DOI: 10.5061/dryad.9kd51c5sw
title: Data from: Epidermal microstructures on the paired fins of marine sculpins suggest new functional hypotheses supporting benthic station-holding

description: Harsh environments, such as those with breaking waves and turbulent flows,
 present extreme challenges to organismal survival. Many animals exploiting
 these habitats possess adaptations to maintain position under dynamic flow
 conditions, such as reversible or permanent attachment systems. However,
 some station-holding fishes (e.g., sculpins) instead rely on morphological
 and behavioral modifications of their pectoral fins to increase friction
 with the substrate and combat drag. Despite epidermal microstructures on
 the fins of other benthic fishes, little exploration of pectoral fin
 surfaces at the microscopic scale has been undertaken in sculpins. Using
 scanning electron microscopy, we discovered microscopic, fibrillar
 projections contained within single cells on the ventral surfaces of the
 paired fin rays of two intertidal and two subtidal species of marine
 sculpins. In contrast to subtidal species, the intertidal species
 possessed epidermal cells with discrete channels separating groups of
 fibrillar projections. These features bear a striking resemblance to
 epidermal microstructures described in other fishes but have distinct
 morphological differences. We suggest the hypothesis that these previously
 overlooked features contribute to sculpin station-holding performance via
 enhanced mechanical interactions with the substrate, suggesting new taxa
 within which to explore potential mechanisms of underwater friction
 enhancement and adhesion.
description: Three specimens from each of four species within the Superfamily
 Cottoidei were examined: intertidal <em>Artedius lateralis
 </em>and <em>Oligocottus maculosus</em>, and subtidal
 <em>Myoxycephalus polyacanthocephalus</em> and
 <em>Leptocottus armatus. </em>Two individuals of each species
 were collected on San Juan Island, WA during the summer of 2022. One
 additional individual per species was provided by the University of
 Washington Burke Museum ichthyology collection. However, epidermal quality
 of specimens obtained from the Museum was poor, rendering data to be
 excluded from formal analysis. Right pectoral and pelvic fins were
 dissected at the base and prepared for imaging with a Hitachi S3000N or
 Thermo Scientific Scios 2 DualBeam scanning electron microscope (SEM).
 Images were taken at 1500X at the approximate midpoint along the free
 margin of each of the 5 ventral-most regionalized fin pectoral fin rays
 and the first pelvic fin ray. Some fin rays required multiple images
 because of the three-dimensional complexity of fin ray shape.
 For <em>Oligocottus maculosus</em>, each fin ray was imaged
 along multiple regions of the free margin to explore morphological
 variability within a single species and individual. Additional images were
 taken at lower magnifications to verify orientation and document other
 nearby features, but these were not used for analysis.
 Following imaging, FIJI (https://fiji.sc/) was used to divide
 each picture into quadrants of 1000 mm each (Figure S2) to quantify cell
 density and protruded area from at least 4 quadrants per fin ray. Cell
 density was calculated by counting the total number of cells per quadrant,
 including partial cells along the edges. Protruded area was determined by
 tracing the outline of the protruded portion (containing the fibrils) of 3
 cells per quadrant. To explore the morphometrics of the fibrils covering
 the surface of cells as well as the width of the channels between the
 protruded area of cells, we selected the single highest quality image of
 the pectoral fin ray surface for each individual at 1500x magnification
 and made estimates of fibril density, diameter, and length, as well as
 channel width. Three protruded areas (or cells) per image per specimen and
 three fibrils per cell were selected for measurement. Fibril density was
 estimated by counting the number of fibrils within a specified area.
