Knights in shining armour don’t get much smaller than this. The Sunda pangolin (sometimes referred to as the Malayan pangolin) is one of Southeast Asia’s most highly-trafficked animals. Now classified as critically endangered, the pangolin is hunted most commonly for its meat and its own shining plate mail. There are eight species of pangolin left across the world, each with crashing populations due to centuries of hunting. Yet despite this ecological massacre, each species still being fiercely poached.
The meat and scales have traditional uses in certain cultures – such as medicine – and some people even feel that the dead cells coating the pangolin make for fashionable clothing. For instance, in 1820, King George III was presented with a jacket made from the scales of the pangolin by the governor-general of Bengal – likely as the item resembled a piece of armour. Today, monarchs seem to prefer more breathable material.
Defences
Pangolins are remarkable creatures with unique adaptations; while they have tough scales, their underbelly is soft and exposed enabling them to move freely. Because of this,pangolins can curl up in a ball when threatened, keeping safe from predator teeth and claws while protecting their own soft underbelly. Such is their marvel, that there has even been research into bio-armour for humans inspired by the pangolins outer-layer of protection, a practice known as bio-mimicry in which nature-inspired designs are used to solve human challenges.
Despite this excellent defence mechanism, and the fact that the pangolin has huge claws, it is near impossible for it to defend itself against effectively humans. Sadly, once they are collected by poachers, they may be boiled alive in a similar manner to lobster. The scales are then removed and prepared for sale. This time-consuming effort (while perhaps not morally-taxing for the poachers), can earn up to $600 per kilo of pangolin meat sold, and $3000 per kilo of scales.
Pangolins do have other means of defending themselves however – if not necessarily against humans – such as through scent. They have anal glands that secrete a foul-smelling chemical to ward off predators. A process not dissimilar to the defences of other animals such as the musk turtle and skunk. Though the chemicals released haven’t been widely studied, the compounds are likely to include thietanes and other sulphur containing compounds providing a powerful defence from predators who have excellent olfactory receptors (a good sense of smell).
A Worthy Suit of Armour: debunking traditional medicine with science.
In traditional Chinese medicine (TCM), pangolin scales were (and still are) believed to remedy rheumatic arthritis, improve blood circulation, and stimulate lactation. In other forms of traditional medicine, such as herbalism, active chemical compounds in plants are thought to target the cause of an ailment. If we are to apply the same logic to pangolin scales, we must first consider the compounds that make up these scales.
The scales themselves are composed of flattened keratinized cells. These cells arise when living cells die and are filled with protein. The cells may die due to a lack of nutrients near the surface of the epidermis, most commonly when they are pushed out of the way to make room for new cells. Keratin filaments (the protein) may also dry out the fluid-like cytoplasm and kill the cell.
Keratin itself is not a singular protein, but actually a group of proteins high in the element sulphur. This sulphur is important as it allows amino acids (the building blocks of proteins) to form bonds known as disulphide bridges. These bonds provide stability between sulfhydryl groups (groups comprising of a sulphur and hydrogen atom, -SH). They can increase durability and strength of the overall protein (useful for making protective armour) and can protect from proteolytic degradation, the method by which protein-digesting enzymes can destroy the keratin. This explains why the keratin armour is resilient and not destroyed by normal bodily mechanisms, although the pangolins do sometimes shed their scales.
Furthermore, keratin is insoluble in water due to the arrangement of the proteins. For instance, an ‘alpha-helix’ formation of keratin may place the non-polar ends of amino acids on the outside of the helix, ensuring that it is immiscible with [polar] water. Already, this is a property that makes it an odd choice for medicine. Compounds used medically often need to be water soluble to enter cells or the blood stream, and it is unlikely that large proteins such as those contained in keratin could enter the cell via the non-polar barrier that protect animal cells. This property thus begins to show some of the holes that are in the use of scales in TCM.
The dorsal plate of the pangolin also contains bound phospholipids and sulfhydryl groups, although this plate is weak in disulphide bridges. Along with keratin, this composition suggests that the scales have a similar structure to human and primate nails. If people are insistent on using keratin in traditional medicine then they need look no further than their own clippings!
Pangolins are also susceptible to many illnesses and diseases, given their low immunity. This makes them incredibly vulnerable when held in captivity. For instance, captive pangolins have been found to have vitamin A deficiency. A condition which can lead to keratinization of respiratory tracks, toughening the soft tissues, making them ineffective for gaseous exchange. While this process is extremely similar to how pangolins make their scales, this keratinization is uncontrolled and can lead to death.
