Herring arrives earlier in the Wadden Sea due to climate change

Due to the changing climate, young herring arrive in the Wadden Sea earlier and earlier in spring. That is shown in a new publication by NIOZ ecologists Mark Rademaker, Myron Peck and Anieke van Leeuwen, in this month's journal Global Change Biology. "The fact that we were able to demonstrate this, was only due to very consistently, for more than 60 years, and continuously sampling the fish every spring and every fall with exactly the same fyke every time," Rademaker says. "Recognizing this kind of change requires extreme precision and endurance!"

NIOZ fyke

Since 1960, NIOZ, Royal Netherlands Institute for Sea Research, has been measuring the number and species of fish that swim in the Marsdiep, between Den Helder and Texel, day in and day out using a standard fyke, in spring and fall. These measurements show that the peak of the number of young herring swimming into the Wadden Sea since 1982 comes at least two weeks earlier now. "Such a calculation is difficult with a species of fish that swims in large schools," Rademaker says. "One day there may be only ten herring, while the next there are suddenly ten thousand fish swimming by. So, if you were to accidentally take a measurement just one day or the other, you would get a completely different picture."

Extremely consistent measurement

According to Rademaker, the solution to that problem lies in extremely consistent measurement, almost to the square meter. "Only by carrying out measurements in the same place over and over again, and almost continuously, year after year, can you reliably reveal changes in the long term."

Unique set of data

The research with the 'NIOZ fyke' is unique in the world. Most other monitoring programs measure only once or a few times per month or even per quarter, and then often not even at exactly the same spot. Rademaker: "When I projected that frequency from other research programs onto the data from the NIOZ fyke, picking out a few random measurement days, the changes in the timing of the herring did not show up."

Read more at Science Daily

How do birds flock? Researchers do the math to reveal previously unknown aerodynamic phenomenon

In looking up at the sky during these early weeks of spring, you may very well see a flock of birds moving in unison as they migrate north. But how do these creatures fly in such a coordinated and seemingly effortless fashion?

Part of the answer lies in precise, and previously unknown, aerodynamic interactions, reports a team of mathematicians in a newly published study. Its breakthrough broadens our understanding of wildlife, including fish, who move in schools, and could have applications in transportation and energy.

"This area of research is important since animals are known to take advantage of the flows, such as of air or water, left by other members of a group to save on the energy needed to move or to reduce drag or resistance," explains Leif Ristroph, an associate professor at New York University's Courant Institute of Mathematical Sciences and the senior author of the paper, which appears in the journal Nature Communications. "Our work may also have applications in transportation -- like efficient propulsion through air or water -- and energy, such as more effectively harvesting power from wind, water currents, or waves."

The team's results show that the impact of aerodynamics depends on the size of the flying group -- benefiting small groups and disrupting large ones.

"The aerodynamic interactions in small bird flocks help each member to hold a certain special position relative to their leading neighbor, but larger groups are disrupted by an effect that dislodges members from these positions and may cause collisions," notes Sophie Ramananarivo, an assistant professor at École Polytechnique Paris and one of the paper's authors.

Previously, Ristroph and his colleagues uncovered how birds move in groups -- but these findings were drawn from experiments mimicking the interactions of two birds. The new Nature Communications research expanded the inquiry to account for many flyers.

To replicate the columnar formations of birds, in which they line up one directly behind the other, the researchers created mechanized flappers that act like birds' wings. The wings were 3D-printed from plastic and driven by motors to flap in water, which replicated how air flows around bird wings during flight. This "mock flock" propelled through water and could freely arrange itself within a line or queue, as seen in a video of the experiment.

The flows affected group organization in different ways -- depending on the size of the group.

For small groups of up to about four flyers, the researchers discovered an effect by which each member gets help from the aerodynamic interactions in holding its position relative to its neighbors.

"If a flyer is displaced from its position, the vortices or swirls of flow left by the leading neighbor help to push the follower back into place and hold it there," explains Ristroph, director of NYU's Applied Mathematics Laboratory, where the experiments were conducted. "This means the flyers can assemble into an orderly queue of regular spacing automatically and with no extra effort, since the physics does all the work.

"For larger groups, however, these flow interactions cause later members to be jostled around and thrown out of position, typically causing a breakdown of the flock due to collisions among members. This means that the very long groups seen in some types of birds are not at all easy to form, and the later members likely have to constantly work to hold their positions and avoid crashing into their neighbors."

The authors then deployed mathematical modeling to better understand the underlying forces driving the experimental results.

Here, they concluded that flow-mediated interactions between neighbors are, in effect, spring-like forces that hold each member in place -- just as if the cars of a train were connected by springs.

However, these "springs" act in only one direction -- a lead bird can exert force on its follower, but not vice versa -- and this non-reciprocal interaction means that later members tend to resonate or oscillate wildly.

"The oscillations look like waves that jiggle the members forwards and backwards and which travel down the group and increase in intensity, causing later members to crash together," explains Joel Newbolt, who was an NYU graduate student in physics at the time of research.

The team named these new types of waves "flonons," which is based on the similar concept of phonons that refer to vibrational waves in systems of masses linked by springs and which are used to model the motions of atoms or molecules in crystals or other materials.

"Our findings therefore raise some interesting connections to material physics in which birds in an orderly flock are analogous to atoms in a regular crystal," Newbolt adds.

Read more at Science Daily

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."

Read more at Science Daily

Predatory fish use rapid color changes to coordinate attacks

Striped marlin are some of the fastest animals on the planet and one of the ocean's top predators. When hunting in groups, individual marlin will take turns attacking schools of prey fish one at a time. Now a new study reported in the journal Current Biology on February 5 helps to explain how they might coordinate this turn-taking style of attack on their prey to avoid injuring each other. The key, according to the new work, is rapid color changes.

"We documented for the first time rapid color change in a group-hunting predator, the striped marlin, as groups of marlin hunted schools of sardines," says Alicia Burns of Humboldt University in Berlin, Germany.

"We found that the attacking marlin 'lit up' and became much brighter than its group-mates as it made its attack before rapidly returning to its 'non-bright' coloration after its attack ended."

Burns and her colleagues, including Jens Krause, explained that the use of drones in their research has given them a new perspective of how marlins move and hunt.

As they examined the video footage they'd captured via drone, they noticed something unexpected: the stripes on individual marlins got obviously brighter as a fish moved in for an attack.

As they swam away, those stripes dimmed again. Were the fish changing colors to communicate with one another?

To explore this question in the new study, the researchers analyzed 12 high-resolution video clips, each containing two separate attacks on a school of sardines by two different marlin.

They also quantified the contrast of the stripes on the two attacking marlins compared to a randomly chosen marlin that wasn't attacking.

Their analysis confirms that the predatory fish rapidly change color, suggesting that the color change might serve as a reliable signal of an individual's motivation to go in for an attack.

"Color change in predators is rare, but especially so in group-hunting predators," Burns said.

"Although it is known that marlin can change color, this is the first time it's been linked to hunting or any social behavior."

The discovery suggests that marlins have more complicated communication channels than had been suspected.

The researchers propose that the color changes might even serve a dual purpose of confusing their prey.

They now hope to explore this idea, alongside other questions.

For example, they want to find out whether marlins use their color-changing abilities in other contexts.

They're curious to know whether they still change color when hunting solo and how the changes affect their prey.

They are also looking into similar color changes in other predatory species of fish.

Read more at Science Daily

Ancient retroviruses played a key role in the evolution of vertebrate brains

Researchers report February 15 in the journal Cell that ancient viruses may be to thank for myelin -- and, by extension, our large, complex brains. The team found that a retrovirus-derived genetic element or "retrotransposon" is essential for myelin production in mammals, amphibians, and fish. The gene sequence, which they dubbed "RetroMyelin," is likely a result of ancient viral infection, and comparisons of RetroMyelin in mammals, amphibians, and fish suggest that retroviral infection and genome-invasion events occurred separately in each of these groups.

"Retroviruses were required for vertebrate evolution to take off," says senior author and neuroscientist Robin Franklin of Altos Labs-Cambridge Institute of Science.

"If we didn't have retroviruses sticking their sequences into the vertebrate genome, then myelination wouldn't have happened, and without myelination, the whole diversity of vertebrates as we know it would never have happened."

Myelin is a complex, fatty tissue that ensheathes vertebrate nerve axons.

It enables rapid impulse conduction without needing to increase axonal diameter, which means nerves can be packed closer together.

