Tuesday, March 29, 2016

5 Diseases That Will Keep You Out Of The Water This Spring Break

Ah, Spring Break is finally upon us...a great time for rafting, surfing, swimming, and rehydrating. Before partaking in all these fun activities, we should remind ourselves about the sinister creatures lurking in waters all around the world just waiting to take us down. These aqueous villains don’t have big teeth and a menacing theme song to make you hydrophobic, but learning about these tiny critters might make you think twice about jumping into the next hot spring you see.

1. Primary amebic meningoencephalitis

Primary amebic meningoencephalitis (or PAM as it is known by those acronym-loving physicians) is caused by an amoeba called Naegleria fowleri. But aren’t amoebas those cute little single-celled organisms that we’ve all spied on through middle school microscopes and laughed at in Far Side comics? Nothing scary there.

This is why Naegleria fowleri should always be referred to as brain-eating amoeba. Yes, BRAIN EATING, as in plowing through your cerebellum like Homer Simpson gorging on a jelly donut. It is the real-life zombie of the parasite world, possessing an insatiable appetite for grey matter.

There’s only one thing the brain-eating amoeba enjoys besides neuronal soup: warm weather. This mind melting nemesis is largely found in still waters in the southern US, but global warming is allowing it to creep up to areas further north. Just one good snort of contaminated water sends this hungry little amoeba to the brain buffet.

This amoeboid parasite is a glutton, and that is its undoing. A smart parasite, like Toxoplasma gondii, goes to sleep in the brain so it won’t kill its host. But Naegleria fowleri goes on a brain devouring binge with no thought to sustainability and literally eats its host to death.

Naegleria fowleri is rather prevalent, but human infection is very rare. The bad news for those who are susceptible is that there is no cure. You will be host to this unwelcome guest for about six days before there isn’t enough brain to support the two of you any longer. So if you can’t resist the urge to go skinny dipping, at least wear some nose plugs.

2. Cryptosporidiosis
Who remembers that childhood classic sung in elementary schools around the world, “When you think your friends are joking, but your pants are brown and soaking…diarrhea, diarrhea!”

If parasites had theme songs, Cryptosporidium would surely claim “The Diarrhea Song”. Sure, Giardia and some other gut pathogens might complain since they are excellent poo liquefiers too, but they’ve never sent an entire city running for the bathrooms at the same time.

In 1993, the single-celled parasite Cryptosporidium brought gastrointestinal misery to over 400,000 people in Milwaukee, overwhelming city hospitals and even killing at least 100 of these unlucky souls. The parasite is a common pathogen in cattle and somehow found its way into the city water supply (in other words, people were drinking water that had cow patties in it).

The Cryptosporidium cysts expelled by infected cattle (or infected people) are very tough, even resistant to chlorine. People can become infected from contaminated water in lakes, pools, or water fountains, or by taking care of infected babies or patients. Once ingested, the cysts break open and the parasites inside invade your intestinal epithelial cells. They steal nutrients from your cells in order to replicate and make more cysts that get back out into the environment after turning your insides into their ultimate water slide.

Cryptosporidium is the microbial equivalent of Turbo-Lax. With no vaccine or effective treatment available, patients just have to stay hydrated, hunker down with plenty of aloe-infused TP, and wait out the unpleasant infection, which can last up to two very long weeks.

3. Cerebral sparganosis

“The magnetic resonance revealed widespread white matter degeneration and cortical atrophy”. If you hear a doctor say that, then there’s a good chance you have a flatworm called Spirometra mansoni in your brain that causes cerebral sparganosis. In everyday language, this means your brain has turned to Swiss cheese.

To be fair, Spirometra mansoni has no desire to infect you, as humans are not the definitive host. It would much rather be left in the water to invade tiny crustaceans, which are then eaten by a second intermediate host (fish, amphibian, or reptile), with the ultimate dream of getting into a dog or cat. But no, you had to take a gulp of water and disrupt this parasite’s travel plans. Since it can’t use you to make eggs and get its offspring back into the environment, the pissed off tapeworm wanders around your body and, in some cases, makes its way to the control center to vent its sexual frustration.

