Giant clams, some of the largest mollusks on Earth, have long fascinated scientists. These impressive creatures can grow up to 4.5 feet in length and weigh over 700 pounds, making them icons of tropical coral reefs.

But these animals don’t bulk up on a high-protein diet. Instead, they rely largely on energy produced by algae living inside them. In a new study led by CU Boulder, scientists sequenced the genome of the most widespread species of giant clam, Tridacna maxima, to reveal how these creatures adapted their genome to coexist with algae.

The findings, Jan. 4 in the journal Communications Biology, offer clues about how such evolution may have contributed to the giant clam’s size.

“Giant clams are keystone species in many marine habitats,” said Jingchun Li, the paper’s senior author and professor in the Department of Ecology and Evolutionary Biology. “Understanding their genetics and ecology helps us better understand the coral reef ecosystem.”

A symbiotic relationship

Unlike popular myths—like the one in Disney’s “Moana 2” where the giant clam eats humans—these vegetarian mollusks rely on algae living within their bodies for energy. If giant clams ingest the right algae species while swimming through the ocean as larvae, they develop a system of tube-like structures coated with these algae inside their body. These algae can turn sunlight into sugar through photosynthesis, providing nutrients for the clams.

“It’s like the algae are seeds, and a tree grows out of the clam’s stomach,” Li said.

At the same time, the clams shield the algae from the sun’s radiation and give them other essential nutrients. This mutually beneficial relationship is known as photosymbiosis.

“It’s interesting that many of giant clams’ cousin species don’t rely on symbiosis, so we want to know why giant clams are special,” said Li.

In collaboration with researchers at the University of Guam and the Western Australian Museum, the team compared the genes of T. maxima with closely related species — such as the common cockle—that lack symbiotic partners. The researchers found that T. maxima have evolved more genes coded for sensors to distinguish friendly algae from harmful bacteria and viruses. At the same time, T. maxima tuned down some of its immune genes in a way that likely helps the animal tolerate algae living in their body long term, according to Ruiqi Li, the paper’s first author and postdoctoral researcher at the CU Museum of Natural History.

As a result of the clam’s weakened immune system, its genome contains a large number of transposable elements, which are bits of genetic material left behind by ancient viruses.

“These aspects highlight the tradeoffs of symbiosis. The host has to accommodate a suppressed immune system and potentially more viral genome invasions,” said Ruiqi Li.

The study also discovered that giant clams have fewer genes related to body weight control, known as the CTRP genes. Having fewer CTRP genes might have allowed giant clams to grow larger.

Conservation concerns

Last year, a giant clam population assessment by Ruiqi Li, prompted the International Union for Conservation of Nature (IUCN) to update the conservation status of multiple giant clam species. Tridacna gigas, the largest and most well-known species, is now recognized as “critically endangered,” the highest level before a species becomes extinct in the wild.  

T. maxima, because of its wide distribution, is currently classified as “.” But Ruiqi Li said it’s possible that different species are lumped into one category simply because they look similar.

“If you think these giant clams are all the same species, you might underestimate the threat they face,” Ruiqi Li said. “Genetic studies like this can help us distinguish between species and assess their true conservation needs.”

The team hopes to sequence the genomes of all 12 known species of giant clams to better understand their diversity.

Similar to corals, giant clams are facing increasing threats from climate change. When the ocean water becomes too warm, the clams expel the symbiotic algae from their tissues. Without the algae, the giant clams can starve.

“The giant clams are very important for the stability of the marine ecosystem and support biodiversity,” Jingchun Li said. She added that many creatures living in the shallow waters rely on their shells for shelter, and giant clams also provide food for other organisms.

“Protecting them is essential for the health of coral reefs and the marine life that depends on them.” 

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Climate change is melting away glaciers around the world, but in the Andes Mountains, a wild relative of the llama is helping local ecosystems adapt to these changes by dropping big piles of dung.

This finding, Dec 30 in Scientific Reports, revealed that the activity of this animal could accelerate the time plants usually take to establish on new land by over a century, highlighting a surprising way organisms are adapting to climate change.

“It’s interesting to see how a social behavior of these animals can transfer nutrients to a new ecosystem that is very nutrient poor,” said , the paper’s co-first author and a research scientist in the Cooperative Institute for Research in Environmental Sciences at CU Boulder. But the current pace of climate change still outpaces the ability of species to find new habitats, he warned. 

Vicuña latrines

The changemakers here are the vicuñas. They are one of two wild South American camelids, a group of animals that includes alpaca and llama, which are domesticated species. They live in the high alpine areas of the Andes. 

