title: Whip spiders (Amblypygi) become water-repellent by a colloidal secretion that self-assembles into hierarchical microstructures.
abstract: BACKGROUND
  Among both plants and arthropods, super-hydrophobic surfaces have evolved that enable self-cleaning, locomotion on water surfaces, or plastron respiration. Super-hydrophobicity is achieved by a combination of non-polar substances and complex micro- and nano-structures, usually acquired by growing processes or the deposition of powder-like materials.
  
  
  RESULTS
  Here we report on a multi-phasic secretion in whip spiders (Arachnida, Amblypygi), which externally forms durable, hierarchical microstructures on the basically smooth cuticle. The solidified secretion crust makes the previously highly wettable cuticle super-hydrophobic. We describe the ultrastructure of secretory cells, and the maturation and secretion of the different products involved.
  
  
  CONCLUSIONS
  Whip spiders represent intriguing objects of study for revealing the mechanisms of the formation of complex microstructures in non-living systems. Understanding the physical and chemical processes involved may, further, be of interest for bio-inspired design of functional surface coatings.
authors.affiliation: Functional Morphology and Biomechanics, Zoological Institute, University of Kiel, Am Botanischen Garten 9, Kiel, 24098 Germany ; Department of Biological Sciences, Macquarie University, Sydney, NSW 2109 Australia.
authors.forename: Jonas O
authors.initials: JO
authors.lastname: Wolff
authors.affiliation: Department of Integrative Zoology, University of Vienna, UZA1 Althanstraße 14, Vienna, 1090 Austria.
authors.forename: Thomas
authors.initials: T
authors.lastname: Schwaha
authors.affiliation: Department of Integrative Zoology, University of Vienna, UZA1 Althanstraße 14, Vienna, 1090 Austria ; Institute of Zoology, Department of Integrative Biology and Biodiversity Research, University of Natural Resources and Life Sciences, Gregor Mendel Straße 33, Vienna, 1180 Austria.
authors.forename: Michael
authors.identifier: 0000-0001-8762-4665
authors.initials: M
authors.lastname: Seiter
authors.affiliation: Functional Morphology and Biomechanics, Zoological Institute, University of Kiel, Am Botanischen Garten 9, Kiel, 24098 Germany.
authors.forename: Stanislav N
authors.initials: SN
authors.lastname: Gorb
keywords: Amblypygi; Anti-wetting; Arachnida; Cerotegument; Colloid; Cuticle; Plastron; Surface coating