So how do you get these nasty things out of your head? Well, you should probably let a surgeon do it, no matter how good your friend claims to be at that Operation game. Your surgeon will likely use a technique called stereotactic aspiration, which is an innocuous way of saying, “poke a hole in your head and suck the larvae out”.

4. Candiru

Our next water dwelling devil is called candiru and it is the star of every man’s nightmare. Candiru is also known as the vampire fish, which is an awesome nickname, but what this toothpick-shaped catfish is purported to do is not cool, bro. Not cool at all. Any guesses?

The slender shape of candiru has gracefully evolved to fit in-between the gills of other fish, where this vampire draws its blood meal. Unfortunately, it is also perfectly suited to tunnel its way into a man’s urethra. Even worse, the victim can’t simply pull the fish out because candiru projects spikes that firmly implant its body into the urethra wall. The only options for slaying this vampire include amputation or expensive surgery, so best wear a condom when swimming with the vampire fishes.

If you’re thinking that it seems quite improbable that an eel-like catfish can hit such a small target, you’re probably right. There are reports that vampire fish can follow urine streams like a yellow-brick road, but this claim was tested experimentally and proven to be a myth. The few reported cases of candiru infiltrating urethras are not without controversy, so you probably only have to fear candiru in your nightmares.

5. Mycobacteriosis

By now you probably won’t be setting foot near lakes, rivers, or even mud puddles ever again. You’ve resigned yourself to just sit at home and take your mind off these terrors by gazing into your tranquil aquarium. Ah, what danger could come of that?

Mycobacteriosis! Otherwise known as fish-handler’s disease or aquarium granuloma, mycobacteriosis is one of the unspoken hazards of maintaining an aquarium. Think about it for a minute. Fish eat. Fish pee. Fish poop. And you haven’t changed the water in three, maybe four, months! That poor fish is swimming in a cauldron of bacteria, including a variety called Mycobacteria. Some species of Mycobacteria cause such lovely diseases as tuberculosis and leprosy, but the one in fish tanks is usually Mycobacteria marinum. If you stick your hand in the water to play tag with Nemo or set up his new SpongeBob pineapple house, Mycobacteria marinum can enter your body through an open wound on your skin.

Like other Mycobacteria, the infection is very stubborn and lasts a long time even with antibiotic treatment. You may also be left with ugly scars and/or arthritis to serve as a permanent reminder that you need to change the water in your fishy friend’s tank frequently. In some cases, especially immunocompromised people, infection with Mycobacteria marinum has resulted in amputation or even death. So ditch the aquarium now and just install a fish tank screensaver on your computer desktop.

Contributed by:  Bill Sullivan
Swim with Bill on Twitter.

The original version of this article appeared on BuzzFeed Community.

Bauer IL (2013). Candiru--a little fish with bad habits: need travel health professionals worry? A review. Journal of travel medicine, 20 (2), 119-24 PMID: 23464720

Tuesday, March 15, 2016

The Search For The Unicorn - Slightly Off-Center

Zootopia opened in movie theatres on March 4 and is on track to be another Disney classic. Among all the animals featured in this feature, you probably recall a few sporting horns...but did you happen to spot any unicorns?

The earliest writings that describe unicorns were those of the Greek, Ctesias, in the late 5th century BCE. He described the Indian Ass, an animal with a white, strong body and perhaps a red head from which sprung a long single horn of red, white, and black. It was said that a cup made from the horn could neutralize any poison.

There are real animals with one horn, like the
unicorn leatherjacket fish in the top left, and the
Indian rhinoceros at the bottom left. The rhinoceros
beetle has one big horn and fairly large part of his
jaw below, so I don’t know if he counts. On the top
right is the Meller’s chameleon. They say he a has a
horn on his nose, but you have to look close and
want to see it.
Four hundred and fifty years later, Pliny the Elder, historian of Rome, also wrote about a very strong animal with a single horn protruding from its forehead. He described an oryx (an antelope with a single horn), an Indian Ox (probably a rhinoceros – rhino = nose and ceros = horn), and the same Indian Ass with a horse-like build and a single horn.

