The Olympic Athlete of the Animal Kingdom: The Circulatory System of a Horse (A Guest Post)

By Emily Fandrey


How do you judge the abilities of an athlete? Is it all about speed? What about endurance? Strength? How would you judge an animal that can run up to 48 kilometers per hour (30 mph), cover 48 kilometers (30 miles) in a day, or clear a 2.4 meter (8 foot) jump, all while carrying a human on its back? Because of these abilities, the horse (Equus caballus) is often considered to be one of the animal kingdom’s best athletes. The major factor behind horses’ advanced athleticism is their unique circulatory system, specialized for delivering large amounts of oxygen throughout the body.

Image by Paul Kehrer at Wikimedia Commons.

A horse’s circulatory system has three major players: the heart, the spleen, and the frog (and no, this has nothing to do with the animal frog, but rather a specialized unit of a horse’s hoof). Due to these three components, horses have one of the best aerobic capacities in the animal kingdom. Let’s look at a racehorse for example: During a race, a thoroughbred can reach a maximum oxygen capacity (the amount of oxygen the blood can carry) of 200 milliliters per kilogram per minute, meaning 200 milliliters of blood per kilogram of weight (or 3.1 ounces per pound) are transported to the body every minute! This is more than twice the oxygen capacity of the most elite human athlete!

This diagram illustrates the horse’s circulatory system,
including the heart, arteries, veins, and spleen. Diagram by Emily Fandrey.

So let’s break down this superior aerobic system, starting with the horse heart. Typically, a horse’s heart weighs 1% of its total body weight; meaning if a horse weighs 450 kilograms (1000 pounds), its heart will be roughly 4.5 kilograms (10 pounds). If this was true for humans, a 68 kilogram (150 pound) human’s heart would be 0.68 kilograms (1.5 pounds), although the average human heart is only about 0.23 kilograms (half a pound). The horse’s heart functions very similarly to a human heart. It contains four chambers and is responsible for getting oxygen to the body by pumping the oxygen-filled blood. After the body systems have used the oxygen in the blood, this deoxygenated blood enters the heart and is sent to the lungs where the blood is resupplied with oxygen from breathing air. This oxygenated blood reenters the heart and is pumped back out to the body. Because of the size of their hearts, horses are able to supply large amounts of blood with oxygen to the body with each heartbeat, averaging a combined 38 liters (10 gallons) per minute (this is about ten times as much as a human).

Horses also have very different heart rates than humans during rest and exercise. A horse’s resting heart rate is 28-44 beats per minute (bpm), compared to the average human’s, which is 60-80 bpm. During exercise, a human’s heart rate is 90-170 bpm, depending on age. A horse’s heart rate, however, rises to 80 bpm during a walk, 130 bpm during a trot, 180 during a canter, and 240 bpm while galloping. At top speed, the fast beating heart of the horse is what allows the heart to pump much more blood to the body than a human, increasing their athletic abilities.

A diagram of how the horse’s frog sends blood back to heart quickly,
working against gravity. Diagram by Emily Fandrey.

With the long legs of horses, the heart also has to work against gravity to get blood from the limbs back to the heart. To combat this, the horse has its “frog”. For a horse, the frog is a vessel-filled tissue structure on each of its four hooves. When weight is placed on the frog, this structure can help the heart work against gravity. How? When the horse’s hoof meets the ground, the ground will push up on the frog, resulting in the frog being compressed and squeezing blood in the vessels out and rapidly up the leg. The frog helps heart work against gravity by sending the blood up the leg and back to the heart, allowing for faster blood circulation, increasing the athleticism of the horse.

The last key factor to the horse’s circulatory system is the spleen. This organ improves aerobic capabilities and the horse’s athleticism. Now, the primary function of the horse’s spleen is to remove damaged blood cells. However, when a horse is relaxed, their spleen will fill with up to 30 liters (8 gallons) of oxygen-filled blood. And then, once the excitement of activities like running or jumping sparks, the spleen will contract and send up to 25 liters (6.6 gallons) of this stored blood back into circulation in mere seconds! So in seconds, the spleen is capable of almost doubling the maximum amount of oxygen the blood can carry, increasing the athleticism of the horse as well.

So if you ever need an excelling athlete on your team, consider an animal with a superior circulatory system: the horse. With a large and powerful heart capable of pumping large amounts of blood, a spleen to provide an extra burst of blood in seconds, and a “frog” to work against gravity, there is no wonder why horse is considered to be one of the world’s superior athletes.


References

Allen, K.J., Young, L.E., and Franklin, S.H. (2016). Evaluation of heart rate and rhythm during exercise. Equine Veterinary Education 28: 99-112. DOI: 10.1111/eve.12405.

Cardiovascular System (2007). In EQUINAvet.

Circulatory System of the Horse (2010). In Helpful Horse Hints.

Equine Circulatory System Vet, Horse First Aid (2012). In Equestrian and Horse.

Norton, J. (2013). The equine circulatory system. In EquiMed: Horse Health Matters.

The Weirdest Animals on Earth: 12 Amazing Facts About Platypuses

What IS that? A photo by Stefan Kraft at Wikimedia Commons.

