A foldable respiratory siphon powers near-surface locomotion through asymmetric rowing in Helophilus larvae

Matsunaga, T.; Nose, A.

doi:10.64898/2026.06.29.735254

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bioRxiv · 10.64898/2026.06.29.735254

A foldable respiratory siphon powers near-surface locomotion through asymmetric rowing in Helophilus larvae

Matsunaga, T.·Nose, A.

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Abstract

Extensible body structures have evolved repeatedly across animals, yet the mechanisms underlying the deployment of extensible organs often remain unknown. Eristalinae hoverfly larvae (rat-tailed maggots) possess exceptionally elongated posterior respiratory siphons, but the mechanism underlying their extension has not been experimentally investigated. Here, using wild-collected Helophilus virgatus larvae, we show that posterior siphon extension is achieved through a folding- unfolding mechanism revealed by fluorescence labeling. Phalloidin staining further demonstrated that, unlike Episyrphus sp. and Drosophila melanogaster, H. virgatus possesses a dense array of transversely oriented muscle fibers in the posterior siphon. Behavioral analyses further revealed that the posterior siphon functions not only in respiration but also as a propulsive organ for near-surface locomotion through asymmetric rowing. Together, our findings identify the structural and kinematic basis of posterior siphon deployment and demonstrate how a specialized respiratory organ can evolve into a multifunctional appendage that supports both respiration and locomotion.

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Matsunaga, T., Nose, A.. 2026-07-03. A foldable respiratory siphon powers near-surface locomotion through asymmetric rowing in Helophilus larvae. https://doi.org/10.64898/2026.06.29.735254

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