Drag Reduction in the Mouthpart of a Honeybee Facilitated by Galea Ridges for Nectar-Dipping Strategy

Some nectarivorous animals have evolved highly specialized tongues to gather nectar from flowers. Here we show that the Italian honeybee, Apis mellifera ligustica, uses the uniformly-distributed ridges on the internal wall of the mouthpart to reduce drag while drinking nectar. We discovered that the tip of the tongue is covered with bushy setae and resembles a brush, and the ridges are parallel distributed on the inner wall of the galeae. Using high-speed camera, we recorded the morphology of the mouthpart when dipping the sucrose water. Considering the ridges and the movement rule of the glossa, we proposed a model for analyzing the mechanism of drag reduction. Theoretical estimation of the friction coefficient with respect to the dipping frequency indicates that the erectable bushy hairs and the ridges can significantly reduce friction when a honeybee drinks nectar. Results show that dimensions of the ridges play a key role in reducing friction. It can be concluded that the ridges on the galeae of honeybee＇s mouthpart can reduce the friction coefficient by 86% compared with the case of the transverse distribution co- efficient S = 40. Finally, the capability of drag reduction in the mouthpart of honeybee may inspire a creative concept for de- signing efficient viscous micropumps.

The Honeybee＇s Protrusible Glossa is a Compliant Mechanism

Many biological structures can perform highly-dexterous actions by using dynamic surfaces. To deal with the contradictive demands of high feeding efficiency and low energy expenditure during nectar feeding, the glossal surface of a honeybee un- dergoes shape changes, in which glossal hairs erect together with segment elongation in a drinking cycle. In this paper, we extracted a transmission link embedded in the glossa from postmortem examination and found that the compliance of the in- tersegmental membranes provides more possibilities for this highly kinematic synchronicity. According to the morphing phe- nomena of honeybee＇s glossa, we proposed a compliant mechanism model to predict the deformation behavior of honeybee considering elastic properties of the glossal intersegmental membranes. The increase of membrane stiffness may improve the capacity of elastic potential energy transfer, but will still result in the increase of mass. An index is introduced to evaluate the contradiction for optimizing structural parameters. This work may arouse new prospects for conceptual design of mi- cro-mechanical systems equipped with bio-inspired compliant mechanisms.

Spermine increases bactericidal activity of silver-nanoparticles against clinical methicillin-resistant Staphylococcus aureus

Methicillin-resistant Staphylococcus aureus(MRSA) has emerged worldwide as a major multidrugresistant pathogen that causes notable morbidity and mortality. Fast emerging of MRSA prevalence requires special attention for strengthening the inventory of antimicrobial compounds. Silver nanoparticles(AgNPs) have been widely used to treat multi-drug resistant pathogens due to the unique antibacterial properties, meanwhile spermine has been proven to exert outstanding inhibition effect to S.aureus with not yet fully understood mechanisms. The aim of this study was to investigate the synergistic effect of AgNPs and spermine as well as to determine the antibacterial activity of their combination against MRSA strains. Several clinical MRSA isolates and ATCC BAA-1026 were used to determine minimum inhibitory concentration(MIC) and fractional inhibitory concentration indices(FICI) of AgNPs and spermine, and a synergistic effect was observed. This phenomenon was further confirmed by growth curve and time-killing assays, showed that spermine could be used as an adjuvant for AgNPs in the treatment of MRSA infections.