Vicuñas may be less famous than their celebrated llama cousins, but they are no less remarkable, particularly because of where they choose to poop.

Much like how humans use bathrooms, these animals get rid of their solid waste using a designated spot shared by multiple members of a social group. Scientists refers to these communal dung piles as latrines.

Over the past two decades, Steven Schmidt, the paper’s senior author and professor in the Department of Ecology and Evolutionary Biology, has studied how microbial life and plants are responding to retreating glaciers in the high-altitude Peruvian Andes.

The deglaciated soils are extremely depleted of nutrients and water—a sea of rocks and gravel that can remain plant-free for over a century.

But during expeditions over the last ten years, Schmidt and his collaborators began noticing patches of plants, all of which seemed to have emerged from vicuña poop piles.

Working with animal ecologist Kelsey Reider at James Madison University, the team trekked to sites in the Peruvian Andes, up to 18,000 feet above sea level, that were previously covered by glaciers. They sampled vicuña latrine soils in these areas and found that, compared to barren soils just a few feet away, soils with vicuña poop contained significantly more moisture and key nutrients, like organic carbon, nitrogen and phosphorus.

For example, latrine soil was made of 62% organic matter. In contrast, deglaciated soil that has been exposed for 85 years at the same location but without latrines contained only 1.5% organic matter.

At high elevations, temperatures tend to fluctuate significantly throughout the day, dropping below freezing every night even during the summer. “It's really hard for things to live, but that organic matter made it so that temperatures and moisture levels didn't fluctuate nearly as much. The latrines created a different microclimate than the surrounding area,” Schmidt said.

The team also found high DNA concentrations and a wide diversity of microorganisms in latrine soil samples, suggesting that the latrines provided vital ground for microbes and plants to thrive.

Adapting to climate change

The team said vicuña dung likely accelerated the timeline for plants to colonize a barren, lifeless habitat by a century. These animals deposit nutrients and plant seeds from lower elevations in their poop onto deglaciated ground, and then the seeds germinate, attracting other organisms, including animals that feed on the plants.

Camera footage showed that the patches of plants have attracted all kinds of animals, including rare species never before seen at such high elevations and large carnivores like puma. Vicuñas also eat the vegetation growing in their own latrines.

It could take hundreds of years for the deglaciated area to transition into grassland, which might help mitigate the negative impacts that many species preferring colder climates face as their habitats shrink from climate change, Reider said.

But even with the vicuña’s help, the rate of species colonizing new ground is much slower than the rate at which the glaciers are retreating.

Glacier melt across the world has accelerated over the past two decades. Between 2000 and 2019, glaciers other than the Greenland and Antarctic ice sheets lost about . If warming continues, the Earth could lose , a prior study estimated.

In parts of the Andes and other mountain ranges, including the Rocky Mountains, many people depend on mountain snow and glacier runoff for water. It is that shrinking glaciers and snow cover could threaten the water supply for nearly a quarter of the world’s population.

“The vicuñas are probably helping some alpine organisms, but we can’t assume they’ll all be okay, because in Earth’s history, we’ve never seen climate change happen at this speed,” Bueno de Mesquita said. “Current anthropogenic climate change is probably the most severe crisis our planet and all living things have faced in the past 65 million years.”

Ruth Quispe Pilco, graduate student in the Department of Ecology and Evolutionary Biology,also contributed to the study.

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Since last Tuesday, a series of ferocious wildfires have broken out in Southern California, with fast-moving flames raging through the Los Angeles area, killing at least and forced tens of thousands to flee their homes.

The state has been grappling with a prolonged drought in recent months, leaving vegetation parched, according to Andrew Winters, assistant professor in the Department of Atmospheric and Oceanic Sciences at CU Boulder. On top of that, the region’s strong winter winds have accelerated the spread of fires and made containment efforts extremely difficult.

The Palisades fire, the largest and most destructive, which has burned more than 23,000 acres along the Pacific Coast, is only as of Monday. The Eaton fire, northeast of L.A., burned down as many as , and is .

The fires’ proximity to densely populated areas could make them one of the costliest wildfires in California history.

With dangerous winds expected to return to the area today, CU Boulder Today sat down with Winters to discuss the role of winds in the fires, how climate change might have influenced fire risks in the West and what individuals living in fire-prone areas can do to prepare for a potential evacuation.

What contributed to the rapid spread of the L.A. fires?

California had a really wet year last year because of the strong El Niño event. They had heavy amounts of rain that allowed for subsequent growth of grasses and plants around the region.