It also provides metabolic support to nerves, which means nerves can be longer.

Myelin first appeared in the tree of life around the same time as jaws, and its importance in vertebrate evolution has long been recognized, but until now, it was unclear what molecular mechanisms triggered its appearance.

The researchers noticed RetroMyelin's role in myelin production when they were examining the gene networks utilized by oligodendrocytes, the cells that produce myelin in the central nervous system.

Specifically, the team was investigating the role of noncoding regions including retrotransposons in these gene networks -- something that hasn't previously been explored in the context of myelin biology.

"Retrotransposons compose about 40% of our genomes, but nothing is known about how they might have helped animals acquire specific characteristics during evolution," says first author Tanay Ghosh, a computational biologist at Altos Labs-Cambridge Institute of Science.

"Our motivation was to know how these molecules are helping evolutionary processes, specifically in the context of myelination."

In rodents, the researchers found that the RNA transcript of RetroMyelin regulates the expression of myelin basic protein, one of the key components of myelin.

When they experimentally inhibited RetroMyelin in oligodendrocytes and oligodendrocyte progenitor cells (the stem cells from which oligodendrocytes are derived), the cells could no longer produce myelin basic protein.

To examine whether RetroMyelin is present in other vertebrate species, the team searched for similar sequences within the genomes of jawed vertebrates, jawless vertebrates, and several invertebrate species.

They identified analogous sequences in all other classes of jawed vertebrates (birds, fish, reptiles, and amphibians) but did not find a similar sequence in jawless vertebrates or invertebrates.

"There's been an evolutionary drive to make impulse conduction of our axons quicker because having quicker impulse conduction means you can catch things or flee from things more rapidly," says Franklin.

Next, the researchers wanted to know whether RetroMyelin was incorporated once into the ancestor of all jawed vertebrates or whether there were separate retroviral invasions in the different branches.

To answer these questions, they constructed a phylogenetic tree from 22 jawed vertebrate species and compared their RetroMyelin sequences.

The analysis revealed that RetroMyelin sequences were more similar within than between species, which suggests that RetroMyelin was acquired multiple times through the process of convergent evolution.

The team also showed that RetroMyelin plays a functional role in myelination in fish and amphibians.

When they experimentally disrupted the RetroMyelin gene sequence in the fertilized eggs of zebrafish and frogs, they found that the developing fish and tadpoles produced significantly less myelin than usual.

Read more at Science Daily

Clown anemonefish seem to be counting bars and laying down the law

We often think of fish as carefree swimmers in the ocean, reacting to the world around them without much forethought. However, new research from the Okinawa Institute of Science and Technology (OIST) suggests that our marine cousins may be more cognizant than we credit them for.

By observing how a colony of clown anemonefish (Amphiprion ocellaris) -- the species of the titular character in Finding Nemo -- reacts to intruders in their sea anemone home, OIST researchers have found that the fish recognize different anemonefish species based on the number of white bars on their bodies.

"The frequency and duration of aggressive behaviors in clown anemonefish was highest toward fish with three bars like themselves," explains Dr. Kina Hayashi from the Marine Eco-Evo-Devo Unit at OIST, first author on the paper published in the Journal of Experimental Biology, "while they were lower with fish with one or two bars, and lowest toward those without vertical bars, which suggests that they are able to count the number of bars in order to recognize the species of the intruder."

The clown anemonefish is normally a gracious host, allowing many different species to visit their sea anemone.

However, should a member of their own species, and which is not part of the colony, enter their home, the largest fish of the colony, referred to as the alpha fish, will aggressively bite and chase out the intruder.

To figure out how these fish determine the species of their visitors, Dr. Hayashi and colleagues conducted two sets of experiments with immature clown anemonefish raised in the lab.

In the first set, they placed different species of anemonefish, with different numbers of white bars, in small cases inside a tank with a clown anemonefish colony and observed how often and for how long the fish would aggressively stare at and circle the case.

In the second set, the researchers presented a colony of clown anemonefish with different plastic discs painted with true-to-life anemonefish coloration and measured the level of aggression towards these models.

The clown anemonefish displayed the most aggressive behavior towards the intruders with three bars like themselves.

Fish and plastic models with two bars were attacked slightly less frequently, while the ones with one or zero bars received the least aggressive response.

Previous studies have shown that clown anemonefish react much stronger to models with vertical rather than horizontal bars, suggesting that the amount of white color or the general presence of white bars is not the deciding factor.

Combined with the observation that the plastic discs, which have no species defining traits other than the vertical bars, received the same response as the live fish, lead the researchers to suggest that the fish appear to be counting the number of vertical white bars to inform their level of aggression toward intruders.

The researchers also discovered a strict hierarchy in the clown anemonefish colonies that determines which fish attack the intruder.

In the wild, a colony typically consists of one alpha female, one beta male, and several gamma juveniles.

The social position within the colony is determined by very slight differences in size.

Anemonefish get their third and final stripe when they metamorphize into either a male or female when they grow large enough, which is why the current alpha uses harsh methods to uphold the status quo, including chasing out colony members if they grow too large.

Though the researchers used immature fish that have yet to metamorphize into males or females, they still observed the same size-based hierarchy, with the largest juvenile taking on the role of alpha and leading the charge against the intruder.

Read more at Science Daily

Can you change a chicken into a frog, a fish or a chameleon?

Gastrulation is one of the most important phases in early embryonic development. Before gastrulation, vertebrate embryos are simple two-dimensional sheets of cells. By the end of gastrulation, an embryo will have begun to differentiate distinct cell types, set up the basic axes of the body and internalize some of the precursors for organs in a three-dimensional structure. Amniotes, like chickens and humans, will have developed a primitive streak, the precursor to the brain and skin, while fish and amphibians will have developed a spherical-shaped blastopore.

Gastrulation is a feat of self-organization, requiring the ballet-like coordinated movements of hundreds to tens of thousands of cells.

But, despite its importance in development, scientists only partially understand the underlying mechanisms that coordinate this large-scale movement of cells.

Now a team of researchers from the Harvard, the University of California San Diego and the University of Dundee in the U.K., have developed a theoretical framework that can reproduce and predict the patterns associated with gastrulation in a chicken embryo.

Building on their experimental findings published earlier this year in Science Advances, and using a combination of theory and experiment, the researchers demonstrated that small changes in cell parameters and behavior can have a dramatic impact on the resulting gastrulation patterns.

The new research was also published in Science Advances.

"Linking the developmental processes underlying morphogenesis in an organism to the variations of these same processes across evolution is an old question in biology," said L. Mahadevan, the Lola England de Valpine Professor of Applied Mathematics at the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS), and Professor of Organismic and Evolutionary Biology, and of Physics in the Faculty of Arts and Sciences (FAS) and senior author of the paper.

"Moving away from the gene-centric molecular focus on this question, we asked if there are emergent biophysical principles that operate on the multi-cellular level and can help explain the self-organized gastrulation patterns from both a developmental and an evolutionary perspective."

Working closely with experimentalists, the researchers developed a theoretical and computational model that could recreate the movement of the epithelial layer of cells in chick embryos during gastrulation.

The team then identified two parameters -- one related to the initial distribution of cells in an embryo and the other related to cell behavior -- to tweak during gastrulation.

"When we changed these two parameters in the model, which was only informed by the mechanisms of chick development, it remarkably showed gastrulation patterns naturally seen in other species," said Mattia Serra, first author of the paper and former Schmidt Science fellow in the Mahadevan group.

Serra is an Assistant Professor in Physics at UC San Diego.

Consistent with the computational results, experiments show that perturbing the same parameters in vivo in a chick embryo caused the chick to form a disk-like blastopore, seen in frogs, a ring-like circular primitive streak, like those seen in fish, or an elongated elliptical canal-like streak seen in chameleon.

"Our work suggests that the general biophysical principles underlying active self-organized flows and forces during embryogenesis have the power to explain developmental processes and their evolutionary variations across different species of vertebrates," said Mahadevan.

"We were surprised to see how simple mechanochemical rules could predict highly distinct coherent flows of thousands of cells measured in a living chick embryo," said Serra.

This research not only sheds light on the principles for self- organization in early development but could also help researchers understand the evolutionary history of developmental processes and suggest ways to control the development of synthetic organoids.

This research looked at the early stages of development, when the embryo is just transforming from two-dimensions into three.

Next, Mahadevan wants to understand what happens when the embryo starts to fold and buckle to create the more complex shapes of organs and eventually whole organisms.

