Crab Lab takes ISU to forefront of climate research with international study

When you think of climate change consequences, the nervous systems of crabs might not be at the top of your list. However, these 10-legged crustaceans could be a bellwether of how the planet’s warming temperatures impact other animals. 

Many species of crabs live in the shallower intertidal zone of oceans where they are exposed to and massively impacted by heat waves induced by climate change. Some species, like the European green crab, have taken advantage of their ability to adapt to different temperatures to spread across the globe. Whereas other crabs, such as the Dungeness that live along the U.S. Pacific Coast, have suffered population loss due to invasive crabs outcompeting them for resources.

These crabs’ responsiveness to temperature changes makes them an ideal candidate for studying the impact of climate change on animals. Dr. Wolfgang Stein’s laboratory, known as the Crab Lab, has been researching how extremely hot temperatures affect crabs’ nervous systems.

“We all know about climate change, but we don’t know at what level that affects animals,” said Stein, a professor of neurophysiology in the School of Biological Sciences. “The nervous system is at the core of all behaviors. So if that fails, the animal is in trouble.”

Stein said the big threat climate change poses for animals is extreme heat more so than the gradual uptick in the average global temperature.

“We’re pumping so much energy into the atmosphere and our ecosystems that the extremes become more extreme,” Stein said. “So we’ve seen a slow increase in the average temperature. That’s true. But more importantly, we see a lot more heat waves and a lot more weather extremes generally.”

Last year, Stein and Dr. Steffen Harzsch, of the University of Greifswald in Germany, were among three research teams to receive Neurobiology and Changing Ecosystems Kavli Exploration Awards. The Kavli Foundation awarded these grants as part of its initial $5 million initiative for research to explore how neural systems adapt to changing environments.

Dr. Wolfgang Stein works with then-undergraduate Charlotte Steiger ‘24 in the Crab Lab. Students like Steiger are conducting many of the experiments for Stein’s Kavli Foundation-supported research project.

The Kavli Foundation was created in 2000 by Fred Kavli, a Norwegian-American entrepreneur whose vision was to advance science for the benefit of humanity. Stein said the foundation had brought together 50 researchers from around the world two years ago to discuss climate change, and the funding initiative was an outcome of that meeting.

Stein and Harzsch are using the grant to figure out how the nervous systems of different crab species respond to temperature change throughout their lives, why some thrive and others don’t, and what’s causing the difference.

“No one really understands how the nervous system responds to (heat waves),” Stein said. “Are there even mechanisms that allow them to acclimate to higher temperatures to keep their nervous system functioning? And where’s the limit? Like, is there a hard limit that you can’t go beyond? Are animals already adapted and are getting close to the limit? 

“No one knows this. And if these mechanisms exist, what are these mechanisms?”

Dr. Rachel Bowden, director of the School of Biological Science and Distinguished Professor, said the researchers’ work is critical to understanding how organisms are currently responding to a warming climate, but also for predicting how they may respond as their environment continues to change. “The Kavli award brings recognition to both the school and to Dr. Stein as it is a highly competitive award. The award will directly benefit ISU by providing critical funding for Dr. Stein’s research program, including providing support for both undergraduate and graduate students to work alongside Dr. Stein as part of his research group.”

Stein’s and Harzsch’s students will research in each other’s labs while being at the forefront of an innovative initiative. The scientists’ approach is complementary. Harzch’s team is studying the effect of climate change on developing crabs, and Stein and his students are examining its effects on adult crabs.

“I’m a neurophysiologist. We look at how the adult nervous system responds to heat waves,” Stein said. “My colleagues are developmental neurobiologists, so they look at how the nervous system develops in different heat wave settings. The fluctuations in temperature have a big impact on how the nervous system is structured as it grows. Together this will give us a good idea about how fluctuating temperatures, like heat waves, impact the nervous system.”

Harzsch and Stein have shared an interest in how the nervous system of crustaceans functions and develops for more than 20 years. This partnership intensified in 2021 when Stein conducted research at Harzsch’s lab as part of a yearlong research fellowship at the Alfred Krupp Institute for Advanced Studies. They co-authored a paper on the impact of global warming on the nervous system. This study, “The Neurobiology of Ocean Change–insights from decapod crustaceans” in Zoology, provided the pair with preliminary data that boosted their Kavli application.

The latest grant follows a nearly $500,000 award Stein’s lab received in 2018 from the National Science Foundation. That comparative study focused on how temperatures impact the nervous system of one specific crab, Cancer borealis.

Stein’s lab found that substances released in the nervous system, called neuropeptides, helped maintain the activity of the neurons as temperatures rise. “We compared the activity of dissected nervous systems with that of intact animals,” Stein said. “We did not really manipulate them, but just did the comparison and then looked at those neuropeptides to see if they enabled the temperature robustness.”

For this new study, the researchers are conducting experiments with four different species of crabs, two from the intertidal area—including the European green crab—that are already experiencing temperature fluctuations, and two that live in deeper parts of the ocean less exposed to these changes. The scientists will test the crabs’ ability to withstand heat waves in a lab and what their threshold is to hotter temperatures.  

Stein expects the nervous systems of crabs from the intertidal waters to be more adaptable to temperature changes but be closer to the limit of what temperatures they can withstand, making them more vulnerable. The crabs living in deeper, colder waters likely cannot adjust to temperature as well but are likely less threatened by climate change, Stein said. “Ultimately, we want to go and see why some can adjust while others cannot adjust.”

The researchers are examining two dozen neurons, which are five to 10 times larger in crabs than in humans. Their larger neurons and other factors make crabs a suitable specimen for this research. “We place electrodes and then record the activities of the neurons much more easily than in other animals,” Stein said. “The connections between the neurons that we study have been very well known for decades so that makes it easy to understand what’s happening.”

Furthermore, crab neurons are very similar across species, Stein said. “No matter what crab we take, we find the very same neuron in all of these species. So we can say, ‘In many species, and in many individuals, how this neuron responds to those temperature fluctuations.’ This is something that you cannot do in other animals.”

Though Stein and his collaborators are conducting their experiments in a lab, Harzch’s team is helping the team bridge neuroscience and ecology. Harzch’s colleagues run a field station on a little island in the North Sea that has hundreds of years of data on the crabs.

“There is a long history of information about where these animals are, what temperatures they are exposed to that can tell us pretty much exactly what the temperatures that these animals experience in their real life when they’re not in our lab,” Stein said. “That’s important because you want to know what that species has experienced in the past, but also more recently, like in the last couple of weeks before they arrived here. And so that’s where our ecology friends come in, that have these measurements and they can directly inform us of that.”

As part of the Kavli grant, Stein and his team will share their data publicly using Neurodata Without Borders. The platform allows researchers to upload all of their original data in a standardized format so their peers can access it for their own research.

The researchers are hoping this initial study will lead to a long-term collaboration. The pilot project will allow the researchers to formulate ideas for what mechanisms within the crabs make some robust to temperature changes, and others less robust, but it will take more research to figure out how these mechanisms exactly work and then see how these apply to other animals.

“This is a timely project in light of global ocean change, specifically the increasing intensity and frequency of marine heat waves that we are facing in our oceans,” Harzsch said. “Marine animals such as crustaceans cannot actively regulate their body temperature to compensate for heat but are exposed to temperature fluctuations in their natural habitat. We want to understand how elevated temperatures affect the nervous system, which is essential for the animal’s survival.”