Sequencing the shark’s genome revealed that it lacks various genes crucial to bone development, said Byrappa Venkatesh, a genome scientist at the Institute of Molecular and Cell Biology in Singapore.
The finding was confirmed by removing the same genes from zebrafish in laboratory that resulted in a significant reduction in bone formation.
The elephant shark is among about 1,000 species of cartilaginous fish, including sharks, rays, skates and chimaeras that diverged from bony vertebrates about 450 million years ago.
Some cartilaginous fish, like the dogfish, have genomes twice the size of humans’. The researchers decided to sequence the elephant shark’s genome because it was relatively small.
The research, published by the journal Nature, also revealed that elephant sharks lack certain immune cells that help fight off viral and bacterial infections and prevent autoimmune reactions like diabetes and rheumatoid arthritis.
Still, since they have survived, “they must have a more primitive immune system,” Venkatesh said, adding that further study might help researchers learn more about autoimmune diseases like rheumatoid arthritis.
By Ruchi Singh
reporter
Park Sae-jin
swatchsjp@ajunews.com