"Using our knowledge of developmental processes at the molecular and cellular level, we eventually hope to provide an integrated framework for how cells form into tissues and tissues into organs, towards a better understanding of morphogenesis," said Mahadevan.

Read more at Science Daily

Study uncovers hundred-year lifespans for three freshwater fish species in the Arizona desert

A recent study found some of the oldest animals in the world living in a place you wouldn't expect: fishes in the Arizona desert. Researchers found the second genus of animal ever for which three or more species have known lifespans greater than 100 years, which could open the doors to aging studies across disciplines, such as gerontology and senescence (aging) among vertebrates.

The study centers around a series of fish species within the Ictiobus genus, known as buffalofishes. Minnesota has native populations of each of the three species studied: bigmouth buffalo, smallmouth buffalo and black buffalo. The importance of this research is underscored by the fact that these fishes are often misidentified and lumped in with invasive species, like carp, and the fishing regulations in many places, including Minnesota, do not properly protect these species, and what could become a wealth of information about longevity and aging.

This new research from the University of Minnesota Duluth (UMD), recently published in Scientific Reports, was a collaboration between Alec Lackmann, PhD, an ichthyologist and assistant professor in the Department of Mathematics and Statistics of the Swenson College of Science and Engineering at UMD; other scientists including from North Dakota State University; and a group of conservation anglers who fish the Apache Lake reservoir in Arizona.

"There is likely a treasure trove of aging, longevity and negligible senescence information within the genus Ictiobus," said Lackmann. "This study brings light to this potential and opens the door to a future in which a more complete understanding of the process of vertebrate aging can be realized, including for humans. The research begs the question: what is the buffalofishes' fountain of youth?"

Lackmann has studied buffalofishes before, and his research from 2019 went so far as to extend the previously thought maximum age of bigmouth buffalo from around 25 years of age, to more than 100 years of age by applying and validating a far more refined aging technique than had been used previously. Instead of examining the fish's scale, "you extract what are called the otoliths, or earstones, from inside the cranium of the fish, and then thin section the stones to determine their age," said Lackmann.

Approximately 97 percent of fish species have otoliths. They're tiny stone-like structures that grow throughout the fish's lifetime, forming a new layer each year. When processed properly, scientists like Lackmann can examine the otolith with a compound microscope and count the layers, like the rings on a tree, and learn the age of the fish.

Results of the study include:

• Unparalleled longevity for freshwater fishes. Namely, three species with lifespans more than a century, with greater than 90 percent of the buffalofishes in Apache Lake more than 85 years old.
• The discovery that some of the original buffalofishes from the Arizona stocking in 1918 are likely still alive.
• A fishery of catch-and-release buffalofish angling that has not only increased our knowledge of fisheries, but also our understanding of how buffalofishes can be identified and recaptured across years, including uniquely-marked centenarians.
• A robust citizens and scientists collaborative effort that has resulted in thorough and consistent scientific outreach and learning.

Buffalofishes are native to central North America, including Minnesota, but those in this recent study were found in Apache Lake, a reservoir in the desert southwest. Originally reared in hatcheries and rearing ponds along the Mississippi River in the Midwest, the government stocked buffalofishes into Roosevelt Lake (upstream of Apache Lake), Arizona in 1918. While Roosevelt Lake was fished commercially, Apache Lake's fish populations remained largely untouched until anglers recently learned how to consistently catch buffalofishes there on rod-and-line.

When these catch-and-release conservation anglers noticed unique orange and black spots on many of the fish they were catching, they wanted to learn more about the markings, and found Lackmann's previous research. An Arizona angler, Stuart Black, reached out and invited Lackmann to a fishing expedition at Apache Lake, where the fish collected would be donated to science.

By studying the fishes collected at the angling event and analyzing their otoliths for age, Lackmann found that some of the buffalofishes from the 1918 Arizona stocking are likely still alive today, and that most of the buffalofishes in Apache Lake hatched during the early 1920s. More importantly, they discovered that the three different buffalofish species found in the lake had ages more than 100 years. To their knowledge, such longevity across multiple freshwater fish species is found nowhere else in the world.

For Lackmann, there are exciting possibilities for the future of studying this unique group of fish, with far-reaching implications.

Read more at Science Daily

Fruit, nectar, bugs and blood: How bat teeth and jaws evolved for a diverse dinnertime

They don't know it, but Darwin's finches changed the world. These closely related species -- native to the Galapagos Islands -- each sport a uniquely shaped beak that matches their preferred diet. Studying these birds helped Charles Darwin develop the theory of evolution by natural selection.

A group of bats has a similar -- and more expansive -- evolutionary story to tell. There are more than 200 species of noctilionoid bats, mostly in the American tropics. And despite being close relatives, their jaws evolved in wildly divergent shapes and sizes to exploit different food sources. A paper published Aug. 22 in Nature Communications shows those adaptations include dramatic, but also consistent, modifications to tooth number, size, shape and position. For example, bats with short snouts lack certain teeth, presumably due to a lack of space. Species with longer jaws have room for more teeth -- and, like humans, their total tooth complement is closer to what the ancestor of placental mammals had.

According to the research team behind this study, comparing noctilionoid species can reveal a lot about how mammalian faces evolved and developed, particularly jaws and teeth. And as a bonus, they can also answer some outstanding questions about how our own pearly whites form and grow.

"Bats have all four types of teeth -- incisors, canines, premolars and molars -- just like we do," said co-author Sharlene Santana, a University of Washington professor of biology and curator of mammals at the Burke Museum of Natural History & Culture. "And noctilionoid bats evolved a huge diversity of diets in as little as 25 million years, which is a very short amount of time for these adaptations to occur."

"There are noctilionoid species that have short faces like bulldogs with powerful jaws that can bite the tough exterior of the fruits that they eat. Other species have long snouts to help them drink nectar from flowers. How did this diversity evolve so quickly? What had to change in their jaws and teeth to make this possible?" said lead author Alexa Sadier, an incoming faculty member at the Institute of Evolutionary Science of Montpellier in France, who began this project as a postdoctoral researcher at the University California, Los Angeles.

Scientists don't know what triggered this frenzy of dietary adaptation in noctilionoid bats. But today different noctilionoid species feast on insects, fruit, nectar, fish and even blood -- since this group also includes the infamous vampire bats.

The team used CT scans and other methods to analyze the shapes and sizes of jaws, premolars and molars in more than 100 noctilionoid species. The bats included both museum specimens and a limited number of wild bats captured for study purposes. The researchers compared the relative sizes of teeth and other cranial features among species with different types of diets, and used mathematical modeling to determine how those differences are generated during development.

The team found that, in noctilionoid bats, certain "developmental rules" caused them to generate the right assortment of teeth to fit in their diet-formed grins. For example, bats with long jaws -- like nectar-feeders -- or intermediate jaws, like many insect-eaters, tended to have the usual complement of three premolars and three molars on each side of the jaw. But bats with short jaws, including most fruit-eating bats, tended to ditch the middle premolar or the back molar, if not both.

"When you have more space, you can have more teeth," said Sadier. "But for bats with a shorter space, even though they have a more powerful bite, you simply run out of room for all these teeth."

Having a shorter jaw may also explain why many short-faced bats also tended to have wider front molars.

"The first teeth to appear tend to grow bigger since there is not enough space for the next ones to emerge," said Sadier.

"This project is giving us the opportunity to actually test some of the assumptions that have been made about how tooth growth, shape and size are regulated in mammals," said Santana. "We know surprisingly little about how these very important structures develop!"

Many studies about mammalian tooth development were done in mice, which have only molars and heavily modified incisors. Scientists are not entirely sure if the genes and developmental patterns that control tooth development in mice also operate in mammals with more "ancestral" sets of chompers -- like bats and humans.

Sadier, Santana and their colleagues believe their project, which is ongoing, can start to answer these questions in bats -- along with many other outstanding questions about how evolution shapes mammalian features. They're expanding this study to include noctilionoid incisors and canines, and hope to uncover more of the genetic and developmental mechanisms that control tooth development in this diverse group of bats.

"We see such strong selective pressures in these bats: Shapes have to closely match their function," said Santana. "I think there are many more evolutionary secrets hidden in these species."

Read more at Science Daily

Prehistoric fish fills 100 million year gap in evolution of the skull

A 455-million-year-old fossil fish provides a new perspective on how vertebrates evolved to protect their brains, a study has found.