1. Platypuses are so strange, that when British scientists first encountered one, they thought it was a joke: A Governor of New South Wales, Australia, sent a platypus pelt and sketch to British scientists in 1798. Even in their first published scientific description of the species, biologists thought that this duck-beaked, beaver-bodied, web-footed specimen may be some Frankenstein-like creation stitched together as a hoax. But this is only the beginning of their oddities…

2. Platypuses are egg-laying mammals. Mammals are animals that have a backbone, are warm-blooded, and females produce milk for their young. Most females that nurse their young also carry their developing babies in their bodies and give birth to live young… But platypuses don’t play by those rules. Platypuses are monotremes, egg-laying mammals that include the platypus and four species of echidna. Most female mammals have two functional ovaries, but female platypuses, like most female birds, only have a functional left ovary. Once a year, a female platypus may produce a clutch of two or three small, leathery eggs (similar to reptile eggs), that develop in her uterus for 28 days. Because female platypuses don’t even have a vagina, when the eggs are ready, she lays them through her cloaca, an opening that serves for reproduction, peeing and pooping. (In fact, monotreme comes from the Greek for “one hole”). She then curls around them and incubates them for another 10 days until they hatch.

3. Platypuses sweat milk! Not only do female platypuses not have vaginas, they don’t have nipples either! Instead, lactating mothers ooze milk from pores in their skin, which pools in grooves on their bellies so the babies can lap it up. …And they’re not even embarrassed about it!

4. Adult platypuses are toothless. Baby platypuses (that is the actual technical term for them, by the way… not “puggles”, which would be way more fun) are born with teeth but they lose them around the time that they leave the breeding burrow. In their place are rigid-edged keratinized pads that they use as grinding plates. When they catch their prey (worms, bugs, shrimp, and even crayfish), they store it in their cheek pouches and carry it to the surface, where they use gravel to crush it in their toothless maw.

5. The platypus “duck bill” is a sensory organ used to detect electric fields. Muscles and neurons use electrical impulses to function, and these impulses can be detected by electroreceptors. Although common in shark and ray species, electroreception is rare in mammals, only having been discovered in monotremes and the Guiana dolphin. Platypuses have rows of around 40,000 electroreceptors on their highly sensitive bill, which they wave back and forth in the water, much like a hammerhead shark, to determine the location of their prey. It’s a good thing this sense is so sensitive, since they close their eyes, nose and ears every time they dive.

6. Platypuses don’t use their tails like beavers do. Whereas beavers use their large, flat, leathery tails for swimming and slapping the water to send signals, platypuses don’t use their tails for any of that. Platypuses have large, flat tails for storing fat in case of a food shortage. Unlike beaver tails, platypus tails are covered in fur, which the mothers use to snuggle with their incubating eggs.

A platypus ankle spur. Photo by E.Lonnon at Wikimedia Commons.

7. Male platypuses have venomous ankle spurs. Their venom is strong enough to kill small animals and to create excruciating pain in humans. Since only males have it and they produce more venom during the breeding season, we think its main function may be to compete for mates and breeding territories.

8. Platypuses are knuckle-walkers with a reptilian gait. Although they are well-built for swimming with their webbed feet and legs on the sides of their bodies, these traits make it quite awkward to get around on dry land. To walk, they pull in their webbing and walk on their knuckles, exposing their claws. Like reptiles and salamanders, platypuses flex their spines from side-to-side, supported by their sprawling legs.

9. Platypuses have unusually low body temperatures. As unusual as they are, platypuses are still mammals, which are defined, in part, by their ability to generate most of their own body heat with their metabolism. Platypuses do this as well, but whereas most mammals maintain body temperatures between 37-40 degrees C (99-104 degrees F), platypuses are happy with a body temperature of 32 degrees C (90 degrees F). This lower metabolism reduces the amount of calories they need to eat.

10. They have no stomach. Stomachs are specialized protein-digesting chambers of digestive tracts that contain protein-digesting enzymes and acids to activate them. Not all animals have them, but most carnivores do. The most common exceptions to this rule are fish… and platypuses. Why? We don’t know for sure, but many of these animals consume diets high in calcium carbonate, which is a natural antacid. If their own diet would constantly neutralize their stomach acid, then the stomach really isn’t going to do them any good anyway.

11. They have 10 sex chromosomes! Most mammals have two sex chromosomes, one from each parent. An individual that has two X chromosomes is usually female and an individual that has one X and one Y chromosome is usually male. Thus, female mammals pass along an X chromosome to each offspring and males can pass along an X or a Y. But platypuses are not content to be normal in any way…They have 10 sex chromosomes: 5 from mom and 5 from dad. All 5 chromosomes from mom are Xs, whereas a male sperm either contains 5 Xs or 5 Ys. Birds also have two sex chromosomes, but in birds, individuals with two of the same type are usually male and individuals with different chromosomes are usually female. Their system is called ZW, where the mammalian system is XY. The platypus X chromosome is more similar than the X chromosome of other mammals to the bird Z chromosome.

12. The platypus genome is as much of a hodgepodge as its body. Only 80% of the platypus’ genes are like other mammals. Some of their genes have only previously been found in birds, reptiles, fish, or amphibians.

