Tag: land animals

the hairy feet of the gecko

Have you ever thought about what it would be like to walk on walls? If you’ve ever watched a Spiderman movie or watched a gecko maneuver around its habitat, you probably have. While geckos don’t fight crime, their climbing ability is as fantastic as that of any superhero. Geckos have one of the most unique climbing adaptations of any animal, and scientists are examining the source of this ability to see if human technology could one day achieve something similar.

Geckos are able to cling to almost any surface, no matter how smooth or rough it is. They are also able to detach quickly and easily from these surfaces as they climb. This climbing ability is due to tiny hairs, called setae, on the bottoms of their feet that can only be seen with a microscope. Each hair branches off into even smaller fibers called spatulae. Each gecko has about three million setae, and a billion spatulae! When the gecko places its foot on a surface, these hairs cling to the surface and form intermolecular bonds, called Van der Waals bonds, with the molecules of that surface. These bonds are strong enough to hold the gecko in place, but can be broken easily when the gecko lifts up its foot.

A close-up view of the bottom of a gecko foot, with the microscopic hairs visible.
Close-up of setae on gecko foot. Image by Science Photo Library

In addition to enabling the gecko to attach itself to surfaces, these hairs on the bottom of the gecko’s feet have the ability to clean themselves. If the gecko did not have some sort of ability to clean its feet, dust and dirt would get stuck on the gecko’s feet and break the connection between the feet and the surface. However, the hairs on the gecko’s feet are shaped so that it is difficult for water to stick to the feet. When the gecko gets water on its foot, the water rolls off of it and takes any particles of dirt with it.

Scientists have long been fascinated by the gecko’s ability to stick to surfaces, and many have been working on creating adhesives with fibers similar to the hairs on the bottom of the gecko’s feet. These adhesives are dry, like the gecko’s feet, and can be attached firmly and removed easily. The possibilities for application of adhesives like this are vast in number, and include everyday fasteners as well as use in electronics, robotics, and even outer space technology. One of the areas being explored by scientists is the use of these adhesives in the medical industry. The manufacture of gecko-hair fibers for bandages could mean farewell to the pain of removing a bandage, as well as the sticky residue left behind on your skin. This type of adhesive could even one day replace stitches after surgery.

Polymer fibrillar adhesive based on gecko foot Setae. Image by G.J. Shah, M. Sitti.

Most people probably don’t think about geckos very often apart from what they see in advertisements for car insurance. But for some scientists, these creatures hold the key to a world of possibilities. So next time you’re at the pet store, take a look in the lizard tanks and watch the geckos climb. Someday, thanks to those geckos, humans might be able to do the same thing.

Read more: https://steemit.com/science/@herpetologyguy/what-makes-gecko-feet-so-sticky

How Mice Could Help You Regenerate a Lost Limb

If you have ever experienced a nasty scrape or burn, you know the process of healing is not very fun. Human skin can take several weeks to regenerate after an injury and that often comes with a fair amount of pain. For a bigger injury that involves tissue damage, there is often little the human body can do to regenerate larger parts. However, thanks to a small rodent – the African spiny mouse – regenerative medicine for humans could be making huge advances in the near future.

The concept of regeneration is not something new in the animal world – we have seen creatures like salamanders regenerate lost tails and starfish regrow lost limbs. However, the African spiny mouse is the only mammal ever observed to be able to completely regenerate tissue such as skin, fur, hair follicles, sweat glands, and even cartilage. Being able to quickly shed skin caught in the mouths of large predators comes in handy for the mouse to be able to escape, but they must also be able to quickly heal those wounds.

African spiny mice in a research lab have spiny hair shown in (a) and (b). A skin wound was administered to a mouse in (c). Scabbing has occurred over the full injury as seen in (d) by Day 3. By Day 30, the original wound has healed and new hair follicles have been regenerated as seen in (e) and (f).
Figure 1. African spiny mice in a research lab have spiny hair shown in (a) and (b). A skin wound was administered to a mouse in (c). Scabbing has occurred over the full injury as seen in (d) by Day 3. By Day 30, the original wound has healed and new hair follicles have been regenerated as seen in (e) and (f). Source: Seifert, A., Kiama, S., Seifert, M. et al. Skin shedding and tissue regeneration in African spiny mice (Acomys). Nature 489, 561–565 (2012). https://doi.org/10.1038/nature11499.