 Fibril diameter was estimated by measuring the diameter of the fibril’s
 tip, while fibril length was estimated by measuring the length of a line
 from the base to the tip of the fibril. This dataset
 includes: All raw analyzed photos, raw measurement data, and a powerpoint
 file indicating the position of each photograph along each fin ray for
 <em>O. maculosus</em>. Manipulations including averages were
 performed external to these files. 
description: # Epidermal microstructures on the paired fins of marine sculpins provide
 new insights into mechanisms supporting benthic station-holding
 [https://doi.org/10.5061/dryad.9kd51c5sw](https://doi.org/10.5061/dryad.9kd51c5sw) ## Description of the data and file structure Data were collected to describe the topographic features of the fin epidermis on 4 species of marine sculpins. ### Files and variables The files and data types contained within them are as follows: * SEM analysis raw data combined 10-01-24.xlsx - A spreadsheet containing a list of all images and whether they were used in analyses, as well as the raw data from all measures. Missing data are indicated by blank cells. Variables include:  * List of images - A list of all images available for analysis and contained within the raw image files. Analyzed excluded images remain in subsequent datasets with an indication that they have been excluded. Museum specimens and base of fin measurements are included for comparison when available, but were excluded from analyzed data. These files are uploaded to Zenodo. * Cell density * No full cells - Number of cells counted per quandrant where the entire border of the protruded portion was contained within the quadrant boundaries. * No partial cells - Number of cells counted per quandrant where the protruded portion crossed quadrant boundaries. * Total cells - A calculation adding No full cells and No partial cells together. * Density full - A calculation dividing No full cells by Area (cells/um^2). * Density total - A calculation dividing Total cells by Area (cells/um^2). * Protruded area (measurements are calculated automatically in FIKI/Image J) * Area - Area of the boundary encircling the protruded portion of the cell (um^2). * Perimeter - Length of the boundary encircling the protruded portion of the cell (um). * Circularity - A measure of closeness of shape to a perfect circle (a value of 1.0), calculated as 4π*area/perimeter^2. As the value approaches 0.0, it indicates an increasingly elongated shape (not used in analyses). * Max Feret - Maximum length or diameter of the encircled boundary of the protruded portion of the cell (um, not used in analyses). * Min Feret - Minimum length or diameter of the encircled boundary of the protruded portion of the cell (um, not used in analyses). * Aspect ratio - A calculation of the major_axis (Max Feret) divided by the minor_axis (Min Feret) (not used in analyses). * Roundness - The inverse of aspect ratio, calculated as 4*area/(π*major_axis^2) (not used in analyses). * Fiber density (measurements are calculated automatically in FIKI/Image J) * Number of fibers - A count of the number of fibers on each cell. * Area -  Area of the boundary encircling the protruded portion of the cell (um^2). * Fiber density - A calculation dividing Number of fibers by Area (fibers/um^2). * Fiber length (measurements are calculated automatically in FIKI/Image J) * Length - The distance from the base to the tip of a fiber (um). * Fiber diameter (measurements are calculated automatically in FIKI/Image J) * Diameter - The width of a fiber near the tip (um). * Channel width (measurements are calculated automatically in FIKI/Image J) * Width - The distance between one protruded area and the next, on adjacent cells (um). * Omac02 positions.pdf - A PDF file containing labeled images to identify the locations of images taken on specimen Omac02. * Omac03 positions.pdf - A PDF file containing labeled images to identify the locations of images taken on specimen Omac03. * Raw images - dataset.zip - A .zip folder containing folders of raw images for each specimen (Alat02, Alat07, Larm04, Larm05, Mpol02, Mpol04, Omac02, and Omac03). Images with the extension .BMP were taken using the Hitachi microscope whereas images with the extension .tif were taken with the Scios microscope. * Raw images - museum specimens.zip - A .zip folder containing folders of raw images for each museum specimen (Alat UW118838, Larm UW155816, Mpol UW156405, and Omac UW156016). Images with the extension .BMP were taken using the Hitachi microscope whereas images with the extension .tif were taken with the Scios microscope. These were not included in formal analyses. ## Code/software All files can be opened in native apps including spreadsheet, PDF, and image viewing softwares. ## Access information Other publicly accessible locations of the data: * N/A Data was derived from the following sources: * Scanning Electron Microscopy images of specimens obtained from: * Preserved collections at the University of Washington Burke Museum * Preserved collections in the research laboratory of Dr. Emily Kane