is one of the rarest sharks in the world. Nature has endowed him with a kind of horn that allows you to dig into the seabed to catch crustaceans and has earned Callorhinchus milii nicknamed elephant shark.
Now, an international team of researchers has sequenced the genome information to owners who claim to know better this animal that lives in temperate waters New Zealand and southern Australia, at depths of between 200 and 500 m . And, beyond its strange appearance, scientists want to investigate how the immune system has evolved to this long-lived species and find out why instead of bones, the skeleton is cartilaginous sharks.
The details of this research, which compared the genome of the elephant with human and other vertebrate species already sequenced shark, published this week in the journal Nature .
Sharks are some particularly interesting animals from the evolutionary point of view, as they are among the oldest vertebrates hinged jaws that have not yet been extinguished.
jawed vertebrates are globally known as gnathostomes and are divided into two groups: those with bony skeletons and possessing a skeleton of cartilage. “Although these two groups diverged about 450 million years ago with the genome of the elephant shark on our hands can begin to identify key genetic adaptations in the evolutionary tree,” says Wesley Warren, a researcher at the Genome Institute of the School of Medicine, University of Washington and co-author of this study.
therapies for osteoporosis
analysis of elephant shark genome and comparison with other species, say the researchers led by Byrappa Venkatesh, offer new insights into the genetic basis of bone formation and the adaptive immune system, which allows agencies better respond to pathogens.
Scientists also argue that this shark research will help better understand human diseases such as osteoporosis, so expect to allow developing more effective therapies and new strategies to improve the immune system of people.
A compact genome
However
behind choosing this shark species to sequence its genome is a practical reason: its genome is compact, since its size is approximately one billion base pairs of DNA (1000 Mb), about third of the human genome. It is also the smallest of the cartilaginous fish, including sharks addition there are numerous species of rays.
When compared with other genomes, scientists discovered a gene family that is not present in the elephant shark but in all vertebrates with bones, such as chickens, cows, mice and humans. When researchers eliminated any of the genes of this family in zebrafish, observed a decrease in bone formation, which would show the role of this gene family in bone development.
To the scientists’ surprise, the analysis of its genome (the first of a cartilaginous fish that has been completely sequenced) revealed that the elephant shark lacks some immune cells apparently play an essential role both in combating viruses and bacterial infections and prevention of autoimmune diseases such as type I diabetes and rheumatoid artriris.
A simple but effective immune system
Although your immune system is very simple, looks very effective as these sharks are long-lived and have good defenses. “Structure of the elephant shark immune system is very different from that of mammals is obvious that are able to effectively fight a variety of infections without that particular cell type, indicating that nature offers different solutions to the same problem “, reflects Thomas Boehm, co-author of the study and director of the Max Planck Institute of Immunobiology and Epigenetics, Germany.
Scientists have also discovered that the elephant shark genome is the most slowly evolved from known vertebrate , surpassing even the coelacanth, a lobe-finned fish that are considered living fossils .
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