Sea creatures reveal the physics behind animal body shape diversity
Variation in animal body shapes is determined by differences in mechanical tissue properties, termed "mechanotypes." In Cnidarians, three mechanical modules explain key shape features—elongation and polarity. Experimental manipulation of these modules in sea anemones confirmed that altering mechanotypes can predictably reshape organisms, highlighting the role of physical forces in morphological diversity.

Animals come in an extraordinary range of body shapes. A starfish looks nothing like an earthworm, a mouse, or a human. Yet even closely related species can appear radically different: corals, jellyfish, and sea anemones all belong to the same biological phylum, but their bodies take strikingly different forms. A new study by EMBL researchers appearing in Cell, shows how such shape diversity is determined by variation in mechanical tissue properties—an idea they termed "mechanotypes."
Genotype—the genetic composition of organisms—plays a central role during growth and development. But genes alone cannot fully explain how tissues bend, stretch, and reorganize to generate body shape—a process called morphogenesis.
Comparing genomes can reveal genetic differences linked to shape diversity, but genes cannot tell us how morphogenesis unfolds.
Even with a genome in hand, we still cannot yet predict the final shape of an organism.
Researchers drew on insights from mechanobiology—the study of how physical forces shape biological processes. During development, morphogenesis is often driven not by individual cells but by forces generated collectively within tissues. They hypothesized that this is the level where different body shapes arise across species.
What matters is how cells work together as a tissue to generate forces and mechanical constraints. If this is where morphogenesis operates, it may also be where shape diversity emerges across evolution, the researchers argue.
Connecting modern biological understanding of morphogenesis to Thompson's ideas of mechanical influences on diversity required cross-disciplinary collaboration. However, to build a framework that explains the physical underpinnings of this process, the study required expertise in theoretical physics and mathematics.
An important idea in physics is that when described on the right scale, emergent features of complex systems can be understood through models involving only a few key parameters.
Part 1

This indeed turned out to be the case for Cnidarian body shape diversity. Based on experimental observations in six different species—two corals, two anemones, and two hydrozoans—the team came up with a list of three "mechanical modules." These modules can be combined to explain two important features of body shape—elongation and polarity.

Elongation is a measure of how stretched or compact a body is along its main axis. Polarity, on the other hand, describes how asymmetric the animal is—whether the top part of the animal, which contains the mouth, is wider or narrower than its base. By adjusting the values of the mechanical modules in their model, like tuning knobs, scientists arrived at different predictions for elongation and polarity. They called this combination, unique for each species, an organism's "mechanotype."

Mechanical changes ultimately arise from molecular changes, but the mechanotype is where that information becomes predictive of form.
Scientists think evolution acts on these modules to generate new forms.
Does this mean that changing the mechanotype would change the shape of the organism? To test this, the scientists performed a series of experiments using the sea anemone Nematostella. Nematostella larvae tend to be elongated and have a narrow oral end. When the scientists introduced genetic changes that affected one of the mechanical modules—nematic order—the larvae ended up being round instead of elongated.

Changing polarity was more difficult though; scientists had to perturb multiple modules simultaneously to get Nematostella to change its polarity to something that resembled another species, Aiptasia.

Together, these "reshaping" experiments showed it is possible to quantitatively predict and manipulate shape using mechanotypes and active surface models. They also demonstrated that different aspects of shape can be more or less complex in how they are determined by combinations of such mechanical modules.

Deciphering mechanical determinants of morphological evolution, Cell (2026). DOI: 10.1016/j.cell.2026.02.010. www.cell.com/cell/fulltext/S0092-8674(26)00175-3

Part 2

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https://theconversation.com/how-birds-are-spreading-plastic-polluti...