DOI: 10.5061/dryad.bk3j9kdm9
title: Data from: Second harmonic generation imaging reveals entanglement of collagen fibers in the elephant trunk skin dermis

description: Form-function relationships often have tradeoffs: if a material is tough,
 it is often inflexible, and vice versa. This is particularly relevant for
 the elephant trunk, where the skin should be protective yet elastic. To
 investigate how this is achieved, we used classical histochemical staining
 and second harmonic generation microscopy to describe the morphology and
 composition of elephant trunk skin. We report structure at the macro and
 micro scales, from the thickness of the dermis to the interaction of 10
 micro-m thick collagen fibers. We analyzed several sites along the length
 of the trunk to compare and contrast the dorsal-ventral and
 proximal-distal skin morphologies and compositions. We find the dorsal
 skin of the elephant trunk can have keratin armor layers over 2mm thick,
 which is nearly 100 times the thickness of the equivalent layer in human
 skin. We also found that the structural support layer (the dermis) of the
 elephant trunk contains a distribution of collagen-I (COL1) fibers in both
 perpendicular and parallel arrangement. The bimodal distribution of
 collagen is seen across all portions of the trunk, and is dissimilar from
 that of human skin where one orientation dominates within a body site. We
 hypothesize that this distribution of COL1 in the elephant trunk allows
 both flexibility and load-bearing capabilities. Additionally, when viewing
 individual fiber interaction of 10 micro-m thick collagen, we find the
 fiber crossings per unit volume are five times more common than in human
 skin, suggesting that the fibers are entangled. We surmise that these
 intriguing structures permit both flexibility and strength in the elephant
 trunk. The complex nature of the elephant skin may inspire the design of
 materials that can combine strength and flexibility. 
description: These are the raw data scans of the Second Harmonic Generation
 Images from the paper, including H&E images. Finally there is the
 raw data, averages, and data plot points for all figures in the
 manuscript. 
description: # Data from: Second harmonic generation imaging reveals entanglement of
 collagen fibers in the elephant trunk skin dermis
 [https://doi.org/10.5061/dryad.bk3j9kdm9](https://doi.org/10.5061/dryad.bk3j9kdm9) Data was collected at Imperial College London, South Kensington, on a 38-year-old female African elephant (*Loxodonta africana*) that initially lived in the United States. The trunk was on loan from the National Museum of Natural History (NMNH), Smithsonian Institution. These samples were shipped on dry ice to Imperial College London by the Smithsonian Institute Collections Department as a scientific exchange between the two CITES-registered institutions. The Animal Plant and Health Agency in the UK (authorization number ITIMP19.0822) approved the tissue shipment. The samples were stored at Imperial College London at -80 degrees C until embedding, sectioning, and imaging were conducted from January to March 2020. Contact Andrew Schulz ([aschulz@is.mpg.de](mailto:aschulz@is.mpg.de)) with any questions.  ## Description files include: PieceDescriptionforSHG.xlsx This Excel file contains information for each of the SHG microscopy TIF stacks, which is included in the Zip file folder. The H&E and SHG images in the zip folders are named by a specific piece number.These piece numbers correspond to the piece number included on this sheet as well as the dorsal or ventral description.  | Variable | Units | Description | | :---------------------------------- | :----- | :------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ | | Trunk Piece Number (for SHG Labels) | Number | The specific number of the specimen. This corresponds to the SHG and H\&E Zip files also included as a simple way to denote which piece is from which section on the trunk.  | | Dorsal or Ventral Trunk | D or V | This is to specify if the piece was from the dorsal (top portion) or ventral (bottom portion) of the trunk.  | | Distance from Tip  | cm | This is the distance the piece is taken from the tip of the trunk given in cm.  | | Dissection Date | date | This is the date of the original dissection that was performed.  | | Detailed Description | text | This provides a detailed description of where the skin piece came from. LNP stands for left nasal passage. We also provide the anatomical description including dorsal, ventral, proximal, and distal.  | FigureData.xlsx This Excel file contains the information and raw data for the figures including figure values, averages, and raw data for Figure 4D, 5C, Figure 6B, as well as the Supplementary figures in the manuscript. Overall the file has four sheets or pages in including "FigureData", "SC* *Thickness", "VE Thickness", and "Dermis Thickness". The first page "FigureData" describes has the following tables: Figure4D Table | Variable | Unit | Description | | :------------------- | :-------------- | :-------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | Location on Trunk | cm | This is the distance from the tip of the elephant trunk in cm ranging from 3 to 133 cm from the point.  | | Normalized Intensity | arbitrary units | This is the normalized intensity for the different sites on the elephant trunk describing the differences of the intensity of the SHG signal in the ImageJ analysis.  | | Dorsal/Ventral | Dorsal/Ventral | These headers indicate if the trunk position was on the dorsal or ventral measurement.  | Figure5C Table | Variable | Unit | Description | | :--------------------- | :--------------------- | :----------------------------------------------------------------------------------------------------------------------------------------------- | | Location on Trunk | cm | This is the distance from the tip of the elephant trunk in cm ranging from 3 to 133 cm from the point.  | | Dorsal/Ventral | Dorsal/Ventral | These headers indicate if the trunk position was on the dorsal or ventral measurement.  | | Perpendicular/Parallel | Perpendicular/Parallel | These headers indicate the perpendicular or parallel data for each of the sections | | Percentage of fiber | % | These are the descriptions for the percentages of the fibers given in mean plus or minus standard deviation shown by the columns in percentage.  | Figure 6 Table | Variable | Unit | Description | | :----------------- | :---------------------- | :----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | Species/site | | This is the specific site as well as species indicating if the data is taken from elephants or humans as well as what site (dorsal/ventral) in elephants or plantar/non-plantar in humans. | | Collagen crossings | crossings per micro-m^3 | This is the number of collagen crossings that occur per micro-m^3 | Sheet Tables "SC Thickness", "VE Thickness", and "Dermis Thickness": | Variable | Unit | Description | | :-------- | :------------- | :--------------------------------------------------------------------------------------------------- | | Location | Dorsal/Ventral | This indicates if the site was from the dorsal or ventral section of the trunk | | Distance | cm | This is the distance in cm the location was from the tip of the elephant trunk | | Thickness | mm | This is the thickness of the location and distance from the H\&E files included in the zip folder.   | ## Data files include: H_E.zip This is a file containing the raw H&E unedited images. Specific files are labeled by their elephant piece number which corresponds to the first column on the "PieceDescriptionforSHG.xlsx" also included in the repo.  SHG_images.zip This file contains both the raw .tif unedited images of the second harmonic generation (SHG) microscopy files as well as the overlayed with scale bar .png files from the SHG scans. Specific files are labeled by their elephant piece number which corresponds to the first column of the "PieceDescriptionforSHG.xlsx" also included in the repo.