Latest news with #Neogene
Yahoo
26-05-2025
- Science
- Yahoo
Giant Megalodon's Prey Finally Revealed, And It's Not What We Thought
Megalodon, the terror of the Neogene, dominated its giant shark niche for just 20 million years before it disappeared from the world's oceans. And, during that time, it hunted anything and everything that crossed its path. It didn't distinguish: if it was large enough to be a snack, megalodon (Odontus megalodon) partook. Scientists have reached that conclusion after studying the teeth of modern sharks, and comparing them to the fossilized teeth of megalodon, almost all we have left of the extinct fish today. This contradicts the theory that the main prey of megalodon was whales. Certainly megalodon could and did eat whales – but its diet as a whole was far more opportunistic. "Our study tends rather to draw a picture of megalodon as an ecologically versatile generalist," says geoscientist Jeremy McCormack of Goethe University Frankfurt in Germany "Megalodon was by all means flexible enough to feed on marine mammals and large fish, from the top of the food pyramid as well as lower levels – depending on availability." Megalodon is an extinct species of shark that lived from around 23 million to around 3.6 million years ago, during which time it occupied a prime position at the top of the food web, before being driven to extinction. We will never know for certain what it looked like; like all sharks, its skeleton was mostly cartilage, and all it left behind was a lot of teeth and a few vertebrae. We know from these remains, however, that megalodon was enormous, with size estimates ranging from around 11 meters to over 40 meters (36 to 131 feet) in length (although the latter is an outlier, and most estimates hover around 13 to 20 meters). That's huge – so huge that scientists think that megalodon may have specialized in large prey. One way to determine the diet of someone who has been dead a long time is to look at isotopes in their teeth. An isotope of an element is an atom that deviates from the norm in the number of neutrons it has in its nucleus, and the ratios of these isotopes vary according to several factors, one of which is diet. This is because when we eat, some of the metals in our food replace some of the calcium in our teeth and bones – not so you notice, obviously, but enough to leave a tracer. McCormack and his colleagues looked specifically at the ratios of two isotopes of zinc – the lighter zinc-64 and the heavier zinc-66. When fish at the bottom of the food web eat, they store less zinc-66 than zinc-64. The fish that eat those fish have even less zinc-66. So when you get to the fish at the very top of the chain, you see the very least zinc-66 compared to zinc-64. This is what the researchers observed in the teeth of megalodon and its cousin, the extinct Odontus chubutensis. The researchers don't really know what was at the bottom of the food chain 18 million years ago, the time from which the megalodon teeth they studied hailed. So, they compared the megalodon teeth with the teeth of sharks that swim the oceans today to work out what the giant predators ate. "Sea bream, which fed on mussels, snails, and crustaceans, formed the lowest level of the food chain we studied," McCormack says. "Smaller shark species such as requiem sharks and ancestors of today's cetaceans, dolphins, and whales, were next. Larger sharks such as sand tiger sharks were further up the food pyramid, and at the top were giant sharks like Araloselachus cuspidatus and the Otodus sharks, which include megalodon." Megalodon's status as a superpredator at the very top of the food web has been established previously. The new research reveals that the isotope difference between megalodon and the animals at the lowest level the researchers studied was not a sharp delineation, suggesting that the shark was not a fussy eater. There were also intriguing differences in megalodon diet depending on where the animals lived. Megalodon teeth found in Passau, Germany, dined more heavily on the lower levels of the food web, the researchers found. This is not dissimilar to the opportunistic hunting approach demonstrated by white sharks (Carcharias carcharodon), which stands to reason: previous work led by McCormack showed that the rise of the white shark was likely one of the drivers that led megalodon to extinction. With competition in its ecological niche, megalodon became more vulnerable. "It gives us important insights into how the marine communities have changed over geologic time," says paleobiologist Kenshu Shimada of DePaul University in the US, "but more importantly the fact that even 'supercarnivores' are not immune to extinction." The research has been published in Earth and Planetary Science Letters. Earth's Core Holds a Vast Reservoir of Gold, And It's Leaking Toward The Surface Scientists Peered Inside The Echidna's Mysterious 'Pseudo-Pouch' Bizarre Three-Eyed Predator Hunted The Ocean Half a Billion Years Ago
