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The first time you see a blue shark in the water, it’s almost impossible not to be taken aback by just how… well, blue they are. Now, scientists have uncovered the secret to their vivid azure hue and discovered that these animals might also be able to change colour. 

Blue sharks (Prionace glauca) have special crystals inside their scales that create their distinctive shade and may also give them chameleon-like abilities, according to research presented at the Society for Experimental Biology Annual Conference.

How blue sharks change colour

“Blue is one of the rarest colours in the animal kingdom,” says Dr. Viktoriia Kamska, City University of Hong Kong, in a statement. “Animals have developed a variety of unique strategies through evolution to produce it, making these processes especially fascinating.”

The blue shark’s strategy? Special crystals inside the tooth-like scales (known as dermal denticles) that these animals have covering their bodies. 

Derman denticles have pulp-like cavities and, inside these, are guanine crystals, which reflect blue light, and tiny sacs that store melanin (a natural pigment that give skin, hair and eyes their colour), which absorb other wavelengths of light. 

“These components are packed into separate cells, reminiscent of bags filled with mirrors and bags with black absorbers, but kept in close association so they work together,” says Kamska. 

The scientists used a combination of advanced technologies to figure out how these tiny structures worked to create the shark’s vibrant colour.

“When you combine these materials together, you also create a powerful ability to produce and change colour,” says Professor Mason Dean. “What’s fascinating is that we can observe tiny changes in the cells containing the crystals and see and model how they influence the colour of the whole organism.”

It’s incredibly difficult to tweak the tiny structures themselves to test different scenarios so they also turned to computer simulations to see what happened when different wavelengths of light were introduced. 

As well as uncovering how the shark creates its bold blue colouring, the experts also realised that it might have the ability to change hues, like a chameleon. When the crystals move closer together, the shark appears its classic blue colour, and when they drift further apart, its skin is tinted with greens and golds. 

This could help the animal stay camouflaged in changing environmental conditions. “In this way, very fine scale alterations resulting from something as simple as humidity or water pressure changes could alter body colour,” says Professor Dean. These “then shape how the animal camouflages or counter-shades in its natural environment.” 

In deeper, darker water, the pressure might push the nanocrystals together more closely and so the shark would turn a darker blue – helping it blend in more seamlessly with its surroundings.  

The researchers now want to see how their hypothesis plays out in the wild – can they observe this happening among blue sharks in their natural habitat?

They’re also curious how the understanding of this mechanism might benefit humans by inspiring ways of creating a blue colour without using potentially harmful chemicals. “A major benefit of structural colouration over chemical colouration is that it reduces the toxicity of materials and reduces environmental pollution,” says Kamska.  

Sharks aren’t the only marine animals that have remarkable colour changing abilities. Cephalopods such as octopus, cuttlefish and squid can alter their colour and pattern in the blink of an eye – sometimes even sending messages through the displays that flash up on their skin.

Even seahorses can blend into their surroundings to hide from potential danger. They are able to do this thanks to tiny balloon-like pouches within their skin called chromatophores. These are filled with pigment and can rapidly grow or shrink to change the animal’s appearance. 

Studying how blue sharks (and perhaps other species, including great whites which may be able to change their shade to creep up on prey without detection) create their colour could give researchers exciting new insights. 

“We know a lot about how other fishes make colours, but sharks and rays diverged from bony fishes hundreds of millions of years ago,” says Professor Dean, “so this represents a completely different evolutionary path for making colour.”

Top image: blue shark. Credit: Getty

More amazing wildlife stories from around the world

Rivers are Earth’s arteries. Water, sediment and nutrients self-organize into diverse, dynamic channels as they journey from the mountains to the sea. Some rivers carve out a single pathway, while others divide into multiple interwoven threads. These channel patterns shape flood risks, erosion hazards and ecosystem services for more than three billion people who live along river corridors worldwide.

Understanding why some waterways form single channels, while others divide into many threads, has perplexed researchers for over a century. Geographers at UC Santa Barbara mapped the thread dynamics along 84 rivers with 36 years of global satellite imagery to determine what dictates this aspect of river behavior.

“We found that rivers will develop multiple channels if they erode their banks faster than they deposit sediment on their opposing banks. This causes a channel to widen and divide over time,” said lead author Austin Chadwick, who conducted this study as a postdoctoral researcher at UCSB.

The results, published in the journal Science, solve a longstanding quandary in the science of rivers. They also provide insight into natural hazards and river restoration efforts.

Two types of rivers

Earth scientists have long divided rivers into single and multi-channel categories, and generally investigate the two separately. While neither type clearly outnumbers the other, most of the world’s largest rivers are multi-channeled. The notable exception is the single-channel Mississippi River, in the United States, where a lot of river research has occurred.

Most field research has focused on single-threaded rivers, partly because they’re simpler. Meanwhile, experimental work has focused on multi-threaded rivers due to the challenges of recreating single-threaded channels in laboratory tank experiments.

