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The Great White shark is a marvel of survival as a result of its sophisticated genome structure which contains almost twice as many as humans. Image: Wikipedia.

 

Scientists have started to unravel the mysterious world of shark genes. A report has just been published in the journal, Proceedings of the National Academy of Sciences, confirming that the genome of the Great White Shark has been fully mapped for the first time ever. It shows that the shark has 41 pairs of chromosomes, which compares with our meagre 23. The expectation is that the results will help to explain why these animals live so long and provide clues as to how they have managed to survive as a species for over 400m years, one of the longest lived of all vertebrates on this planet. .

It has been known for some time that sharks have some pretty peculiar abilities to cope with infections and injuries. Fishermen have often remarked upon that fact that injured sharks have been seen to have healed remarkably quickly, with some species appearing to be able to rebuild tissue and fins within a matter of days. In addition, sharks, in keeping with some other larger animals, seem to be much more resistant than humans to diseases such as cancer.

This last point is particularly relevant to a recent study of the Great White Shark, for it can live to over 70, assuming it is not killed by another predator.  Such a long-lived creature should, by all accounts, be exposed to as much of a problem with unstable cells and other life-threatening malfunctions of an aging body as are we humans. And yet, the incidence of serious diseases is remarkably low.

The fact that the shark has been around for such a long time is possibly one clue to its highly developed genome. The struggle to survive in the wild can be helped by evolution if an animal-type lives for enough time on this planet. One example is the way that some of the Australian reptiles have developed incredibly powerful toxins as a result of being in a relatively isolated and stable “island” eco-system, allowing them to refine their food-killing weaponry over the aeons of time.

One of the key findings of the study is that the Great White seems to have very stable genomes. Genome “instability” is one of the reasons we become more susceptible to diseases as we age; as we get older these instabilities build up in our system until they reach a point where something seemingly trivial can spark of the development of a full-blown disease.

The link between self-healing and genome-stability is thought to be important.  Great Whites have the ability to heal, but they also have to be able to carry out some fairly fundamental and immediate first-aid after sustaining a serious wound such as an attack by other sharks who occupy the same level in the food chain. They have developed a gene that promotes rapid blood-clotting after an injury, which keeps them alive long enough for the other healing genes to get to work. (Which has clear implications in terms of possible battlefield-injury treatment, for example.)

The research is of great interest to scientists trying to unlock the secrets to humans being able to live increasingly long and healthy lives. However, it is also important to find out how we can assist these animals as the struggle to survive the onslaught from their only really deadly enemy – us.

It has been emphasised by biologists that eating the meat of these creatures will have absolutely no benefits in terms of disease resistance. There is a concern that, as we understand more about their remarkable self-healing and disease fighting abilities, some will misinterpret the findings as a reason to go out and “harvest” more sharks, adding to the pressure they are already facing: some 100m are already being killed each year. Many shark-types might die-out completely unless we do more to protect them.

The Great white is the only one of the 500-plus shark species in the waters of our planet to have its genome sequenced. However, the findings are sufficiently interesting to justify the high-cost of studying more shark-types. The likelihood is that we will learn as much about ourselves as we do from the sequencing of animals that, on the face for things, seem most similar to us. It also reinforces the point that we cannot make any assumptions about the sophistication (or otherwise), of the natural world around us.

(After all, whereas humans have 3 billion DNA base pairs in their genomes, grasses such as rye have a genome of 8 billion base pairs and oats has 11.3 billion.  And, like the shark, they have also been around for a lot longer than us!)

 

For more information about shark-conservation activities around the world, please see this link: https://scubadiverlife.com/top-5-shark-conservation-groups/

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