To learn about more weird animals, go here.

References:

Scheich, H., Langner, G., Tidemann, C., Coles, R., & Guppy, A. (1986). Electroreception and electrolocation in platypus Nature, 319 (6052), 401-402 DOI: 10.1038/319401a0

Warren, W., Hillier, L., Marshall Graves, J., Birney, E., Ponting, C., Grützner, F., Belov, K., Miller, W., Clarke, L., Chinwalla, A., Yang, S., Heger, A., Locke, D., Miethke, P., Waters, P., Veyrunes, F., Fulton, L., Fulton, B., Graves, T., Wallis, J., Puente, X., López-Otín, C., Ordóñez, G., Eichler, E., Chen, L., Cheng, Z., Deakin, J., Alsop, A., Thompson, K., Kirby, P., Papenfuss, A., Wakefield, M., Olender, T., Lancet, D., Huttley, G., Smit, A., Pask, A., Temple-Smith, P., Batzer, M., Walker, J., Konkel, M., Harris, R., Whittington, C., Wong, E., Gemmell, N., Buschiazzo, E., Vargas Jentzsch, I., Merkel, A., Schmitz, J., Zemann, A., Churakov, G., Ole Kriegs, J., Brosius, J., Murchison, E., Sachidanandam, R., Smith, C., Hannon, G., Tsend-Ayush, E., McMillan, D., Attenborough, R., Rens, W., Ferguson-Smith, M., Lefèvre, C., Sharp, J., Nicholas, K., Ray, D., Kube, M., Reinhardt, R., Pringle, T., Taylor, J., Jones, R., Nixon, B., Dacheux, J., Niwa, H., Sekita, Y., Huang, X., Stark, A., Kheradpour, P., Kellis, M., Flicek, P., Chen, Y., Webber, C., Hardison, R., Nelson, J., Hallsworth-Pepin, K., Delehaunty, K., Markovic, C., Minx, P., Feng, Y., Kremitzki, C., Mitreva, M., Glasscock, J., Wylie, T., Wohldmann, P., Thiru, P., Nhan, M., Pohl, C., Smith, S., Hou, S., Renfree, M., Mardis, E., & Wilson, R. (2008). Genome analysis of the platypus reveals unique signatures of evolution Nature, 453 (7192), 175-183 DOI: 10.1038/nature06936

The Physiology of Your “Sense of Self”

Quick! Name all of your senses!

Now, close your eyes and wave your arms over your head. Which of those senses are helping you know where your arms are in space?

The answer is the often-forgotten sense of proprioception. Proprioception (derived from the Latin for “sense of self”) is an animal’s sense of its body’s position in space. We have several different specialized receptor cells that all detect a change in body position in different ways.

Grays muscle picture by Mikael Haggstrom
at Wikimedia Commons.

If you raise your arms over your head as if you are going to grab a pull-up bar, then some muscles in your back (like your trapezius muscles), shoulders (like your deltoids and rotator cuff muscles), and arms (like your triceps) will contract. Muscles are all connected with tendons to the bones they pull on. When a muscle contracts, its tendons are stretched. Specialized proprioceptor cells called Golgi tendon organs merge with tendons and detect when their corresponding muscle is being stretched. Together, they inform the brain about muscle tension in muscles all across the body.

Grays muscle picture by Mikael Haggstrom
at Wikimedia Commons.

However, while some muscles will contract during your movement, other muscles in your chest (like your pecs) and arms (like your biceps) will stretch. Each muscle contains muscle spindles, another kind of specialized proprioceptor cell. Muscle spindles are wrapped around individual muscle fibers within the muscles. They send signals to the brain to let it know when the muscle is stretched and by how much.

Joint receptors are specialized proprioceptor cells located between bones in the capsular tissue of joints. When the angle of a joint changes, the bones and tissues put pressure on the joint receptor, causing it to send a signal to the brain. Your brain collects information from all of your Golgi tendon organs, muscle spindles and joint receptors to know the angle of each joint and the tension and length of each muscle in your body, and thus, your body’s position in space.

gif by Extremistpullup at Wikimedia Commons.

Some animals, and some individuals, are better at this than others. This guy should be pretty proud of his proprioceptive abilities (and strength). But then again, let’s see him try this:

Who Can Swim Further: A Race to the Depths and Back (A Guest Post)

By Jefferson Le

The blue whale (Balaenoptera musculus) is the largest mammal on the planet. Image by
NMFS Northeast Fisheries Science Center (NOAA) available at Wikimedia Commons.

Helloooooo! My name is Bailey and I am a 25 meter long blue whale, the largest living mammal on Earth! My friend Finley, a 21 meter long fin whale comes in second for largest in size. We had an interesting adventure recently where we were followed by humans. While Finley and I were foraging for food, I overheard the humans talking about investigating our diving behavior when we hunt and not hunt. With that, I will tell you what these foreigners did to investigate our behavior and also what happens when we dive.

A chart of whales of different sizes. Image by Smithsonian Institute.

