Latest news with #MarineBiology
Forbes
3 days ago
- Science
- Forbes
Do Sharks Really ‘Play Dead'? The Complicated Truth About Tonic Immobility.
The team also documented the first-ever data on a chimaera species (Callorhinchus milii), which ... More showed no TLR response, adding an important piece to the evolutionary puzzle of this behavior in early vertebrates. Tonic immobility (TI) is a strange and fascinating behavior that turns up across the animal kingdom. From insects to fish to mammals, at its core, it's a sudden and temporary stop in movement where animals appear to freeze in place. In some, this looks like muscles locking up. In others, like many fish, the body goes limp. The causes vary why TI happens vary: pressure to a certain body part, flipping the animal upside down, or even sensory overload. And while this reaction has been seen as a defense mechanism — sort of like a opossum 'playing dead' to avoid predators — that explanation doesn't fit all species or situations. For sharks, rays, and chimaeras (collectively known as chondrichthyans), TI takes the form of muscle relaxation when inverted, something researchers call the 'tonic limp response,' or TLR. Marine biologists often take advantage of TLR during data collection, temporarily flipping these predators to keep them still, but its evolutionary role remains… well, a mystery. To explore this, scientists Joel H. Gayford and Dr. Jodie L. Rummer from James Cook University conducted a combination of hands-on experimentation and a broad literature review to better understand how widespread and variable the tonic limp response (TLR) is across cartilaginous fishes. In their experimental trials, they carefully inverted individuals from 13 different shark and ray species to see if this common method of inducing tonic immobility would cause the animals to relax, stop struggling, and begin deep rhythmic breathing, all hallmarks of TLR. Their approach was consistent, gentle, and quick to avoid stress, mimicking the standard protocol used in field research. Of the 13 species tested, just over half (seven species, to be exact) displayed the expected TLR when flipped onto their backs, while the remaining species showed no response at all. For those that did respond, the time it took for the behavior to kick in ranged from just 7 seconds in the common smooth-hound (Mustelus mustelus) to 25 seconds in the blacktip reef shark (Carcharhinus melanopterus). Once immobile, the duration of stillness varied dramatically too, lasting anywhere from a brief 12 seconds to over two minutes (131 seconds) in the Atlantic guitarfish (Rhinobatos lentiginosus). Importantly, the behavior was remarkably consistent within species. Every individual of a species either consistently entered a tonic state or consistently didn't, suggesting that TLR is a fixed trait at the species level, not influenced by individual variability or environmental context in the short term. Looking at all the data, the duo found no connection between TLR and body size, habitat depth, geographic range, or whether the species was a predator or not. This suggests that ecological factors (i.e. like where a shark lives or how it feeds) don't strongly predict whether it has this trait. Instead, the presence or absence of TLR seems to be deeply rooted in evolutionary history. This line of thinking would make sense with the results from the very first empirical test of TLR in a chimaera species, Callorhinchus milii, also known as the elephant fish. This cartilaginous species showed no signs of TLR when inverted, which opens up new questions about whether this trait existed in their common ancestor, was lost in chimaeras, or perhaps never evolved in this group at all. In fact, the study's models suggest TLR was likely present in the common ancestor of all chondrichthyans and has since been lost at least five times across the group (and no evidence suggests it evolved anew in any lineages). This pattern hints that TLR may be a plesiomorphic trait, or something inherited from a distant ancestor that has stuck around in some species, even if it no longer serves a clear function. Scientists tested 13 species for their TLR response and reviewed published studies of 29 additional ... More species. Some sharks froze when flipped. Others didn't. The study found that seven of the 13 species tested exhibited TLR, while six did not. There are a few ideas about what TLR might have evolved for. One is predator avoidance (that playing dead to escape danger scenario). But in the case of sharks, there's no solid evidence this works, and the mechanics of predator attacks on sharks (like suction or tearing) make it unlikely that flipping over and going limp helps. Another theory suggests TLR plays a role in mating, especially since sharks have been seen inverting females during copulation. But again, this theory has issues. TLR doesn't differ between males and females, and if going limp made females more vulnerable to unwanted mating, natural selection would likely weed that behavior out. A third idea suggests TLR might protect animals from sensory overload, like hitting a reset button. But no one's tested that theory in sharks. Taken together, the explanations don't hold up well. What's perhaps most interesting finding in this study is that among the sharks and rays that lack TLR, all are small-bodied species that live in shallow, complex habitats like coral reefs or kelp forests. These environments are 'complex' in that they are full of tight spaces and tangled structures. So, if a shark goes limp in one of these spots, especially upside down, it could get stuck or injured. That could be a strong enough risk for evolution to get rid of the trait in those environments. On the other hand, larger sharks or those living in open water wouldn't face the same risk and could hang onto TLR without much cost. As highlighted in this new research, there's still much we don't know. The chimaera tested in this study didn't exhibit TLR, but with just one species sampled, it's hard to say whether that holds true for the whole group. And some species may respond to other triggers besides inversion, like touch to sensory organs, but this study didn't test for that. Ultimately, they Australian team cautions against one-size-fits-all assumptions when it comes to evolutionary biology. Just because a trait looks similar across species doesn't mean it evolved for the same reason — or even that it's still useful today. TLR in sharks and rays might once have served a purpose that's long gone. Or it might still matter in ways we haven't figured out yet. Either way, these animals hold clues to their deep evolutionary past. And it's this very behavior that will possibly unlock more answers.