Since this summer, as we've transitioned out of an El Niño into a La Niña, conditions have dried out considerably. Usually this time of year, California would see a fair amount of rain, but we barely saw any this winter. In fact, California is looking at some of their driest conditions on record over this period.

The lack of rainfall has allowed for the growth that occurred last year to dry out. The dried vegetation became particularly susceptible to wildfires and at the same time provided a lot of fuel for wildfire growth.

Then the strong Santa Ana winds blowing in the area created a condition that allowed these fires to take off and spread quickly.

What are the Santa Ana winds?

The Santa Ana winds are an intermittent strong wind flow that blows from Nevada and Utah into Southern California almost every year from fall to the early part of winter.

They are part of a normal weather pattern commonly observed in the Los Angeles area. What's rare about this particular situation is that these winds are occurring within an environment that has been suffering from a severe drought.

How are the winds making firefighting more difficult?

The winds create hostile environments for firefighters. When some of the fires in California first started, the winds were gusting to 80, 90 or even 100 miles an hour— similar to that of a Category 2 or 3 hurricane.

During the 2021 Marshall fire here in Colorado, winds were also blowing at 100 miles an hour, and that allowed the fire to spread rapidly and become highly destructive.

Things also got more difficult as the L.A. fires moved into an urban location. The burning of structures and their contents can release considerable harmful nonorganic chemicals into the atmosphere.

Moreover, the wind can take embers and spread them far away from the current location of the fire. This can lead to rapid development of wildfire spread that gets out of hand very quickly.

Does climate change play a role in causing these fires?

It’s tough to say at this point whether the Santa Ana wind pattern is becoming more or less frequent under climate change. But research has shown that climate change is increasing the intensity and frequency of .

We’re expecting droughts to become drier and more exacerbated under future climate scenarios. So climate change is likely involved in the development of the antecedent drought that's created more susceptible fuels for wildfires to start.

Additionally, some research has suggested that climate change could increase the likelihood of whiplashes between very wet periods to very dry periods. Such conditions allow for periods of intense growth of grasses that will then dry out. That means we might have more fuel available to burn if there’s a fire.

Lastly, as the climate warms, more water tends to evaporate from the ground and vegetation, causing fuels like grasses to dry out faster than they would in a cooler climate.

Can we predict these conditions in advance to reduce damage?

Prior to the fires, forecasters at the National Weather Service had done a really good job predicting these strong winds. There was an indication multiple days in advance of very critical fire weather conditions, both in terms of the dry fuels and the strong winds that may accelerate rapid fire spread. It's just unfortunate that the fire transpired into a remarkably catastrophic event.

In a lot of these cases, with strong winds that promote rapid wildfire spread, you may only have a couple of minutes to evacuate. For individuals, there's just not going to be enough time to work through everything you might want to pack up and bring with you.

So start taking some time to think ahead and prepare a go-bag . That includes not only what's important and valuable to you, but also thinking about how are you going to take care of pets and kids, and potentially your neighbors who may have less ability to move quickly. 

Planning ahead and knowing how to act when you need to is probably the best way to go. 

CU Boulder Today regularly publishes Q&As with our faculty members weighing in on news topics through the lens of their scholarly expertise and research/creative work. The responses here reflect the knowledge and interpretations of the expert and should not be considered the university position on the issue. All publication content is subject to edits for clarity, brevity and university style guidelines.

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A refined mathematical model is now capable of predicting carbon inputs and outputs for freshwater lakes around the world, according to new research from INSTAAR’s Isabella Oleksy and collaborators. Their work could help scientists understand the role of freshwater lakes in the global carbon cycle.

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In CUriosity, experts across the CU Boulder campus answer pressing questions about humans, our planet and the universe beyond.

This week, Jingchun Li, associate professor in the Department of Ecology and Evolutionary Biology at CU Boulder, answers: “How do sea creatures make light?”

From shallow reefs to pitch-black depths, the ocean is alive with sparkling lights. Fish, squid, clams and plankton have found a wide range of ways to glow, shimmer and flash, lighting up the dark water like stars in the night sky.

Scientists estimate that in the deep ocean where sunlight cannot reach, can produce some kind of light.

“Light is important for signaling,” said Li, who has spent much of her career working in oceans around the world to study marine life. “It helps animals of the same species communicate and recognize each other, and it can also serve as a warning to other animals.”

  Previously in CUriosity

Do animals have emotions?

Bioluminescence is one of the most common methods animals use to do this. By triggering a chemical reaction between oxygen, a molecule called luciferin and an enzyme, luciferase, in their bodies, they can light up.