Yahoo
28-04-2025
- Science
- Yahoo
The Mariana Trench is home to some weird deep sea fish, and they all have the same, unique mutations
When you buy through links on our articles, Future and its syndication partners may earn a commission. Fish that survive in extreme deep-sea environments have developed the same genetic mutation despite evolving separately and at different times, researchers say. The scientists also found industrial chemicals in fish and in the ground in the Mariana Trench, meaning human-made pollutants can reach some of the deepest environments on Earth. Deep-sea fish have developed unique adaptations to survive extreme pressure, low temperatures and almost complete darkness. These species adapt to extreme conditions through unique skeletal structures, altered circadian rhythms and either vision that's extremely fine-tuned for low light, or are reliant on non-visual senses. In a new study, published March 6 in the journal Cell, researchers analyzed the DNA of 11 fishes, including snailfish, cusk-eels and lizardfish that live in the hadal zone — the region about 19,700 feet (6,000 meters) deep and below — to better understand how they evolved under such extreme conditions. The researchers used crewed submarines and remotely operated vehicles to collect samples from about 3,900 to 25,300 feet (1,200 to 7,700 m) below the water's surface, in the Mariana Trench in the Pacific and other trenches in the Indian Ocean. Tracing the evolution of deep-sea fishes, the researchers' analysis revealed that the eight lineages of fish species studied entered the deep-sea environment at different times: The earliest likely entered the deep sea in the early Cretaceous period (about 145 million years ago), while others reached it during the Paleogene (66 million to 23 million years ago), and some species as recently as the Neogene period (23 million to 2.6 million years ago). Despite different timelines for making the deep sea their home, all the fishes studied living below 9,800 feet (3,000 m) showed the same type of mutation in the Rtf1 gene, which controls how DNA is coded and expressed. This mutation occurred at least nine times across deep-sea fish lineages below 9,800 feet, study author Kun Wang, an ecologist at Northwestern Polytechnical University, told Live Science in an email. This means all these fishes developed the same mutation separately, as a result of the same deep-sea environment, rather than as the result of a shared evolutionary ancestor — showing just how strongly deep-sea conditions shape these species' biology. Related: How deep is the Mariana Trench? "This study shows that deep-sea fishes, despite originating from very different branches of the fish tree of life, have evolved similar genetic adaptations to survive the harsh environment of the deep ocean — cold, dark, and high-pressure," Ricardo Betancur, an ichthyologist at the University of California San Diego who was not involved in the new study, told Live Science in an email. It's an example of convergent evolution, where unrelated species independently evolve similar traits in response to similar conditions. "It's a powerful reminder that evolution often reuses the same limited set of solutions when faced with similar challenges — in this case, adapting to the extreme conditions of the deep sea," Betancur said. RELATED STORIES —Scientists thought sharks didn't make sounds — until this accidental discovery —Octopus spotted riding on top of world's fastest shark —Golden scaleless cave fish discovered in China shows evolution in action The expeditions also revealed human-made pollutants in the Mariana Trench and Philippine Trench. Polychlorinated biphenyls (PCBs) — harmful chemicals used in electrical equipment and appliances until they were banned in the 1970s — contaminated the liver tissues of hadal snailfish, the scientists discovered. High concentrations of PCBs and polybrominated diphenyl ethers (PBDEs), flame retardant chemicals used in consumer products until they fell out of popularity in the early 2000s, were also found in sediment cores extracted from more than 32,800 feet (10,000 m) deep in the Mariana Trench. Previous research has also found chemical pollutants in the Mariana Trench, as well as microplastics in the deep sea. The new findings further reveal the impacts of human activity even in this ecosystem that's so far removed from human life. Editor's note: This article was originally published on March 28, 2025
