What's quieter than a fish? A school of them

Swimming in schools makes fish surprisingly stealthy underwater, with a group able to sound like a single fish.

The new findings by Johns Hopkins University engineers working with a high-tech simulation of schooling mackerel, offers new insight into why fish swim in schools and promise for the design and operation of much quieter submarines and autonomous undersea vehicles.

"It's widely known that swimming in groups provides fish with added protection from predators, but we questioned whether it also contributes to reducing their noise," said senior author Rajat Mittal.

"Our results suggest that the substantial decrease in their acoustic signature when swimming in groups, compared to solo swimming, may indeed be another factor driving the formation of fish schools."

The work is newly published in Bioinspiration & Biomimetics.

The team created a 3D model based on the common mackerel to simulate different numbers of fish swimming, changing up their formations, how close they swam to one another, and the degrees to which their movements synched.

The model, which applies to many fish species, simulates one to nine mackerel being propelled forward by their tail fins.

The team found that a school of fish moving together in just the right way was stunningly effective at noise reduction: A school of seven fish sounded like a single fish.

"A predator, such as a shark, may perceive it as hearing a lone fish instead of a group," Mittal said.

"This could have significant implications for prey fish."

The single biggest key to sound reduction, the team found, was the synchronization of the school's tail flapping -- or actually the lack thereof.

If fish moved in unison, flapping their tail fins at the same time, the sound added up and there was no reduction in total sound.

But if they alternated tail flaps, the fish canceled out each other's sound, the researchers found.

"Sound is a wave," Mittal said. "Two waves can either add up if they are exactly in phase or they can cancel each other if they are exactly out of phase. That's kind of what's happening here though we're talking about faint sounds that would barely be audible to a human."

The tail fin movements that reduce sound also generate flow interaction between the fish that allow the fish to swim faster while using less energy, said lead author Ji Zhou, a Johns Hopkins graduate student studying mechanical engineering.

"We find that reduction in flow-generated noise does not have to come at the expense of performance," Zhou said.

"We found cases where significant reductions in noise are accompanied by noticeable increases in per capita thrust, due to the hydrodynamic interactions between the swimmers."

The team was surprised to find that the sound reduction benefits kick in as soon as one swimming fish joins another.

Noise reduction grows as more fish join a school, but the team expects the benefits to cap off at some point.

"Simply being together and swimming in any manner contributes to reducing the sound signature," Mittal said.

"No coordination between the fish is required."

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Evolutionary chance made this bat a specialist hunter

Ask a biologist why predators don't exterminate all their prey, part of the answer often is that there is an ongoing arms race between predators and prey, with both parties continuously evolving new ways to cheat each other.

The hypothesis is particularly prevalent for bats and their prey; insects. 50 million years ago, the first bats evolved the ability to echolocate and thus hunt in the dark, and in response to this, some insects evolved ultrasound-sensitive ears so they could hear and evade the bats.

But if there is an ongoing arms race, bats should have responded to this, says University of Southern Denmark biologist, associate professor and bat expert Lasse Jakobsen, co-author of a new study published in Current Biology, In the study, he and colleagues question the evolutionary arms race between bats and insects.

The other authors are Daniel Lewanzik and Holger R. Goerlitz from the Max Planck Institute for Biological Intelligence and John M. Ratcliffe and Erik Etzler from the University of Toronto.

The main argument supporting the arms race hypothesis is that some bats do not call as loudly as others when hunting, and thus cannot be heard as easily by the insects. These are the barbastelles (Barbastella barbastellus), and they are approx. 20 dB quieter than other bats that hunt flying insects, which means that the sound pressure they emit is 10 times lower.

- The barbastelle is traditionally highlighted as the bat that has "struck back" at the insects, says Lasse Jakobsen.

But something puzzled him and his colleagues: If you look at the barbastelle's close relatives, there are virtually no other members catching insects in the air. Instead, they eat insects that sit on surfaces such as leaves and branches, and those species are all quieter than the species that hunt flying insects.

In bat research circles, the bats that catch insects in the air are called hawking bats, while the bats that pick insects from a surface, so to speak, are called gleaning bats. The barbastelle is a hawking bat.

- If most of the barbastelle's family are gleaners, then their ancestor was very likely also a gleaner, says Lasse Jakobsen.

Accordingly, it is therefore unlikely that the ancestor of the barbastelle was a loud hawker that evolved into the whispering barbastelle as a response to insect hearing.