How exactly does this happen? Researchers have found that the skin of the spiny mice is much weaker than that of most other mammals – think 20 times weaker than the skin of your regular old house mouse. Upon being handled, the skin is quick to shed leaving gaping wounds across the backs of these mice. This is due to the density of hair follicles found in their skin – a greater proportion of follicles means there is much less connective tissue to hold the skin leading to very easy tears. The weakness of the skin is contrasted by the rapidity by which it heals – the wounds can shrink to two thirds of their original size in a single day!

To understand a little bit more about the biomechanics of this process, we must look at how exactly the skin heals. As it turns out, collagen, the structural protein found in tissues which is responsible for skin elasticity among other things, is partly responsible for this phenomenon. Whereas mammals like you and I heal injuries through the generation of dense layers of collagen fibers aligned in parallel layers, these mice produce collagen fibers in crisscross networks that resemble the original makeup of tissue. This leaves the healed skin completely scar-free.

In addition, researchers have noted that ear wounds in the mice heal in a way similar to salamander tail regeneration. When a mouse’s ear gets injured, a ball of cells forms at the site of the wound that resembles cells in the embryonic state. This cell clump, called a blastema, is what allows the lost tissue to regrow on the ear. Scientists hope to use this information to study regeneration of tissue in humans.

An experiment was performed on both an African spiny mouse (Acomys) and another genus of rodents comparable to a house mouse (Mus) by making 4mm punctures in each species' ears. The size of the puncture was then observed over the following days showing that Acomys completely healed the ear puncture after 56 days while the size of the ear puncture in Mus remained relatively the same size showing no regeneration.
Figure 2. An experiment was performed on both an African spiny mouse (Acomys) and another genus of rodents comparable to a house mouse (Mus) by making 4mm punctures in each species’ ears. The size of the puncture was then observed over the following days showing that Acomys completely healed the ear puncture after 56 days while the size of the ear puncture in Mus remained relatively the same size showing no regeneration. Source: Matias Santos D, Rita AM, Casanellas I, et al. Ear wound regeneration in the African spiny mouse Acomys cahirinus. Regeneration (Oxf). 2016;3(1):52-61. Published 2016 Mar 9. doi:10.1002/reg2.50.

While there is still more research to do on the healing mechanism of the spiny mice tissue, the research done on these little mammals provides an excellent foundation for regenerative medicine for humans – something that studying regeneration in other animal species has not been able to accomplish. Being able to regenerate a lost limb was something once found only in science-fiction but could be a real possibility in the future.

Read More:

Insights into the regeneration of skin from Acomys, the spiny mouse

Optimal skin regeneration after full thickness thermal burn injury in the spiny mouse, Acomys cahirinus

Unique behavior of dermal cells from regenerative mammal, the African Spiny Mouse, in response to substrate stiffness

African spiny mice can regrow lost skin

How the Largest Land Animal Stays Cool – And What We Can Learn From It

African Elephant raising tusk
African Elephant. Credit: Wolfgang Schlaifer

African Elephants have the largest volume to surface-area ratio of any living land mammal; it’s not a surprise then that they have to dissipate a tremendous amount of heat. You and me eat 2,500 calories a day – an adult male elephant might consume over 70,000 calories each day! This means these gigantic beasts need to remove several kilowatts of heat. So how do they do it? And can we learn anything from these biological marvels?

Physical Features

Close up of an elephant's ears. Details on blood vessels going through ear flap.
Close up of elephant’s ear, credit: Magda Ehlers

In order to combat the heat, elephants have developed several unique features. First is the large, flapping ears. Phillips and Heath have studied the heat exchange by the ears extensively, finding remarkable advantages. It may not look like it, but those ears make up 20% of an elephants surface area – this essentially transforms them into large heat sinks. But that’s not the end of their ears’ advantages. Elephants are able to regulate heat transfer through vasomotion; this is an oscillation of blood vessels that is unrelated to heart beat. Thus, elephants are able to store heat in their ears by expanding the blood vessels, then releasing this heat during the nighttime when it is more efficient. Modeling has shown that nearly 100% of heat loss requirements can be met through the movement of the ear.

Close up of African Elephant hair. The hair is not very dense and very thin.
Close up of African Elephant hair on head. Credit: Conor L. Myhrvold in the Woodland Park Zoo, Seattle, Washington.

