In the dazzlingly diverse kingdom of animals, body shapes vary tremendously—from the radial symmetries of starfish to the cylindrical forms of earthworms, and the complex anatomies of mammals. Even among closely related species within the same phylum, morphological divergence can be stark. Corals, jellyfish, and sea anemones, all members of the phylum Cnidaria, present a strikingly varied array of body architectures despite sharing evolutionary lineage. Unpacking the roots of this morphological diversity has challenged biologists for decades, often focusing on genetic explanations. However, a groundbreaking study spearheaded by a collaborative team from the European Molecular Biology Laboratory (EMBL) and the University of Geneva ushers in a new paradigm by revealing how mechanical properties inherent in tissues—termed ‘mechanotypes’—define the evolutionary landscape of organismal forms.
The foundation of this novel conceptual framework draws inspiration from D’Arcy Thompson’s seminal 1917 work, On Growth and Form, which posited physics as a primary agent shaping biological forms. Thompson’s visionary ideas illuminated how physical laws and mechanical forces modulate living architectures, yet for much of the 20th century, genetics overshadowed mechanistic insights in explaining morphogenesis and evolutionary form variation. This latest study bridges that gap by harnessing mechanobiology, an interdisciplinary realm exploring how biological processes are influenced and governed by physical forces within tissues.
Genotypic data, while invaluable, fall short when it comes to predicting how an organism’s shape emerges during development. Morphogenesis—the process by which cells organize, bend, stretch, and remodel tissues to sculpt form—is complex, dynamic, and contingent on both molecular signals and mechanical interactions. As Aissam Ikmi, the study’s senior author and Group Leader at EMBL Heidelberg, explains, “Genes provide the blueprint, but cannot predict how tissues physically behave to create the final shape.” This recognition prompted the team to investigate morphogenesis at the mesoscopic scale, focusing on the collective mechanical forces within tissues rather than isolated cellular behaviors or gene sequences.
Central to the investigation was the idea that body shape evolves through variations in tissue mechanical properties, which can be distilled into a set of modular parameters. Ikmi’s group employed cnidarians as their biological models due to their relatively simple but highly variable body plans at both larval and adult stages, making them ideal subjects for unraveling mechanical underpinnings of shape diversity. However, to translate complex biological phenomena into predictive frameworks, the collaboration engaged theoretical physicists and mathematicians specializing in systems modeling—most notably Guillaume Salbreux and Nicolas Cuny from the University of Geneva, alongside former EMBL postdoctoral mathematician Richard Bailleul.
Their cross-disciplinary synergy yielded a concise mechanical model constructed from three principal “mechanical modules” that collectively govern two critical aspects of cnidarian morphology: elongation and polarity. Elongation quantifies how an organism stretches along its main body axis, defining whether it adopts a slender, elongated form or a compact, rounded shape. Polarity captures asymmetry along this axis, identifying whether the oral end (housing the mouth) is narrower or wider compared to the aboral base. These modules function analogously to tunable dials within an active surface model, where adjusting parameter values predicts the continuum of natural body forms observed across species. Each species’ specific set of module values defines its unique mechanotype, effectively translating molecular variations into mechanical blueprints of form.
Investigating the interplay between these modules elucidated how mechanical forces at the tissue level are the proximate drivers of morphological outcomes. The mechanotype framework demystifies how evolutionary changes act on mechanical parameters rather than solely on genetic sequences to produce morphological novelty. This perspective resonates with physical principles wherein complex emergent behaviors arise from simple constituent rules, underscoring the importance of scale in deciphering biological form.
To probe these conceptual insights experimentally, the team performed ‘reshaping’ interventions on the sea anemone Nematostella, a model cnidarian larva exhibiting a naturally elongated body with a narrow oral end. By genetically manipulating components underpinning one mechanical module associated with nematic order—a measure of how cells organize and orient themselves—the larvae’s morphology shifted markedly from elongated to more spherical shapes. Although altering polarity proved more challenging, requiring perturbations across multiple modules, the researchers managed to induce polarity changes that led Nematostella larvae to resemble the body form of a different cnidarian species, Aiptasia. These experiments compellingly demonstrate the predictive power of mechanotypes and active surface modeling in capturing and controlling morphological evolution.
Beyond experimental validation, this work exemplifies the profound value of interdisciplinary collaboration in contemporary biology. As Salbreux reflects, the partnership between experimentalists and theorists was made possible by a shared curiosity about form variation, and the mutual inspiration catalyzed creative breakthroughs in unraveling the physics of developmental morphology. Ikmi enthusiastically endorses the relationship, highlighting its rarity and depth: “We found intellectual and personal synergy with all collaborators—Richard, Nicolas, Guillaume—each bringing crucial expertise to elevate the project’s scope and resolution.”
The implications of this study ripple far beyond cnidarian biology. By articulating mechanical determinants of shape, the mechanotype concept opens new avenues for understanding morphological evolution across metazoans. It empowers scientists to predict developmental outcomes from mechanical principles and fosters the integration of physical modeling into evo-devo research. Furthermore, it suggests that evolution may leverage mechanical constraints and properties as selective substrates independently or alongside genetic mutation, broadening the canonical evolutionary synthesis.
Looking ahead, the research team aims to expand their mechanistic explorations into the polyp stages of cnidarian life cycles and incorporate additional species to refine and generalize the mechanotype model. These next steps promise to deepen insights into how life’s myriad forms emerge and diversify through an intricate interplay of genes, physics, and evolution, reviving and modernizing D’Arcy Thompson’s century-old vision with transformative technological and conceptual tools.
This landmark contribution, published in Cell, heralds a significant leap in our comprehension of biological form. It challenges reductionist genetics-centered narratives and champions a holistic vision where physical forces and mechanical modules provide a foundational framework for the evolution of morphology. As the burgeoning field of mechanobiology presses forward, such integrated approaches may rewrite textbooks and revolutionize the design principles underlying life itself.
Subject of Research: Animals
Article Title: Deciphering mechanical determinants of morphological evolution
News Publication Date: 20-Mar-2026
Web References: 10.1016/j.cell.2026.02.010
Image Credits: Daniela Velasco/EMBL
Keywords: Evolutionary developmental biology, Mechanobiology, Morphogenesis, Cnidarians, Morphological evolution, Mechanotypes, Tissue mechanics, Physical modeling, Developmental biology, Active surface models