Pliny wrote, “The unicorn (uni = one, and ceros = horn) is the fiercest animal, and it is said that it is impossible to capture one alive. It has the body of a horse, the head of a stag, the feet of an elephant, the tail of a boar, and a single black horn three feet long in the middle of its forehead. Its cry is a deep bellow.” Uh-huh. That doesn’t sound much like an antelope or a rhino, so I guess he meant the Indian Ass.

Soon, Romans were trading long spiral tusks, but no one was telling where exactly they had come from. These “unicorn” horns were snow white with a tight spiral. As a result of these horns, the unicorn in the West settled down to be a pure white horse with a very long, pure white, spiraled horn. This is the image we generally see in tapestries and illustrations.

Kirin Beer from Japan uses a unicorn (kirin) as its
logo. Look closely and you can see the single
horn on its head.
In the Far East there were unicorns as well. Known as the qilin (pronounced chee-lin) in China, there was a version in Japan too, the kirin. This was a benevolent animal, with shiny scales like a dragon and one or perhaps two horns. It avoided fighting and walked so softly that it would not disturb or harm a blade of grass. An animal like this (perhaps the saola) is most likely the one referred to in the North Korea stories. In 2012, North Korea announced that its archaeologists discovered a unicorn lair. 

But back to the real world. Most likely, those horns in the Roman markets were really narwhal tusks, as discussed in a 2011 paper. It is very likely that the narwhal played into the unicorn legend, as their tusks could be offered as concrete proof of unicorn existence.

The narwhal (Monodon monoceros) is an amazing animal, and one that abandoned bilateral symmetry. Monodon means one tooth, and monoceros means one horn; a pretty accurate name, all in all.

Our post today uncovers many of the problems
with these cartoon narwhals. Yes, they love where
there is ice. But they don’t have all those teeth, the
tusk isn’t centered and doesn’t come out of their
forehead, and they don’t have a dorsal fin
to speak of.
Narwhals are a species of whale, meaning that they are mammals. They live way up north. From Baffin Bay, around Greenland, to the north of Russian, they swim in pods of 10-100, but you’ll rarely see them even if you live near there. There are perhaps 45,000-50,000 narwhals today.

This is a steady number because it’s so hard to get to where they live. Consequently, narwhals haven’t been hunted into extinction. They spend a lot of their time on deep dives under the ice floes, so they aren’t seen often. No narwhal has ever been seen feeding; we only know what they eat from examining stomach contents.

Their most distinctive feature is the long (up to 10 ft/3 m) tusk on the males. Just one tusk, mind you, like a unicorn horn. The narwhal tusk - like elephant, walrus or warthog tusks - is a tooth.

Very young narwhals have six maxillary (upper jaw) tooth buds and two pairs of tooth buds in the lower jaw (mandible). However, only one pair develops any further. A tooth bud is what you find on an X-ray of a child (see picture).

You can see the teeth developing from crown to
root in the darker tooth buds. The pulp is usually
dark, but the middle tooth has had a root canal
and a filling has been placed in the whole pulp
chamber. The large tooth to the left is the first
molar. It doesn’t have a baby tooth to push out
of its way.
Teeth form in the jawbones as tooth buds. Most narwhal teeth never go past the tooth bud stage, but occasionally a tooth will erupt where one shouldn’t. These are often misshapen or caught between the bone and the palate, or in the wrong place. This is all good evidence that the teeth are vestigial; they serve no functional purpose for the normal narwhal.

Just one tooth, almost always the left cuspid (most people call it a canine), does develop. Hold on though, it isn’t that simple. Instead of developing in a vertically directed tooth bud and erupting down through the jaw, the left canine stays horizontal and erupt right through the front of the jaw and through the narwhals lip!

Since the tusk is derived from the left cuspid, it erupts left of center, making the narwhal bilaterally asymmetric! A 2012 study showed that the bony attachment and length proves that the narwhal tusk is a canine, not an incisor as so many people think. But, it’s not just the location that makes the narwhal tusk amazing, it’s how it’s made and what it can do.

A 1988 study suggests that the tight spiral as it grows keep the tusk from curving. A curved tusk would make it hard of the narwhal to swim in a straight line. Whatever the reason, the spiral is an iconic image for both narwhals and unicorns.

