Styrker træning udvikling? I søanemonen betyder den måde, du bevæger dig på,

Som mennesker ved vi, at en aktiv livsstil giver os en vis kontrol over vores form. Når vi rammer fortovet, sporer vores skridt og går til fitnesscentret, kan vi opretholde muskeludvikling og reducere kropsfedt. Vores fysiske aktivitet er med til at forme vores fysiske figur. Men hvad nu hvis vi opretholdt lignende aerobic i vores tidligere former? Er det muligt, at vores embryoner også motionerede?

Forskere ved EMBLs Ikmi-gruppe vendte disse spørgsmål mod søanemonen for at forstå, hvordan adfærd påvirker kropsformen under tidlig udvikling. Havanemoner, viser det sig, har også gavn af at opretholde en aktiv livsstil, især da de vokser fra ægformede svømmelarver til stillesiddende, rørformede polypper. Denne morfologiske transformation er en fundamental overgang i livshistorien for mange cnidarian-arter, herunder de udødelige vandmænd og bygherrerne af vores planets rigeste og mest komplekse økosystem, koralrev.

Under udviklingen udfører stjernesøanemonelarver (Nematostella) et specifikt mønster af gymnastiske bevægelser. For meget eller for lidt muskelaktivitet eller en drastisk ændring i organiseringen af ​​deres muskler kan afvige søanemonen fra dens normale form.

I et nyt papir offentliggjort i Current Biology , udforsker Ikmi-gruppen, hvordan denne form for adfærd påvirker dyrenes udvikling. Med ekspertise inden for levende billeddannelse, beregningsmetodik, biofysik og genetik forvandlede det tværfaglige team af forskere 2D og 3D levende billeddannelse til kvantitative funktioner til at spore ændringer i kroppen. De fandt ud af, at havanemoner under udvikling opfører sig som hydrauliske pumper, regulerer kropstrykket gennem muskelaktivitet og bruger hydraulik til at forme larvevævet.

"Mennesker bruger et skelet lavet af muskler og knogler til at træne. I modsætning hertil bruger søanemoner et hydroskelet lavet af muskler og et hulrum fyldt med vand," sagde Aissam Ikmi, EMBL gruppeleder. De samme hydrauliske muskler, der hjælper de udviklende søanemoner med at bevæge sig, ser også ud til at påvirke, hvordan de udvikler sig. Ved at bruge en billedanalysepipeline til at måle kropssøjlenængde, diameter, estimeret volumen og bevægelighed i store datasæt, fandt forskerne ud af, at Nematostella-larver naturligt deler sig selv i to grupper:langsomt og hurtigt udviklende larver. Til holdets overraskelse, jo mere aktive larverne er, jo længere tid tager de at udvikle sig. "Vores arbejde viser, hvordan udvikling af søanemoner i det væsentlige 'motioner' for at opbygge deres morfologi, men det ser ud til, at de ikke kan bruge deres hydroskelet til at bevæge sig og udvikle sig samtidigt," sagde Ikmi.

Making microscopes and building balloons

"There were many challenges to doing this research," explains first author and former EMBL predoc Anniek Stokkermans, now a postdoc 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, resulting in blurry images, especially when you want to look at it in 3D. Additionally, the animal is quite dense, so most microscopes cannot even see halfway through the animal."

To look both deeper and faster, Ling Wang, an application engineer in the Prevedel group at EMBL, built a microscope to capture living, developing sea anemone larvae in 3D during its natural behavior.

"For this project, Ling has specifically adapted one of our core technologies, Optical Coherence Microscopy or OCM. The key advantage of OCM is that it allows the animals to move freely under the microscope while still providing a clear, detailed look inside, and in 3D," said Robert Prevedel, EMBL group leader. "It has been an exciting project that shows the many different interfaces between EMBL groups and disciplines."

With this specialized tool, the researchers were able to quantify volumetric changes in tissue and body cavity. "To increase their size, sea anemones inflate like a balloon by taking up water from the environment," Stokkermans explained. "Then, by contracting different types of muscles, they can regulate their short-term shape, much like squeezing an inflated balloon on one side, and watching it expand on the other side. We think this pressure-driven local expansion helps stretch tissue, so the animal slowly becomes more elongated. In this way, contractions can have both short-term and a long-term effects."

Balloons and sea anemones

To better understand the hydraulics and their function, researchers collaborated with experts across disciplines. Prachiti Moghe, an EMBL predoc in the Hiiragi group, measured pressure changes driving body deformations. Additionally, mathematician L. Mahadevan and engineer Aditi Chakrabarti from Harvard University introduced a mathematical model to quantify the role of hydraulic pressures in driving system-level changes in shape. They also engineered reinforced balloons with bands and tapes that mimic the range of shapes and sizes seen in both normal and muscle-defective animals.

"Given the ubiquity of hydrostatic skeletons in the animal kingdom, especially in marine invertebrates, our study suggests that active muscular hydraulics play a broad role in the design principle of soft-bodied animals," Ikmi said. "In many engineered systems, hydraulics is defined by the ability to harness pressure and flow into mechanical work, with long-range effects in space-time. As animal multicellularity evolved in an aquatic environment, we propose that early animals likely exploited the same physics, with hydraulics driving both developmental and behavioral decisions."

As the Ikmi group previously studied the connections between diet and tentacle development, this research adds a new layer to understanding how body forms develop.

"We still have many questions from these new findings. Why are there different activity levels? How do cells exactly sense and translate pressure into a developmental outcome?" Stokkermans asked as she considers where this research leads. "Furthermore, since tube-like structures form the basis of many of our organs, studying the mechanisms that apply to Nematostella will also help gain further understanding in how hydraulics play a role in organ development and function." + Udforsk yderligere

Eat more to grow more arms… if you're a sea anemone