- A species does not have free choice when it evolves in a new direction. For example, it is a condition for mammals that their ancestor did not have feathers, so their descendants will never evolve a wing with feathers. Instead, they have found another solution for flying: modified skin between the fingers, explains Lasse Jakobsen.

But if the barbastelle didn't evolve its ability to be quieter when hunting in the air, as part of the arms race between insects and bats; where does it come from?

- It is not an evolved ability. It just cannot produce louder calls than it does, because as a descendant of a gleaner it is probably morphologically limited. But it has found a niche, where it can use its low amplitude calls. It is an evolutionary coincidence; it sort of fell into this niche, where there was something to eat.

This niche is populated by flying, nocturnal insects that can hear and are thus good at avoiding nocturnal bats. But they cannot hear well enough to register the barbastelle, so they end up as their prey.

The reason for the morphological limitation must be found in how bats emit their sound. Most bats call out of their mouths, and this allows them to emit loud sounds. Many gleaners, on the other hand, emit sound with their noses, and this makes their calls 20 dB lower.

- So, the reason why the barbastelles are so quiet today is not an expression of an arms race between bats and insects, but rather simply an expression of the fact that it is descended from bats that cannot call as loudly as others, says Lasse Jakobsen.

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Apex predator of the Cambrian likely sought soft over crunchy prey

Biomechanical studies on the arachnid-like front “legs” of an extinct apex predator show that the 2-foot (60-centimeter) marine animal Anomalocaris canadensis was likely much weaker than once assumed. One of the largest animals to live during the Cambrian, it was probably agile and fast, darting after soft prey in the open water rather than pursuing hard-shelled creatures on the ocean floor. The study is published today in the journal Proceedings of the Royal Society B.

First discovered in the late 1800s, Anomalocaris canadensis—which means “weird shrimp from Canada” in Latin—has long been thought to be responsible for some of the scarred and crushed trilobite exoskeletons paleontologists have found in the fossil record.

“That didn’t sit right with me, because trilobites have a very strong exoskeleton, which they essentially make out of rock, while this animal would have mostly been soft and squishy,” said lead author Russell Bicknell, a postdoctoral researcher in the American Museum of Natural History’s Division of Paleontology, who conducted the work while at the University of New England in Australia.

Recent research on the armor-plated, ring-shaped mouthparts of A. canadensis lays doubt on the animal’s ability to process hard food. The latest study set out to investigate whether the predator’s long, spiny front appendages could do the job instead.

The first step for the research team, which included scientists from Germany, China, Switzerland, the United Kingdom, and Australia, was to build a 3D reconstruction of A. canadensis from the extraordinarily well-preserved—but flattened—fossils of the animal that have been found in Canada’s 508-million-year-old Burgess Shale. Using modern whip scorpions and whip spiders as analogues, the team was able to show that the predator’s segmented appendages were able to grab prey and could both stretch out and flex.

A modeling technique called finite element analysis was used to show the stress and strain points on this grasping behavior of A. canadensis, illustrating that its appendages would have been damaged while grabbing hard prey like trilobites. The researchers used computational fluid dynamics to place the 3D model of the predator in a virtual current to predict what body position it would likely use while swimming.

The combination of these biomechanical modeling techniques—used together in a scientific paper for the first time—paint a different picture of A. canadensis than was previously assumed. The animal was likely a speedy swimmer, zooming after soft prey in the water column with its front appendages outstretched.

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A healthy but depleted herd: Predators decrease prey disease levels but also population size

Nature documentaries will tell you that lions, cheetahs, wolves and other top predators target the weakest or slowest animals and that this culling benefits prey herds, whether it's antelope in Africa or elk in Wyoming.

This idea has been widely accepted by biologists for many years and was formalized in 2003 as the healthy herds hypothesis. It proposes that predators can help prey populations by picking off the sick and injured and leaving healthy, strong animals to reproduce.

The healthy herds hypothesis has even been used to suggest that manipulating predator numbers to protect prey might be a useful conservation strategy. Even so, hard evidence supporting the hypothesis is scarce, and in recent years many of its assumptions and predictions have been questioned.

In a study published online April 26 in the journal Ecology, a University of Michigan-led research team used a pint-sized predator-prey-parasite system inside 20-gallon water tanks to test the healthy herds hypothesis.

