The Secret Behind Fly Flight Unveiled by UMH Research

As if it were a biological gyroscope, helping the insect stabilize in the air. This is how a small organ, the haltere, functions in flies, aiding them in maintaining balance and performing complex aerial maneuvers. A study involving the UMH-CSIC Institute of Neurosciences has unveiled how this structure, located behind the main wings, is formed. Published in the journal Current Biology, the work reveals the existence of an internal network of cellular 'tensors' that is crucial for giving the haltere its characteristic shape.

The research was led by José Carlos Pastor Pareja, head of the Cellular and Tissue Architecture Laboratory in the Nervous System at the Institute of Neurosciences. It demonstrates that, contrary to previous beliefs, the haltere is not a hollow structure; rather, its two surfaces are internally connected through a sophisticated cellular system that stabilizes its rounded shape. "This structure is a stabilization system reminiscent of architectural supports: without these internal connections, the haltere elongates and loses its shape, much like a tent without tensors," explains Pastor Pareja.

During the process known as fly metamorphosis, the transition from larva to adult, the wings and halteres develop from a thin layer of cells. In the case of the haltere, the team discovered that an extracellular matrix rich in collagen, which separates its two sides, is first degraded. This degradation allows cellular projections to form, connecting both surfaces through a matrix with another protein, laminin, forming a kind of internal framework.

These connections act as biological tensors, allowing the organ to resist forces that would otherwise deform it. When this system fails, as observed in genetically modified fruit fly models (Drosophila melanogaster) by the team, the haltere loses its rounded shape, which is crucial for its function.

Furthermore, the study reveals that the haltere is under constant tension: a force pulling from its base and another anchoring it to the insect's outer cuticle. It is precisely this internal tensor system that balances both forces to maintain its geometry.

To observe these effects, the team used advanced electron microscopy techniques and live recordings during the fly's metamorphosis. "We have seen that a series of cellular projections are produced that stabilize the haltere's rounded shape by counteracting forces that would otherwise deform it," explains Pastor Pareja, adding: "When we remove this support structure in mutant models, the organ loses its functional geometry."

The use of mutant models and the analysis of the extracellular matrix have been key to unraveling this mechanism, which combines collagen degradation, cellular adhesion, and internal tensors that reinforce the structure from within. The results of this work go beyond the particular case of the fruit fly, as they provide general insights into how organs acquire their shape in animals, a fundamental question in developmental biology. Moreover, they may inspire new ways to address issues such as tissue engineering or the design of biomimetic structures.

The study was conducted in collaboration with researchers Yuzhao Song and Tianhui Sun from Tsinghua University (China); researchers Paloma Martín and Ernesto Sánchez Herrero from the Severo Ochoa Molecular Biology Center (CBMSO-CSIC-UAM); and researcher Jorge Fernández Herrero from the University of Alicante.