Elephant ears aren’t the only heat-reducing mechanism. Myhrvold et al. propose that a low density of hair could also be a method to remove heat. As humans we often think of hair as a mechanism to keep us warm – this is true as it will serve as insulation against our skin. Low density hair, however, provides a larger surface area (they act as small little heat fins) that offsets any increased insulation they may cause. Researchers found the break-even point to be 0.3 million hairs/m2 – elephants only have 1500 hairs/m2.

Internal Control

A thermal image of elephants; the animals are much brighter compared to their environment.
Thermal image of elephants, credit: Endangered Wildlife Trust/LJMU

Us humans are homeotherms – this means our internal body temperature is kept stable regardless of outside temperatures. Most other mammals follow homeothermic tendencies, but there is recent evidence that elephants are actually heterotherms – their bodies are both self-regulating and adaptive to the environment. In fact, elephant body regulation is very similar to desert mammals like camels. During the day elephants will increase their body temperatures, and during the night they will lower them (this also helps for when the night is very cold and the animal wishes to conserve instead of dissipate heat). Weissenböck et al. discovered that elephants can have a body temperature range from 35.0°C – 37.5°C (95°F – 99.5°F), a range that is about twice as large compared to humans.

What We Can Learn

African Elephants present a unique natural problem: how do you cool something so large that produces so much heat? This problem is also present in our own human world from cooling down skyscrapers to making sure your computer CPU doesn’t overheat. One of the more promising developments is thermal energy storage and how it can heat, cool, and provide electricity for the modern world. Elephants’ physiological adaptations can serve as the blueprints for future innovation in heat transfer and dissipation.

Sources and Additional Readings

Polly K Phillips &James Edward Heath. “Heat exchange by the pinna of the african elephant (Loxodonta africana)”, Comparative Biochemistry and Physiology Part A: Physiology, Volume 101, Issue 4, 1992.

P.G. Wright & C.P. Luck. “Do elephants need to sweat”, South African Journal of Zoology, Volume 19, Issue 4, 1984.

Myhrvold et al. “What is the Use of Elephant Hair?” PLOS One. 2012.

Alex Fowler & Adrian Bejan. “Forced convection from a surface covered with flexible fibers”, International Journal of Heat and Mass Transfer, Volume 38, Isssue 5, 1995.

Weissenbock et al. “Taking the heat: thermoregulation in Asian elephants under different climatic conditions”, Journal of Comparative Physiology B, Issue 182, 2011.

Down to the Bear Bones: How Polar Bears evolved from Grizzlies to hunt in the Arctic

Katmai National Park in Alaska holds an annual “Fat Bear Week”, in which Twitter followers are asked to vote for the fattest bear in the park. This year’s winner was Holly, somewhere in the range of 500 to 700 lbs. That’s a big bear. However, in 1960, a male polar bear in Kotzebue Sound, Alaska, weighed in at 2,209 lbs. In fact, on average, polar bears weight up to 60% more than Grizzly bears, their closest animal relative. 

A very fat grizzly bear standing on rocks.
Holly, aka Bear 435, the 2019 winner of the Fat Bear Contest. From Katmai National Park via Twitter.

So just how did Polar Bears get so big? Well, as anyone in the Midwest knows, a harsh winter requires a good winter coat. The advantage of thick skin and fur, as well as a higher capacity to put on weight made heavier polar bears more adept to survive. However, bigger bears that could survive the cold were more likely to fall through the ice, so these adaptations required better foot mechanics.

Consequently, polar bears developed a distinctive gait. A rotary gait is a “double suspension” gait, meaning the animal bounces both off the hind limbs and then the fore limbs . This is contrasted from the grizzly bear’s transverse gallop, which involves only one “bounce,” — this loads each limb for a longer time and more vertically. The rotary gait improves stability, giving the polar bear the ability to travel quickly and smoothly on icy surfaces. 

A series of drawings depicting the gait of a galloping polar bear.
A series of drawings depicting the gait of a polar bear. Modified from S. Renous, J.P. Gasc, and A. Abourachid, Netherlands Journal of Zoology (1998).

Another significant difference between the species are their skulls, which, while similar in size, vary greatly in bite force and bone strength. The polar bear has a stronger bite, but a weaker skull. Polar bears are one of the most rapid instances of evolution in surviving species of animals, having evolved from the grizzly bear within the last five hundred thousand years. So why are their skulls weaker if their bite is stronger? 

