Mechanisms of Fluid Feeding in Insects, from Nanoscale to Organism

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Fluid-feeding insects are among the most abundant organisms on Earth. Their success can be attributed in part to their tubular mouthparts, engineered by natural selection to acquire a remarkable variety of fluids, such as blood and nectar. These feeding devices - proboscises - must take up fluids while remaining free of sticky residues and debris that might impede fluid uptake; in other words, they must be capable of self-cleaning. The fundamental organization of the proboscis consists of a slender tube with a surface of minute valleys and ridges that form canals connected by pores to a central food canal. The research focuses on the hypothesis that fluid feeding can be explained by a single model based on unifying principles of capillarity and wetting. To examine this primary hypothesis, two major insect groups, butterflies and flies, will be used to study the structure and function of the proboscis. The study is organized around three objectives: (1) to explain the role of wettability of the proboscis as the first step in acquiring fluid, (2) to elucidate the mechanisms of fluid uptake as the second step in fluid acquisition, and (3) to explain how the availability of fluid, whether in pools or films, determines the means of uptake. The project offers a new framework for explaining biological phenomena, such as dietary choices and the diversification of insect life. It also provides a platform for transferring Nature-inspired principles of fluid uptake and transport to the development of new engineering devices, such as flexible microfluidic probes. The research program emphasizes cross-disciplinary interaction between biologists and physical scientists and translation into interdisciplinary education of students, from high school onward. Outreach to students, including those in under-represented groups, by providing research opportunities and by hosting science teachers to develop teaching modules emphasizing the relation of physical principles to aspects of Nature, such as butterfly feeding and pollination. Research results will be incorporated into courses at two universities and will be disseminated through paper and electronic publications, professional and public presentations, and student-developed web sites and blogs.The proposed study launches from preliminary work by the investigators, which indicates that fluid feeding by insects can be captured under a single model based on unifying principles of capillarity and wetting (hydrophilicity and hydrophobicity), which heretofore have been poorly explored. Tools and principles will be used to provide a quantitative, comparative analysis of the (1) micro-architecture of the mouthparts (e.g., scanning electron microscopy, X-ray tomography), (2) role and function of micro-architecture in acquiring and transporting fluids into and through the mouthparts (e.g., X-ray phase-contrast imaging, fluorescent and dark-field optical microscopy, and mathematical image analysis), (3) materials wetting and fluid flow through different conduits (physical and mathematical modeling augmented by full characterization of fluid properties such as food rheology, surface tension, and contact angles), and (4) hydrophilic-hydrophobic properties of the mouthparts (e.g., confocal microscopy, fluorescent imaging, Atomic force microscopy).