Morphological features of mammalian hairs have proven to be useful in a variety of academic and biological studies, including predator diet analyses, conservation management, forensic studies, medical uses, and even archaeological studies (Deedrick and Koch 2004, Wentworth et al. 2011, Braczkowski et al. 2012, Mbizah et al. 2012, Verma and Joshi 2012, Davidson et al. 2013, Taru and Backwell 2013, 2014). Hair is made mostly of keratin, which is more resistant to decay and digestive alteration than other mammalian tissues, such as dentin or bone (Deedrick and Koch 2004, Backwell et al. 2009, Mansilla et al. 2011, Taru and Backwell 2013).
Previous catalogs have used several terms to describe the different common cuticular scale patterns. These terms include imbricate, mosaic, chevron, coronal, and petal-like or spinous (Homan and Genoways 1978, Keogh 1983, Deedrick and Koch 2004). In addition to the shape of the scales, distances between two adjacent scale margins are often used as descriptors and identification markers, and the scale margins can be described as smooth, crenate, or rippled (illustrated in Keogh 1983).
In several studies, cuticular scale patterns of hairs were used to aid in the process of species identification (Johnson and Hansen 1979, Rosas-Rosas et al. 2003, Manfredi et al. 2004, Breuer 2005, Ott et al. 2006, Wentworth et al. 2011, Braczkowski et al. 2012, Mbizah et al. 2012, Davidson et al. 2013). This is often accomplished by creating a scale imprint by mounting a hair on a slide using clear nail polish or a gelatin and allowing it to dry (Homan and Genoways 1978, Keogh 1983, Mizutani 1999, Ott et al. 2006, Wentworth et al. 2011, Mbizah et al. 2012). Once dry, the hair is removed and the remaining mold is then observed under a light microscope. However, with a scanning electron microscope (SEM), scales can be observed on the hair. The SEM provides higher contrast images of the cuticle scale patterns, yielding better resolution than light microscopes (Sahajpal and Goyal 2009), revealing different scale shapes, scale margin patterns, and accurate distances between scales.
Short (1978) and Taru and Backwell (2014) argued that scale patterns are not enough to accurately identify mammalian species to a taxonomic level finer than genus. The purpose of this catalog is not to address this point, but rather to provide a clear reference system for those who are looking to use scale patterns to aid in the identification of African fauna from hair samples.
Materials and methods
Most hairs were collected from specimens in a taxidermy office located in Phalaborwa, Limpopo Province, South Africa. Lion hairs were collected from the Louisville Zoo, located in Louisville, KY, USA. Gemsbok, lion, and leopard hairs were donated by the Thomas M. Baker collection of Bowling Green, KY, USA. Most guard hairs were collected from the dorsocapular, scapular, chest, or axillary region of each animal, as was done in previous studies (Homan and Genoways 1978, Short 1978, Keogh 1983, Hess et al. 1985, Seiler 2010). If bristle hairs were present, they were collected as well. The bristle hairs were always taken from the mane of the species. Dark and light colored leopard hairs were collected from the lower left flank, and gemsbok guard hairs were collected from the sternal region. Lion hairs were collected from lion feces gathered by the Louisville Zoo in Louisville, KY, USA, and from the axillary region and mane of a taxidermic specimen from the Thomas M. Baker collection of Bowling Green, KY, USA.
Hair shafts were soaked in 91% isopropyl alcohol for about 1 h for cleaning, and then soaked in distilled water for 3–5 min to rinse. After air-drying, they were prepared for observation under a SEM. They were mounted onto stubs using very smooth tabs (Cat #16084-20, Ted Pella) and sputter-coated with gold-palladium alloy (60% gold, 40% palladium) for 3 min. The stub was then turned 180° and again sputter-coated with the gold-palladium alloy. Whole hairs were mounted; in some cases long hairs had to be mounted in sections to fit on the stubs.
Samples were observed using a JEOL JSM-6510LV SEM at 10 kV and 500× magnification (unless otherwise specified) and photographed in three different locations – the proximal, medial, and distal regions.These settings gave the best resolution with the least amount of contrast on the edges of hairs. The same magnification was used for most hairs to give a reference for size differences among hairs and among different regions of the same hair. If more detail was needed, or if the hair was too big for the frame, the magnification was altered. Two hairs from each species and type of hair (i.e. guard or bristle) were observed with the SEM to ensure scale patterns were consistent before imaging.