Simply put: seals are easy to chew. Grizzlies are omnivores, as most bear species. Their diet subsists of salmon, elk, and small game, but includes a hefty amount of vegetation. Polar Bears, in the ice and cold, were forced to eat seals (as well as penguins, fish, even belugas). Seals are largely blubber, providing the caloric intake necessary to sustain these large beasts, but offering little resistance in the chewing process. 

Two line drawings of skulls, one of a polar bear and a grizzly bear
Skulls of the polar (left) and grizzly bear (right). Modified from P. Christiansen, Journal of Zoology (2006).

The polar bear’s skull morphed quickly, elongating to allow it to hunt for seals and fish through small holes in the ice. This weakened and lowered the density of the skull; however, because the seal-heavy diet required less effort to chew than vegetation, there was no selective advantage to a skull reinforcing. So, with a more efficient gait and a stronger bite, the polar bear developed into a killing machine in the icy north.

Interested in more of the polar bear’s hunt? Learn about how they can swim for hundreds of miles, or to see these arctic advantages in action, check out this video of a polar bear hunting a seal.

Canine Hip Dysplasia: What You Should Know

Canine hip dysplasia (CHD) is a degenerative hip disease that tends to develop in large breed dogs, such as the Bernese Mountain Dog, affectionately referred to as Berners. CHD significantly decreases the quality of life of a dog and often leads to complete immobility if left untreated. Experts estimate that about 28% of Berners are affected by dysplastic hips, making them the 8th most susceptible dog breed.

Bernese mountain dog with superimposed image of hip ball and socket joint.
Image from Packerland Veterinary Clinic.

At birth, puppy skeletal structures are largely composed of cartilage that is much softer than bone. This softer cartilage is able to adapt much more easily to the rapid growth that occurs during the early months of a dog’s life. In their first few months, Berners will typically gain 2-4 pounds per week, which adds increasingly large stresses to their developing bones and joints. While genetics play a large role in the susceptibility of a dog to develop CHD, the loading cycles and forces on the cartilage greatly shape the development of the dog’s hip.

Correctly formed hip versus a deformed femur head and shallow hip socket.
Image from Dog Breed Health.

The hip is a ball and socket joint, where the head of the femur, the very top of the dog’s leg, should fit perfectly into a socket in the pelvis. If the ligaments that hold the femur in the hip socket are too weak or damaged at all, the positioning of the

Evenly distributed forces on a correctly developed hip joint versus force concentration acting on a dysplastic hip joint.
Modified from The Institute of Canine Biology.

hip joint will be off and the hip will be subjected to unbalanced forces and stresses over the course of the dog’s life. The distribution of forces experienced by the hip joint in normal hips is evenly spread, while dysplastic hips are subjected to a stress concentration on the tip of the femur. These unnatural forces will cause laxity in the hip joint, leading to instability, pain, and often times the development of osteoarthritis.

 

There are also a number of environmental factors, many of which are inherent to large dog breeds, that dramatically increase a dog’s susceptibility to CHD. A study by Dr. Wayne Riser concluded that factors such as oversized head and feet, stocky body type with thick, loose skin, early rapid growth, poor gait coordination, and tendency of indulgent appetite all contributed to the development of CHD. All of these features are generally inherent to large breed dogs, such as Berners, so great care must be taken in order to mitigate their effects on the quality of life for these dogs.

Multiple studies have shown that treatment that is implemented early in the dog’s life is much more effective than late-in-life treatments. CHD warning signs can be seen in puppies as young as 4 months old, and most veterinary professionals agree that if scans occur at 2 years of age, the most optimal time for treatment has passed. Since larger stresses will be put on the hip joint as the dog grows, surgical repairs, or changes in diet and exercise, are most effective if implemented before the dog’s skeletal frame is completely developed.

 

timeline of canine hip dysplasia development
Modified from The Institute of Canine Biology

Additional information regarding this topic can be found at The US National Library of Medicine or The Journal of Veterinary Pathology.

3-D Print a New Leg for Your 4-Legged Friend

3-D printing is a quite exciting technology that has come to light in recent years. The process involves a nozzle much like in a regular inkjet printer that layers material upon material to build up a 3D structure. The printer receives this data from a computer designed file that maps out where the printer should add material. Combine this with filler material that serves to hold everything in its final upright position, and the final product is born, after setting and clearing off the filler. This process has been used to make many different things, from simple objects like phone cases and luggage tags to complex scaffolds used to hold cells for tissue engineering, or as in this post, specific implants for dogs and other animals. The usual types of orthopedic implants that have somewhat of a cookie cutter size distribution for humans do not always fit in dogs or other animals. So, 3-D printing has been employed to create implants used to repair and replace bones in veterinary situations.

