutions.

 

Lee Jae-yeong, head of the Marine Ecology Division of the Ministry of Oceans and Fisheries, mentioned, “We did this wonderful work to publicize our research results on the gangchi internationally, and we will make various efforts, through not only related eDNA research but also continuous promotion and education, to ensure that the gangchi is not forgotten.”

 

 

Reference 1

Description of gangchi

 

Species	Gangchi
Photo
Scientific name	Zalophus japonicus
Size	Adult male 2.3-2.5m, female 1.6m, male weight 450-560kg
Distribution	North Pacific coast (Korea, Russia Sakhalin, and Japanese coast)
Characteristics	- Elongated, spindle-shaped body with short, thin, cone-shaped ear flaps and tail - Varied skin color: young female is grayish brown with dark gray in the center of the back, and young male is yellowish brown - Polygamous, breeding season is May to August, mainly on sandy coasts, but Dokdo sea lions breed on rocks - Prey on various fish and squid - It is known that Dokdo sea lions stayed in and around the waters of Dokdo and did not migrate long distances. - Dokdo sea lions were overhunted by Japan at Dokdo between 1904 and 1941: in 1904, for instance, about 3,200 sea lions were killed by Japan. - There were reports of sea lion sightings at Dokdo until 1976, but no sightings were reported after that time.
Note	Classified as extinct species by IUCN (in the mid-90s)

 

 

 

Reference 2

Excavations of gangchi remains on Ulleungdo

 

Gajaegul Cave on Ulleungdo (inside)	Gajaegul Cave on Ulleungdo (inside)
Gajaegul Cave on Ulleungdo (outside)	Excavated remains

 

 

 

Reference 3

Skeletal remains of gangchi and 3D images

 

Rotated view	Pelvis, 3D image (front)	Rotated view
Rotated view	Rib, 3D image (front)	Rotated view

 

 

 

Reference 4

Skeletal remains of gangchi

 

Tibia and fibula	Rib
Pelvis	Rib
Coccyx	Lumbar vertebrae

 

 

 

Reference 5

Analytical results of gangchi mitochondrial gene sequences (Pukyong National University)

 

DNA sequencing is the analytical process of identifying the nucleic acid sequence to find out how four nucleotides of a DNA strand are arranged within a specific gene. Each species has its own unique sequence and can be identified through comparison and analysis of the sequencing.

 

□ D-loop^* region 97.56-99.39% match (registered in 2007, Japanese paper^**)

 

* Some regions of DNA present in the mitochondrial matrix inside the cell

 

** Sakahira F, Niimi M., 2007, Ancient DNA analysis of the Japanese sea lion (Zalophus californianus japonicus Peters, 1866): preliminary results using mitochondrial control-region sequences. Zool Sci 24:81–85.

 

 

NCBI analysis report