Scientists have identified four new species of walking shark in the waters off Australia and New Guinea.
While that might sound like the stuff of horror films, researchers say that the foot-long fish, which have evolved to use their fins to walk on land or in shallow water, are actually adorable.
"They're incredibly cute little animals and are really more like a gecko walking around than a shark," Mark Erdmann, a coral reef ecologist at the California Academy of Sciences and vice president of the Asia-Pacific Field Division of Conservation International, told VICE.
Erdmann was part of a team of scientists who spent 12 years studying the walking sharks. Their efforts, published in Marine and Freshwater Research Tuesday, nearly doubled the number of known species, raising it from five to nine, the University of Queensland reported.
The walking sharks all belong to the genus Hemiscyllium, according to Science Alert. The sharks have evolved to succeed in their unique coral reef environment and hunt during low tides.
"At less than a metre long on average, walking sharks present no threat to people but their ability to withstand low oxygen environments and walk on their fins gives them a remarkable edge over their prey of small crustaceans and molluscs," study coauthor Dr. Christine Dudgeon of the University of Queensland said in the press release.
The researchers used tissue samples taken from live sharks to determine that DNA linked the new shark species to the Hemiscyllium genus, according to Science Alert.
DNA testing also revealed that the walking sharks are the youngest type of shark on Earth, VICE reported.
"With our molecular clock, we've been able to show that this group really only branched off from their nearest ancestor about nine million years ago and they've been actively radiating ever since," Erdmann told VICE. "Obviously in human terms, that still seems like a long time ago, but for sharks, and for speciation in general, that's actually very recent."
Dudgeon explained in the press release how the sharks may have ended up in their current form and their current location:
"Data suggests the new species evolved after the sharks moved away from their original population, became genetically isolated in new areas and developed into new species," she said.
"They may have moved by swimming or walking on their fins, but it's also possible they 'hitched' a ride on reefs moving westward across the top of New Guinea, about two million years ago."
Because each species has a very small, unique range, they are vulnerable to natural disasters like volcanic eruptions and tsunamis, as well as human pressures like habitat loss and their increasing desirability for aquariums, VICE reported. Three of the nine species have been added to the International Union for Conservation of Nature Red List.
At the same time, the researchers don't think they have yet accounted for every species of walking shark out there.
"We believe there are more walking shark species still waiting to be discovered," Dudgeon said in the press release.
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In Major Win for Indigenous Rights, Supreme Court Rules Much of Eastern Oklahoma Is Still a Reservation
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It is undisputed that vitamin D plays a role everywhere in the body and performs important functions. A severe vitamin D deficiency, which can occur at a level of 12 nanograms per milliliter of blood or less, leads to severe and painful bone deformations known as rickets in infants and young children and osteomalacia in adults. Unfortunately, this is where the scientific consensus ends.
Where Does the Deficiency Begin?<p>Nobody knows exactly how much vitamin D a person actually needs. The question of when a deficiency starts is correspondingly controversial. However, vitamin D is becoming increasingly popular.Not only is the pseudo-scientific literature on the "sun vitamin" experiencing an upswing, but the number of published studies has also increased enormously in recent years. For example, in 2019 <a href="https://academic.oup.com/edrv/article/40/4/1109/5126915" target="_blank">a study found that</a> Vitamin D is responsible for keeping the skeleton functional and is associated with cardiovascular diseases, type 2 diabetes and various types of cancer. <br></p>
An All-Rounder<p>Vitamin D levels in the body rise and fall according to sun exposure. If sufficient UV rays reach the skin, the body is able to produce the vitamin itself. However, the human body only derives an estimated 10 to 20 percent of its daily requirement from food.</p><p>The vitamin D that we synthesize from sunlight or food is not biologically active at first. Before the kidneys can produce the biologically active form of the vitamin, known as calcitriol, and release it into the blood, some metabolic processes must take place beforehand.</p><p>In addition, many organs have receptors to which the precursor of calcitriol binds. Further, this substance is also present in blood.</p><p>From this precursor, the organs then produce calcitriol themselves, which the body then uses for countless other processes in the body. This form of vitamin D thus regulates insulin secretion, inhibits tumor growth, and promotes the formation of red blood cells as well as the survival and activity of macrophages, which are important for the <a href="https://www.mdpi.com/2072-6643/5/7/2502/htm" target="_blank">immune system.</a></p>
Low Vitamin D, Severe COVID-19 Disease?<p>A research study carried out <a href="https://www.sciencedirect.com/science/article/pii/S2352364620300067?via%3Dihub" target="_blank">at the University of Hohenheim</a> has now established a link between vitamin D deficiency, certain previous diseases, and severe cases of COVID-19.</p><p>According to the study, "there is a lot of evidence that several non-communicable diseases (high blood pressure, diabetes, cardiovascular diseases, metabolic syndrome) are associated with low vitamin D plasma levels. These comorbidities, together with the often accompanying vitamin D deficiency, increase the risk of severe COVID-19 events."</p><p>"This statement is completely correct," said Martin Fassnacht, head of endocrinology at the University Hospital of Würzburg. However, he qualifies that it is a pure association, "i.e. a mere observation that these events occur together.</p><p>Dr. Fassnacht is very critical of the hype surrounding vitamin D, but not because he denies the vitamin serves important functions. However, studies on humans have not been able to show that vitamin D has the healing powers many often propagate.</p><p>Fassnacht says, "If you take a closer look, the hopes that the administration of vitamin D has a healing effect have not been confirmed so far."</p>
Association Versus Intervention Studies<p>Many studies on the vitamin are association or observational studies. "By definition, these studies cannot prove the causal relationship, but only point to mere correlations," said Fassnacht. The physician tries to illustrate this with an example:</p><p>"Imagine two groups of 80-year-olds. One group is spry, active and does sports. If you compare them with another group living in nursing homes, the difference in vitamin D levels will be dramatic. Life expectancy would also be extremely different."</p><p>But to try to explain the difference in fitness by vitamin D status alone is far too simplistic. "Vitamin D levels are a good measure of how sick someone is. But not more," says Fassnacht. </p><p>According to Fassnacht, none of the intervention studies carried out to date -- that specifically examined the effect of vitamin D on various diseases -- has been able to confirm the previous association and laboratory studies or the presumed positive effect of vitamin D.</p>
Further Research Is Needed<p>"If a coronavirus infection is suspected, it is therefore absolutely necessary to check the vitamin D status and quickly correct any possible deficit," said the recommendation of the paper published by the University of Hohenheim.</p><p>"Studies are underway to see whether vitamin D helps in COVID-19 infection, but I personally do not believe that this is really the case," says endocrinologist Fassnacht. Nevertheless, he says it is of course useful to carry out these studies.<br></p><p>"I don't want to rule out that there are actually subgroups of people who benefit from an additional vitamin D dose," he says. After all, this has been proven to be the case with a severe deficit.</p><p>In view of the study situation, Fassnacht does not think much of preventive, nationwide vitamin D substitutes. "My belief that the vitamin helps somewhere is very low. But, of course, I can be wrong."</p>
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