Cascade Gold Akhal-Tekes

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Metallic Sheen as Observed in Individuals of the Akhal-Teke Breed

By Danielle Westfall, Zoology major, Ohio Wesleyan University

Advisor, Dr. Laura Tuhela-Reuning

This project was first suggested by a project of a similar nature involving cat fur from the Bengal domestic cat.  The surface structure of the Bengal cat affected the degree of glitter exhibited, and several Akhal-Teke breeders wondered if a similar glitter effect in their horses was related to the surface structure of the horse hair.  They sent samples to Ohio Wesleyan University in the hopes of discovering if the metallic hair had different structural features than the nonmetallic hair.

                 For years, Akhal-Teke owners have marveled over the metallic quality of the coats of some of their horses.  In fact, individuals such as Fara Shimbo, author of “The Akhal-Teke Glow” and Dr. Philip Sponenberg have studied the hair structure of these “glowing hairs”.  They studied the inner features of the hair using light microscopy.  My study picks up at analyzing the surface morphology of the hair using the scanning electron microscope (SEM).  I believe this is the first study to employ the SEM to examine the surface morphology of metallic Akhal-Teke hair.

                 In researching the subject, some may find it interesting to note that other breeds of horses also exhibit a similar glow.  Namely, horses carrying the Champagne gene, in breeds such as the Quarter Horse, Thoroughbred, Saddlebred, and Tennessee Walking Horse, have been known to have a metallic sheen to their coat.  The sheen is not the same, however, because the gene lightens the coat, eyes, skin, and the sheen is less strong than in the Akhal-Teke.  So this gene not only effects the coat but the entire pigmentation of the horse.  The Turkoman strain effects only the coat - not to change the color, but to make it glow.  I will attempt to explain what is unique about the hair of this horse and suggest how the structure of the hair contributes to such a phenomenon. 

figure 1

 

SEM photograph of Akhal-Teke hair with characteristic scaling of metallic hairs.  Note the straight, flat, smooth edges of the scales.

 

                 Not to get too technical, but I will give you the bare bones of my methodology for examining the hair.  For a more detailed description, you can visit my website, which includes the entire technique, at:  www.owu.edu/~sem/methods.html.  First, I examined the hairs longitudinally by cutting them down to fit on small aluminum stubs that could be placed in the SEM viewing chamber.  A scanning electron microscope works by shooting a beam of electrons at the sample and recording the pattern of how those electrons bounce off the sample to create a black and white image.  Thus the samples had to be coated with a thin layer of gold first so they would conduct electrons.  The gold layer is so thin, however, that it has no effect on the surface features of the hair.  Photos were taken of all the samples.  Then I analyzed the hairs in cross-section by cutting them into pieces under liquid nitrogen.  Freezing the hairs before cutting them kept them intact.  I then stood them up in carbon paste so I could observe the inner structure of the hair in cross section with the SEM.

                 The hair structure differed as one progressed from the root to the tip.  The root showed fine scaling or none at all.  Then towards the middle section, scales were short and fairly flat, sometimes with an irregular arrangement.  The tip of the hair showed longer scales with “choppy” edges, but a regular pattern.  Thus, the most variation was seen in the middle of the hair, which became the focus of the study.  After analyzing the hairs, I categorized them into two classes.  In the longitudinal investigation, two classes were evident based on the pattern of scaling and the shape of individual scales.  Class I exhibited a regularly spaced arrangement of scales, known as coronal.  The scales also had straight, flat, smooth edges and looked somewhat like a stepladder (see figure 1). Scales of Class II

figure 2

SEM photograph of Akhal-Teke hair with characteristic scaling of nonmetallic hairs.  Note the serrated, choppy, jagged edges of the scales.

 

hairs, however, were in an irregular pattern, called imbricate.  Scales of this class had choppy or serrated edges and resembled tree bark  (see figure 2).  I also examined the hair of several other breeds such as the Quarter Horse and Thoroughbred.  Hair from these horses had very choppy and irregularly shaped scales that looked like fringe in the mid section.  There was a high correlation between metallic hairs and Class I and non-metallic hairs and Class II.  Thus, I concluded that the pattern and shape of cuticular scales must be related to the metallic properties of the hair.  The more regular and flat the cuticle edges, the more glowing the hair.  There are many possibilities as to how the cuticle pattern may affect the metallic properties of the hair.  Perhaps more smooth scales are better able to focus and concentrate refracted light.  Or maybe the thicker scales of nonmetallic horses are more easily peeled away from the shaft and consequently are more likely to become damaged and “fringed”.

                 The cross-sectional analysis also resulted in two distinctions of hair.  Class A hairs had a larger medulla than cortex.  Also, there was more variation in cortex size within Class A.  Hairs belonging to Class B were just the opposite. 

 

SEM photograph of cross-section of Class A Akhal-Teke hair with characteristic inner structure of metallic hair.  Note the large medulla relative to the inner cortex.

 

SEM photograph of cross-section of Class B Akhal-Teke hair with characteristic inner structure of nonmetallic hair.  Note the larger size of the cortex compared to that in the Class A photo.

 

The cortex was larger than the medulla.  Also, the cortex size was more uniform throughout the representatives of this class.  After categorizing  the images, I matched the amount of glow with the class of hair.  The initial grouping was done blindly so as not to bias the results.  After degrees of metallic nature were assigned, I found that most of the metallic hair fell into Class A while for the most part, non-metallic hairs were of a Class B nature.  Thus, there was a strong correlation between the cortex/medulla size and the metallic nature of the hair.  In this procedure, I was not able to distinguish cuticle layers, as this layer was too fine to detect.  Since the hair is so fine and silky, it has a very small cuticle, which may account for the large amount of light refracting through the hair to produce the glow.

                 There are many possibilities for the further study of the metallic properties of hair.  For example, it would be useful to trace the hereditary nature of the metallic trait in order to determine what type of gene carries the property.  Also, investigation of the Champagne gene and hair of the champagne color that also exhibit this metallic sheen would be interesting.  A comparison could be made between champagne colored metallic hairs and Akhal-Teke metallic hairs, since they represent the same metallic property, but have different origins and different accompanying characteristics.

This article was first printed in the ATQ in July of 1999.  It has been suggested that I reprint this for those of you that haven’t had a chance to read it.