In a vital move for the protection of the species, pangolin scales were removed from the list of approved ingredients for TCM in June 2020, in spite of the 400,000 pangolins in black market trafficking. Despite this, the Chinese regulating body (SFGA) still allows TCM pharmaceuticals to use stockpiled scales, which may attract more trafficking as it serves to keep demand for the scales high. Harsher restrictions are still required on the use of scales if we are to ever reduce the number of trafficked pangolins and prevent their extinction.
On a more positive note, the structure of the scales may offer an insight into how we may protect pangolins in the future. The alpha-helix structure of some of the keratin compounds may make the scales partially porous, especially when they form microtubules. In other endangered animals, such as the white rhino, conservation projects have involved injecting a [pink] dye into the keratinized horns of the rhinos, making them worthless to hunters. The nature of the dye and the horns means that they do not harm the animal, other than in potential predation issues. If this project is refined and funded, a similar process may help conserve the pangolin.
A Pandemic Problem
In the early months of the coronavirus (COVID-19) pandemic, much research went into determining the origin of the virus. Early studies of genetic material extracted from pangolins showed that the SARS-CoV strain was the most widely distributed coronavirus in particular samples. At the beginning of 2020, a pangolin was found with a viral nucleic acid sequence that was 99% identical to the human strain in the receptor binding region – this being only one amino acid difference among thousands. The similarity suggested that pangolins could be the source of the virus.
A study on deceased pangolins (and approved by the ethics committee at Guangdong Institute) had similar findings. In the process, nucleic acids are extracted from viral particles and synthesised into DNA (from RNA). The DNA is then ‘cut’ into manageable parts and separated by electrophoresis (a technique which uses electricity to separate molecules based on electrical charge/polarity) into long fragments (consisting of around 350 base pairs). The contigs (reconstituted DNA) that were later formed were compared to known DNA/RNA of certain viruses to measure the similarity of the genetic material. Close sequences were found between pangolin viral genes, and SARS-CoV-2, however later research showed that most pangolin coronaviruses are only up to 92% similar, suggesting that they weren’t the original source of the virus.
It was later considered that bats could be the origin of the virus. However, the bat virus genome doesn’t contain the particular sequence of base pairs that code for proteins allowing the virus to bind to human cells. This suggests that there is an intermediate host between bats and humans responsible for modifying the virus. The pathway for Covid 19 transmission to humans is still one requiring much research.
Whether or not pangolins contributed to the global pandemic, it is clear that the human-driven trafficking of animals helped to spread the coronavirus form SARS-CoV-2.
Conservation
The monitoring of species is an incredibly useful tool in conservation to estimate population sizes and get a sense of how well the species is doing. Sunda pangolins are mostly nocturnal creatures, making it difficult to monitor them with common conservation practices. Instead, remains of prey, faecal matter, or shed skin act as important presence markers for conservationists. Techniques similar to those used to monitor mountain gorilla populations have been used to estimate pangolin population sizes, such as identifying individual DNA. However, this often only works on populations with extremely small numbers. In the future, if numbers continue to decline, it may become a primary method of monitoring the species.
The living burrows of pangolins, which can usually be located under large boulders or tree bases also indicate their presence. The entrances have an unusually round entrance, making it quite unmistakable from other animal burrows. Similarly, they mark their burrow with urine, faeces, and even with their anal gland chemical mentioned earlier. They also create markings with their claws when digging for termites, though these are harder to identify, particularly where the undergrowth is prevalent such as in forest habitats. Searching for pangolin tracks may be more useful in the savannah habitats of certain pangolins.
Today, the conservation of these animals often involves attempting to change legislative practices, and raising awareness of them, as well as keeping track of populations. It is vital that modern trafficking is halted as soon as possible to ensure their continuing existence as a species. For this to occur, education needs to happen around topics such as the futility of using pangolins in traditional medicine, and harsher restrictions should be made around their use in food and medicine. With enough immediate action we may be able to prevent our tiny knights from going extinct, like so many animals before them.
Here at WAWA Conservation, we value the natural world for what it is and we believe that the variety that lies in all earth’s biodiversity makes the world a more wondrous and better place to be. If you too want to help save weird and wonderful animals from extinction, then please consider supporting WAWA and together we can help keep the wild weird.
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Article written by Luke Curran
Featured Image: “Pangolin” by Smithsonian’s National Zoo is licensed under CC BY-NC-ND 2.0
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