It was while working on one of these tank experiments at University of Minnesota’s St. Anthony Falls Laboratory that Chadwick got the inspiration for this study. While examining multi-channel rivers in the lab, he noticed that they were constantly widening and splitting. “I was banging my head on the wall because I kept measuring more erosion than deposition. And that was not what we’re taught in school,” he recalled. “That led me to read some old books from the Army Corps and other sources about examples where there’s more bank erosion than deposition.” Eventually, he became curious whether this occurred in nature.

It was a classic example of the scientific method: “You generate a hypothesis in a laboratory setting and then you’re able to test it in nature,” said co-author Evan Greenberg, a former doctoral student at UCSB who received the prestigious Lancaster Award for best dissertation.

Long-term data at 2,300,000 feet

The team leveraged Landsat data housed at the Google Earth Engine repository, focusing on 84 rivers in different regions of the globe. They tracked erosion and deposition on each river’s banks using an image-processing algorithm called particle image velocimetry. The authors adapted this algorithm — originally designed to track particle motion in lab photos of a fluid — to track channel position in satellite images of their floodplains.

In single-threaded rivers, erosion and deposition balanced out. As a result, the channel’s width remains constant, allowing these rivers to lean into their bends and form wide, meandering paths across the landscape. In contrast, bank erosion outpaced deposition in multi-channel rivers, causing a given channel to widen over time until it splits in two. As a result, multi-channel rivers reshuffle their channels before they can meander too far across the floodplain.

Each of these dynamics occurs while a river is in a steady state (neither growing nor shrinking). “It is not like multi-threaded rivers are gaining water on average. They are still conveying the same amount of water through time, but they are doing that by constantly shuffling the size of the individual threads,” explained senior author Vamsi Ganti, an associate professor of geography at UCSB.

When the authors say that erosion exceeds deposition, they’re referring to the river’s banks. For multi-channel rivers, the extra sediment eroded from the banks is redeposited on the river bottom, eventually forming the islands and bars that separate the different channels.

Rivers can follow one of two trajectories depending on the balance between bank erosion and deposition.

The researchers tallied a few exceptions to the erosion-deposition trend, but they discovered that each of them coincided with apparent changes in the watershed that forced the river out of its natural steady state. For instance, the Sao Francisco River in Brazil didn’t exhibit excess erosion like other multi-channel rivers because the river has been shrinking in response to the damming of its headwaters and water extraction for irrigation.

“The question of what causes a river to be single-threaded or multi-threaded is pretty much as old as the field of geomorphology,” said Ganti.

Generally, geographers have understood river dynamics in terms of myriad variables, including downstream slope, water flow rate, sediment type and bank stability. The new model explains river type solely in terms of the balance between deposition and erosion. The various geographic factors affect this balance, explaining why specific environments tend to favor certain kinds of rivers.

Giving rivers space to flow

The 20th century has seen many rivers boxed into narrow channels disconnected from their historic floodplains. This reclaims more land for settlement and mitigates some of the inherent hazards of living near a river. However, this is disastrous for riparian ecosystems and can even exacerbate long-term hazards. Cutting a river from its floodplain means sediment settles on the riverbed, elevating the river relative to the neighboring, sediment-starved floodplain. This makes it more likely to jump its banks in the event of a flood or a levee failure, a phenomenon the team has investigated in depth.

“Consider Hurricane Katrina,” Chadwick said. “When the levee broke, there was widespread flooding in part because the floodplain had been cut off from the Mississippi for so long that it had sunk relative to the river, allowing the floodwaters to pond there.”

There’s a growing effort to reconnect channelized rivers with their floodplains and give them more space to move. Nature-based restoration efforts require figuring out how wide a corridor a given river needs in order to return to its natural state, as well as how long it will take to do so. With their newfound understanding of river dynamics, the team devised a formula for this, which includes variables like how long a river takes to abandon a channel. The formula also describes whether a river returns to a single- or multi-channel state. They calculated the restoration widths and times for various types of rivers based on their satellite observations.

Vamsi Ganti’s research seeks to quantify and understand the mechanics of physical processes that shape the landscapes on Earth and other planets, and to unravel the expression of these processes in the ancient sedimentary record. He works on a range…

Chadwick, Ganti and Greenberg found that the time and space a river needs to reestablish its natural behavior varied widely between single and multi-threaded rivers. A single-threaded river requires about ten times more space and time to reestablish itself as a multi-threaded river of the same stream power, which is the amount of energy the stream has to erode and move sediment.

The paper’s insights can guide infrastructure and revitalization projects. The formula developed by the authors enables engineers and scientists to estimate the width a restoration project will need, a deciding factor in a project’s feasibility and cost. The analysis can also help policymakers prioritize candidates for recovery. Research, restoration and hazard mitigation have historically focused on single-threaded channels, but shifting toward projects on multi-threaded waterways could yield greater returns for lower costs.