The top image shows how the narwhal tusk is off
center. The bottom image is my analogy. The tusk
is offset like a knight with his jousting lance. This
is Heath Ledger in A Knight’s Tale. Um….why isn’t
he wearing armor?
Despite being a tooth, the tusk is quite flexible. It can bend up to a foot (0.3 m) in any direction without breaking. It’s awfully long, we said 10 ft. above, but most are in the 8-9 foot range. This is huge when you think that most male narwhals are only about 15 foot long in the body.

Teeth are normally built with the hard enamel on the outside. Enamel is harder than bone and protects the teeth from breakage when chewing. The mouth is a rough environment and teeth have to put up with a lot of abuse.

Deep to the enamel is a material called dentin. This stuff has a lot of similarity to bone, although it isn’t quite as hard and doesn’t have living cells within it (like osteocytes – see this post). The dentin does contain millions of tubules that go from the enamel junction all the way to the pulp in the center. The pulp has a nerve and blood vessels.

The dentinal tubules have fluid and small processes of the neuron in them. When you eat something cold or have a cavity, the fluid in these tubules moves and changes the pressure in the pulp chamber. The single neuron in the tooth is a pain neuron, so any pressure change is interpreted by your brain as pain. It teaches you to take care of your teeth, but it ain’t the most pleasant of all evolutionary adaptations.

The cartoon on the left shows the enamel crown
covering the dentin and the dentinal tubules.
Inside the tubules are the odontoblasts that lay
down dentin all during the life of the tooth and the
nerves that go into the tubules. The right image is
an electron photomicrograph of the tubules.
The narwhal tusk is different. It is the only tooth known that has the dentin on the outside, although a 1987 study showed that it has no enamel, so it isn’t really an inside out tooth. The dentin is covered by a thin layer of cementum. This is what normally covers the roots of the teeth and helps attach them to bone. The dentin of the narwhal tusk has about 10 million of those tubules, but it is different from human dentin.

A 1990 study compared calcium content and hardness between human teeth and narwhals. The narwhal cementum was more mineralized than human, but the dentin of narwhals was less mineralized than human dentin and was softer. This may be why the narwhal tusk is so flexible.

The tubules of the narwhal tusk dentin connect to channels in the cementum, so there is a communication to the outside. A group in 2014 showed this and used the information to hypothesize that the tusk is a mechanosensor. Experiments showed that their heart rate changed when the water touching the tusk was switched from freshwater to salt water. They hypothesize that the tusk senses temperature, salinity, pressure, and perhaps touch to help in navigation and hunting.

But if that’s the case, why do only males have them? Females have to hunt too. The group from the 2014 paper offers that males and females have sexually dimorphic foraging techniques – they eat different things and hunt differently, so females don’t need horns. This is not well-supported. Many scientists believe the long tusk is a sign of health and genes and is therefore an ornament for mate selection.

The dorsal fin of the narwhal is greatly reduced. It
has notches that scientists hope to use to identify
individuals. The lack of a dorsal fin is believed to
be so they don’t injure it on the underside of the
ice floes when they surface, but it could also be so
they don’t run it into the ocean floor as they feed
upside down.
Occasionally, one will see females with a tusk, but like with many tusked females (elephants, etc), they are usually shorter. You can also find narwhal males with two tusks. But two tusks doesn’t mean that they are returned to bilateral symmetry. Both tusks spiral to the left! There must be some strong left-hand genes at work.

One last thing. The offset tusk lead to another weird narwhal behavior. A group in 2007 put cameras and positional monitors on some narwhals and found that they tend to swim upside down a lot. Almost 70% of their time on the ocean floor was spent in the supine position. Since the tusk points down just slightly, scientists believe they hunt upside down so that the tusk won’t get stuck in the ocean floor and break! The tusk must be pretty important - or they just like lounging on their backs.

Contributed by:  Mark Lasbury, MS, MSEd, PhD
A version of this post was originally published on his blog, As Many Exceptions As Rules.