Their study system consisted of predatory fly larvae that feed on the water flea Daphnia dentifera, which hosts a virulent fungal parasite.

The researchers found that while high predation levels reduced parasitism in Daphnia -- providing partial support for the healthy herds hypothesis -- populations of those poppy seed-sized crustaceans were often dramatically reduced, as well. In some cases, Daphnia populations were nearly wiped out by predation.

The findings may have implications for conservation efforts involving much larger animals, according to the study authors. Specifically, the results suggest that caution is warranted when wildlife managers manipulate predator numbers in the hopes of promoting healthy herds of prey.

"The appeal of the healthy herds hypothesis lies in the alignment of multiple conservation goals -- simultaneous conservation of predators, reduction of parasitism, and protection of vulnerable populations -- as well as the potential to reduce spillover risk to other populations, including humans," said U-M aquatic and disease ecologist Meghan Duffy.

"But even when predators reduce disease in their prey populations, that does not necessarily lead to increased prey population size, as our study shows," said Duffy, senior author of the new study and a professor in the U-M Department of Ecology and Evolutionary Biology.

One well-known example of "healthy herds" gone wrong involves the culling of badgers in the United Kingdom in an effort to reduce bovine tuberculosis in livestock. In that case, the culling can be viewed as a particularly efficient form of predation by humans.

The assumption behind those campaigns was that higher predation of badgers, which are a wildlife reservoir of bovine tuberculosis, would drive healthy livestock herds. Instead, the campaigns increased bovine tuberculosis in cattle. In another example, the culling of bats to reduce the spread of rabies has not been effective at reducing rabies in domestic dogs or wildlife.

Findings of the new study, and others like it, could help explain why some attempts to control disease by manipulating predators fail, according to the authors.

"Unless we develop a more comprehensive understanding of when and how predators influence disease, management strategies that propose to reintroduce or augment predator populations could backfire," said study lead author Laura Lopez, a former postdoctoral researcher in Duffy's lab who now works for the National Centre for Immunisation Research and Surveillance in Australia.

Duffy has used Daphnia as a model organism to investigate the causes and consequences of infectious disease outbreaks for nearly 20 years -- work that has included several studies of the healthy herds hypothesis.

For the latest study, the researchers experimentally manipulated the density of a predator in their three-organism study system, then monitored Daphnia population sizes and infection levels.

The predators were larvae of the phantom midge, which commonly prey on Daphnia in North American temperate lakes. The parasite was the virulent fungus Metschnikowia bicuspidata.

The predator-prey-parasite interactions occurred inside 48 experimental water tanks called mesocosms, which also contained nutrients and green algae.

At the highest levels, predation completely eliminated the fungal pathogen. However, the highest predation levels often dramatically reduced Daphnia population sizes, as well -- an outcome that does not support the healthy herds hypothesis.

"If your primary concern is the overall population size of a vulnerable animal species, then adding high levels of predation that eliminate disease could be detrimental," Duffy said.

"Interestingly, intermediate predation levels reduced parasitism in our study without incurring a cost in terms of overall prey density. Any management decisions would need to weigh the potential costs and benefits associated with increasing predation."

The authors of the Ecology study warned that achieving and maintaining a predation level that reduces parasitism without harming prey population size "might be equivalent to threading the proverbial needle."

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Low-impact human recreation changes wildlife behavior

Even without hunting rifles, humans appear to have a strong negative influence on the movement of wildlife. A study of Glacier National Park hiking trails during and after a COVID-19 closure adds evidence to the theory that humans can create a "landscape of fear" like other apex predators, changing how species use an area simply with their presence.

Washington State University and National Park Service researchers found that when human hikers were present, 16 out of 22 mammal species, including predators and prey alike, changed where and when they accessed areas. Some completely abandoned places they previously used, others used them less frequently, and some shifted to more nocturnal activities to avoid humans.

"When the park was open to the public, and there were a lot of hikers and recreators using the area, we saw a bunch of changes in how animals were using that same area," said Daniel Thornton, WSU wildlife ecologist and senior author on the study published in the journal Scientific Reports. "The surprising thing is that there's no other real human disturbance out there because Glacier is such a highly protected national park, so these responses really are being driven by human presence and human noise."

