sharks

Great white sharks are appearing off the Alicante coast. The problem is that we don’t know if it’s good news or bad news.

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On April 20, 2023, by pure chance, some fishermen caught a juvenile-sized white shark. No one would have been surprised if it weren’t for the fact that the fishermen were in Spanish waters, right in front of the Alicante Cape of La Nao. Two meters 10 centimeters of white shark in the middle of the Mediterranean, what was happening here? Do we have to worry? That is the question that was asked at the Spanish Institute of Oceanography and, in collaboration with the University of Cádiz, has carried out a deep review of the presence of white sharks in the Mediterranean Sea. It is not something superficial: they have collected all the records (direct and indirect) from 1862 to 2023 and have reached a surprising conclusion. The presence of this type of specimen has been “persistent” (although “extremely rare”) in the Spanish Mediterranean. It is not something, a priori, worrying. As explained José Carlos Báezresearcher at the IEO-CSIC, “we have only found two attacks: one in 1862, in which a person died in Malaga who was swimming, and another in the eighties, when a shark bit a surfer’s board in Tarifa and caused serious injuries.” But the problem is not that. And, although “with the available data, it is not possible to affirm that the Mediterranean white shark population is recovering”, it is inevitable to think about what will happen in an increasingly warmer sea. In the end, “the presence of young individuals provides key information about the demographic structure of the species” and, one way or anotherthis leads us to seriously consider the risks of having breeding spaces in Spanish waters. However, everything seems to indicate that there is a relationship between the presence of the shark and the routes of the bluefin tuna. If so, it would be another symptom of the problems that sharks have to keep their populations healthy and robust. Should we worry? It doesn’t seem like it. Against the media angle about the “return of the monster”, international evidence tells us that attacks are extremely rare and the role of sharks in the conservation of aquatic ecosystems is very important. Be that as it may, monitoring and conservation programs must be developed. And it has to be done soon. Image | Oleksandr Sushko In Xataka | The white shark is an exceptional swimmer. Its secret is in its “teeth”

sharks appear that shouldn’t be there

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Our planet still has many mysteries that we are still understanding today. We found the last one in Mammoth Cave in the United States, where The longest known cave system on the planet is located and where they were ‘hiding’ two new species of prehistoric sharks. These have been trapped in the limestone rock for 325 million years, and thanks to their great state of conservation, they are allowing us to rewrite what we knew about the evolution of these predators. A mystery. The question in this case is mandatory: how did two sharks end up in a cave system and not in an underground lake? To understand how these two species ended up in these Kentucky caves, you have to look at the geological clock. In this way, we know that about 325-340 million years ago, during the period MississippianNorth America did not have its current configuration. The area now occupied by Mammoth Cave was submerged under a shallow tropical sea that was part of the sea route that connected to the supercontinent Pangea. Its fossilization. When these sharks died, their bodies sank into the soft sediment of the sea, but over millions of years this sediment became the limestone that today forms the caves where they have been found. This was in addition to the subsequent erosion that created the Mammoth Cave tunnels, which has acted as a natural excavator and exposed fossils that would otherwise have been encased in the solid rock. Over millions of years, that sediment became the limestone that today forms the walls of the cave. The subsequent erosion, which created the Mammoth Cave tunnels, has acted as a natural excavator, exposing fossils that would otherwise be encased in the solid rock. The protagonists. The species that have been identified belong to the order Ctenacanthus, a lineage of primitive sharks with defensive spines on their dorsal fins. Specifically we have Troglocladodus trimblei, a shark baptized thus in honor of the park guard and his troglodyte origin and whose teeth are key, suggesting that he fed on soft prey such as small fish, catching them quickly instead of crushing them. The other protagonist is Glikmanius careforumwhich is the bone crusher. This is because it had a powerful jaw and teeth designed for cutting and crushing. In this way, it was very easy to crush bones and shells, which is why it fed on other small sharks, fish and orthocones. The importance. This finding is undoubtedly an ‘abnormality’ for science. This is because sharks have skeletons made of cartilage and not bone. This means that the cartilage (being softer) decomposes very quickly, which is why 99% of the shark fossils we find are just teeth. However, the tranquil and protected environment of Mammoth Cave has allowed for unusual three-dimensional preservation. Not only teeth, but also jaws, cranial cartilage and fossil fins have been found preserved in the walls and ceilings of the cave passages. Images | David Clode In Xataka | We thought dinosaurs were on the verge of extinction before the meteorite. we were wrong

