Hydrophobic-hydrophilic crown-like structure enables aquatic insects to reside effectively beneath the water surface

Chiaki Suzuki,Tateo Shimozawa,Daisuke Ishii,Hiroshi Suzuki,Masatsugu Shimomura,Takahiko Hariyama,Shuhei Nomura,Yasuharu Takaku

doi:10.1038/s42003-021-02228-5

Abstract

Various insects utilise hydrophobic biological surfaces to live on the surface of water, while other organisms possess hydrophilic properties that enable them to live within a water column. Dixidae larvae reside, without being submerged, just below the water surface. However, little is known about how these larvae live in such an ecological niche. Herein, we use larvae of Dixa longistyla (Diptera: Dixidae) as experimental specimens and reveal their characteristics. A complex crown-like structure on the abdomen consists of hydrophobic and hydrophilic elements. The combination of these contrasting features enables the larvae to maintain their position as well as to move unidirectionally. Their hydrophobic region leverages water surface tension to function as an adhesive disc. By using the resistance of water, the hydrophilic region serves as a rudder during locomotion.

Highlights

Various insects utilise hydrophobic biological surfaces to live on the surface of water, while other organisms possess hydrophilic properties that enable them to live within a water column
We reported the remarkable ability of Dixidae larvae to use hydrophobic hairy structures on the ventral side of the abdomen to attach to a water surface and reside just below it (Figs. 1–5)
The effect can be explained by two proposed hypotheses: (1) The roughness of the structures increases the surface area, which leads to the hydrophobic property (Wenzel model)[10]

Summary

Introduction

Various insects utilise hydrophobic biological surfaces to live on the surface of water, while other organisms possess hydrophilic properties that enable them to live within a water column. A complex crown-like structure on the abdomen consists of hydrophobic and hydrophilic elements The combination of these contrasting features enables the larvae to maintain their position as well as to move unidirectionally. This pattern of behaviour suggests that their diving ability may be related to feeding and predator avoidance[8] In contrast to these organisms, the larvae of Dixidae, a family of aquatic Nematocera flies (Diptera), exhibit a unique characteristic[9,10]. We used larvae of Dixa longistyla (Diptera: Dixidae) as experimental specimens We examined their ability to live just below the water surface, focusing on crown-like structures on the ventral side of the hind segments[10]. We provide evidence that a combination of hydrophobic and hydrophilic structures enables the larvae to reside in such an ecological niche

Methods

Results

Conclusion