Yahoo
17-07-2025
- Science
- Yahoo
Why bull sharks are staying in Sydney Harbour longer than ever
Bull sharks are spending more time than ever before in Sydney Harbour, and in the future, they might not leave. Video transcript Bull sharks are spending more time than ever before in Sydney Harbour, and in the future, they might not leave. A new study from James Cook University has revealed the sharks, which spend their winters in Queensland, are now lingering around Sydney for an average of 15 days longer during summer than they did in 2009. Dr. Nicholas said the change is driven by rising sea temperatures, with average water temperatures between October and May steadily increasing over the past 40 years. He warned that the changing migration patterns extend the potential for human shark encounters, and if warming continues, bull sharks may begin inhabiting Sydney waters year round.
CTV News
16-07-2025
- Science
- CTV News
Belugas spotlighted on Arctic Sea Ice Day
Arctic Sea Ice Day this year is focused on Beluga whales, launching a live cam in Hudson Bay for people to watch them swim.
Sustainability Times
13-07-2025
- Science
- Sustainability Times
'These Depths Hide Monsters': Marine Biologists Staggered by Discovery of a Brand-New Deep-Sea Predator Species Lurking 26,250 Feet Below the Surface
IN A NUTSHELL 🌊 Atacama Trench : A deep-sea canyon off South America's coast, home to unique and rare fauna adapted to extreme conditions. : A deep-sea canyon off South America's coast, home to unique and rare fauna adapted to extreme conditions. 🦐 Discovery of Dulcibella camanchaca : A new species of predatory crustacean, showcasing unexpected ecological behavior in the abyss. : A new species of predatory crustacean, showcasing unexpected ecological behavior in the abyss. 🔬 Abyssal Gigantism : The newly found crustacean exemplifies this phenomenon, achieving disproportionate size in resource-poor environments. : The newly found crustacean exemplifies this phenomenon, achieving disproportionate size in resource-poor environments. 🚢 Advanced Expeditions: Sophisticated technology reveals the ocean's hidden biodiversity, emphasizing the importance of ongoing exploration. In the depths of the Pacific Ocean, beneath nearly 26,000 feet of water, a recent discovery is reshaping our understanding of extreme marine ecosystems. This discovery, a previously unknown crustacean, goes beyond zoological significance; it introduces a new predator into the abyssal food chain. The Atacama Trench, carved by tectonic forces off the coast of Chile, was thought to host only scavenging organisms adapted to scarce life. Yet, an unknown crustacean, morphologically designed for hunting, reveals an unsuspected predator capable of thriving in this harsh environment. The Unique Ecosystem of the Atacama Trench Off the west coast of South America, the Atacama Trench plunges nearly 26,000 feet deep. This underwater canyon, formed by the subduction of the Nazca and South American plates, harbors a rare fauna, uniquely adapted to some of the planet's most hostile conditions. The trench is shrouded in darkness, with temperatures nearing freezing and immense pressure crushing down. The Atacama Trench stands out among oceanic trenches for its isolation and rich sediments, which are nourished by nutrient-rich surface waters. Since the 1960s, numerous expeditions have explored this remote area, uncovering remarkable biodiversity adapted to extreme conditions. Holothurians, mollusks, and scavenging amphipods have been recorded, playing a crucial role in cleaning up ocean floor carcasses. 'A New Monster From the Abyss': Scientists Stunned as Unknown Deep-Sea Predator Emerges From Earth's Darkest Depths Until recently, all amphipods recorded at these depths were scavengers. No active predators had been observed, leaving the trench an ecosystem misunderstood. The discovery of Dulcibella camanchaca challenges this model, indicating a more complex ecological dynamic. What This Abyssal Predator Reveals About Species Evolution Described in the journal Systematics and Biodiversity, this crustacean, measuring under 1.5 inches, belongs to a new species and genus. Its name, Dulcibella camanchaca, evokes both the gentle beauty of medieval poetry and the dense fog of the Atacama Desert, symbolizing its dark habitat. 