Saturday, April 19, 2014

Intermediate Host: The Delivery Boy of the Parasitic World

Why use an intermediate host?
Parasites have often been known to take a skewed path to their ideal host. What is the point of an intermediate host? What makes the longer path the better one? It seems more time and energy consuming, and overall inefficient. Well, sometimes it is. But more often than not, an intermediate host is beneficial, even necessary, to a parasite’s life cycle. Intermediate hosts can increase the probability of infection the definitive host[1], provide transport to the definitive host, or even supply nutrients for the parasite’s development until a suitable host comes along[2].  

Types of Transmission
Before we talk about all the different instances in which using an intermediate/ host is helpful to a parasite, it’s important to know that there are 2 kinds of transport through a host: passive and active. Passive transmission is essentially the host’s accidental ingestion/inhalation/etc of an infective source. For example, Dracunculiasis, or more commonly referred to as Guinea Worm Disease, is the result of passive transport. The nematode responsible for the disease, Dracunculus medinensis, is ingested by a copepod in its L1 stage. The parasite develops into the L3 phase while in the copepod, which can be swallowed by a human (the definitive host) when clean water is unavailable[3]. This parasite did not manipulate its host’s behavior in attempt to reach another host, but rather just let things happen as they did. Active transmission, on the other hand, is displayed when a parasite manipulates the paratenic host’s behavior or deliberately performs some kind of action to open the encounter filter and increase the probability of reaching its definitive host. The human Bot Fly, or Dermatobia hominis, is a good example of active transport. The fly lays its eggs on the abdomen of a mosquito (the intermediate host) that will be stimulated and released when the mosquito comes in contact, or takes a bloodmeal from, a human [4].

Compilation of Boy Fly removals. [8]



Infective vs. Infestive
Trichinella's Life Cycle [6]
Both passive and active transmission can be divided further into categories; active transmission, for example, can be attained by either an infected source or an infested source. An infested source essentially implies that the parasite is free-living, while infective sources utilize a living organism as an intermediate host [4]. Pigs and cows are both infective sources/intermediate hosts for certain Trichinella species. T. spiralisis the most common, and therefore most devastating, species in the Trichinella family. The T. spiralis life cycle is direct, meaning that it can be completed within a single host, and therefore does not need an intermediate host. However,  there often are multiple hosts that T. spiralis will go through during its life. T. spiralis larvae encase themselves in cysts inside the muscle of its current host (usually a pig), which affects the mobility of the infected muscle. If the host’s muscles are rigid and immobile, it will be more likely to get caught, and therefore eaten, which will pass the nematode onto another host. The parasite increases its chances of continuing its life cycle by shortening that of its current host.

Mind Control of Mice?
Several parasites exhibit mind control
 over their hosts.[7]
Another example of a parasite using an intermediate host to increase its chances of ingestion is Toxoplasma gondii. T. gondii can only reproduce in cats, but it is often found in rats and other rodents. Why on earth would a parasite be found in both rodents and cats? Because the protozoa controls its host’s (the rodent) mind to decrease fear of cats. Usually, when a rodent/rat smells cat urine, it turns and runs as fast as it can. But when infected with T. gondii, the rodent is intrigued by the smell, and it sticks around to find the source of the smell leading to its imminent consumption[5]. The effects of T. gondii on human brains is currently being studied, and so far it looks like humans are also susceptible to parasitic mind control. Apparently, humans infected with T. gondii are more likely to take on dangerous tasks and get into car accidents. Science North talks about T. gondii more in the video below.

                   
          More info about T. gondii. [9]


Sources:
1. Art of Being  A Parasite, by Claude Combes
9. https://www.youtube.com/watch?v=Ri1-Y0rocSA


Wednesday, April 16, 2014

Mudpies As A Defense?

A little background for you . . .
Alright, we are no longer young children out here making mudpies and eating dirt. However, what if eating small amounts of dirt could lessen the impacts of side effects from parasites and make us healthier against them? So what if we ingest a few parasites in the process, as Zuk says: “remember, the idea that we- or any other organism- should be completely parasite-free is a modern invention, not a natural state of affairs.”[1] The concept of geophagy, or eating dirt or clay like materials, has been around for centuries amongst animals and humans alike. Research has shown both positive and negative effects on the body and on the protection from parasites from eating small amounts of dirt consistently. However, we must question, why dirt?