There are sharks losing teeth

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Sharks are seen as The perfect predator being the hunting machine perfected for millions of years in our seas. His most iconic weapon, a mouth full of rows of sharp teeth like blades, has assured them A place at the top of the oceanic food chain. However, an invisible and silent threat This formidable tool could be weakening: The acidification of the oceans. Sharks placed to the test. A new study published by A team of German researchershas tested the resistance of these teeth in the chemical conditions that are expected in our seas for the year 2300. The results, observed through powerful microscopes, reveal that even the teeth of the sharks are vulnerable, showing obvious signs of corrosion and structural degradation. This could compromise your ability to hunt, and therefore, your survival. Why the ocean becomes more acidic. Before entering the experiment methodology you have to know what oceanic acidification means. In summary, it is one of the direct effects of the increase in carbon dioxide, and it is that A quarter of the co₂ we emit is absorbed by the oceans. When coming into contact with water there is a reaction that forms carbonic acid that decreases the pH of the water causing it to be much more acidic. The forecasts are not promising. In this way, to understand how our seas pH will evolve, you just have to observe CO₂ release forecasts for the coming years. In this case, IPCC projections (Intergovernmental panel of climate change) are very worrying. If emissions continue to the current rhythm, the reality we will face is that the pH of sea water will fall from the current 8.1 to 7.3 in the year 2300. This change, although it may seem small, represents a mass chemical alteration with serious consequences for marine life. Teeth in the water of the future. To verify the hypothesis, the scientists collected teeth that black tips sharks had naturally lost in the Sealife Aquarium in Oberhausen (Germany) so as not to damage any alive animal. Specifically, there were 16 selected teeth that submerged two controlled environments. The first one was the control group where the teeth were exposed to a pH of 8.2, that is, the one that is now in the seas. The second group was the experimental where the teeth were exposed to artificially acidified marine water with CO₂ until a pH of 7.3 is achieved. In this way, it was about simulating the conditions to which they will be exposed in 2300. The microscope verdict. The results They were clear and alarming: while the teeth of the control group remained in good condition, those who were submerged in acidic water showed significant deterioration. The most affecting part was the base of the tooth, known as the root, where the corrosion level was 8.2% instead of the 5.3% suffered by the control group. The crown, the visible and cutting part of the tooth, also suffered changes with cracks and holes in the outer layer. But the most worrying thing is that the secondary rows of teeth, crucial to tear the meat from the dams, degraded. Interestingly, when measuring the perimeter of the teeth, those of the acid group showed a slight “increase.” This does not mean that they grew, but that their stress became more irregular and rough by corrosion in a clear sign of degradation. Why imports a damaged shark tooth. A damaged tooth is not just an aesthetic problem, since for a predator like the shark It is a matter of survival. Weak and less sharp teeth mean lower efficiency when hunting. This could force them to spend more energy to feed, affecting their growth and general physical state. They have not taken into account other factors. It is important to clarify that this study focused on the purely chemical effects on teeth already detached, without taking into account the possible biological repair mechanisms that a living shark could have. In fact, other studies with living sharks They have shown less drastic resultssuggesting that some species could have some compensation capacity. However, what this investigation demonstrates unequivocally is that the material from which the shark teeth are made, despite its incredible hardness (They contain fluoroapatitaa more acid -resistant mineral than our teeth), is not invulnerable. Images | Trust “Tru” Katsande In Xataka | The increase in the surface temperature of the ocean has accelerated: four times faster than in the 80s

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