We have presented the cuticular scale patterns of hairs from 12 mammalian species commonly found in the South African lowveld. In most cases, the process of Seiler (2010) was followed, and the three regions of hair shafts (proximal, medial, and distal) were photographed to display changes in the scale pattern along the length of the hair. These photographs support the conclusions of other studies stating that viewing hairs under an SEM is beneficial by contributing higher resolution and clarity of scale patterns than light microscopy (Sahajpal and Goyal 2009, Seiler 2010).
The samples of nyala bristle hair and Burchell’s zebra guard hair had damage to the hair shafts that destroyed the cuticle. In these cases, damaged regions of the hairs could not be photographed. Seiler (2010) also noted damaged, unrecognizable cuticular patterns in a number of her hair samples. She contributed this damage to museum storage. Keogh (1983), however, records that hairs collected from specimens in museum storage do not show a significant difference from those that are collected from live specimens. Depending on the type of processing a specimen undergoes, museum storage or processing may affect the scale patterns found on hairs of the pelage. If a significant amount of processing is involved, this is possible.
Lion guard hairs collected from the axillary region of a specimen in the Thomas M. Baker collection had no cuticle scale patterns, so only hairs collected from the fecal sample were imaged. When observing bristle and guard hairs collected from the taxidermic specimen, it was noted that bristle hairs are longer, thicker, and wavier in appearance than guard hairs. These differences allowed them to be distinguished from one another in the fecal samples. However, because guard hairs were collected from feces, it is uncertain from which part of the body these hairs originated.
As noted in similar studies, the most limiting factor of this study was the lack of hairs collected from different body regions of each species. Most guard hairs were collected from the dorsoscapular region of the pelage, and all of the bristle hairs were collected from the mane of the pelage. No hairs were collected from the posterior, ventral, or cranial regions of the animals. There are also no scale patterns representing hairs from juveniles; all hairs came from adults. Cuticular scales from different parts of the pelage, as well as hairs from juveniles, are thought to be different in appearance (Day 1966, Perrin and Campbell 1980, Keogh 1983, Seiler 2010). Another limiting factor is that only male nyalas were available for hair collection. Nyalas exhibit sexual dimorphism, so it is possible for genders to display differences in cuticular scale patterns.
We found two species that have unique scale patterns, making them easily identifiable under the use of a microscope. Impala have two types of scale patterns. The first scale pattern (Figure 1) appears streaked, with a raised surface running down the center of the hair shaft. The second (Figure 2) appears imbricate overall, with smooth, yet irregularly waved scales. Hairs containing both types of scale patterns were collected from the dorsoscapular area of the pelage, and there is no relationship between hair color and type of scale pattern. The same process was used to collect all hairs, so there is no correlation indicating why there are two distinct scale patterns. Steenbok hair contains scales that appear mosaic proximally and slowly transition into a smooth, coronal shape.
There are slight differences in appearance of the scale patterns between dark and light colored leopard guard hairs, indicating that different colored hairs could display differences in cuticular scale patterns. This was unexpected, as the hairs were collected from the same region of the pelage. This question was not addressed in this study, but could prove to be an important subject during similar future studies.
To produce a fully diagnostic key, the scale patterns found in this study should be studied along with medullary characteristics, color patterns, dimensions, and other diagnostic features of known reference hairs. We did also observe hairs from each species at 10 kV and 10,000× magnification to search for distinguishing characteristics at the extremely microscopic level. However, no additional distinctive features were found to discriminate among different species.
We thank all of the volunteers at Transfrontier Africa for their encouragement and support. We also thank Limpopo Taxidermy, the Louisville Zoo, and the Thomas M. Baker Collection for supplying hairs used for this project. Dr. John Andersland directs the electron microscopy facility and ensured best results. Funding for the project was provided by the Honors College and FUSE program at Western Kentucky University, Grant/Award Number: “15-FA218”.
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About the article
Published Online: 2017-02-21
Published in Print: 2017-12-20