Why dirt?
[6]When first thinking about dirt, soil, or Georgia red clay for instance, one does not typically think that it would be a desired food. However, dirt with high amounts of clay contain high amounts of minerals such as calcium. Studies have shown that geophagy is a common practice among children and pregnant women in rural areas where proper healthcare and nutrition are lacking.[2] The origins of this practice date back to various tribes and cultural practices across the world on all continents from centuries ago. Some site homesickness, or desire to regain lost nutrients as a cause for eating dirt. Others often use it for medicinal purposes since it has anti-diarrheal properties. Pregnant women often use it as a home remedy for morning sickness.[4] A common practice is for the soil to be mixed with other things and then baked. It is common to find baked soil in local rural stores. Some cultures use dirt and clay as food when they do not have enough, although the nutritional value is very low.

So is this safe?
Not exactly, with eating dirt many risks arise. There are many STH’s (soil transmitted helminthes) that can live dormant in soil for years such as roundworm eggs. Additionally, most STH eggs are passed through human feces. In rural areas without proper plumbing and running water, defecation takes place in the dirt. Infected individuals would then be passing the eggs through the stool into the dirt, which over time could wash away, however still leaving the eggs behind. When the dirt is collected for consumption, albeit small amounts, the eggs are also collected and can be transferred once eaten.
[7]

So the benefits are?
For centuries pregnant women have eaten soil as a way to retrieve necessary nutrients that is shared with the fetus during pregnancy. Some cultures have been known to use certain types of soil in medicine. Keep in mind, were not talking the average potting soil you can find in the stores. We are talking about soil high in clay levels. Clay has been known to have adsorbing characteristics that help in removing toxins from the body. [3] For centuries, those without access to proper healthcare or those who could not afford healthcare turned to clays and soils as a way to help detox their bodies and keep them safe. Colloidal clays, such as those used for medicinal purposes, have been found to have anti-diarhheal properties. [3] This is where we see the benefits for parasites. As we have learned in class, a common side effect of any parasitic infection is diarrhea. Therefore, the side effects are reduced. As mentioned above by Zuk, humans are expected to have a few parasites. Having low amounts of parasites allows our innate immunity to build a response to them. In that case, the parasite load is not enough to cause a full-blown infection, but enough for our body to realize that they are a toxin and must be protected against.

Still not convinced?
We all have probably eaten dirt at one point in our life, whether it be through playing outside, or having vegetables and fruits that were not completely clean. With that being said, I am not saying go outside and eat a handful of dirt. Not exactly a good idea, but small amounts every now and then are not completely bad. The amount of parasites you may get by eating small amounts of dirt as children, or as adults are typically not enough to cause infection, unless dirt is eaten daily.

[5]
1. Zuk, M. Riddled with Life: Friendly Worms, Ladybug Sex, and the Parasites That Make Us Who We Are. Orlando: Harcourt, 2007. Pp 207-211.
2. Peter, A. Human Geophagy: a review of its distribution, causes and implications. In: Catherine, H., Skinner, W., Berger, A. R. geology and Health: closing the gap. Oxford University press, USA. 2003. ISBN 0-19-516204-8.
3. Sing, D.; Sing, C.F. Impact of Direct Soil Exposures from Airborne Dust and Geophagy on Human Health. Int. J. Environ. Res. Public Health 2010, 7, pp 1205-1223.
4. Elom, M.; Alo, M.; Ugah, U.; Ibiam, G. Intestinal Helminthes Associated with Geophagy in Pregnancy in Afikpo North Ebonyi State. World Journal of Medicine and Medical Science. 2013, 1, pp 92-97.
5. http://waxturds.com/wp-content/uploads/2009/12/1Dec2009_geophagy.jpg
6. http://spectregroup.wordpress.com/2008/04/21/haitians-eating-mud/
7. https://www.youtube.com/watch?v=vATmFHhLKHE
8. http://www.mnn.com/sites/default/files/user-1071/clay2_530.jpg

Monday, April 14, 2014

Ornaments and Opportunity

The Age of Acne
I’m sure we all remember those awkward middle school days of acne and bed head. You walked around school avoiding bullies, eyeing the crush of your dreams and trying for the life of you to figure out some way to talk to him or her without making yourself look more inept than you may have already felt . (If you’ve never experienced this, consider yourself a step above the normal human race.) However, I’m even more certain that we’re all grateful those middle school days are long behind us, with only a hidden yearbook picture as a dreaded reminder.

http://ineedashouldertocryon.wordpress.com/category/personal/


Imagine if you will though, that those acne spots and uncontrolled hair were all that mattered in your future for finding that special someone. And even now, whatever blemishes you may or may not have, will signify to a future mate the compatibility and long life you may (or may not) be able to have. Such a terrifying concept is, fortunately for us, just a  dream world for the human race as few people hold an unsightly stage of adolescents, or an unfortunate week of pimples, against someone they could see as a potential mate.