In a paper published in Nature today (Wednesday 20th September), researchers from the University of Birmingham, Naturalis Biodiversity Centre in Leiden, Netherlands; and the Natural History Museum have pieced together the skull of Eriptychius americanus.

The research, funded by the Leverhulme Trust, suggests that the ancient jawless fish found in ancient deposits in Colorado, USA has a skull unlike that of any previously seen, and fills a gap currently spanning 100 million years in the evolutionary history of the vertebrate skull.

Using computed tomography, a form of x-ray technique, scientists recreated a detailed 3D representation of the skull of Eriptychius and is the first time that such a comprehensive recreation has been done on the specimen which was collected in the 1940s, originally described in the 1960s and is housed in the Field Museum of Natural History, Chicago.

This ancient fish had separated, independent cartilages encasing the brain, rather than the solid bone or cartilage structure of jawless and jawed fish that followed it.

While later specieshave a fully bound cage of cartilage that holds the brain, these results suggest that the early evolution of structures to separate the brain from other parts of the head may have begun with Eriptychius.

Dr Ivan Sansom, Senior Lecturer in Palaeobiology at the University of Birmingham and senior author of the paper said:

"These are tremendously exciting results that may reveal the early evolutionary history of how primitive vertebrates protected their brains. Eriptychius americanus appears to be the first evidence for a series of cartilages separating the brain from the rest of the head. This study emphasises the importance of museum collections and the application of new techniques in studying them."

Read more at Science Daily

This fish doesn't just see with its eyes -- it also sees with its skin

A few years ago while on a fishing trip in the Florida Keys, biologist Lori Schweikert came face to face with an unusual quick-change act. She reeled in a pointy-snouted reef fish called a hogfish and threw it onboard. But later when she went to put it in a cooler she noticed something odd: its skin had taken on the same color and pattern as the deck of the boat.

A common fish in the western Atlantic Ocean from North Carolina to Brazil, the hogfish is known for its color-changing skin. The species can morph from white to mottled to reddish-brown in a matter of milliseconds to blend in with corals, sand or rocks.

Still, Schweikert was surprised because this hogfish had continued its camouflage even though it was no longer alive. Which got her wondering: can hogfish detect light using only their skin, independently of their eyes and brain?

"That opened up this whole field for me," Schweikert said.

In the years that followed, Schweikert started researching the physiology of "skin vision" as a postdoctoral fellow at Duke University and Florida International University.

In 2018, Schweikert and Duke biologist Sönke Johnsen published a study showing that hogfish carry a gene for a light-sensitive protein called opsin that is activated in their skin, and that this gene is different from the opsin genes found in their eyes.

Other color-changing animals from octopuses to geckos have been found to make light-sensing opsins in their skin, too. But exactly how they use them to help change color is unclear.

"When we found it in hogfish, I looked at Sönke and said: Why have a light detector in the skin?" said Schweikert, now an assistant professor at the University of North Carolina Wilmington.

One hypothesis is that light-sensing skin helps animals take in their surroundings. But new findings suggest another possibility -- "that they could be using it to view themselves," Schweikert said.

In a study appearing Aug. 22 in the journal Nature Communications, Schweikert, Johnsen and colleagues teamed up to take a closer look at hogfish skin.

The researchers took pieces of skin from different parts of the fish's body and took pictures of them under a microscope.

Up close, a hogfish's skin looks like a pointillist painting. Each dot of color is a specialized cell called a chromatophore containing granules of pigment that can be red, yellow or black.

It's the movement of these pigment granules that changes the skin color. When the granules spread out across the cell, the color appears darker. When they cluster together into a tiny spot that's hard to see, the cell becomes more transparent.

Next, the researchers used a technique called immunolabeling to locate the opsin proteins within the skin. They found that in the hogfish, opsins aren't produced in the color-changing chromatophore cells. Instead, the opsins reside in other cells directly beneath them.

Images taken with a transmission electron microscope revealed a previously unknown cell type, just below the chromatophores, packed with opsin protein.

This means that light striking the skin must pass through the pigment-filled chromatophores first before it reaches the light-sensitive layer, Schweikert said.

The researchers estimate that the opsin molecules in hogfish skin are most sensitive to blue light. This happens to be the wavelength of light that the pigment granules in the fish's chromatophores absorb best.

The findings suggest that fish's light-sensitive opsins act somewhat like internal Polaroid film, capturing changes in the light that is able to filter through the pigment-filled cells above as the pigment granules bunch up or fan out.

"The animals can literally take a photo of their own skin from the inside," Johnsen said. "In a way they can tell the animal what it's skin looks like, since it can't really bend over to look."

"Just to be clear, we're not arguing that hogfish skin functions like an eye," Schweikert added. Eyes do more than merely detect light -- they form images. "We don't have any evidence to suggest that's what's happening in their skin," Schweikert said.

Rather, it's a sensory feedback mechanism that lets the hogfish monitor its own skin as it changes color, and fine-tune it to fit what it sees with its eyes.

"They appear to be watching their own color change," Schweikert said.

The researchers say the work is important because it could pave the way to new sensory feedback techniques for devices such as robotic limbs and self-driving cars that must fine-tune their performance without relying solely on eyesight or camera feeds.

"Sensory feedback is one of the tricks that technology is still trying to figure out," Johnsen said. "This study is a nice dissection of a new sensory feedback system."

"If you didn't have a mirror, and you couldn't bend your neck, how would you know if you're dressed appropriately?" Schweikert said. "For us it may not matter," she added. But for creatures that use their color-changing abilities to hide from predators, warn rivals or woo mates, "it could be life or death."

Read more at Science Daily

River erosion can shape fish evolution

New findings could explain biodiversity hotspots in tectonically quiet regions.

If we could rewind the tape of species evolution around the world and play it forward over hundreds of millions of years to the present day, we would see biodiversity clustering around regions of tectonic turmoil. Tectonically active regions such as the Himalayan and Andean mountains are especially rich in flora and fauna due to their shifting landscapes, which act to divide and diversify species over time.

But biodiversity can also flourish in some geologically quieter regions, where tectonics hasn't shaken up the land for millennia. The Appalachian Mountains are a prime example: The range has not seen much tectonic activity in hundreds of millions of years, and yet the region is a notable hotspot of freshwater biodiversity.

Now, an MIT study identifies a geological process that may shape the diversity of species in tectonically inactive regions. In a paper appearing in Science, the researchers report that river erosion can be a driver of biodiversity in these older, quieter environments.

They make their case in the southern Appalachians, and specifically the Tennessee River Basin, a region known for its huge diversity of freshwater fishes. The team found that as rivers eroded through different rock types in the region, the changing landscape pushed a species of fish known as the greenfin darter into different tributaries of the river network. Over time, these separated populations developed into their own distinct lineages.

The team speculates that erosion likely drove the greenfin darter to diversify. Although the separated populations appear outwardly similar, with the greenfin darter's characteristic green-tinged fins, they differ substantially in their genetic makeup. For now, the separated populations are classified as one single species.

"Give this process of erosion more time, and I think these separate lineages will become different species," says Maya Stokes PhD '21, who carried out part of the work as a graduate student in MIT's Department of Earth, Atmospheric and Planetary Sciences (EAPS).

The greenfin darter may not be the only species to diversify as a consequence of river erosion. The researchers suspect that erosion may have driven many other species to diversify throughout the basin, and possibly other tectonically inactive regions around the world.

"If we can understand the geologic factors that contribute to biodiversity, we can do a better job of conserving it," says Taylor Perron, the Cecil and Ida Green Professor of Earth, Atmospheric, and Planetary Sciences at MIT.

The study's co-authors include collaborators at Yale University, Colorado State University, the University of Tennessee, the University of Massachusetts at Amherst, and the Tennessee Valley Authority (TVA). Stokes is currently an assistant professor at Florida State University.

Fish in trees

The new study grew out of Stokes' PhD work at MIT, where she and Perron were exploring connections between geomorphology (the study of how landscapes evolve) and biology. They came across work at Yale by Thomas Near, who studies lineages of North American freshwater fishes. Near uses DNA sequence data collected from freshwater fishes across various regions of North America to show how and when certain species evolved and diverged in relation to each other.

Near brought a curious observation to the team: a habitat distribution map of the greenfin darter showing that the fish was found in the Tennessee River Basin -- but only in the southern half. What's more, Near had mitochondrial DNA sequence data showing that the fish's populations appeared to be different in their genetic makeup depending on the tributary in which they were found.