The researchers had also expected to find an effect known as "human shielding," when human presence causes large predators to avoid an area, providing opportunity for smaller predators and perhaps some prey species to use an area more frequently. In this case, they found this potential effect for only one species, red fox. The foxes were more present on and near trails when the park was open-perhaps because their competitors, coyotes, avoided those areas when humans were around.

Several species showed a decline in use of trail areas when the park was open, including black bear, elk and white-tailed deer. Many decreased their day-time activities, including mule deer, snowshoe hare, grizzly bears and coyotes. A few, including cougars, seemed indifferent to human presence.

While the influence of low-impact recreation is concerning, the researchers emphasized that more research is needed to determine if it has negative effects on the species' survival.

"This study does not say that hiking is necessarily bad for wildlife, but it does have some impacts on spatiotemporal ecology, or how wildlife uses a landscape and when," said Alissa Anderson, a resent WSU master's graduate and first author on the study. "Maybe they are not on the trails as much, but they're using different places, and how much does that actually impact species' ability to survive and thrive in a place, or not? There are a lot of questions about how this actually plays into population survival."

The study came about in part because of the pandemic. Both humans and wildlife like to use trails, so the researchers had set up an array of camera traps near several trails to study lynx populations in Glacier National Park when COVID-19 hit. In an effort to keep the virus from spreading to the nearby Blackfeet Indian Reservation, the eastern portion of the park was closed in 2020 with only minimal access allowed to administrators and researchers.

This allowed Anderson, Thornton and co-author John Waller of Glacier National Park to conduct a natural experiment. They captured images in summer of 2020 when the park was closed as well as in 2021 when it opened again.

Glacier, which covers nearly 1,600 square-miles of northwestern Montana, sees more than 3 million human visitors a year. It is also home to diverse range of animals with almost the full complement of mammal species that has existed in the region historically.

Thornton said park managers are faced with a balancing act between conservation and public use missions.

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Dinosaur teeth reveal what they didn't eat

Scratches on dinosaur teeth could reveal what they really ate. For the first time, dental microwear texture analysis (DMTA) has been used to infer the feeding habits of large theropods, including Allosaurus and T. rex. By taking 3D images of individual teeth and analyzing the pattern of marks scratched into them, researchers could reason which dinosaurs may have frequently crunched on hard bone and which may have regularly eaten softer foods and prey. This technique opens up a new avenue of research for paleontology, helping us to better understand not only dinosaurs themselves but also the environment and communities in which they lived.

From Fantasia to Jurassic Park, the T. rex is seen as a terrifying apex predator that would chase down its prey and crunch on it whole. But how much did this iconic dinosaur actually chow down on bones? And what about other predatory dinosaurs that existed long before it?

Researchers from the University of Tokyo, in collaboration with teams from the University of Mainz and the University of Hamburg in Germany, have used dental microwear texture analysis (DMTA), a scanning technique to examine topographical dental wear and tear in microscopic detail, on individual dinosaur teeth from more than 100 million years ago to better understand what they may have eaten. "We wanted to test if we could use DMTA to find evidence of different feeding behaviors in tyrannosaurids (from the Cretaceous period, 145 million to 66 million years ago) compared to the older Allosaurus (from the Jurassic period, 201 million to 145 million years ago), which are both types of theropods," explained postdoctoral fellow Daniela Winkler from the Graduate School of Frontier Sciences. "From other research, we already knew that tyrannosaurids can crack and feed on bones (from studies of their feces and bite marks on bone). But allosaurs are much older and there is not so much information about them."

DMTA has mainly been used to study mammal teeth, so this is the first time it was used to study theropods. The same research team from the University of Tokyo also recently pioneered a study on DMTA in Japanese sauropod dinosaurs, famous for their long necks and tails. A high-resolution 3D image was taken of the tooth surface at a very small scale of 100 micrometers (one-tenth of a millimeter) by 100 micrometers in size. Up to 50 sets of surface texture parameters were then used to analyze the image, for example, the roughness, depth and complexity of wear marks. If the complexity was high, i.e., there were different-sized marks which overlaid each other, this was associated with hard object feeding, such as on bone. However, if the complexity was low, i.e., the marks were more arranged, of a similar size and not overlapping, this was associated with soft object feeding, like meat.

