Researchers have sequenced the genome of a strange fish that has an elephant trunk-like snout.
The "elephant shark" is a member of the group that includes "sharks, rays, skates and chimaeras," these are believed to be the oldest-living jawed creatures; and have cartilage in place of bones, a Washington University of St. Louis news release reported.
Researchers have discovered why these creatures have a cartilaginous skeleton by comparing their genetics to humans'.
"We now have the genetic blueprint of a species that is considered a critical outlier for understanding the evolution and diversity of bony vertebrates, including humans," said senior author Wesley Warren, PhD, research associate professor of genetics at The Genome Institute at Washington University School of Medicine. "Although cartilaginous vertebrates and bony vertebrates diverged about 450 million years ago, with the elephant shark genome in hand, we can begin to identify key genetic adaptations in the evolutionary tree."
The elephant shark, which lives off the coasts of Australia and New Zealand, was chosen for study because of its "compact genome" that is only a third the size of a humans'.
The team uncovered a family of genes that is found in the elephant shark but not in other bony vertebrates such as the "chicken, cow, mouse and human." The gene was detected in the zebrafish, and also observed a connected to "reduction in bone formation." These findings suggest the genes are involved in the bone-making process.
The team was surprised to find the elephant shark does not have immune cells crucial in preventing viruses, infections and autoimmune diseases such as rheumatoid arthritis and diabetes. Despite the lack of these cells elephant sharks tend to sustain realtively long and healthy lives.
The researchers suggested the shark's genome is one of the "slowest-evolving among all vertebrates," similar to the coelacanth which has been nicknamed the "living fossil."
The shark did have a number of genetic similarities to humans; researchers hope the findings can help them better-understand the human genome and even gain insight into bone disease.
"The slow-evolving genome of the elephant shark is probably the best proxy for the ancestor of all jawed vertebrates that became extinct a long time ago," lead author Byrappa Venkatesh, PhD, research director at the Institute of Molecular and Cell Biology at the Agency for Science, Technology and Research (A*STAR), said. "It is a cornerstone for improving our understanding of the development and physiology of human and other vertebrates as illustrated by our analysis of the skeletal system and immune system genes."
