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Christmas tree worms, as you might guess from their festive name, are colourful reef critters that look like tiny Christmas trees. But when potential danger gets too close – whoosh – these shy little worms vanish back into their burrows. 

But one marine scientist noticed that when certain fishes sit on top of them, they don’t vanish. He thinks this might be a special symbiotic relationship between the two species. The findings have been published in the journal Symbiosis.

As an underwater photographer, the study’s lead author Morgan Bennett-Smith had spent hours watching these little polychaetes (marine worms) disappear like a puff of smoke whenever there was the slightest hint of a disturbance nearby. “I’d been filming them in slow motion to capture the instant they withdraw into their tubes,” he says.

“Then, during fieldwork for another project in Kimbe Bay, Papua New Guinea, I saw a fish just sitting on top of one of the worms… and the worm didn’t flinch,” he adds. “After seeing countless worms vanish at the slightest shadow, this was bizarre.” 

The more he looked, the more he spotted this strange interaction. When blennies (Blenniidae) or gobies (Gobiidae) were resting daintily on top, the Christmas tree worms (Spirobranchus corniculatus) didn’t recoil like they usually do when sensing potential danger. 

These small, agile fishes are “experts at tucking into crevices or perching on small structures,” says Bennett-Smith who is a Ph.D. student at Boston University. They often have a small territory and spend a lot of time in one specific spot so sitting on top of the little ‘trees’ could give them a better vantage point. 

Gobies are already familiar with the concept of teamwork with other species as these fishes are known to form symbiotic relationships with other animals, including shrimps. “The shrimp digs and maintains a burrow while the goby acts as a lookout,” says Bennett-Smith.

Because of the lack of response from the colourful worms, Bennett-Smith wonders if this relationship might have mutual benefits for the different species. “The fish may provide a service, such as removing algae or detritus from around the worm’s tube, and in return, the worms stay extended, offering the fish a perfect vantage point and camouflage,” he says, noting that they did see some behaviours that looked like cleaning. 

Another possibility is that the worms gain nutrients and protection from the blennies and gobies. “The fish’s waste products could benefit the worms,” he says. “Some blennies are also known to be territorial and might chase away worm predators.”

There is another reason the worms might not withdraw when these fishes land on top, although it’s less likely says Bennett-Smith: “The other possibility is that the fish have simply figured out how to bypass the worms’ defences and are tolerated ‘uninvited guests’,” he says. “The truth is we don’t yet know, and we’d love to test these ideas further in the field!”

Although we’re learning more about the ocean every day, this new discovery of yet another example that fascinating findings could be unfolding right in front of our eyes, if we notice them. Although technology can be helpful, we can still learn a lot just by looking. 

“I think there’s still huge value in simply being present in an ecosystem and watching, really watching, until patterns emerge,” says Bennett-Smith. “That’s when you sometimes notice the surprising, often overlooked relationships that help shape ecosystems.”

“There’s still so much we don’t know about coral reefs, even after decades of research,” he adds. “Many interactions like this may be happening all the time, unnoticed, just because we haven’t been watching closely enough.”

Top image: blenny and Christmas tree worms. Credit: Morgan Bennett-Smith, Boston University | www.bennettsmith.media

More amazing wildlife stories from around the world

In a study published in the journal Proceedings of the National Academy of Sciences (PNAS), a team of British and German scientists revealed the structure of the extracellular matrix in Volvox carteri, a type of green algae that is often used to study how multicellular organisms evolved from single-celled ancestors.

The extracellular matrix (ECM) is a scaffold-like material that surrounds cells, providing physical support, influencing shape, and playing an important role in development and signalling. Found in animals, plants, fungi and algae, it also played a vital part in the transition from unicellular to multicellular life.

Because the ECM exists outside the cells that produce it, scientists believe it forms through self-assembly: a process still not fully understood, even in the simplest organisms.

To investigate, researchers at the University of Bielefeld genetically engineered a strain of Volvox in which a key ECM protein called pherophorin II was made fluorescent so the matrix’s structure could be clearly seen under a microscope.

What they saw was an intricate foam-like network of rounded compartments that wrapped around each of Volvox’s roughly 2,000 somatic, or non-reproductive, cells.

Working with mathematicians at the University of Cambridge, the team used machine learning to quantify the geometry of these compartments. The data revealed a stochastic, or randomly influenced, growth pattern that shares similarities with the way foams expand when hydrated.

These shapes followed a statistical pattern that also appears in materials like grains and emulsions, and in biological tissues. The findings suggest that while individual cells produce ECM proteins at uneven rates, the overall organism maintains a regular, spherical form.

That coexistence – between noisy behaviour at the level of single cells and precise geometry at the level of the whole organism – raises new questions about how multicellular life manages to build reliable forms from unreliable parts.

“Our results provide quantitative information relating to a fundamental question in developmental biology: how do cells make structures external to themselves in a robust and accurate manner,” said Professor Raymond E. Goldstein from Cambridge’s Department of Applied Mathematics and Theoretical Physics, who co-led the research. “It also shows the exciting results we can achieve when biologists, physicists and mathematicians work together on understanding the mysteries of life.”

“By tracking a single structural protein, we gained insight into the principles behind the self-organisation of the extracellular matrix,” said Professor Armin Hallmann from the University of Bielefeld, who co-led the research. “Its geometry gives us a meaningful readout of how the organism develops as it grows.”