To investigate the reasons for this pattern, Stokes gathered greenfin darter tissue samples from Near's extensive collection at Yale, as well as from the field with help from TVA colleagues. She then analyzed DNA sequences from across the entire genome, and compared the genes of each individual fish to every other fish in the dataset. The team then created a phylogenetic tree of the greenfin darter, based on the genetic similarity between fish.

From this tree, they observed that fish within a tributary were more related to each other than to fish in other tributaries. What's more, fish within neighboring tributaries were more similar to each other than fish from more distant tributaries.

"Our question was, could there have been a geological mechanism that, over time, took this single species, and splintered it into different, genetically distinct groups?" Perron says.

A changing landscape

Stokes and Perron started to observe a "tight correlation" between greenfin darter habitats and the type of rock where they are found. In particular, much of the southern half of the Tennessee River Basin, where the species abounds, is made of metamorphic rock, whereas the northern half consists of sedimentary rock, where the fish are not found.

They also observed that the rivers running through metamorphic rock are steeper and more narrow, which generally creates more turbulence, a characteristic greenfin darters seem to prefer. The team wondered: Could the distribution of greenfin darter habitat have been shaped by a changing landscape of rock type, as rivers eroded into the land over time?

To check this idea, the researchers developed a model to simulate how a landscape evolves as rivers erode through various rock types. They fed the model information about the rock types in the Tennessee River Basin today, then ran the simulation back to see how the same region may have looked millions of years ago, when more metamorphic rock was exposed.

They then ran the model forward and observed how the exposure of metamorphic rock shrank over time. They took special note of where and when connections between tributaries crossed into non-metamorphic rock, blocking fish from passing between those tributaries. They drew up a simple timeline of these blocking events and compared this to the phylogenetic tree of diverging greenfin darters. The two were remarkably similar: The fish seemed to form separate lineages in the same order as when their respective tributaries became separated from the others.

"It means it's plausible that erosion through different rock layers caused isolation between different populations of the greenfin darter and caused lineages to diversify," Stokes says.

Read more at Science Daily

Researchers develop model for how the brain acquires essential omega-3 fatty acids

Researchers at the UCLA David Geffen School of Medicine, the Howard Hughes Medical Institute at UCLA and the National Institutes of Health have developed a zebrafish model that provides new insight into how the brain acquires essential omega-3 fatty acids, including docosahexaenoic acid (DHA) and linolenic acid (ALA). Their findings, published in Nature Communications,have the potential to improve understanding of lipid transport across the blood-brain barrier and of disruptions in this process that can lead to birth defects or neurological conditions. The model may also enable researchers to design drug molecules that are capable of directly reaching the brain.

Omega-3 fatty acids are considered essential because the body cannot make them and must obtain them through foods, such as fish, nuts and seeds. DHA levels are especially high in the brain and important for a healthy nervous system. Infants obtain DHA from breastmilk or formula, and deficiencies of this fatty acid have been linked to problems with learning and memory. To get to the brain, omega-3 fatty acids must pass through the blood-brain barrier via the lipid transporter Mfsd2a, which is essential for normal brain development. Despite its importance, scientists did not know precisely how Mfsd2a transports DHA and other omega-3 fatty acids.

In the study, the research team provides images of the structure of zebrafish Mfsd2a, which is similar to its human counterpart. The snapshots are the first to detail precisely how fatty acids move across the cell membrane. The study team also identified three compartments in Mfsd2a that suggest distinct steps required to move and flip fatty acids through the transporter, as opposed to movement through a linear tunnel or along the surface of the protein complex. The findings provide key information on how Mfsd2a transports omega-3 fatty acids into the brain and may enable researchers to optimize drug delivery via this route. The study also provides foundational knowledge on how other members of this transporter family, called the major facilitator superfamily (MFS), regulate important cellular functions.

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Most of world's salt marshes likely to be underwater by 2100, study concludes

Cape Cod's salt marshes are as iconic as they are important. These beautiful, low-lying wetlands are some of the most biologically productive ecosystems on Earth. They play an outsized role in nitrogen cycling, act as carbon sinks, protect coastal development from storm surge, and provide critical habitats and nurseries for many fish, shellfish, and coastal birds.

And, according to new research from the Marine Biological Laboratory (MBL), more than 90 percent of the world's salt marshes are likely to be underwater by the end of the century.

The findings come from a 50-year study in Great Sippewissett Marsh in Falmouth, Massachusetts. Since 1971, scientists from the MBL Ecosystems Center have mapped vegetative cover in experimental plots in this marsh to examine whether increased nitrogen in the environment would impact species of marsh grass. Due to the study's length, they also were able to detect the effects of climate change on the ecosystem, especially those driven by accelerating sea level rise.

The researchers found that increased nitrogen favored higher levels of vegetation and accretion of the marsh surface, but that no matter what the concentration of nitrogen they applied to the marsh, these ecosystems won't be able to outpace submergence from global sea level rise.

"Places like Great Sippewissett Marsh will likely become shallow inlets by the turn of the century," says MBL Distinguished Scientist Ivan Valiela, lead author of the study. "Even under conservative sea level estimates…more than 90% of the salt marshes of the world will likely be submerged and disappear or be diminished by the end of the century."

"This is not a prediction from isolated scientists worried about little details. Major changes are going to be taking place on the surface of the Earth that will change the nature of coastal environments," says Valiela.

An Ecosystem Engineer

Salt marshes are gently sloping ecosystems and their plants have very narrow preferences for the elevations in which they can grow. Different species grow in the upper elevations (high marsh) versus the low elevation closer to the ocean (low marsh) and have different responses to changes in nitrogen supply. When change happens slowly enough, the grasses can migrate to their preferred elevation.

In the low marsh, cordgrass (Spartina alterniflora) prospered as scientists increased the nitrogen supply. Among high marsh species, the abundance of marsh hay (Spartina patens) in the experimental plots decreased with sea level rise. Saltgrass (Distichlis spicata) increased with nitrogen supply and also acted as what the researchers called an "ecosystem engineer" -- increasing the rate at which marsh elevation rose. Accretion of biomass left behind by the decomposing saltgrass compensated for the increased submergence resulting from rising sea level in these areas.

"Saltgrass disappeared after a few decades, but it left a legacy behind," says MBL Research Scientist Javier Lloret, adding that it was "extremely cool to see that interaction in the dataset."

Regardless of how much nitrogen was added to the environment, the research showed that at the current and future forecasted sea level rise, low marsh species will completely replace high marsh species. As sea levels continue to rise, even these species will be submerged.

"At some point, if sea level continues to increase at the rates that we anticipate, there will even be no more room for the low marsh plants. They're just going to be too submerged to survive." says Valiela.

The only alternative would be for salt marshes to migrate landward.

A Coastal Squeeze

Marshes around the world face what Lloret calls a "coastal squeeze," where sea level rise pushes from one direction and human development pushes from the other. A seawall that may protect a home from flooding will prevent the migration of a marsh naturally moving to higher ground.

"These barriers, whether they be geographic like a hill or a cliff, or people building along the edges of the ecosystem, constrain the potential for landward marsh migration," says MBL Research Assistant Kelsey Chenoweth. "On top of that, sea level rise is accelerating and marshes are having a hard time keeping up."

In a sea level rise scenario like the one we're facing, "the only solution for the plants will be to colonize new areas, to go uphill," says Lloret. "But that migration may just be impossible in some places."

"Sea level rise is the most important threat to salt marshes. We really need to figure out what's going to happen to these ecosystems and learn how to prevent some of the losses from happening or try to adapt to them, so marshes can continue to play these important roles for nature as well as humans," says Lloret.

Half a Century of Science

In 1971, the scientists at the MBL Ecosystems Center had no idea they would be using their data to study global sea level rise.

"This was an experiment that started looking at one ecological control (nitrogen), and then because of the longevity of the project, we were able to add new knowledge about this major accelerating agent of global change -- global sea level rise," says Valiela.

That's the benefit of long-term datasets like the one at Great Sippewissett Marsh.

"You're setting a baseline to the problems that haven't even happened yet," says Chenoweth.

When measuring ecological processes like climate change and eutrophication, the data can ebb and flow over the course of years as the ecosystem responds to external stimuli. The changes operate on a much longer time scale than changes on other biological systems.

"To study a tree, you look at changes through seasons and you should be able to see its whole cycle. For a leaf, you look at patterns between day and night. In single cells, you look at processes that take place at the timescale of minutes or seconds … but for an entire ecosystem, we're talking many years or decades," says Lloret. "You need to be thinking at the scale of decades or even centuries in order to be able to see substantial changes."