In total, the team studied 48 teeth, 34 from theropod dinosaurs and 14 from crocodilians (modern crocodiles and alligators), which were used as a comparison. The team was able to study original fossilized teeth and take high-resolution silicon molds, thanks to loans provided by natural history museums in Canada, the U.S., Argentina and Europe. "We actually started dental microwear research of dinosaurs in 2010," said Lecturer Mugino Kubo from the Graduate School of Frontier Sciences. "My husband, Dr. Tai Kubo, and I had started collecting dental molds of dinosaurs and their contemporaries in North and South Americas, Europe, and of course Asia. Since Daniela joined my lab, we utilized these molds to make a broader comparison among carnivorous dinosaurs."

"It was especially challenging to carry out this research during the pandemic," said Winkler "as we rely on being able to gather samples from international institutions. The sample size might not be so large this time, but it is a starting point."

Winkler says what they found surprising was that they didn't find evidence of much bone crushing behavior in either Allosaurus or tyrannosaurids, even though they know that tyrannosaurids ate bone. There may be several reasons for this unexpected outcome. It could be that although Tyrannosaurus was able to eat bone, it was less commonly done than previously thought. Also, the team had to use well-preserved teeth, so it might be that extremely damaged teeth that were excluded from this study were in such a condition because those animals fed more on bone.

Something the team did find with both the dinosaurs and crocodilians was a noticeable difference between juveniles and adults. "We studied two juvenile dinosaur specimens (one Allosaurus and one tyrannosaurid) and what we found was a very different feeding niche and behavior for both compared to the adults. We found that there was more wear to juvenile teeth, which might mean that they had to more frequently feed on carcasses because they were eating leftovers," explained Winkler. "We were also able to detect different feeding behavior in juvenile crocodilians; however, this time it was the opposite. Juvenile crocodilians had less wear on their teeth from eating softer foods, perhaps like insects, while adults had more dental wear from eating harder foods, like larger vertebrates."

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Neanderthals appear to have been carnivores

For the first time, zinc isotope ratios in tooth enamel have been analysed with the aim of identifying the diet of a Neanderthal. The Neanderthal to whom the tooth belonged was probably a carnivore. Other chemical tracers indicate that this individual did not consume the blood of their prey, but ate the bone marrow without consuming the bones.

A new study published on October 17th in the journal PNAS, led by a CNRS researcher, has for the first time used zinc isotope analysis to determine the position of Neanderthals in the food chain. Their findings suggest that they were in fact carnivores.

Were Neanderthals carnivores? Scientists have not yet settled the question. While some studies of the dental tartar of individuals from the Iberian Peninsula appear to show that they were major consumers of plants, other research carried out at sites outside Iberia seem to suggest that they consumed almost nothing but meat. Using new analytical techniques on a molar belonging to an individual of this species, researchers1 have shown that the Neanderthals at the Gabasa site in Spain appear to have been carnivores.

To determine an individual's position in the food chain, scientists have until now generally had to extract proteins and analyse the nitrogen isotopes present in the bone collagen. However, this method can often only be used in temperate environments, and only rarely on samples over 50,000 years old. When these conditions are not met, nitrogen isotope analysis is very complex, or even impossible. This was the case for the molar from the Gabasa site analysed in this study.

Given these constraints, Klevia Jaouen, a CNRS researcher, and her colleagues decided to analyse the zinc isotope ratios present in the tooth enamel, a mineral that is resistant to all forms of degradation. This is the first time this method has been used to attempt to identify a Neanderthal's diet. The lower the proportions of zinc isotopes in the bones, the more likely they are to belong to a carnivore. The analysis was also carried out on the bones of animals from the same time period and geographical area, including carnivores such as lynxes and wolves, and herbivores like rabbits and chamois. The results showed that the Neanderthal to whom this tooth from the Gabasa site belonged was probably a carnivore who did not consume the blood of their prey.

Broken bones found at the site, together with isotopic data, indicate that this individual also ate the bone marrow of their prey, without consuming the bones, while other chemical tracers show that they were weaned before the age of two. Analyses also show that this Neanderthal probably died in the same place they had lived in as a child.

Compared to previous techniques, this new zinc isotope analysis method makes it easier to distinguish between omnivores and carnivores. To confirm their conclusions, the scientists hope to repeat the experiment on individuals from other sites, especially from the Payre site in south-east France, where new research is under way.

