Abrasion resistance of snakeskin
By R. David Whitby, Contributing Editor | TLT Worldwide November 2024
Snake species living in different habitats have different abrasion patterns but all show a gradient in material properties.
In an article in the July 2020 issue of TLT, I wrote about snakes making use of their bodies when dealing with friction as they slide along.
1 As their skin is constantly exposed to high friction forces, particularly on the ventral side of their bodies, this can promote abrasion.
In 2012, two researchers at Kiel University, Kiel, Germany,
2 studied the abrasion resistance of four species of snakes. The skin of a snake only needs to last until it molts, which is usually every two to three months. However, in between moltings, snakes may suffer significant levels of abrasive wear. The different species, the rainbow boa
(Epicrates cenchria cenchria), the sand boa
(Gongylophis colubrinus), the green tree python
(Morelia viridis) and the king snake
(Lampropeltis getula californiae) inhabit different environments, from the desert to tropical trees.
It is known that the epidermis of snakes consists of six main layers, but there have been few studies that compare the cross-section architecture of these layers between different snake species inhabiting different environments. Several studies have found that the scale surface microstructure of different snake species can vary significantly even between representatives of the same family. These microstructures have been used for taxonomic purposes, although with limited success. Scale microstructures vary between dorsal, lateral and ventral body regions within a single species. As I noted previously, these microstructures have been shown to influence the frictional properties of different skin regions.
The Kiel researchers observed that snakeskin has material and surface specializations, which they presumed to be optimized for friction and abrasion resistance. They found that different snake species living in different habitats have different abrasion patterns and hypothesized that this correlates with specific epidermal architecture and surface topography.
2 To test this hypothesis, artificial scratches, under controlled load conditions, were created on the ventral skin material (epidermis) of each of the four snake species.
Abrasion appearance of the skin surface was examined using scanning electron microscopy and white light interferometry. The researchers focused on the ultrastructure of the ventral epidermis and on the qualitative abrasion pattern of the ventral scales. Scanning and transmission electron microscopy revealed variations in the structure, thickness, layering and material composition of the epidermis between the species.
2 In addition, scanning electron microscopy and white light interferometer images of the scale surface showed that the abrasion patterns differed, even when the snakes were reared on the same substrate. The data supported the idea that a specific gradient in material properties may be due to a variation in epidermis architecture (thickness/ultrastructure) and that this variation may be an optimization of material properties for specific ways of life.
They found that the skin architecture differs depending on the snake’s habitat. However, all showed a gradient in material properties. This means that the skin of all four species has a stiff and hard outside and becomes more flexible and soft toward the inside, even though the skin differs in thickness and structure, depending on the species.
2 The four snake species achieve this mechanical effect by developing different cell types. One species has a relatively thick skin with round cells, while the other has a relatively thin skin with elongated cells. The material failure was different between the species, which the researchers attributed to differences in the epidermis’ response to the same abrasive challenge.
A material that has a transition from a stiff outside to a flexible inside can distribute an impacting force over a larger area, therefore decreasing the force on one single point. These materials can be likened to a flexible armor, combining durability with flexibility. The research suggested that artificial materials of a similar construction might be useful in the development of innovative implants in which friction and wear are optimized. Also, conveyer systems could benefit from the findings of abrasion resistance, since lubrication would have to be used less frequently.
The research in Keil University appears to confirm the assumption that the skin of snakes is optimized against abrasive wear.
REFERENCES
1.
Whitby, D. (2020), “Snakes and friction,” TLT,
76 (7), p. 72. Available at
www.stle.org/files/TLTArchives/2020/07_July/Worldwide.aspx.
2.
Klein, M.-C. G. and Gorb, S. N. (August 2012), “Epidermis architecture and material properties of the skin of four snake species,”
Journal of The Royal Society Interface, 9 (76), pp. 3140-3155.
David Whitby is chief executive of Pathmaster Marketing Ltd. in Surrey, England. You can reach him at pathmaster.marketing@yahoo.co.uk.