Read more at Science Daily

How fishermen benefit from reversing evolution of cod

Leipzig. Intense fishing and overexploitation have led to evolutionary changes in fish stocks like cod, reducing both their productivity and value on the market. These changes can be reversed by more sustainable and far-sighted fisheries management. The new study by researchers from the German Centre for Integrative Biodiversity Research (iDiv), Leipzig University and the Institute of Marine Research in Tromsø, which was published in Nature Sustainability, shows that reversal of evolutionary change would only slightly reduce the profit of fishing, but would help regain and conserve natural genetic diversity.

The impact of global fisheries on marine ecosystems is severe: fish stocks have declined and the degradation of marine habitats as well as the loss of biodiversity have been accelerated. Less visible, intense fishing has also affected the age and size structure of fish stocks and caused evolutionary change, often towards lower growth rates, smaller maturation sizes and earlier reproduction age. For example, cod in the North Sea, which has been heavily exploited in the past, matures at sizes just above 50 cm, compared to more than 70 cm expected in an unfished population.

Earlier reproduction can increase stock resilience in the short-term, but over time results in populations with smaller fish that have less offspring. "At the end of the day, this can reduce both the productivity of a stock and the value on the market," says first author Hanna Schenk from iDiv and Leipzig University. "Apart from this, we don't know much about potential consequences such as trophic cascades and other ecosystem changes that feed back onto the harvested species and may interfere with critical ecological functions."

Only long-term planning can reverse evolutionary decline

But evolution is not a one-way street. This is why the researchers from iDiv, Leipzig University and the Institute of Marine Research in Tromsø (Norway) wanted to find out what it takes to reverse evolutionary decline after decades of intensive exploitation, in particular with regard to planning horizons in fisheries management. For this, they developed a model that took various processes into account: Biological growth and reproduction as well as economic harvesting costs and consumer preferences. The researchers also analysed potential trade-offs between economic profit and conservation targets.

They found that evolutionary decline is profitable to reverse under century-long planning horizons. With more typical short-term planning, stock recovery in terms of biomass is achieved, but evolutionary decline continues, albeit at much lower rates. "Fisheries typically consider short planning horizons of a few years. This stands in contrast to long-term sustainability and biodiversity targets," says Hanna Schenk. The researchers found that more far-sighted planning horizons would help to rebuild the stock but evolutionary decline continues. According to Schenk, reversing this process takes much longer than the recovery of the stock biomass and is only achieved with century-long planning horizons.

Appropriate conservation targets only slightly reduce profit

The researchers also show that setting conservation targets for restoring not only fish stocks, but also their genetic composition would only slightly reduce profits. The cost and time of evolutionary reversal could be reduced further if fisheries can select fish depending on their genes, which may be possible to some extent by choosing the time and place of harvest. However, current conservation agendas do not include the restoration of genetic diversity, for example target 14 of the Sustainable Development Goals (SGDs), which calls for an end to overfishing.

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Mild fever helps clear infections faster, new study suggests

It may be better to let a mild fever run its course instead of automatically reaching for medication, new University of Alberta research suggests.

Researchers found that untreated moderate fever helped fish clear their bodies of infection rapidly, controlled inflammation and repaired damaged tissue. "We let nature do what nature does, and in this case it was very much a positive thing," says immunologist Daniel Barreda, lead author on the study and a joint professor in the Faculty of Agricultural, Life & Environmental Sciences and the Faculty of Science.

Moderate fever is self-resolving, meaning that the body can both induce it and shut it down naturally without medication, Barreda explains. The health advantages of natural fever to humans still have to be confirmed through research, but the researchers say because the mechanisms driving and sustaining fever are shared among animals, it is reasonable to expect similar benefits are going to happen in humans.

That suggests we should resist reaching for over-the-counter fever medications, also known as non-steroidal anti-inflammatory drugs, at the first signs of a mild temperature, he says. "They take away the discomfort felt with fever, but you're also likely giving away some of the benefits of this natural response."

The study helps shed light on the mechanisms that contribute to the benefits of moderate fever, which Barreda notes has been evolutionarily conserved across the animal kingdom for 550 million years. "Every animal examined has this biological response to infection."

For the study, fish were given a bacterial infection and their behaviour was then tracked and evaluated using machine learning. Outward symptoms were similar to those seen in humans with fever, including immobility, fatigue and malaise. These were then matched to important immune mechanisms inside the animals.

The research showed that natural fever offers an integrative response that not only activates defences against infection, but also helps control it.The researchers found that fever helped to clear the fish of infection in about seven days -- half the time it took for those animals not allowed to exert fever. Fever also helped to shut down inflammation and repair injured tissue.

Read more at Science Daily

319-million-year-old fish preserves the earliest fossilized brain of a backboned animal

The CT-scanned skull of a 319-million-year-old fossilized fish, pulled from a coal mine in England more than a century ago, has revealed the oldest example of a well-preserved vertebrate brain.

The brain and its cranial nerves are roughly an inch long and belong to an extinct bluegill-size fish. The discovery opens a window into the neural anatomy and early evolution of the major group of fishes alive today, the ray-finned fishes, according to the authors of a University of Michigan-led study scheduled for publication Feb. 1 in Nature.

The serendipitous find also provides insights into the preservation of soft parts in fossils of backboned animals. Most of the animal fossils in museum collections were formed from hard body parts such as bones, teeth and shells.

The CT-scanned brain analyzed for the new study belongs to Coccocephalus wildi, an early ray-finned fish that swam in an estuary and likely dined on small crustaceans, aquatic insects and cephalopods, a group that today includes squid, octopuses and cuttlefish. Ray-finned fishes have backbones and fins supported by bony rods called rays.

When the fish died, the soft tissues of its brain and cranial nerves were replaced during the fossilization process with a dense mineral that preserved, in exquisite detail, their three-dimensional structure.

"An important conclusion is that these kinds of soft parts can be preserved, and they may be preserved in fossils that we've had for a long time -- this is a fossil that's been known for over 100 years," said U-M paleontologist Matt Friedman, a senior author of the new study and director of the Museum of Paleontology.

The lead author is U-M doctoral student Rodrigo Figueroa, who did the work as part of his dissertation, under Friedman, in the Department of Earth and Environmental Sciences.

"Not only does this superficially unimpressive and small fossil show us the oldest example of a fossilized vertebrate brain, but it also shows that much of what we thought about brain evolution from living species alone will need reworking," Figueroa said.

"With the widespread availability of modern imaging techniques, I would not be surprised if we find that fossil brains and other soft parts are much more common than we previously thought. From now on, our research group and others will look at fossil fish heads with a new and different perspective."

The skull fossil from England is the only known specimen of its species, so only nondestructive techniques could be used during the U-M-led study.

The work on Coccocephalus is part of a broader effort by Friedman, Figueroa and colleagues that uses computed tomography (CT) scanning to peer inside the skulls of early ray-finned fishes. The goal of the larger study is to obtain internal anatomical details that provide insights about evolutionary relationships.

In the case of C. wildi, Friedman was not looking for a brain when he fired up his micro-CT scanner and examined the skull fossil.

"I scanned it, then I loaded the data into the software we use to visualize these scans and noticed that there was an unusual, distinct object inside the skull," he said.

The unidentified blob was brighter on the CT image -- and therefore likely denser -- than the bones of the skull or the surrounding rock.

"It is common to see amorphous mineral growths in fossils, but this object had a clearly defined structure," Friedman said.

The mystery object displayed several features found in vertebrate brains: It was bilaterally symmetrical, it contained hollow spaces similar in appearance to ventricles, and it had multiple filaments extending toward openings in the braincase, similar in appearance to cranial nerves, which travel through such canals in living species.

"It had all these features, and I said to myself, 'Is this really a brain that I'm looking at?'" Friedman said. "So I zoomed in on that region of the skull to make a second, higher-resolution scan, and it was very clear that that's exactly what it had to be. And it was only because this was such an unambiguous example that we decided to take it further."

Though preserved brain tissue has rarely been found in vertebrate fossils, scientists have had better success with invertebrates. For example, the intact brain of a 310-million-year-old horseshoe crab was reported in 2021, and scans of amber-encased insects have revealed brains and other organs. There is even evidence of brains and other parts of the nervous system recorded in flattened specimens more than 500 million years old.