Examples of computer-modeled custom implants
Examples of computer-modeled custom implants on dog legs

The most prominent veterinary application for 3-D printed implants is dogs. This is due to their slight differences in body type, even within breeds, that can make finding a pre-sized and pre-made implant difficult to find. One such example of this is a dachshund, named Patches, that received a custom made skull implant after other implants were found to be ineffective or dangerous to her long term health. Patches had a brain tumor, one that grew to a very large size and began encroaching on her eyes. The tumor was successfully removed, but the process involved the removal of large portions of her skull, leaving her brain unprotected. If a preexisting implant were tried, the way it would fit would leave her head vulnerable to an impact, making the implant quite pointless. A 3-D printed implant was made, and old Patches made a full recovery.

The process involves taking a CT scan of the area in question and gaining an understanding as to the layout of the area. This allows designers to make a 3-D model of the implant using a computer, and that model can be printed out using a 3-D printer. In the case of implants, titanium is usually used due to its biocompatibility and great mechanical strength. The implants can be used for surgery and repair, or an array of other applications, even studying the cranial activities of primates. In any case, these exciting new developments in 3-D printing are leading to advancements in the medical and biological fields. So, the next time you fire up you 3-D printer to make a cool-looking hood ornament, know that the same technology is at work, saving lives and giving scientists new knowledge about animals they previously had no good way of studying.

Sources:

<https://www.3dprintingmedia.network/dog-3d-printed-titanium-bone/>

<https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5482398/>

<https://www.nytimes.com/2018/09/25/science/3d-print-dog-skull.html>

Secret Behind Kangaroos’ Tail

Red kangaroos can reach speed of more than 35 miles an hour, they can also cover an area 25 feet long and get up to 6 feet high in one jump using their tail like a spring to give them more power. When kangaroos want to move slowly, they do kind of lean on their tail, to support their

Schematic representation of the tail involved in accelerating. Photograph: Heather More (theguardian.com)

body. When kangaroos are grazing they move their hind pairs of feet together which makes their movement awkward but the power behind them in their tail is keeping them balanced.There was always a question of why Kangaroos are placing their tail on the ground when they are walking slowly.

Most of the researchers believed that the tail is only used for the purpose of balancing. Professor Max Donelan from Simon Fraser University, collaborated with his colleagues Shawn M. O’Connor, Terence J. Dawson, Rodger Kram trained kangaroos to walk on a measuring device called the force plate, what they found was that the tail was doing a lot more than anyone have realized.  They Found that kangaroos actually used their tail like a fifth leg when they are hopping around or walking. For this study, they documented the movement of five red kangaroos in Sydney Australia which are the largest species of kangaroo and the biggest marsupial on the planet. They observed that kangaroos when walking first put their forelimbs on the ground and when it is the time for their hind limbs to move forward, they use their tail to accelerate and push the whole body forward and then they put their hind limbs on the ground.

They have published a paper in Biology Letters which presents that the tail exerted as much force as four other legs combined. By measuring the commonly work in physics called the mechanical force, the kangaroos tail is as important when it walks as one of our legs as we walk. They found that the kangaroos’ tails are involved on their movement in three ways. First of all, most of the propulsive force which is needed for the movement is provided by the tail. Furthermore, the previous belief that the tail is needed to balance the body weight have been examined and turned out to be that although the tail plays an important role in the balancing, it only provides the 13% of the vertical force needed to balance the body. Besides, investigating on the mechanical work that the tail applies to the whole body for pushing forward, it demonstrates a substantial role of the tail in performing positive mechanical work.

The mechanical representation of the Kangaroo’s movement on the force plate (Shawn M. O’Connor et. al. 2014)

Human’s back leg helps to push the body forward when walking (wikihow.fitness)

 

In simple words, it can be compared with the role of one of human’s leg when walking. You probably are thinking what exactly makes a leg a leg? The answer could be simple, if a leg exists to play a key role in walking, then kangaroo has five legs.

Kangaroos are the only animals that use their tails as a leg, Max Donelan said.

 

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