Christen AG, & Christen JA (2011). The unicorn and the narwhal: a tale of the tooth. Journal of the history of dentistry, 59 (3), 135-42 PMID: 22372187

Kingsley, M., & Ramsay, M. (1988). The Spiral in the Tusk of the Narwhal ARCTIC, 41 (3) DOI: 10.14430/arctic1723

Nweeia, M., Eichmiller, F., Hauschka, P., Donahue, G., Orr, J., Ferguson, S., Watt, C., Mead, J., Potter, C., Dietz, R., Giuseppetti, A., Black, S., Trachtenberg, A., & Kuo, W. (2014). Sensory ability in the narwhal tooth organ system The Anatomical Record, 297 (4), 599-617 DOI: 10.1002/ar.22886

Dietz, R., Shapiro, A., Bakhtiari, M., Orr, J., Tyack, P., Richard, P., Eskesen, I., & Marshall, G. (2007). Upside-down swimming behaviour of free-ranging narwhals BMC Ecology, 7 (1) DOI: 10.1186/1472-6785-7-14

For more information or classroom activities, see:

Narwhals –

Tooth structure –

Tuesday, March 8, 2016

A Tale Of Monkey Tails, And Why Curious George Is Not A Monkey.

“George was a good little monkey and always very curious.”

This line opens nearly every one of the adventures that Curious George has set upon since he was first brought to life by HA Rey in the 1939 children’s book “Cecily G. and the Nine Monkeys.” These stories, which have sold over 25 million copies over the last 75 years, and are beloved by child and parent the world over, begin with a lie – a big fat lie because, in fact, Curious George is NOT a monkey.

We at THE ‘SCOPE thought it would be a good idea – in this Year of the Monkey – to clarify some things about our beloved primate pal, George. So what is a monkey, and why is George not one? Generally speaking, monkeys are haplorhine primates with external tails. Another way of saying this is that they have dry, furry noses (not wet ones like lemurs or dogs or cats) with more than just the vestigial tailbone that apes have, including humans. All monkeys have tails,* although some are longer than others. And because Curious George does not have a tail (along with other reasons explained elsewhere), he is not a monkey but an ape.

Frankly, and we’re just gonna throw this out there… Curious George would be way cooler if he were a monkey, precisely because he would have a tail. And monkey tails are fascinating structures because they come in so many varieties: long, short, skinny, fat, hairy, partially bare, prehensile, nonprehensile… wait, what does that mean?

We’ll tell ya!

Prehensile tails are ones that are capable of suspending the entire body weight of the animal. So, an animal with a prehensile tail can hang from its tail, which frees up its hands and feet for other activities like picking fruit or leaves to eat. Based on observations of living and fossil species, it is generally thought that prehensile tails evolved at least 14 times independently among 40 different genera of extant mammals. And this doesn’t include all the other living vertebrates with prehensile tails, like some snakes, lizards, salamanders, and seahorses, to name a few.

Not all monkeys have prehensile tails, which is a shame for those that don’t because prehensile tails are much more interesting than nonprehensile ones. In fact, the only monkeys that have prehensile tails are in Central and South America (platyrrhines or New World monkeys), but not even all those have prehensile tails. Prehensile tails likely evolved twice in the New World monkeys that have them: once in the ateline monkeys, which include spider monkeys, woolly monkeys, howling monkeys, and muriquis, and then a second time in the capuchin monkeys.

Left: Capuchin monkey (Cebus apella); Right: Spider monkey (Ateles geoffroyi)
In most respects, both instances of prehensile tail evolution in monkeys resulted in similar anatomical structures. Monkey prehensile tails are comprised of vertebrae that are structured to resist higher bending and torsional forces. This seems intuitive because animals that hang from their tail put more stress on the bones in their tail. So having bones that can resist higher forces would safeguard against accidental fracture. The ends of these tail vertebrae are more convexly rounded at the point where they articulate with one another, which allows for a greater range of motion than in nonprehensile tails. Also fascinating is that some of the muscles in prehensile tails are structured to produce higher contraction forces than those of nonprehensile tails, while other muscles have developed shorter extrinsic tendons that cross fewer joints along the tail, enabling the animal to have tighter control of the tail to wrap around substrates.