The preserved brain of a 300-million-year-old shark relative was reported in 2009. But sharks, rays and skates are cartilaginous fishes, which today hold relatively few species compared to the ray-finned fish lineage containing Coccocephalus. Early ray-finned fishes like Coccocephalus can tell scientists about the initial evolutionary phases of today's most diverse fish group, which includes everything from trout to tuna, seahorses to flounder.

There are roughly 30,000 ray-finned fish species, and they account for about half of all backboned animal species. The other half is split between land vertebrates -- birds, mammals, reptiles and amphibians -- and less diverse fish groups like jawless fishes and cartilaginous fishes.

The Coccocephalus skull fossil is on loan to Friedman from England's Manchester Museum. It was recovered from the roof of the Mountain Fourfoot coal mine in Lancashire and was first scientifically described in 1925. The fossil was found in a layer of soapstone adjacent to a coal seam in the mine.

Though only its skull was recovered, scientists believe that C. wildi would have been 6 to 8 inches long. Judging from its jaw shape and its teeth, it was probably a carnivore, according to Figueroa.

When the fish died, scientists suspect it was quickly buried in sediments with little oxygen present. Such environments can slow the decomposition of soft body parts.

In addition, a chemical micro-environment inside the skull's braincase may have helped to preserve the delicate brain tissues and to replace them with a dense mineral, possibly pyrite, Figueroa said.

Evidence supporting this idea comes from the cranial nerves, which send electrical signals between the brain and the sensory organs. In the Coccocephalus fossil, the cranial nerves are intact inside the braincase but disappear as they exit the skull.

"There seems to be, inside this tightly enclosed void in the skull, a little micro-environment that is conducive to the replacement of those soft parts with some kind of mineral phase, capturing the shape of tissues that would otherwise simply decay away," Friedman said.

Detailed analysis of the fossil, along with comparisons to the brains of modern-fish specimens from the U-M Museum of Zoology collection, revealed that the brain of Coccocephalus has a raisin-size central body with three main regions that roughly correspond to the forebrain, midbrain and hindbrain in living fishes.

Cranial nerves project from both sides of the central body. Viewed as a single unit, the central body and the cranial nerves resemble a tiny crustacean, such as a lobster or a crab, with projecting arms, legs and claws.

Notably, the brain structure of Coccocephalus indicates a more complicated pattern of fish-brain evolution than is suggested by living species alone, according to the authors.

"These features give the fossil real value in understanding patterns of brain evolution, rather than simply being a curiosity of unexpected preservation," Figueroa said.

For example, all living ray-finned fishes have an everted brain, meaning that the brains of embryonic fish develop by folding tissues from the inside of the embryo outward, like a sock turned inside out.

All other vertebrates have evaginated brains, meaning that neural tissue in developing brains folds inward.

"Unlike all living ray-finned fishes, the brain of Coccocephalus folds inward," Friedman said. "So, this fossil is capturing a time before that signature feature of ray-finned fish brains evolved. This provides us with some constraints on when this trait evolved -- something that we did not have a good handle on before the new data on Coccocephalus."

Comparisons to living fishes showed that the brain of Coccocephalus is most similar to the brains of sturgeons and paddlefish, which are often called "primitive" fishes because they diverged from all other living ray-finned fishes more than 300 million years ago.

Friedman and Figueroa are continuing to CT scan the skulls of ray-finned fish fossils, including several specimens that Figueroa brought to Ann Arbor on loan from institutions in his home country, Brazil. Figueroa said his doctoral dissertation was delayed by the COVID-19 pandemic but is expected to be completed in summer 2024.

The Nature study includes data produced at U-M's Computed Tomography in Earth and Environmental Science facility, which is supported by the Department of Earth and Environmental Sciences and the College of Literature, Science, and the Arts.

The other authors of the paper are Sam Giles of London's Natural History Museum and the University of Birmingham; Danielle Goodvin and Matthew Kolmann of the U-M Museum of Paleontology; and Michael Coates and Abigail Caron of the University of Chicago.

Friedman and Figueroa said the discovery highlights the importance of preserving specimens in paleontology and zoology museums.

Read more at Science Daily

The other paleo diet: Rare discovery of dinosaur remains preserved with its last meal

Microraptor was an opportunistic predator, feeding on fish, birds, lizards -- and now small mammals. The discovery of a rare fossil reveals the creature was a generalist carnivore in the ancient ecosystem of dinosaurs.

Finding the last meal of any fossil animal is rare. When McGill University Professor Hans Larsson saw a complete mammal foot inside the rib cage of the small, feathered dinosaur, his jaw dropped. Of the many hundreds of carnivorous dinosaur skeletons, only 20 cases preserve their last meals. This new find makes 21.

"At first, I couldn't believe it. There was a tiny rodent-like mammal foot about a centimeter long perfectly preserved inside a Microraptor skeleton. These finds are the only solid evidence we have about the food consumption of these long extinct animals -- and they are exceptionally rare," says Larsson, who came across the fossil while visiting museum collections in China.

Microraptor was not a picky eater

Fully feathered with wings on both its arms and legs, this dinosaur is closely linked to the origin of birds. Microraptor was about the size of a crow and one of the smallest dinosaurs. The first specimen was discovered in deposits in Liaoning, China, in the early 2000s.

"We already know of Microraptor specimens preserved with parts of fish, a bird, and a lizard in their bellies. This new find adds a small mammal to their diet, suggesting these dinosaurs were opportunistic and not picky eaters," says Larsson who is a Professor of Biology at the Redpath Museum of McGill University.

"Knowing they were not specialized to any particular food is a big deal," he adds. According to the team of researchers, this could be the first evidence of a generalist carnivore in dinosaur ecosystems. Generalist predators are important stabilizers in today's ecosystems, like foxes and crows, because they can feed among several species that may have differing population abundances.

"Knowing that Microraptor was a generalist carnivore puts a new perspective on how ancient ecosystems may have worked and a possible insight into the success of these small, feathered dinosaurs," says Larsson.

From Science Daily

Genetic barriers, a warming ocean, and the uncertain future for an important forage fish

In the vast oceans, one would assume their inhabitants can travel far and wide and, as a result, populations of a species would mix freely. But this doesn't appear to be the case for a vital forage fish called the sand lance.

Sand lance are small schooling fish impressively rich in lipids, which makes them a fantastic and significant food source for at least 70 different species ranging from whales and sharks to seabirds, says UConn Associate Professor of Marine Sciences Hannes Baumann.

The Northern sand lance can be found from the waters off New Jersey all the way north to Greenland. Researchers, including Baumann and Ph.D. student Lucas Jones, were interested to see if sand lance constitute a massive, homogenous population, or whether there are genetically distinct groups. Their findings are published in the ICES Journal of Marine Science.

Baumann explains these are important questions to answer when considering conservation and sustainable management of the species, especially since the regions where sand lance live are warming faster than many areas of the planet due to climate change.

Sampling fish from such a broad range is no small task, but two years ago, Baumann and Jones began reaching out to other researchers to see if they had tissue samples to spare. Baumann credits the work to the international group of colleagues who contributed samples including co-authors from Canada and Greenland, and who helped sequence and analyze the data including co-authors from Cornell University.

In all, Baumann, Jones, and the team were able to sequence and analyze nearly 300 samples from a variety of locations across the sand lance's range using a technique called low-coverage whole genome sequencing. They also sequenced the first reference genome for sand lance.

In a nutshell, Baumann says they found an area on the Scotian Shelf, off the coast of Nova Scotia, where a genetic break occurs. The researchers distinguished two distinct groups, one north and one south of the divide, with parts of the genome differing quite dramatically -- namely on chromosomes 21 and 24. Without obvious physical barriers like a mountain range separating the groups, Baumann says it's logical to ask how these differences are possible.

"That is the scientific conundrum," says Baumann, and the answer, it appears, lies in the currents.

"When fish from the north reproduce and drift south, they are genetically less adapted to warmer southern waters, even if it's five or six degrees warmer in the winter, they are just not surviving," Baumann says. "These populations may be linked by the ocean currents, but the realized connectivity is basically zero."

This finding is a first for the sand lance, but it has been shown in other species such as lobsters, cod, and scallops, and this research adds further evidence to an apparent temperature divide at the Scotian Shelf, and helps demonstrate that temperature is an important factor in survival.

"Example after example shows that the ocean is not as homogeneous a place as expected, and there are all kinds of things that prevent that constant mixing,"Baumann says. "We found another striking example of that."