The research was carried out by postdoctoral researchers Dr Benjamin von der Heyde and Dr Eva Laura von der Heyde and Hallmann in Bielefeld, working with Cambridge PhD student Anand Srinivasan, postdoctoral researcher Dr Sumit Kumar Birwa, Senior Research Associate Dr Steph Höhn and Goldstein, the Alan Turing Professor of Complex Physical Systems in Cambridge’s Department of Applied Mathematics and Theoretical Physics.

The project was supported in part by Wellcome and the John Templeton Foundation. Raymond Goldstein is a Fellow of Churchill College, Cambridge.

Reference:

B. von der Heyde, A. Srinivasan et al. ‘Spatiotemporal distribution of the glycoprotein pherophorin II reveals stochastic geometry of the growing ECM of Volvox carteri,’ Proceedings of the National Academy of Science (2025). DOI: 10.1073/pnas.2425759122

Most people picture a doctor checking for a broken bone when they think of an X-ray. But the technology is just as important in places like airport security, manufacturing, quality control and scientific research, each with its own criteria for size and shape.

A team led by Florida State University Professor of Chemistry and Biochemistry Biwu Ma has developed a new form for X-ray materials that can meet the needs of large-area applications, changing out complex crystal structures for an adaptable and scalable thin-film detector. The work was published in Angewandte Chemie.

“We took a material we developed and made it better,” Ma said. “This new form can be made reliably and quickly, giving end users a new way to incorporate X-ray detection in their work.”

Ma and his group are pioneers of materials known as zero-dimensional organic metal halide hybrids, or 0D OMHHs. These combine organic components, which have a carbon backbone or carbon-hydrogen bond, with inorganic metal halides, which are compounds made from metal and halogen atoms. Their hybrid form allows scientists and engineers to harness the best properties of both components, and they provide low-cost, adjustable and high-performance materials for direct X-ray detection.

In previous research, the group showed how 0D OMHH single crystals can be used for X-ray detectors. However, their scalability is limited by a slow and complex crystal growth process.

In this new work, Ma’s team developed amorphous OMHH films, millimeter-thin sheets of organic metal halide hybrids that can be shaped in myriad ways. These films can be readily fabricated into large-area and custom-shaped detectors, enabling broader use in fields such as astronomy, materials science and medical imaging.

“If a doctor wants to take an X-ray image of someone’s chest, it’s important to have a detector large enough to cover the whole area for an accurate image,” Ma said. “Growing single crystals of that size is extremely difficult. With our new approach and this new amorphous film material, we now have the potential to create much larger and more versatile X-ray detectors for a wide range of applications.”

HOW IT WORKS

0D OMHHs consist of positively charged organic cations ionically bonded to negatively charged metal halide units, forming structures with highly adjustable properties. These materials have already shown promise in applications such as light-emitting diodes, or LEDs, anti-counterfeiting applications and more.

In this study, the team created amorphous films by combining non-crystalline organic molecules with metal halides, enabling efficient conversion of X-rays into electrical signals for image generation. Like single crystals, the amorphous films also exhibit high-sensitivity, low detection limits and excellent stability, reinforcing their potential to be widely adopted in the construction of detectors.

APPLICATIONS AND FUTURE DIRECTIONS

X-rays are critical in applications ranging from medical diagnostics, including radiography and fluoroscopy, to non-destructive industrial testing, where they are used to inspect welding, detect cracks in materials and examine the integrity of structures.

Detectors are also used in security. They are in the machines that scan your luggage as you walk through an airport’s screening area, and they’re used to identify hazardous materials in packages sent via mail. They play a crucial role in manufacturing, in uses such as inspecting food products for contaminants.

Large-area X-ray detectors make imaging easier, enabling higher resolution images, improving detection and allowing for faster throughput of scanned objects. Their ability to cover more area in a single scan is particularly beneficial in industries like cargo inspection, where speed and efficiency are essential.

“The significance of this work lies in the enabling of possible industrial processing for large-area detection, which is crucial for the material’s applicability,” said Department of Chemistry and Biochemistry chair Wei Yang. “This work is a significant step in a highly innovative effort pioneered by Biwu that showcases the unique strength of our department in this promising area.”

A provisional patent application titled “Direct X-ray Detectors Based on Solution-Processed Amorphous Zero-Dimensional Organic Metal Halide Hybrid Films” was filed with the U.S. Patent and Trademark Office in April. Ma is also in the process of launching a company with an industry partner to commercialize the technologies developed by his group, including this new way of facilitating X-ray technologies.

“Since first publishing on these materials almost a decade ago, I have worked with my colleagues to push the boundaries of what they can achieve,” Ma said. “We see 0D OMHHs as versatile and powerful, with the potential to offer a better alternative in many fields.”

COLLABORATORS AND SUPPORT

Additional contributors to this work include chemistry doctoral student Oluwadara Olasupo, the lead author of the publication; other current and former members of Ma’s research group, including Abiodun M. Adewolu, Mohammad Khizr, Tarannuma F. Manny, He Liu, Md S. Islam, Sahel Moslemi, J.S. Raaj V Winfred and Ranjan Das; chemistry professor Yan-Yan Hu; and FSU Ph.D. alumnus Tunde Shonde, now a lecturer in the Department of Chemistry at the University of West Florida. High school student Ethan Kim also participated in this research through FSU’s Young Scholars Program.

This research was supported by the National Science Foundation and the FSU Office of Research.

To learn more about Ma’s work and research conducted in the Department of Chemistry and Biochemistry, visit chem.fsu.edu.