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To keep up with evolving prey, rattlesnakes tap genetically diverse venom toolbox

In the evolutionary arms race between rattlesnakes and their prey, rodents, birds and other reptiles develop resistance to the snakes' deadly venom to survive. But new research led by the University of Colorado Boulder and University of Texas at Arlington sheds light on how snakes manage to keep the upper hand: They maintain a broad and diverse toolkit of genes that encode snake venom, allowing them to adapt as local prey and conditions change.

The findings, published today in Nature Ecology and Evolution, help explain how rattlesnakes have kept up with prey species evolving resistance to their venoms over millions of years. This research overturns decades of thought on what factors shape venom gene evolution and venom variation, and sheds new light on why developing effective antivenom treatments for snakebites remains so challenging.

"We found these rattlesnakes had a more diverse venom repertoire, more genetic tools in the toolkit, than their venom composition alone might suggest," said Drew Schield, lead author on the paper and postdoctoral fellow in Ecology and Evolutionary Biology at CU Boulder.

Snake venom, an evolutionary adaptation, is made up of different enzymes and toxins that enable snakes to capture their prey. For decades, biologists have thought that co-evolution between predator and prey would drive snake venom to become highly specialized: the venom evolving to effectively kill specific prey and unused venom gene genetic diversity disappearing along the way. Known in evolutionary biology as "directional selection" this process is like the sharpening of a knife -- while the weapon gets more deadly, it loses a bit of itself in the process.

The new study proposes that instead, "balancing selection" is the mechanism at play, an evolutionary process where multiple versions of a gene -- in this case, genes that encode venom proteins -- are maintained instead of eliminated. This could be the key to how snakes prevent themselves from going down evolutionary dead ends.

"The existence of these resistance mechanisms in prey led us to wonder: If there's selection pressure imposed back on the snakes, then it might make sense evolutionarily to have a more expanded venom arsenal," said Schield.

As rattlesnakes prey on a variety of animals, including mice, voles, birds and lizards, selection over time may not only maintain, but proactively select for a greater venom gene diversity, something no research has shown before.

"Our findings help explain decades of seemingly contradictory theory and evidence for what drives the extreme variation observed in snake venoms. It turns out that the arms-race between snakes and prey ends up favoring the constant re-shuffling of venom variants that are favored, leading to the retention of lots of venom variants over time, some of which are ancient," said Todd Castoe, co-author on the study and professor of biology at the University of Texas at Arlington.

Population level insights

During his work as a graduate student and postdoctoral researcher at the University of Texas at Arlington in 2019, Schield and his colleagues figured out where the venom genes reside in the rattlesnake genome, which up until that point was mostly a mystery. Now knowing the genetic architecture of venom as a trait (published in Genome Research), he realized scientists could investigate what evolutionary mechanisms have been operating on the venom genes.

Snake venom is a popular study subject, a promising model for understanding the origins of gene novelty. But previous studies in this field have not explored how selection has shaped this trait within closely related populations, so the researchers focused on select populations of rattlesnakes in Colorado, Montana, California and Idaho.

After scouting out locations where these snakes live, Schield and his co-authors traveled to a series of sites over several years in late spring and early summer from 2017 to 2020, where they collected 68 rattlesnakes belonging to two different species occupying the western United States in order to sample their blood, venom and take physical measurements.

They sequenced and analyzed genomes from these rattlesnake species, investigating genetic variation in regions of the genome housing venom genes. They found striking genetic diversity and strong evidence for natural selection maintaining multiple forms of different venom genes, adding to a growing body of evidence that balancing selection is more pervasive in nature than previously thought.

Based on the new study, Schield suspects that while directional selection may have driven the origins of venom, in more recent timescales, there may be an equilibrium shift towards balancing selection favoring diverse venom repertoires.

This may be one reason that snakebite is notoriously difficult to treat.

"These evolutionary mechanisms ramp up the complexity that you're contending with when you develop antivenoms, as venom composition within the same species but in different geographic regions might be totally different," said Schield.

Understanding how diverse venomous snake genomes truly are -- from rattlesnakes to cobras and coral snakes -- can inform advances in anti-venom therapeutics and save lives around the world, Schield said.

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Fossil reveals evidence of 200-million-year-old 'squid' attack

Scientists have discovered the world's oldest known example of a squid-like creature attacking its prey, in a fossil dating back almost 200 million years.

The fossil was found on the Jurassic coast of southern England in the 19th century and is currently housed within the collections of the British Geological Survey in Nottingham.

