Sea anemones ‘exercise’ to build their bodies •

Sea anemones begin their lives as oval-shaped, free-swimming larvae that turn into long, tubular adults attached to rocks with claws around their mouths. This includes drastic changes in behavior and life form, along with large-scale changes in tissues. Although embryonic development has received research interest in the past, and the behavior of early fetuses has been studied, it is not clear to what extent the physical activity of the fetus is. fetus Affects its change in the shape of the body.

In the past, scientists wishing to map the links between dynamic behavior and body changes that occur during transformation have been hampered by a lack of live imaging strategies that capture the dynamics of this transformation in life history. Researchers at the European Molecular Biology Laboratory (EMBL) have now overcome this hurdle using their expertise in live imaging, computational methodology, biophysics and genetics. They managed to get around Live 2D and 3D imaging to quantitative features to track changes in developing anemone bodies (Nematostella). The results were published in the journal current biology.

The experts created a method for high-throughput live imaging using a specially adapted microscope and observed the changes that occur during the transition from larva to appendage in 707 anemones. This happened over about seven days and the researchers recorded the changes at 5-minute intervals. They found that larval turnover was significantly reduced during migration, mostly due to a 3-4-fold increase in the body length of the polyps as they became more tubular and developed oral claws.

During this time, anemones acted like hydraulic pumps, absorbing water and regulating body pressure through muscle activity. The researchers performed specific patterns of gymnastic movements that put pressure on specific tissues, thus sculpting the shape of the body as the elongation increased. 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.

“Humans use a skeleton made of muscle and bone for exercise. In contrast, anemones use a watery skeleton made of muscle and a cavity that is filled with water.” The same hydraulic muscles that help growing anemones move also seem to influence how they develop. Using an image analysis pipeline to measure body shaft 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 sea anemones have essentially evolved ‘exercise’ to build their morphology, but it appears that they cannot use their aquatic skeleton to move and evolve simultaneously,” said Ekme.

Growing anemones use this hydraulic system to reshape their tissues during this time. Through the use of peristaltic waves, pressure and longitudinal contractions, they stimulate tissue proliferation in some places and cell death in others, thus changing the shape of body tissues.

“There were many challenges to conducting this research,” explained 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 record fast enough to keep up with the animal’s movements, which results in blurry images, especially when you want to view it in 3D. Additionally, the animal is very dense, so most microscopes cannot even see in Halfway through the animal.”

To search deeper and faster, Ling Wang, an applications engineer in EMBL’s Prevedel group, has built a microscope to capture live larvae, and develop 3D 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 still 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 pressing an inflated balloon on one side, and watching it expand on the other. We think this pressure-driven local stretch helps the tissues stretch, so the animal becomes elongated. Slowly. In this way, contractions can have both short-term and long-term effects.”

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 suggests that muscular-active hydraulics play a broad role in the design principle of soft-body 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. Given the evolution of animal pluripotency in an aquatic environment, we suggest that early animals likely exploited the same Physics, where hydraulics drive both developmental and behavioral decisions.”

“We still have many questions from these new findings,” Stokkermans said. “Why are there different levels of activity? Exactly how do cells sense and translate stress into a developmental outcome? Furthermore, because tube-like structures underlie many of our organs, we study the mechanisms that apply to them Nematostella It will also help in gaining more understanding of how hydraulics play a role in organ development and function. “

by Alison BosmanAnd the crew clerk