But the parallel evolution of prehensile tails in New World monkeys has also led to some pretty interesting anatomical differences that reflect functional differences in the way the tail is used. In addition to hanging from the tail during feeding bouts, ateline monkeys use their prehensile tails during locomotion to assist with moving through the forest canopy – much like a fifth limb. This is fundamentally different from the way that capuchin monkeys use their tails because capuchins tend to brace themselves with their feet and tail (like a tripod) for stability while feeding on fruits at the ends of thin tree branches, but they do not use their tails while moving. And this basic distinction in the way the tail is used can be seen in specific anatomical differences between ateline and capuchin prehensile tails.

Friction pad on tail of mantled howling
monkey (Alouatta palliata) at Hacienda La Pacifica,
Guanacaste, Costa Rica, 2004.
Capuchin monkeys, like most other primates, have tails that are completely covered in hair. The skin underlying the hair is replete with slow-adapting pressure and touch receptors (Ruffini endings) that allow the animal to detect the position of the tree branch substrates during postural behaviors like sitting or lying down. The ateline monkeys, however, uniquely possess a hairless friction pad on the ventral (anterior) and distal (tip) of the tail. This friction pad senses touch and pressure with slow-adapting sensors like the skin of the capuchin tail, but it is also full of rapid-adapting sensors (Meissner’s and Pacinian corpuscles) that are useful for detecting the substrate during locomotion. Additionally, the ateline tail friction pad contains dermatoglyphics, or “finger” prints, similar to those found on fingers and toes. This pad, with its dermal ridges, provides the source of friction so that the tail does not slip during suspension and locomotion.

So, as you can see, if Curious George was actually a monkey, there is no question that he would be infinitely more interesting** because monkey tails are interesting. And if he were a New World monkey with a prehensile tail, I have no doubt his curiosity would get him into so many more pickles because he would have the ability to hang from his tail and manipulate things with his hands and feet. Unfortunately, for over 75 years George has been given credit for being a monkey, when all signs point to him being an ape – the biggest clue being that he does not have a tail.

*Ok… so almost all monkeys have tails. There is an interesting case of near taillessness in Macaca sylvanus, also called the Barbary macaque. These monkeys, who live in Gibraltar and constitute Europe’s only wild population of monkeys, have a vestigial, stumpy, soft tail – a bulbous nubbin. And although they have tail vertebrae like every other monkey, these vertebrae do not actually extend into the external tail at all, so they are more like the tailbone (coccyx) that apes have than those of a typical monkey tail. For this reason, Barbary macaques are mistakenly called Barbary apes. But they are not apes. They are monkeys – unlike Curious George.

**Tamping down the hyperbole for a moment, the truly most interesting aspect of George, given that he is not a monkey, is the history of how he came to be so beloved by so many. You can read this fascinating history here.

Contributed by: Jason Organ, Ph.D.

Tail Jason on Twitter.

Organ JM, Teaford MF, & Taylor AB (2009). Functional correlates of fiber architecture of the lateral caudal musculature in prehensile and nonprehensile tails of the platyrrhini (primates) and procyonidae (carnivora). Anatomical record (Hoboken, N.J. : 2007), 292 (6), 827-41 PMID: 19402068

Organ JM (2010). Structure and function of platyrrhine caudal vertebrae. Anatomical record (Hoboken, N.J. : 2007), 293 (4), 730-45 PMID: 20235328

Organ JM, Muchlinski MN, & Deane AS (2011). Mechanoreceptivity of prehensile tail skin varies between ateline and cebine primates. Anatomical record (Hoboken, N.J. : 2007), 294 (12), 2064-72 PMID: 22042733

Deane AS, Russo GA, Muchlinski MN, & Organ JM (2014). Caudal vertebral body articular surface morphology correlates with functional tail use in anthropoid primates. Journal of morphology, 275 (11), 1300-11 PMID: 24916635

Russo GA (2015). Postsacral vertebral morphology in relation to tail length among primates and other mammals. Anatomical record (Hoboken, N.J. : 2007), 298 (2), 354-75 PMID: 25132483