When researchers find adaptation in an environment where mixing is continuous, like in the ocean, Baumann says, the question is how it is possible that groups stay different, even though they are constantly encountering other genotypes. That is where powerful genomic methods, like the ones used in this paper, come in handy.

"Parts of the genome in many species have what we call a 'genetic inversion,' which means that the genes on the chromosome from one parent have a certain order and the genes on the same chromosome that come from the other parent that code for the same thing, and they're the same area, but they're flipped," Baumann says.

These inversions mean recombination cannot occur; therefore, the genes are passed down through the generations and play an important role in adaptation.

"We discovered on chromosomes 21 and 24 there are whole regions that are completely different and that is like the trademark signature of what we call an inversion because there's no recombination going on."

Baumann says that knowing there are genetic and ecological barriers on the Scotian Shelf is important, because with climate change, this barrier may move north and while that may be good news for southern fish, it's bad news for the fish currently there.

The researchers were also a little relieved in finding two clusters, because had there been many smaller clusters, it could make management and conservation more challenging, especially considering scenarios like the construction of offshore wind parks. Areas potentially well situated for wind turbines can also be habitats for sand lance, and construction disrupts habitats. If there were many, smaller population clusters, a single construction project could pose the risk of completely wiping out a cluster, whereas with more widely dispersed populations, though the local population may be temporarily disturbed, it will not be long before they are able to re-establish after construction is completed.

Baumann plans to focus further research on studying the genetic basis of the thermal divide.

"We want to make sure that this fish is productive and resilient, despite climate change, so we should make sure these areas where they are occurring are protected," Bauman says. "These decisions should include experts to ensure if there's an area that is very critical to sand lance, that any disturbance is temporary."

It isn't an unsolvable conflict, but it is something that we need to do, says Baumann, who also notes that it is possible that sand lance north of the thermal divide are already suffering more from warming because the region is warming faster.

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Oldest evidence of the controlled use of fire to cook food, researchers report

A remarkable scientific discovery has been made by researchers from the Hebrew University of Jerusalem (HU), Tel Aviv University (TAU), and Bar-Ilan University (BIU), in collaboration with the Steinhardt Museum of Natural History, Oranim Academic College, the Israel Oceanographic and Limnological Research (IOLR) institution, the Natural History Museum in London, and the Johannes Gutenberg University in Mainz. A close analysis of the remains of a carp-like fish found at the Gesher Benot Ya'aqov (GBY) archaeological site in Israel shows that the fish were cooked roughly 780,000 years ago. Cooking is defined as the ability to process food by controlling the temperature at which it is heated and includes a wide range of methods. Until now, the earliest evidence of cooking dates to approximately 170,000 years ago. The question of when early man began using fire to cook food has been the subject of much scientific discussion for over a century. These findings shed new light on the matter and was published in Nature Ecology and Evolution.

The study was led by a team of researchers: Dr. Irit Zohar, a researcher at TAU's Steinhardt Museum of Natural History and curator of the Beit Margolin Biological Collections at Oranim Academic College, and HU Professor Naama Goren-Inbar, director of the excavation site. The research team also included Dr. Marion Prevost at HU's Institute of Archaeology; Prof. Nira Alperson-Afil at BIU's Department for Israel Studies and Archaeology; Dr. Jens Najorka of the Natural History Museum in London; Dr. Guy Sisma-Ventura of the Israel Oceanographic and Limnological Research Institute; Prof. Thomas Tütken of the Johannes Gutenberg University in Mainz and Prof. Israel Hershkovitz at TAU's Faculty of Medicine.

Dr. Zohar and Dr. Prevost: "This study demonstrates the huge importance of fish in the life of prehistoric humans, for their diet and economic stability. Further, by studying the fish remains found at Gesher Benot Ya'aqob we were able to reconstruct, for the first time, the fish population of the ancient Hula Lake and to show that the lake held fish species that became extinct over time. These species included giant barbs (carp like fish) that reached up to 2 meters in length. The large quantity of fish remains found at the site proves their frequent consumption by early humans, who developed special cooking techniques. These new findings demonstrate not only the importance of freshwater habitats and the fish they contained for the sustenance of prehistoric man, but also illustrate prehistoric humans' ability to control fire in order to cook food, and their understanding the benefits of cooking fish before eating it."

In the study, the researchers focused on pharyngeal teeth (used to grind up hard food such as shells) belonging to fish from the carp family. These teeth were found in large quantities at different archaeological strata at the site. By studying the structure of the crystals that form the teeth enamel (whose size increases through exposure to heat), the researchers were able to prove that the fish caught at the ancient Hula Lake, adjacent to the site, were exposed to temperatures suitable for cooking, and were not simply burned by a spontaneous fire.

Until now, evidence of the use of fire for cooking had been limited to sites that came into use much later than the GBY site -- by some 600,000 years, and ones most are associated with the emergence of our own species, homo sapiens.

Prof. Goren-Inbar added: "The fact that the cooking of fish is evident over such a long and unbroken period of settlement at the site indicates a continuous tradition of cooking food. This is another in a series of discoveries relating to the high cognitive capabilities of the Acheulian hunter-gatherers who were active in the ancient Hula Valley region. These groups were deeply familiar with their environment and the various resources it offered them. Further, it shows they had extensive knowledge of the life cycles of different plant and animal species. Gaining the skill required to cook food marks a significant evolutionary advance, as it provided an additional means for making optimal use of available food resources. It is even possible that cooking was not limited to fish, but also included various types of animals and plants."

Prof. Hershkovitz and Dr. Zohar note that the transition from eating raw food to eating cooked food had dramatic implications for human development and behavior. Eating cooked food reduces the bodily energy required to break down and digest food, allowing other physical systems to develop. It also leads to changes in the structure of the human jaw and skull. This change freed humans from the daily, intensive work of searching for and digesting raw food, providing them free time in which to develop new social and behavioral systems. Some scientists view eating fish as a milestone in the quantum leap in human cognitive evolution, providing a central catalyst for the development of the human brain. They claim that eating fish is what made us human. Even today, it is widely known that the contents of fish flesh, such as omega-3 fatty acids, zinc, iodine and more, contribute greatly to brain development.

The research team believe that the location of freshwater areas, some of them in areas that have long since dried up and become arid deserts, determined the route of the migration of early man from Africa to the Levant and beyond. Not only did these habitats provide drinking water and attracted animals to the area but catching fish in shallow water is a relatively simple and safe task with a very high nutritional reward.

The team posits that exploiting fish in freshwater habitats was the first step on prehistoric humans' route out of Africa. Early man began to eat fish around 2 million years ago but cooking fish -- as found in this study -- represented a real revolution in the Acheulian diet and is an important foundation for understanding the relationship between man, the environment, climate, and migration when attempting to reconstruct the history of early humans.

It should be noted that evidence of the use of fire at the site -- the oldest such evidence in Eurasia -- was identified first by BIU's Prof. Nira Alperson-Afil. "The use of fire is a behavior that characterizes the entire continuum of settlement at the site," she explained. "This affected the spatial organization of the site and the activity conducted there, which revolved around fireplaces." Alperson-Afil's research of fire at the site was revolutionary for its time and showed that the use of fire began hundreds of thousands of years before previously thought.

HU's Goren-Inbar added that the archaeological site of GBY documents a continuum of repeated settlement by groups of hunter-gatherers on the shores of the ancient Hula Lake which lasting tens of thousands of years. "These groups made use of the rich array of resources provided by the ancient Hula Valley and left behind a long settlement continuum with over 20 settlement strata," Goren-Inbar explained. The excavations at the site have uncovered the material culture of these ancient hominins, including flint, basalt, and limestone tools, as well as their food sources, which were characterized by a rich diversity of plant species from the lake and its shores (including fruit, nuts, and seeds) and by many species of land mammals, both medium-sized and large.

Dr. Jens Najorka of the Natural History Museum in London explained: "In this study, we used geochemical methods to identify changes in the size of the tooth enamel crystals, as a result of exposure to different cooking temperatures. When they are burnt by fire, it is easy to identify the dramatic change in the size of the enamel crystals, but it is more difficult to identify the changes caused by cooking at temperatures between 200 and 500 degrees Celsius. The experiments I conducted with Dr. Zohar allowed us to identify the changes caused by cooking at low temperatures. We do not know exactly how the fish were cooked but given the lack of evidence of exposure to high temperatures, it is clear that they were not cooked directly in fire, and were not thrown into a fire as waste or as material for burning."

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