To record our dives, the humans travelled to Mexican waters to attach recorders onto our mid-backs using a crossbow. Now, it didn’t hurt much due to my thick blubber. These devices recorded depth of how far we dived, time of dives, and our location. These recorders eventually came off between 5 to 13 hours later. Finley and I were not the only test subjects. Other members of our species were also tagged. After all the data on the devices were collected, the humans finally left our waters and did statistical analyses on our diving behavior.

The fin whale (Balaenoptera physalus) rarely exposes its fluke when it prepares to dive
to the abyss. Image by Aqqa Rosing-Asvid at Wikimedia Commons.

Now, before we talk about what the humans found, I want to share with you the whale secret to a great dive. In case that you ever find yourself in the ocean or your local pool, you can try it! The nose for Finley and I are called blowholes, which are found on top of our heads. This tract is separated from our digestive tract so we do not have to worry about having food go down our blowhole. When I am about to dive, instead of gulping in lots of oxygen, I exhale out as much as I can. This causes my lungs to collapse and flexible walls in my chest allow even more compression. Also, tiny structures in my lungs called alveoli collapse which halts any gas exchange. All of the decrease in lung space decreases buoyancy so I can descend down to the depths.

As I descend, my heart rate lessens to reduce energy used during the dive. The oxygen that I had obtained before the dive is stored in my blood and muscle tissue. Since the deep depths are really cold, blood flow is temporarily halted at the thinner areas of my body, like flippers, and some organs to keep the main body going. When I ascend back up, I gradually increase space in my lungs and my alveoli regain full function to allow gas exchange. If you were to ascend too quickly, you could get shallow water blackout or even worse, the “bends” (where nitrogen bubbles in your blood) and I heard it is painful. After ascending is complete, I can release my blowhole open and take in fresh oxygen again.

I was secretly told what the results to the humans’ experiments were. They found out that fin and blue whales dove deeper when hunting on shallow dives when not hunting. It makes sense! Why spend so much energy diving when not hunting? Also, they noted that our lunge feeding frequency was different. Lunge feeding is where we propel ourselves towards our prey with our mouth open and grab as much food as we can into our mouth. Blue whales lunged about 2.5 times more than fin whales! That’s a point for the blue! However, the record dive depth came from a fin whale. Hmm… I wonder if Finley broke that record.

Did you find my secret and what the humans found interesting? I surely did. I never thought about how I dive and how I behave as it is practically in my blood! Well, the next time you are at a deep pool, try those secrets I spilled to you. It might be fun! Then again, you might be thinking, how does a whale communicate with a human and understand scientific data? That is a secret you may never know…


Literature Cited:

Croll DA, Acevedo-Gutiérrez A, Tershy BR, & Urbán-Ramírez J (2001). The diving behavior of blue and fin whales: is dive duration shorter than expected based on oxygen stores? Comparative biochemistry and physiology. Part A, Molecular & integrative physiology, 129 (4), 797-809 PMID: 11440866

Hill, R. W., G. A., Wyse, M. Anderson. (2008). Animal Physiology. 2:641-660

Body Armor is Not Always for Protection

When we see an animal covered in scales and plates, we assume that it has this armor to protect itself from predators. It seems obvious, which is probably why scientists had not really tested it… until now. And they found that it is not necessarily true.

An armadillo girdled lizard has some impressive body armor, but does it do what we think it does?
Image by Handre Basson at Wikimedia Commons.

Today at Accumulating Glitches, I talk about new research on the functions of plates and scales in cordylid lizards. Check it out here.

And to learn more, check this out:

Broeckhoven, C., Diedericks, G. and le Fras Mouton, P. What doesn’t kill you might make you stronger: functional basis for variation in body armour, Journal of Animal Ecology, 84, 1213–1221 (2015). DOI: 10.1111/1365-2656.12414.

How Fungus Makes Ant Zombies

"Ants biting the underside of leaves as a result of infection
by O. unilateralis. The top panel shows the whole leaf with
the dense surrounding vegetation in the background and the
lower panel shows a close up view of dead ant attached to
a leaf vein. The stroma of the fungus emerges from the back
of the ant's head and the perithecia, from which spores are
produced, grows from one side of this stroma, hence the
species epithet. The photograph has been rotated
to aid visualization." Image and caption by David P. Hughes
and Maj-Britt Pontoppidan at Wikimedia Commons.

The parasitic fungus, Ophiocordyceps unilateralis sensu latu (O. unilateralis, for short), infects the brains of Carpenter ants, turning them into zombies that live and die for the sole purpose of helping the fungus thrive and reproduce. Under the influence of the fungus, zombie Carpenter ants leave their nests at an odd yet specific time, move randomly and convulsively, and climb up the north side of a plant to almost exactly 25 cm, where they bite the leaf vein. Once they bite the leaf, the muscles of their mandibles (mouth parts) deteriorate, causing lockjaw and fixing the ant victim in place while its legs kick and twitch. After a few hours, the movement stops as the fungus kills the ant, continues to grow throughout the victim's head, and then sprouts out of the back of the head. The fungus anchors itself to the plant and releases antimicrobial chemicals to protect itself and grows fruiting bodies from the ant's head to release its spores, spawning the next generation of fungus. O. unilateralis has been known to infect and wipe out entire Carpenter ant colonies, leaving dense aerial graveyards of ant carcasses in its wake.