In fact, the team’s findings suggest that river restoration may be less costly than anticipated. There’s growing recognition that many single-threaded rivers were historically multi-threaded before human intervention, especially in the western U.S. For instance, photos of the Los Angeles River from the 1930s, before it was channelized, show it with multiple threads. A project currently considered prohibitively large or expensive may actually be affordable if a river was misclassified, Chadwick explained.

Ganti’s lab is currently studying the acceleration and deceleration of rivers, as well as changes in the number of threads a river has over time. “These temporal trends are likely signatures of how climate change and human interference are affecting river dynamics,” he said.

Chadwick is still curious why erosion outpaces deposition in some rivers. He plans to further investigate the diversity of multi-threaded rivers as a postdoctoral research scientist at Columbia University’s Lamont-Doherty Earth Observatory, with a particular interest in how they form. Meanwhile, Greenberg, now at the Jet Propulsion Laboratory (JPL), is using remote sensing to measure sediment transport in rivers. He’s also finishing up work looking at how dams influence river shape over time and the development of the river corridor.

Rivers have played an important role in human history. They irrigate the crops we grow on their fertile plains and convey our goods to and fro. But they also flood our cities and suddenly forsake well-worn channels. Learning more about rivers will enable us to better coexist with these mercurial natural features in a time of unprecedented change.

Reference: Chadwick AJ, Greenberg E, Ganti V. Single- and multithread rivers originate from (im)balance between lateral erosion and accretion. Science. 2025. doi:10.1126/science.ads6567

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A new microchip invented by Scripps Research scientists can reveal how a person’s antibodies interact with viruses—using just a drop of blood. The technology offers researchers faster, clearer insights that could help accelerate vaccine development and antibody discovery.

“This lets us take a quick snapshot of antibodies as they are evolving after a vaccine or pathogen exposure,” says Andrew Ward, professor in the Department of Integrative Structural and Computational Biology at Scripps Research and senior author of the new paper published in Nature Biomedical Engineering on June 3, 2025. “We’ve never been able to do that on this timescale or with such tiny amounts of blood before.”

When someone is infected with a virus, or receives a vaccine, their immune system creates new antibodies to recognize the foreign invader. Some antibodies work well against the pathogen, while others attach to it only weakly. Figuring out exactly which parts of the virus the best antibodies stick to is key information for scientists trying to optimize vaccines, since they want to design vaccines that elicit strong, reliable immune responses.

“If we know which particular antibodies are leading to the most protective response against a virus, then we can go and engineer new vaccines that elicit those antibodies,” says Leigh Sewall, a graduate student at Scripps Research and first author of the new paper.

In 2018, Ward’s lab unveiled a technique known as electron microscopy-based polyclonal epitope mapping (EMPEM). This method allowed scientists to visualize how antibodies in blood samples attach to a virus. Although groundbreaking, it had downsides: it took a full week to complete and required relatively large amounts of blood.

“During the COVID-19 pandemic, we began really wanting a way to do this faster,” says Alba Torrents de la Peña, a Scripps Research staff scientist who helped lead the work. “We decided to design something from scratch.”

With the new system, known as microfluidic EM-based polyclonal epitope mapping (mEM), researchers start with four microliters of blood extracted from a human or animal–about one hundred times less than what’s required in original EMPEM. The blood is injected in a tiny, reusable chip where viral proteins are stuck to a special surface. As the blood flow through the chip, antibodies recognize and bind to those. Then, the viral proteins—with any antibodies attached—are gently released from the chip and prepared for imaging using standard electron microscopy. The entire process only takes about 90 minutes.

To test the value and effectiveness of mEM, the research team used the system to map antibodies in humans and mice that had either received a vaccination against or been infected with a virus, including influenza, SARS-CoV-2 and HIV. The new technique was not only fast at mapping out the interactions between antibodies and those viruses, but more sensitive than EMPEM; it revealed new antibody binding sites on both influenza and coronavirus proteins that had not been picked up by EMPEM.

To track how antibodies evolved over time in individual mice after they received a vaccination against one of the pathogens, the team took small blood samples from a mouse at different time points.

“That was something that wouldn’t have been possible in the past, because of the amount of blood needed for EMPEM,” says Sewall. “So to be able to look at an individual over time was really exciting.”

The researchers are now working to automate and multiplex the system, which could eventually allow dozens of samples to be processed in parallel. Ultimately, they envision mEM becoming a widely adopted tool to monitor and guide vaccine development in pathogens ranging from coronaviruses to malaria.

“This technology is useful in any situation where you have really limited sample volume, or need initial results quickly,” says Torrents de la Peña. “We hope this becomes accessible to more researchers as it is simplified and streamlined.”

Reference: Sewall LM, de Paiva Froes Rocha R, Gibson G, et al. Microfluidics combined with electron microscopy for rapid and high-throughput mapping of antibody–viral glycoprotein complexes. Nat Biomed Eng. 2025. doi: 10.1038/s41551-025-01411-x

This article has been republished from the following materials. Note: material may have been edited for length and content. For further information, please contact the cited source. Our press release publishing policy can be accessed here.