Diving with sharks is awesome! I know, I’ve dived with Oceanic White Tips. Once demonized as the voracious maneaters who decimated the crew of the bombed American destroyer, the Indianapolis, it became clear to me that this characterization was unfair. Of course, when diving with sharks the diver must always obey their rules. After all, we are in their world. But some research has suggested that you are 75 times more likely to be killed by lightning than by a shark. And what could be more impressive than the sight of a White Tip cruising their ocean domain? Or more elegant than a thresher shark with its long, ribbon-like tail? But besides the sheer power, strength, and beauty of these animals, there are other reasons to admire and conserve these underwater icons.
The Oceans Need Sharks
Sharks have existed for over 400 million years almost unchanged. That’s long before the dinosaurs came and went. With roughly 500 known species, sharks fill many ecological niches. They range in size from the Whale Shark, which can reach up to 60 feet (18 meters) to the Dwarf Lantern Shark which can fit in the palm of a human hand. They can be found in the deep sea, open ocean, coral reefs and even under the Arctic ice. These amazing animals come in a variety of colors including the bubblegum pink goblin shark! The ‘cookie cutter’ shark can even light up its belly with a greenish glow to fool prey species.
As so-called apex predators sharks are extremely important to ocean ecosystems. And a recent study, authored by marine archaeologist Rick Stafford, has indicated how the decline of predatory fish like sharks can increase the numbers of smaller fish and plankton. These then compete with each other and other species for food and thus disturb the food web. The increase in smaller fish also results in a higher level of CO2. And this, of course, contributes to global warming.
Research has also shown that the interaction between predators and prey can also affect marine ecosystems such as salt marshes. The organic material within these areas can be released back into the ocean by the action of smaller fish. Higher numbers of them due to fewer predators can increase this activity and result in a lessening of the carbon stored within these ecosystems. The correct predator-prey relationship is obviously very important for the health of our oceans.
We Need Sharks
Besides amazing us with their variety, size, and beauty, it is increasingly clear that sharks can be important in combatting many human diseases. For example, the tooth-shaped scales of a shark’s skin are designed to help the animal move swiftly and easily through the water. But now this shape has been mimicked in biotechnological research for its ability to repel barnacles and algal growth. Additionally, in hospital settings, it is very diffcult to prevent the transmission of so-called ‘superbugs’ such as MRSA. These infections obviously put already vulnerable patients at further risk. But a recent research project involving a micropattern called ‘Sharklet’, based on the ridges in shark skin, showed that such a pattern harbored many fewer bacteria than a smooth surface. It’s encouraging news in the fight against the spread of infections in hospitals.
Sharks also have an enviable reputation for healing quickly from wounds and resisting infections. This ability has been put to use in human medicine. A two-layered skin repair product called Integra Omnigraft Dermal Regeneration Matrix has been developed to deal with persistent foot ulcers caused by diabetes. It is also being used to help heal life-threatening burns. And it’s made partly by chondroitin a natural protein derived from shark tissue! Paired with bovine (cow) collagen (part of the tissue that help keeps skin firm) and topped by a thin silicon layer it is proving more successful in many cases than conventional healing methods.
Sharks, in common with camels and llamas, have another secret weapon against disease. These animals produce mini-antibodies that are only about half the size of conventional ones. Antibodies are the disease-fighting cells in the body. Still being researched, it is thought that these small antibodies may be able to find their way deeper into tissues which their larger relatives have trouble penetrating. For example, the Blood-Brain barrier in humans rejects most large molecules including standard antibodies and many useful drugs. This protective ‘wall’ of cells around the brain’s blood vessels is intended to stop foreign, possibly harmful, substances in the bloodstream from entering and harming the brain. But it can also prevent life-saving drug treatments from entering to do their job of fighting disease. Ossianix, a Philadelphia-based biotech firm, has made use of part of a shark mini-antibody that binds to a receptor controlling access to the B-B barrier. This may allow entrance for cancer-killing larger antibodies. This approach could also be used to fight Alzheimer’s and Parkinson’s.
Another possible treatment for human disease is derived from the Wobbegong shark. La Trobe University has gained funding to trial AD-114, a human protein that is based on the shape one of the Wobbegong’s antibodies. It is hoped to be used in treating pulmonary fibrosis. This is a respiratory disease which results in scarring of the lungs.
And there are more exciting possibilities for the future too. Recently, the genome of the Great White shark has been completely decoded. It turns out to be one and a half times the size of the human genome. This study found genes relating to adaptations for the healing of wounds. This included a key blood-clotting gene. Besides being known for their ability to heal wounds, sharks also appear to suffer from cancers less than expected. Cancers can occur when changes happen as cells age. Large and long-lived creatures such as whale sharks ought to develop cancer more readily than humans as they have more cells to misfire as they age. But they don’t. According to Dr. Mahmoud Shivji, co-leader of the shark study at Nova Southeastern University in Florida, shark DNA has evolved to be more stable than human DNA. Sharks are better able than we are to maintain and even repair their DNA. If researchers can figure out how sharks do this, it is hoped that they can apply this knowledge to the treatment of cancers and age-related human diseases.
Conclusion
The decoding of the shark’s genetic blueprint is important for sharks as well as humans. Many shark populations are declining because of environmental changes and over-fishing, both accidental (getting caught in nets) and deliberate (for shark-fin soup for example). It is estimated that a quarter of shark and ray species are threatened by extinction. And sharks have slow growth and reproduction rates so they cannot keep up with such losses to their numbers. The more we know about sharks, the more able we will be to stop this decline. After all, it is increasingly clear that the oceans need sharks to remain healthy. It is also clear that sharks may one day help us to combat diseases like cancer. Sharks are also becoming increasingly important to the economy of some countries. For example, a study done in North Carolina in the US showed that the loss of the great sharks resulted in an increase in the ray population. The rays, in turn, decimated the scallop population. This was an important element of the fishing economy in North Carolina. Their loss caused one fishery to close. Quahogs, an element in classic American chowder, have also declined with the loss of the shark population which used to maintain the balance between the quahogs predators and the quahog population. In the Bahamas, sharks are important to dive tourism and in Belize, it is estimated that a Whale Shark can bring in $12 million dollars in tourism during its lifetime.
But it is equally, if not more important, that we conserve sharks for their power, their beauty, and, yes, even for the terror they may sometimes inspire in us. They are an irreplaceable part of our world. It is our responsibility to see that they do not disappear.