On land, fireflies use bioluminescence to emit their electric green light. In the deep ocean, anglerfish, a terrifying antagonist seen in Finding Nemo, use the same method to shine in the abyss.

The fish has a bony structure on its forehead that lights up like a lantern, thanks to the large number of bioluminescent bacteria living inside the fish.

But not all animals are born with the right chemical ingredients to generate light on their own. Some still find ways to shine.

The disco clam (Ctenoides ales), a mollusk living in the shallow waters of the Indo-Pacific Ocean, has evolved a unique strip of tissue on their mantle that can reflect ambient light. has found that the clam’s reflective strip contains silica, the main component in glass. When disco clams furl and unfurl their mantles quickly, they reflect sunlight, creating an effect reminiscent of a disco ball.

Li said scientists are still working to understand how disco clams developed their reflective tissue through evolution. Other closely related species, such as rough file clams (Ctenoides scaber), lack the silica structure in their tissue.

The disco clam’s dazzling display might serve as a defense mechanism. Disco clams regularly open and close their shells, but Li and her team found that when the clams sense a shadow looming over them—a sign that a predator might be approaching—they flash much faster, up to six times per second, like a strobe light.

Anglerfish, on the other hand, light up to draw smaller fish toward them, helping to attract prey in the dark. The ostracod, a tiny, bioluminescence crustacean that looks like a shrimp inside a pod, glows to attract mates. Males spit out a glowing mucus to create a special pattern during mating rituals.

The question of why deep-sea animals produce light remains an intriguing scientific mystery.

“To survive in extremely dark and cold water, every bit of energy matters. But having a vision is energetically demanding,” Li said. “From an evolutionary perspective, it’s surprising that so many animals in the deep ocean retained the ability to see and even evolved ways to illuminate their surroundings.”

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In CUriosity, experts across the CU Boulder campus answer pressing questions about humans, our planet and the universe beyond.

This week, Marc Bekoff, professor emeritus in the Department of Ecology and Evolutionary Biology at CU Boulder, answers: “Do animals have emotions?”

Pet owners tend to see their animals’ feelings clearly. Dogs wagging their tails when the owners get home? Happiness. Crouching down after being caught raiding the trash? Embarrassment. Barking, and jumping up and down when they see their friends? Excitement.

But what about less cuddly creatures? Do crustaceans and birds have emotions, too?

  Previously in CUriosity

What does an all-nighter do to your body?

“Of course they do,” Bekoff said “There's solid science showing very clearly that a wide diversity of animals have emotions, from mammals to all the vertebrates and invertebrates.”  

Bekoff has spent decades observing animals from coyotes in the Rocky Mountains to Adélie penguins in Antarctica. He has written multiple books about animal sentience including “The Emotional Lives of Animals: A Leading Scientist Explores Animal Joy, Sorrow, and Empathy—and Why They Matter.”

He said emotions play an important role in helping animals make decisions about how to respond to social situations, such as whether to run from a potential danger or to approach a mate. For group-living animals like coyotes and wolves, having emotions is fundamental to forming packs.

Evidence has shown that mammals—including humans—emit similar brain chemicals during emotional situations. For example, birds secrete dopamine, a chemical that makes humans feel good, when they sing songs to attract a potential mate.

But even invertebrates like insects and crustaceans could experience emotions, according to a growing body of . While scientists can't definitively say lobsters experience happiness the same way as humans do, they certainly avoid painful situations.

“There is a biodiversity of emotions,” Bekoff said. He explained that the feeling of joy varies even between different people, but that doesn’t mean animals like lobsters or ants don’t experience happiness. “It may simply look different than in humans.”

Recognizing all animals have emotions can help people develop more empathy toward wildlife and support wildlife conservation efforts, he added.

In a published earlier this year, Bekoff and his collaborators proposed that treating individual animals as creatures with emotions and personalities, in addition to understanding the species as a whole, could help preserve biodiversity.

For example, people might be more willing to use loud sounds or strong scents to scare away predators they encounter rather than resort to killing.

Bekoff said Colorado could apply these approaches to help manage its wildlife, including grey wolves, which were reintroduced in the state in December following a voter-approved initiative. For social animals like wolves, if the leader dies, it can lead to the dissolution of the entire pack, he said.

“Wolves have very tight bonds with their pack members,” Bekoff said. “Pups have very tight bonds with their mom. Killing any of these individuals will not support a sustainable population.”

In the end, Bekoff says humans shouldn’t be so quick to brush off other animals. 

“It's really easy to write off an ant or a lobster or a crayfish, but there's no reason to. My take as a scientist is to keep the door open until we are sure that it is not true.” 

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