Today at Accumulating Glitches, I talk about new research that has used genetic techniques to determine how this parasitic fungus takes over the minds of its ant victims. Check it out here.

And to learn more, check this out:

de Bekker, C., Ohm, R.A., Loreto, R.G., Sebastian, A., Albert, I., Merrow, M., Brachmann, A. and Hughes, D.P. Gene expression during zombie ant biting behavior reflects the complexity underlying fungal parasitic behavioral manipulation, BMC Genomics, 16:620, 1-23 (2015). DOI 10.1186/s12864-015-1812-x.

Loony Locomotion (A Guest Post)

By Emma Doden

For those of us who have worn fins while snorkeling or swimming before, we know how much faster you are able to cut through the water with them on your feet. But as soon as you try to walk on land with those big flippers on, that grace and speed turns into awkward and ungainly steps. You have to concentrate very hard on not falling flat on your face and find yourself thinking that your own two small feet are much more convenient for walking on land than the flippers.


The common loon in flight. Notice how far back on the body its feet are placed!
Photo by Ano Lobb from Wikimedia Commons.

The common loon is a familiar flipper-footed bird for those of us residing in the Northern Midwest. Found on many lakes in the North Woods from late March to September, their black and white plumage, ruby red eyes, and haunting calls make them unforgettable. However, just like any other waterbird, as soon as they come onto land, all of their beauty and poise vanish. Loons do not have the luxury of removing their flippers when they come onto land. Instead they flip and flop clumsily on their bellies, probably feeling just as frustrated as any person frog-stepping with flippers on.

So why do loons have so much trouble walking on land?

Because most of their lives are spent in water, the common loon’s legs and feet are located extremely far back on their bodies, allowing them to swim and dive more efficiently. Loons don’t use their wings to aid in propulsion while underwater, so they need all the power they can get from their legs and feet to catch tasty fish.

The placement of their legs means that they must slide on their belly while on land. Their legs can’t support the weight of their body and so they instead use them to push off of the ground and slide forward. The only time you will find a loon on land is for mating or nesting. Common loons will build their nests on the shore, usually no more than 5 meters from the water, because it takes a lot of effort to belly flop even that short distance!

Watch the video below to see how comical a loon looks when stranded on land:

Though loons are strong fliers as well as divers, coming in for a landing can also be challenging. Their legs are too far back to thrust forward and use as landing gear, so they stick them straight back and make a splash-landing on their bellies, penguin style!

But what makes their legs and flippers so good for swimming and diving?

Common loons propel themselves through the water with sideways strokes of their legs and feet, similar to oars on a boat. Diving birds have leg bones with a long spike-like extension at the knee where very strong muscles connect. This part of their leg acts like a lever when a loon paddles, allowing the leg and foot to be powerfully propelled through the water. Each foot is fairly large with webbing between each toe. When a loon paddles through the water, the webbing fans out and the foot rotates slightly in relation to the body on the downstroke, allowing the maximum surface area to push off of the water. On the upstroke the toes will compress together and the webbing will bunch up so that there is minimal resistance cutting through the water. The motion of the foot splaying out and compressing in with each stroke creates an efficient mode of transportation for the water-loving loon. With legs and feet like these, they are able zoom through the water as fast as fish and dive up to 200 feet!

Loons rarely come onto land, and so it is not often that you will find one of these majestic creatures floundering through the mud of a lakeshore. You are much more likely to see them gliding effortlessly across a lake, until they disappear below the surface. Then you can imagine them easily hunting fish using their powerful legs and feet to propel them while diving. Even more so than wearing flippers to help you swim, just think how much faster you could be in the water with the streamlined body and strong legs and feet of a common loon!

To learn more about common loons and their flipper-foot conundrums visit these websites:

Piper, Walter. The Loon Project.

The Cornell Lab of Ornithology. 2011. Common Loon, Life History. All About Birds.

Evers, David C., James D. Paruk, Judith W. Mcintyre and Jack F. Barr. 2010. Common Loon (Gavia immer), The Birds of North America Online (A. Poole, Ed.). Ithaca: Cornell Lab of Ornithology; The Birds of North America Online.

Michigan Department of Natural Resources. 2014. Common loon (Gavia immer).

Shearwater Seabird Osteology. 2013. Divers/loons: Osteology.

Caught in My Web: Chimpanzee Memory, Beatbox-Dancing Cockroach Legs, Cute Animals Behaving Badly, Behavioral Catastrophe, and Scientifically Accurate Spider Man

This week in Caught in My Web, I share some quirky web pages that open our eyes to some aspects of animal behavior that we don't often think about:

1. Lee Rannals describes on redOrbit research that discovered that chimpanzees use long-term memory of how various trees produced fruit in previous years to forage today.

2. On TEDEd, Greg Gage hooks up a cockroach leg to a device that allows us to hear nerve impulses! And if that wasn’t cool enough, he then gets the cockroach leg to dance to a human beatbox. You have to see this.