'Thousands of Giant Eggs Found': Underwater Volcano Unleashes Terrifying Discovery That Has Marine Scientists in Total Shock Unlike scavenging species, Dulcibella exhibits an anatomy tailored for hunting. Its streamlined body, flexible limbs, and mouth adapted for shredding suggest it preys on small bottom-dwelling species like Hirondellea amphipods. Although stomach examinations have yet to confirm this diet, its morphology suggests predatory behavior. This discovery highlights that marine trenches harbor not just unique life forms but also unexpected ecological behaviors. This species is the first in its family to combine morphological and genetic traits distinct enough to warrant a new genus. Toronto's Stunning Green Revolution Turns Canada's Largest Metropolis Into a Vast Urban Forest Visible From Space The predator also exemplifies a fascinating case of abyssal gigantism. At nearly 26,000 feet deep, it achieves a size disproportionate to its shallower relatives. Though not fully understood, this phenomenon might reflect an adaptation strategy to resource-poor environments. Increasingly Sophisticated Expeditions to Explore Marine Life In October 2023, a lander deployed from the vessel R/V Abate Molina captured Dulcibella camanchaca at 25,928 feet deep. Developed by the Instituto Milenio de Oceanografía, the device was equipped with bait traps, measuring instruments, and cameras. Ironically, the camera malfunctioned before reaching the seabed, depriving researchers of real-time footage. Only after weeks of analysis did the team identify the specimen's novelty through a cross-taxonomic approach combining morphological observation and DNA sequencing. This integration confirmed genetic kinship with other genera while highlighting differences sufficient to establish a distinct lineage. This discovery underscores that oceanic trenches still harbor a largely underestimated reservoir of biodiversity. The emergence of an active predator at such depths reveals more complex trophic interactions than previously thought. It also reminds us that each hadal expedition can bring surprises, emphasizing the importance of exploration amid the global biodiversity crisis. As the mysteries of the Atacama Trench continue to unfold, the recent discovery of Dulcibella camanchaca prompts a reevaluation of deep-sea ecosystems. With advanced technology and persistent exploration, the ocean's hidden depths hold potential breakthroughs for understanding life's adaptability. What other secrets might the abyss conceal, waiting to transform our insights into the natural world? This article is based on verified sources and supported by editorial technologies. 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Miami Herald
04-07-2025
- Science
- Miami Herald
Divers make ‘monumental' rediscovery of Galápagos species not seen in 24 years
Divers have rediscovered a rare marine species believed to have been extinct for 24 years. Last seen in 2000, Rhizopsammia wellingtoni — a 'unique and well-known' black stony coral species known only from the Galápagos — was found thriving, according to a June 26 news release from the California Academy of Sciences. 'Finding something that was previously thought to be extinct is one of the most exciting discoveries a biologist can make,' Terry Gosliner, academy curator of invertebrate zoology and geology, said in the release. The coral, known to prefer cool shallow waters like those found in the Galápagos, was first discovered in 1975, then 'abruptly disappeared' from the region when an El Niño event warmed the waters between 1982 and 1983, according to the release. In January 2024, the team discovered more than 250 colonies near Isabela Island's Tagus Cove, including some in deeper waters than had ever been recorded, according to the release. Experts said the 'monumental' discovery provides 'evidence that the species isn't merely clinging to survival, but thriving at multiple localities and depths.' It is plausible that the coral species survived in 'deeper, cooler or more sheltered environments, avoiding detection during previous surveys,' according to a study published June 23 in the journal Marine Biology. Experts said cooler La Niña conditions between 2020 and 2023 may have offered a 'reprieve from thermal stress, allowing the coral to reemerge in shallower water.' Researchers plan to use genetic analysis to learn more about the new colonies, according to the release. The research team included Inti Keith, Terry Gosliner and Rebecca Albright.
