Mucus Matters: The Slippery and Complex Surfaces of Fish

  • Dylan K. WainwrightEmail author
  • George V. Lauder
Part of the Biologically-Inspired Systems book series (BISY, volume 10)


Teleost scales are extremely diverse in morphology, with different categories (cycloid, crenate, spinoid, ctenoid) once used to define major groups of fish. We describe these different classical categories of scales and discuss the structure and potential function of small features of scale morphology such as spines, ctenii, radii, and circuli. Modern techniques now make analysis of scale morphology using three-dimensional quantitative data possible. This ability is crucial because many of the hydrodynamic and protective hypotheses concerning the function of scales are dependent on three-dimensional structure. We discuss different techniques to investigate and image the structure of fish scales and skin, and we highlight gel-based surface profilometry as a new valuable tool for studying fish skin. In addition to bony scales, fish skin is also covered by an epidermis that secretes mucus that can coat the exterior of scales. Fish scales are often studied in isolation with the epidermis removed; here we present topographic, three-dimensional, analyses of fish skin surfaces from seven species with the mucus, epidermis, and relative positions of scales intact. We compare these images qualitatively and quantitatively to the same individuals with the epidermis and mucus removed to show a previously unexplored axis of diversity in fish: how mucus and epidermis interact with scale morphology to create surface texture. The three-dimensional structure of fish skin has important implications for hydrodynamic function during locomotion, but this remains a largely unexplored area.



We would like to acknowledge James Weaver for his imaging expertise (in particular for the images in Fig. 10.5), and Kimo Johnson for his assistance with GelSight profilometry measurements. We acknowledge Karsten Hartel and Andrew Williston with assistance in accessing specimens and Dr. Lex Smits for introducing us to k+. The research reported here was supported by ONR MURI Grant N000141410533 monitored by Dr. Bob Brizzolara, HFSP Young Investigators Grant (RGY0067- 2013) to James Weaver, and NSF GRF 2014162421 awarded to D.K.W.


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Authors and Affiliations

  1. 1.Department of Organismic and Evolutionary BiologyHarvard UniversityCambridgeUSA

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