3. Cute animals behaving badly. Need I say more?

4. Animals will sometimes continue their behaviors even when they end in catastrophe. George Dvorsky at IO9 describes 8 of the most deadly.

5. And if ADHD's Scientifically Accurate DuckTales was too much for you, DO NOT WATCH Scientifically Accurate Spider Man:

Just Another Day (A Guest Post)

By Cassie Apostolou

The zooplankton picture on the left was provided by the EPA at Wikimedia Commons.
The human picture on the right was provided by Cassie Apostolou.

Check out the two pictures above. It doesn’t look like those two animals share a lot in common, right? Obviously the two organisms don’t look alike and the zooplankton (the odd looking microorganism creature in the left picture) lives in water and us humans typically like to stay dry on land. But if you dig a little deeper than just what you see, you’ll notice that most humans (probably you too) tend to endure specific daily migration patterns just as these little creatures do as well. Curious? Or maybe even offended that I pretty much just compared you to a zooplankton? Then continue reading and obtain the information you can throw in a friend’s face next time they are on an ego trip!

Whether you are in school or have a job, I’m sure you have a daily schedule you stick to. A daily example most people can relate to is this: you wake up to the annoying beeping of your alarm, maybe take a shower, change clothes, eat some breakfast, and then are headed off to work or school, you stay there for so many hours and then turn around and head on home (probably even taking the same routes most days too!) Well, as we do this on a daily basis, many zooplankton have a regular schedule too.


Photo of drifting zooplankton by
NOAA at Wikimedia Commons.

Zooplankton means “animal/water drifters”. Most get this name from performing daily vertical migrations cycles by floating or swimming to the surfaces of waters at night, while during the day time they stay in deeper depths of the waters. Why do they do this though? Well, research has shown that some zooplankton perform these daily cycles to escape fish predators and to obtain their food source. Also, daily migration occurs for the prevention of solar damage (just like humans and sunburn). There is also current research testing if metabolic advantages are also a cause for these migration patterns. Furthermore, studies have looked into external changes (such as temperature, salinity, and even acidity changes) as being a reason.

Photo of zooplankton under the microscope
by Ma.C. Mingorance Rodriguez at Wikimedia.

How do these animals with hardly any external features perform these day-to-day migrations? These creatures have to be in good physical shape to out-swim the predators. Also, they have to be able to adapt to the changing temperatures due to the sun or even the temperature changes in their environment. Plus, they have to be able to swim within a large group of other zooplankton to push against the ocean factors. Lastly, the zooplankton that perform the daily migrations are physically able to do so because some have evolved a pseudopodia (aka “false feet”) or flagella (tail like structure) adaption to help them move.

Still think you are way different than a zooplankton? Well, don’t you return to a safe area at the end of the night? I’m sure you eat at certain times and not at others and the food you get is mainly from the same places (probably your refrigerator or favorite restaurant). So in the end aren’t we all just walking around to obtain the necessities we need in life, just like zooplankton? I think when it comes down to the basics yes, but humans have put their own twists on life too.


References:

1. Forward, R.B. Diel Vertical Migration: Zooplankton Photobiology and Behaviour. in Oceanography and Marine Biology Vol. 26, ed. H. Barnes and M. Barnes, Aberdeen University Press, 1988, 361- 393.

2. Haney, J.F. (1988). Diel Patterns of Zooplankton Behavior Bulletin of Marine Science, 43 (3), 583-603

3. Iwasa, Y (1982). Vertical Migration of Zooplankton: A Game Between Predator and Prey The American Naturalist, 120 (2), 171-180 DOI: 10.1086/283980

What Has No Legs And The Most Amazing Feet Ever?

 

This starfish photo is by Mike Murphy at Wikimedia.

We often think of echinoderms, like starfish, sand dollars, and sea urchins, as static ocean decorations. But if you watch them for long enough (or on fast-forward if you lack the patience) you will find that they have exciting motile lives. They hunt, they flee predators, and they mate. But how do they get around without any legs to stand on? Their secret is tube feet.

If you look at the underbelly of these critters, you will see lots and lots of little tubes with suction cups on the ends. These are the tube feet. Tube feet work through hydraulic pressure, the pressure created when incompressible fluids are pushed around. Tube feet extend when a muscular bulb at the top of the foot (called an ampulla) contracts, forcing water down the length of the tube. As the tube foot extends, it swings like a pendulum and then lands and plants itself on the surface. If the surface is smooth, muscles can contract causing the cup-shaped tip to form a vacuum, sticking the foot to the surface. When the ampulla relaxes, the tube foot retracts. To get around, the animal contracts and releases these ampullae in waves, causing the tube feet to extend and retract in a coordinated way that moves the animal in a particular direction (albeit very slowly). They can also use their tube feet in a coordinated way to manipulate objects, like food items.


If you take a close look at this Pycnopodia helianthoides, you can
see the structure of its tube feet. Photo by Stickpen at Wikimedia.