In a new analysis, researchers say it appears to show a creature -- which they have identified as Clarkeiteuthis montefiorei -- with a herring-like fish (Dorsetichthys bechei) in its jaws.

They say the position of the arms, alongside the body of the fish, suggests this is not a fortuitous quirk of fossilization but that it is recording an actual palaeobiological event.

They also believe it dates from the Sinemurian period (between 190 and 199 million years ago), which would predate any previously recorded similar sample by more than 10 million years.

The research was led by the University of Plymouth, in conjunction with the University of Kansas and Dorset-based company, The Forge Fossils.

It has been accepted for publication in Proceedings of the Geologists' Association and will also be presented as part of Sharing Geoscience Online, a virtual alternative to the traditional General Assembly held annually by the European Geosciences Union (EGU).

Professor Malcolm Hart, Emeritus Professor in Plymouth and the study's lead author, said: "Since the 19th century, the Blue Lias and Charmouth Mudstone formations of the Dorset coast have provided large numbers of important body fossils that inform our knowledge of coleoid palaeontology. In many of these mudstones, specimens of palaeobiological significance have been found, especially those with the arms and hooks with which the living animals caught their prey.

"This, however, is a most unusual if not extraordinary fossil as predation events are only very occasionally found in the geological record. It points to a particularly violent attack which ultimately appears to have caused the death, and subsequent preservation, of both animals."

In their analysis, the researchers say the fossilised remains indicate a brutal incident in which the head bones of the fish were apparently crushed by its attacker.

They also suggest two potential hypotheses for how the two animals ultimately came to be preserved together for eternity.

Firstly, they suggest that the fish was too large for its attacker or became stuck in its jaws so that the pair -- already dead -- settled to the seafloor where they were preserved.

Alternatively, the Clarkeiteuthis took its prey to the seafloor in a display of 'distraction sinking' to avoid the possibility of being attacked by another predator. However, in doing so it entered waters low in oxygen and suffocated.
From Science Daily

Predators help prey adapt to an uncertain future

What effect does extinction of species have on the evolution of surviving species? Evolutionary biologists have investigated this question by conducting a field experiment with a leaf galling fly and its predatory enemies. They found that losing its natural enemies could make it more difficult for the prey to adapt to future environments.

According to many experts, the Earth is at the beginning of its sixth mass extinction, which is already having dire consequences for the functioning of natural ecosystems. What remains unclear is how these extinctions will alter the future ability of remaining species to adapt.

Researchers from the University of Zurich have now pursued this question with a field experiment in California. They investigated how the traits of a tiny fly changed when a group of its natural enemies was removed. From their observations, they drew conclusions about changes in the genetic diversity of the flies.

Specific elimination of parasitoids

The fly Iteomyia salicisverruca lives on willow leaves in tooth-shaped growths called galls, which it induces in its larval stage. The natural enemies of this fly include several species of parasitic wasps. These wasps lay their eggs inside the fly larva within the gall, where they then develop into parasitic predators known as parasitoids. Before the adult wasp leaves the gall, it devours its host, the fly.

Some species of these parasitoids attack before the gall is formed, while others parasitize fly larvae later in their development and pierce through the gall. The researchers specifically eliminated the latter group of natural enemies by attaching fine-meshed nets over leaves with galls before they were attacked.

After three months, the biologists collected about 600 galls and checked if the fly larvae had survived. They also measured three traits that influence a fly's survival from parasitoid attack: the size of the gall; the number of flies within a gall; and the fly's preference to create galls on particular genetic varieties of willow trees. Using these data they then created "fitness landscapes" using computer models, which visualize the adaptability of a species.

Fewer enemies, less variability

It turned out that different combinations of these three traits helped flies survive ? when all of the fly's natural enemies were present. "So there are several equally good solutions that ensure the survival of the fly," says Matt Barbour, the study's lead author. In contrast, after some natural enemies were removed, only one specific combination of traits helped flies survive. "This suggests that the extinction of natural enemies constrains fly evolution toward only one optimal solution." Genetic variations that lead to a different development of the traits could thus be permanently lost in the flies' genome.

This loss of diversity might be of consequence: "The diversity of potential solutions for survival acts to preserve genetic variability in the gall's traits," says Barbour. And since genetic variation provides the raw material for evolution, the findings suggest that the extinction of this fly's natural enemies may make it more difficult for it to adapt to a changing environment.

Read more at Science Daily