Extreme suction attachment performance from specialised insects living in mountain streams (Diptera: Blephariceridae).

Victor Kang,Simon Chen,Walter Federle,Robin T White

doi:10.7554/elife.63250

Abstract

Suction is widely used by animals for strong controllable underwater adhesion but is less well understood than adhesion of terrestrial climbing animals. Here we investigate the attachment of aquatic insect larvae (Blephariceridae), which cling to rocks in torrential streams using the only known muscle-actuated suction organs in insects. We measured their attachment forces on well-defined rough substrates and found that their adhesion was less reduced by micro-roughness than that of terrestrial climbing insects. In vivo visualisation of the suction organs in contact with microstructured substrates revealed that they can mould around large asperities to form a seal. We have shown that the ventral surface of the suction disc is covered by dense arrays of microtrichia, which are stiff spine-like cuticular structures that only make tip contact. Our results demonstrate the impressive performance and versatility of blepharicerid suction organs and highlight their potential as a study system to explore biological suction mechanisms.

Highlights

Of the approximately one million known species of insects, only 325 attach using muscle-controlled suction organs (Stork, 2018; Roskov et al, 2020)
H. lugubris larvae have six ventromedian suction organs, with each organ comprising a suction disc, a central opening and a piston, a suction chamber surrounded by a thick-w alled cuticular cuff, and a V-notch (Figure 1c-f and Video 2)
The ventral disc surface of H. lugubris is covered in a dense array of microtrichia (Figure 2a-e)

Summary

Introduction

Of the approximately one million known species of insects, only 325 attach using muscle-controlled suction organs (Stork, 2018; Roskov et al, 2020). These species belong to a single dipteran family, the Blephariceridae, and their larvae and pupae develop on rocks in torrential alpine streams where flow rates can exceed 3 ms–1 (Frutiger and Buergisser, 2002; Zwick, 2004; Figure 1a & b; Video 1). Each blepharicerid larva has six ventral suction organs to attach to biofilm-covered rock surfaces, where it feeds on diatoms. The larva can locomote relatively quickly and possibly over long distances: blepharicerid larvae migrate from one stone to another to find the swiftest regions of the stream (Frutiger, 1998; Mannheims, 1935). We have shown that a dedicated active detachment system allows the larva to rapidly detach its suction organ during locomotion (Kang et al, 2019)

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Conclusion