But tube feet aren’t just for movement! They can also be used for breathing, smelling, tasting, and even seeing! These abilities relate to the structure of the membrane in the tube feet. Echinoderms are slow moving and have a low metabolism, so they can get away with taking in oxygen and expelling carbon dioxide at low rates. The membranes in the tube feet are permeable to both of these gasses, and thus play an important role in respiration in these species. Additionally, tube feet often have chemoreceptors (receptors sensitive to smell and taste chemicals) and photoreceptors (receptors sensitive to light). It is largely through their tube feet that echinoderms perceive their world.

Echinoderm tube feet are far simpler than our own feet, with fewer muscles, no bones, and no toenails to trim. Yet their feet can look out for predator shadows, grab and taste prey and walk up walls. Sometimes, simplicity is just cooler than complexity.

Want to know more? Check these out:

1. Lesser, M., Carleton, K., Bottger, S., Barry, T., & Walker, C. (2011). Sea urchin tube feet are photosensory organs that express a rhabdomeric-like opsin and PAX6 Proceedings of the Royal Society B: Biological Sciences, 278 (1723), 3371-3379 DOI: 10.1098/rspb.2011.0336

2. Santos, R. (2005). Adhesion of echinoderm tube feet to rough surfaces Journal of Experimental Biology, 208 (13), 2555-2567 DOI: 10.1242/jeb.01683

A Sixth Sense

Birds have long been known for their incredible navigational abilities. More than 4000 years ago, ancient Egyptians used carrier pigeons, the domesticated descendants of wild rock doves, to carry urgent messages to distant lands. They proved to be cheaper, faster and more efficient than human messengers and their use spread throughout the Mediterranean, central and northern Europe, and then throughout the world. Yet it wasn’t until the mid-1800s that scientists began to ask how they do it. To this day, how animals accurately navigate on long migrations is still one of biology’s great mysteries.

A modern day rock dove. Photo by Ingrid Taylar at Wikimedia.

That’s not to say science hasn’t made a lot of headway on this investigation. Scientists have found that some animals learn landmarks when they travel in one direction, and use those landmarks to find their way back. Some animals follow odor cues. But one of the more intriguing theories is that animals have an internal map and compass… but not a literal map and compass. The “map” is how the brain knows where things are in relation to each other and the “compass” is how the animal knows what direction it is facing with respect to where it wants to be.

How might such a compass work? One internal compass is a sun compass, in which an animal can use the position of the sun and the time of day to determine what direction it is facing. Some of the most convincing evidence supporting the existence of such a compass is that pigeons that are kept in a room with a time-shifted light cycle will fly in a predictably wrong direction on a sunny day. They will fly this wrong direction for long distances and even when they can see known landmarks. So pigeons clearly rely on the sun to achieve their great navigational feats… But what do they do on cloudy days… or at night?

A cartoon of the Earth's magnetic field by Zureks at
Wikimedia. In reality, the directions of magnetic pull
are not this straight and uniform, but you get the idea.

Maybe pigeons have another compass based on the Earth’s magnetic field. Over 30 years ago, researchers found that racing pigeons (the new profession of decedents of carrier pigeons after mailmen in trucks and airplanes took their previous jobs) arrive at their destinations a little bit later when there have been recent magnetic storms due to sunspots. Pigeons also get disoriented in places with magnetic anomalies, such as areas with lots of iron ore. But experiments in which researchers have placed magnets or magnetic coils on the backs, wings, necks, heads or legs of pigeons have not had consistent effects, particularly on sunny days (when the sun compass likely comes into play).

Enter Cordula Mora and Michael Walker from the University of Aukland, New Zealand. Cordula and Michael reasoned that because the magnetic field gets weaker with distance and because we think that magnetoreception (the ability to perceive magnetic fields) occurs in or around the head, maybe these previous studies had inconsistent results because the magnets used were too far away and/or too weak to affect the receptors in a consistent way. So they did their own study with smaller, stronger magnets applied to pigeon beaks.

Cordula and Michael glued magnets to the cere of pigeons. The diagram on the left shows how they did it and the photo on the right is a pigeon showing off his new nosepiece. (Check out the rock dove image above to see what a naked cere looks like). Diagram and image from Mora and Walker 2012 Animal Behaviour paper.

Cordula and Michael glued either a magnet or a brass weight (as a control) to the cere (the fleshy upper-part of the beak that contains the nostrils) of experienced racing pigeons right before a flight. In one experiment, researchers released the pigeons 11 consecutive times from the same place (called Gernsheim), and alternated whether they had a magnet or a brass weight glued to their cere. In a second experiment, the researchers released every bird once from each of 25 different places, each time with either a magnet or a brass weight glued to their cere. The birds were always flying to the same place (their loft), but the direction and distance they needed to fly was different for each of the release sites. Thus, the first experiment provides the birds with an opportunity to learn and compensate for any effect of the magnet, while the second experiment does not. All of the flights were done on sunny days.

The places the researchers released the pigeons from were all
different directions and distances from their home loft (at the center).
Diagram from Mora and Walker 2012 Animal Behaviour paper.

For each flight, the researchers watched the bird through binoculars until it vanished from view, at which point they recorded the vanishing bearing (the direction the pigeon was flying before it vanished from view). They also timed how long it took the bird to return to the loft and recorded any instances in which the bird did not return to the loft.

