Royal Society Newton Fellow; EPA Cephalosporin Junior Research Fellow, Linacre College

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Vinod Saranathan

Vinod Saranathan

Details

Name: Dr. Vinod Kumar Saranathan
Position: Royal Society Newton Fellow; EPA Cephalosporin Junior Research Fellow, Linacre College
Email: vinod.saranathanATzoo.ox.ac.uk

Autobiography

I obtained my bachelor's degree in Physics with a minor in Philosophy (Ohio Wesleyan University, 2001-2004), where I worked on such diverse topics as synchronisation in Josephson junction ladders and surface reconstructions of starspots in LO Peg. There, I became gradually interested in ornithology investigating the plumage ecology of feather-degrading micro-organisms, thanks to Jed Burtt. During my PhD (Yale University, 2005-2011) advised by Rick Prum, I studied the nano-scale structure, optical function, development and evolution of non-iridescent structural colours of bird feather barbs that are produced by complex 3D amorphous nanostructures of β-keratin and air, and the iridescent structural colours of wing scales of butterflies, beetles, and bees that are produced by chitinous cuticular photonic crystals, both using synchrotron small angle X-ray scattering (SAXS). I joined EGI in April 2011 to work with Ben Sheldon on sexual selection and social hierarchy in blue tits using a robust biophysical approach.

Research Activities

My research lies at the interface of soft matter physics, photonics, evolution and ornithology. I am primarily interested in Evolutionary Photonics: the meso-scale (100-300 nm) structure and organisation, optical function, development and evolution of bio-photonic nanostructures that produce organismal structural colours.

Self-assembly of bio-photonic nanostructures

Structural colours are prominent in nature and constitute an important aspect of the organismal phenotype, and are frequently used in social and intersexual communication. The underlying colour-producing or biophotonic nanostructures are diverse in form and function. Their structural and optical characterisation have hitherto remained challenging despite a century of research. I have developed the use of synchrotron Small Angle X-ray Scattering (SAXS) as a precise, high-throughput tool for diagnosing biophotonic nanostructures, as well as predicting their single scattering optical function.

In birds, the two classes of spongy medullary structural colour-producing nanostructures observed are strikingly similar to self-assembled morphologies seen during the phase separation of synthetic soft matter systems via spinodal decomposition (polymer blends, de-alloying) and nucleation-and-growth (beer foam), suggesting the hypothesis that multiple independent lineages of birds have independently evolved quasi-ordered feather nanostructures that are self-assembled by the phase separation of polymerising β-keratin from the cytoplasm of medullary cells.

The complex photonic nanostructures found in the iridescent, structurally coloured scales (modified setae) of some butterflies, weevils, long-horned beetles and a few bees represent a broad diversity of chitin and air nanostructures with corresponding analogues in synthetic soft matter systems (di- and tri-block copolymer melts, lyotropic lipid-water phases) suggesting that the insects have apparently evolved their diversity of photonic scale nanostructures by manipulating membrane-folding energetics, likely mediated by the binding of curvature-inducing proteins to arrive at different evolutionarily stable self-assembled phase states.

The self-assembly hypothesis for the development of photonic nanostructures in birds and insects offers a coherent and elegant explanation for the repeated independent evolution of distinctive and highly stereotyped versions of a variety of biophotonic nanostructures in ecologically and evolutionarily diverse lineages. These results are also wholly in the spirit of a pioneering classical analysis of growth and function by D’Arcy Thompson (Thompson 1942). I am interested in deciphering the specifics of intra-cellular phase separation and self-arrest mechanisms in medullary barb cells as well as the hypothesized self assembly of insect scales cells via membrane-folding processes during pupation. The self-assembled, amorphous photonic nanostructures in bird feather barbs with a pronounced isotropic short-range order and the diversity of self-assembled insect scale nanostructures could therefore offer a useful biotemplate for the design and manufacture of a variety of optically-tunable, self-assembled mesophases for photonic applications, based on biomimicry or direct dielectric infiltration.

Sexual selection and social hierarchy in blue tits: A biophysical approach

A burgeoning question in behavioural ecology is on the signal content of structurally coloured plumage in birds. While the role of carotenoid-based secondary sexual plumage traits in mediating female mate-choice and social hierarchy through condition-dependent honest-signalling is reasonably documented, the signal content of structurally coloured plumage, particularly the ultra-violet (UV) ornaments, remains unknown and difficult to understand. The UV reflective crown colouration in blue tits (Parus (Cyanistes) caeruleus) are prominently used in female mate-choice and as a badge of male social status. I am currently working with Prof. Ben Sheldon on a project whereby I propose to collect feather samples from well-studied, local populations of blue tits (wytham and bagley woods, Oxford) to precisely assay inter-individual differences in crown colouration using optical spectrophotometry and SAXS and compare them with a rich of set of pedigree and social network data on the blue tits, so that we can better understand the biological function and evolution of secondary sexual traits such as structural colours.

Selected Recent Papers

D’Alba, L., V. Saranathan†, J. A. Clarke, J. A. Vinther, R. O. Prum & M. D. Shawkey†. (2011) Colour producing β-keratin nanofibres in Blue Penguin (Eudyptula minor) feathers. Biology Letters In press. | Read abstract/paper online
†indicates equal contribution

Saranathan, V., C. O. Osuji, S. G. J. Mochrie, H. Noh, S. Narayanan, A. Sandy, E. R. Dufresne, & R. O. Prum. (2010) Structure, Function and Self-Assembly of Single Network Gyroid (I4132) Photonic Crystals In Butterfly Wing Scales. PNAS 107(26): 11676-11681. | Read abstract/paper online

Dufresne, E. R., H. Noh, V. Saranathan, S. Mochrie, H. Cao & R. O. Prum. (2009) Self-Assembly of Amorphous Biophotonic Nanostructures by Phase Separation. Soft Matter 5: 1792-1795. | Read abstract/paper online

Shawkey, M. D., V. Saranathan, H. Palsdottir, J. Crum, M. H. Ellisman, M. Auer & R. O. Prum. (2009) Electron tomography, three-dimensional Fourier analysis and colour prediction of a three-dimensional amorphous biophotonic nanostructure. Journal of the Royal Society Interface 6: S213-S220. | Read abstract/paper online

Vinther, J., D. E. G. Briggs, R. O. Prum & V. Saranathan. (2008) The colour of fossil feathers. Biology Letters 4: 522-525. | Read abstract/paper online

Saranathan, V., D. Hamilton, G. Powell, D. Kroodsma, & R. O. Prum. (2007) Genetic Evidence Supports Song Learning in the Three-wattled Bellbird Procnias tricarunculata (Cotingidae). Molecular Ecology. 16(17): 3689-3702. | Read abstract/paper online

Saranathan, V. &l E. H. Burtt, Jr. (2007) Sunlight on feathers inhibits feather-degrading bacteria. Wilson Journal of Ornithology 119(2): 239-245. | Read abstract/paper online

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