Liquid Marbles in Nature: Craft of Aphids for Survival

Abstract

Some aphids that live in the leaf galls of the host plant are known to fabricate liquid marbles consisting of honeydew and wax particles as an inner liquid and a stabilizer, respectively. In this study, the liquid marbles fabricated by the galling aphids, Eriosoma moriokense, were extensively characterized with respect to size and size distribution, shape, nanomorphology, liquid/solid weight ratio, and chemical compositions. The stereo microscopy studies confirmed that the liquid marbles have a near-spherical morphology and that the number-average diameter was 368 ± 152 μm, which is 1 order of magnitude smaller than the capillary length of the honeydew. The field emission scanning electron microscopy studies indicated that micrometer-sized wax particles with fiber- and dumpling-like shapes coated the honeydew droplets, which rendered the liquid marbles hydrophobic and nonwetting. Furthermore, the highly magnified scanning electron microscopy images confirmed that the wax particles were formed with assemblage of submicrometer-sized daughter fibers. The contact angle measurements indicated that the wax was intrinsically hydrophobic and that the liquid marbles were stabilized by the wax particles in the Cassie-Baxter model. The weight ratio of the honeydew and the wax particles was determined to be 96/4, and the honeydew consisted of 19 wt % nonvolatile components and 81 wt % water. The 1H nuclear magnetic resonance, Fourier transform infrared spectroscopy, and mass spectroscopy studies confirmed that the wax mainly consisted of triglycerides and that the honeydew mainly consisted of saccharides (glucose and fructose) and ribitol. The atomic force microscopy studies confirmed that honeydew is sticky in nature.

Shape‐Designable Polyhedral Liquid Marbles/Plasticines Stabilized with Polymer Plates

“…The Laplace pressures of near‐spherical LM stabilized with 0.2 mm‐sized PET plates and cuboid LM/LP stabilized with 2 mm‐sized PET plates were estimated using the capillary method. [ 42–44 ] First, the tip of the glass capillary was plugged into pure water, and the height ( H ) to which the water has risen inside the capillary was measured. The surface tension of pure water (γ ΑW ) was determined from the H value using Jurin's law (Equation ).…”

Seasonal changes in cuticular hydrocarbons in response to polyphenism in the host‐alternating aphid Prociphilus oriens

“…The secreted wax is hydrophobic and can protect aphids from contamination of honeydew and provide some protection against enemies and unfavorable environmental conditions (Smith 1999;Pike et al 2002;Moss et al 2006;Ammar et al 2013;Kasahara et al 2019;Depa et al 2020). However, there should be fitness costs to the production of external waxes (Pope 1983).…”

Biological applications of the NanoSuit for electron imaging and X-microanalysis of insulating specimens

“…Scanning electron microscopy (SEM) is widely used to observe fine details of organisms in high vacuums. In particular, field emission SEM (FESEM) needs a higher level of vacuum (10 − 3 to 10 − 7 Pa) for high-resolution imaging than conventional SEM (Kasahara et al, 2019 ). The effects of high vacuums on organisms include rapid evaporation of water across their surface layer as well as the collapse and death of organisms (Takaku et al 2013 ).…”