The pigeons with magnets consistently flew just a little to the right of pigeons with brass weights. The effect was very small (ranging from 11° to 22°), but it almost always happened, regardless of the bird or the release site. The effect was also consistent over consecutive years, even in birds tested repeatedly from the same release site. However, although the vanishing bearing of birds with magnets was regularly to the right of the birds with brass weights, the magnets did not prevent the pigeons from finding their loft and did not even cause them to take longer to get home. This shows that some time after the vanishing distance, the pigeons with magnets compensated for their originally slightly-off bearing.

The fact that the pigeons with magnets almost always started off flying too-far right suggests that they do have and use a magnetic compass, or perhaps even a magnetic map. But the fact that they always got back to the loft just as fast as their brass weight carrying counterparts shows that they also rely on other mechanisms, like a sun compass and landmarks. Perhaps magnetoreception is only important to determine take-off direction. Or alternatively, maybe the birds learn to ignore the confusing signals of the magnets after awhile.

We still have a lot to learn about how animals use magnetic fields. And how does magnetoreception even work? How animals navigate over long distances is still a great mystery, but scientists are on the case.

Want to know more? Check these out:

1. Mora, C.V., & Walker, M.M. (2012). Consistent effect of an attached magnet on the initial orientation of homing pigeons, Columbia livia. Animal Behaviour, 84, 377-383 DOI: 10.1016/j.anbehav.2012.05.005

2. Wiltschko, R., & Wiltschko, W. (2003). Avian navigation: from historical to modern concepts. Animal Behaviour, 65, 257-272 DOI: 10.1006/anbe.2003.2054

3. Bingman, V. P., & Cheng, K. (2005). Mechanisms of animal global navigation: comparative perspectives and enduring challenges. Ethology Ecology & Evolution, 17, 295-318 DOI: 10.1080/08927014.2005.9522584

4. Winged Migration, a fantastic movie by Jacques Perrin

Don’t Challenge a Fruit-Eating Bat to a Drinking Contest

Did you think humans invented inebriation? Guess again!

Frugivores (animals that eat fruit) and nectarivores (animals that eat nectar) are limited to food sources that last a relatively short time before they ripen, then ferment, then completely rot. So you would think that a fruit-eating animal would be much more successful at feeding itself if it could eat foods in various stages of fermentation, right? Not only would the ability to eat fermented fruits increase food abundance, but alcohol also has high caloric content (ehem: beer bellies), and makes the food easier to find by that distinctive alchy-smell. So rock on, little frugivores! It’s all good!

Watch this drunk squirrel try to escape the

"predator"-people with the camera. You're welcome.



Or is it? Imagine you’re drunk: kinda happy, stumbling occasionally, saying things you’ll likely regret in the morning, and getting lost on the way to the bathroom. Now imagine you’re being chased by a mountain lion. Crikey! You were so busy getting blitzed on fermented fruit, you forgot that you are a prey animal… and it’s a dangerous world out there!

If frugivores, such as fruit-eating bats, consumed a lot of fermented fruit, you would think they would be drunk all the time and would fly wonky and get lost and generally be less likely to survive… unless they had developed an ability to tolerate alcohol. Dara Orbach, Nina Veselka, Louis Lazure and Brock Fenton at the University of Western Ontario and Yvonne Dzal at the University of Regina decided to test the ability of several fruit-eating bats to hold their liquor. The researchers went to Belize and caught bats from six different fruit-eating species. They fed them either sugar-water or sugar-water with 1.5% alcohol in it (that’s less than a Molson Light) and later measured their blood alcohol level (BAC) in their saliva.

A little yellow-shouldered bat being fed it's alcoholic cocktail.
Photo provided by Nina Veselka.

Then the researchers put the bats in an obstacle course. That’s right, an obstacle course! They timed how long it took each bat to traverse the obstacle course (if they completed it) and counted how many times they ran into something or went in a circle. Afterwards, they gave them time to sober up before they released them back into the wild… presumably to go tell their friends about the crazy night they had. Ooohhh, was this gonna be funny!

Scientists building the drunk-bat obstacle course in Lamanai, Belize.
Photo provided by Nina Veselka.

To the researchers’ surprise, despite the fact that several bats had a BAC over 0.3% (the equivalent to a 150 pound person after 10 drinks), the bats on alcohol did not seem to be impaired in any way! They traversed the obstacle course just as fast and completed the course just as often as their kiddie-cocktail sugar-water drinking counterparts. They never even ran into anything.

So, I guess we’re not going to be entertained by drunken bat antics. But this is good news for the fruit-eating bats – Somehow, they are able to metabolize fermented fruit to get the caloric benefit without the risks of impairment. Now, if we could just figure out how they do that…

The moral of this story: Don’t drink alcohol when there are predators around unless you are a fruit-eating bat. And don’t challenge a fruit-eating bat to a drinking contest. He will drink you under the table!

Want to know more? Check this out:

Orbach DN, Veselka N, Dzal Y, Lazure L, & Fenton MB (2010). Drinking and flying: does alcohol consumption affect the flight and echolocation performance of phyllostomid bats? PloS one, 5 (2) PMID: 20126552