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As humans, we know that an active lifestyle gives us some control over how we look. When we hit the pavement, retrace our steps, and head to the gym, we can maintain muscle growth and reduce body fat. Our physical activity helps shape our physical character. But what if we experienced similar aerobics in our previous forms? Is it possible that our fetuses exercised too?
Researchers at EMBL’s Ikmi Group turned these questions toward sea anemones to understand how behavior affects body shape during early development. It turns out that sea anemones also benefit from maintaining an active lifestyle, especially as they grow from oval-shaped swimming larvae to sedentary tubular polyps. This morphological shift is a fundamental shift in the life history of many hollow species, including the immortal jellyfish and the builders of the richest and most complex ecosystem on our planet, corals.
During development, star anemone larvae (NematostellaPerform a specific pattern of gymnastic movements. Too little or too much muscle activity or a drastic change in the organization of their muscles can cause anemones to deviate from their normal shape.
In a new paper published in current biology, ICMEI’s group explores how this type of behavior affects animal development. With expertise in live imaging, computational methodology, biophysics, and genetics, the multidisciplinary team of scientists has transformed 2D and 3D live imaging into quantitative features to track changes in the body. They found that developing anemones act like hydraulic pumps, regulating body pressure through muscle activity, and using hydraulics to sculpt larval tissue.
“Humans use a skeleton made of muscle and bone for exercise. In contrast, anemones use a water skeleton made of muscle and a cavity filled with water,” said Issam Ekmi, EMBL group leader. The same hydraulic muscles that help growing anemones move also seem to influence how they develop. Using an image analysis pipeline to measure body column length, diameter, estimated volume, and motion in large data sets, the scientists found that Nematostella Larvae are naturally divided into two groups: slow-growing and fast-growing larvae. To the team’s surprise, the more active the larvae, the longer they developed time. “Our work shows how developing sea anemones is essentially an ‘exercise’ to build their morphology, but it appears that they cannot use their aquatic skeleton to move and evolve simultaneously,” said Ekme.
Making microscopes and building balloons
“There were many challenges to conducting this research,” explains first author and former EMBL Predock, Anniek Stokkermans, now a postdoctoral researcher at the Hubrecht Institute in the Netherlands. “This animal is very active. Most microscopes cannot register fast enough to keep up with the animal’s movements, which results in blurry images, especially when you want to look at it in 3D. Additionally, the animal is very dense, so most microscopes can’t even see Halfway through the animal.”
To search deeper and faster, Ling Wang, an applications engineer in the Prevedel group at EMBL, has built a microscope to capture live larvae, and develop 3D sea anemone larvae as they naturally behave.
“For this project, Ling specifically adapted one of our core technologies, optical coherence microscopy, or OCM. The main advantage of OCM is that it allows animals to move freely under the microscope while providing a clear and detailed look inside and in 3D.” said Robert Prifedel, EMBL Group Leader. “It was an exciting project that shows the many different interfaces between EMBL’s groups and disciplines.”
Using this specialized tool, the researchers were able to determine volumetric changes in tissues and body cavities. “To increase their size, anemones inflate like a balloon by absorbing water from the environment,” Stokkermans explained. “Then, by contracting different types of muscles, they can regulate their shape in the short term, like squeezing an inflated balloon on one side and watching it expand on the other. We think that this localized pressure-induced stretch helps the tissues stretch, so the animal slowly becomes elongated. In this way, contractions can have both short-term and long-term effects.”
Balloons and sea anemones
To better understand hydraulic components and their functions, the researchers collaborated with experts from various disciplines. Prachiti Moghe, an EMBL tester in Hiiragi’s group, measured pressure changes that lead to body deformities. In addition, mathematician L. Mahadevan and engineer Aditi Chakrabarti of Harvard University introduced a mathematical model to estimate the role of hydraulic stresses in driving system-wide changes in shape. They also designed balloons reinforced with ribbons and ribbons that mimic the range of shapes and sizes we see in both normal and muscular animals.
“Because hydrostatic skeletons are ubiquitous in the animal kingdom, especially in marine invertebrates, our study indicates that muscular-active hydraulics play a broad role in the design principle of soft animals,” Eckmee said. “In many engineered systems, hydraulics are defined by the ability to harness pressure and flow in mechanical action, with far-reaching effects in spacetime. As multicellular animals evolved in an aquatic environment, we suggest that early animals likely exploited the same physics, with The hydraulics that drive developmental and behavioral decisions.”
Because the Ikmi group has previously studied the links between diet and tentacle evolution, this research adds a new layer to understanding how body shapes evolve.
“We still have many questions from these new findings. Why are there different levels of activity? How exactly do cells sense and translate stress into a developmental outcome?” Stokkermans reflects on what this research leads to. “Moreover, since tube-like structures underlie many of our organs, we study the mechanisms by which they apply Nematostella It will also help in gaining a greater understanding of how hydraulics play a role in organ development and function. “
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