The animal world, on the other hand, is not so forgiving. Often features that animals consider attractive, such as a jungle foul’s cock comb or the yellow of a gold finch’s feathers, make all the difference in the world in being forever alone or happily mated in the animal kingdom. While many people struggling with acne are trying all sorts of treatments from ProActiv to home remedies, animals must deal with treatments of their own in order to maintain attractiveness whether they are conscious of this fact or not. 

Take Care of those Carotenoids
Male partridges are prized by their female counterparts for their red beaks and red accents around their eyes1.  Such attractive feature can be attributed to carotenoids. These pigments can act to either brighten an animal’s coloration or increase its immune response5.  Although carotenoids are highly valuable for their attracting tendencies, they can only be found in food and cannot be self made. Therefore, the allocation of carotenoids is very important in being able to attract a mate with one’s bright and bold ornamentation.

http://www.carotenoidsociety.org


The Hamilton-Zuk hypothesis explains that these vibrant ornaments are an indication of an individual’s health 4. Females look for those males with big bold secondary sex characteristics because they can indicate his parasite load and overall genetic vigor. As an individual’s parasite load increases, his health decreases and, subsequently, so does the attractiveness of his secondary sex characteristics4.

Although testosterone is, by itself an immunosuppressant, it does act to increase an individual’s dietary carotenoid uptake1,2 . As testosterone increases so does the uptake of dietary carotenoids which can either be used to fight free radicals in the blood stream in an anti-oxidant capacity, which increases the cell-mediated immune response, or as pigmentation to make ornaments flashier and brighter. The more carotenoids used in an immune response to build T-cells, the less there will be for pigmentation of ornaments3.

A relatively recent study was performed on Alectoris rufa, also known as the red-legged partridge, in which scientists infected the birds with an intestinal parasite, coccidian and then tested the birds for their immune response and the effect that response had on secondary sex characteristics2. The study found that males with a redder beak and eye rings also had less parasites and higher carotenoid levels. This indicates that while testosterone provides information to potential mates about long-term health and potentially resistant genes passed to offspring, carotenoid levels indicate the individual’s current health and virility.

http://www.english-country-garden.com/birds/red-legged-partridge.htm

In summary, testosterone is a hormone that starts functioning at the onset of puberty to increase size and structure of prominent secondary sex characteristics. If an individual is infected by parasites from the beginning, and has nonresistant genes to such parasitic attacks, then that individual's ornamentation will be lacking in form and structure. However if an individual can afford high testosterone levels and attractive ornamentation he must have good genes. Furthermore, if an individual has attractive ornamentation that is also bright in coloration, then he must have an ample supply of carotenoids to spare. 

It's hard to cheat in the animal world. No amount of plumage serum or beak brightener can help turn an awkward pubescent partridge into a strapping specimen to mate with. It either has it or it hasn't. I'm grateful that I can safely say no braces and acne stage can be held against anyone in the big scheme of things. At least…I hope not.
http://www.dxpnet.com/opinion/pisces/Hooked-yourself-a-fish-3895146.asp


References
1)   Blas, J., L. Perez-Rodriguez, G. R. Bortolotti, J. Vinuela, and T. A. Marchant. "Testosterone Increases Bioavailability of Carotenoids: Insights into the Honesty of Sexual Signaling." Proceedings of the National Academy of Sciences 103.49 (2006): 18633-8637.
2) Mougeot, Francois, Lorenzo Perez-Rodriguez, Nuria Sumozas, and Julien Terraube. "Parasites, Condition, Immune Responsiveness and Carotenoid-based Ornamentation in Male Red-legged Partridge Alectoris Rufa." Journal of Avian Biology 40 (2009): 67-74.
3) Peters, Anne. "Testosterone and Carotenoids: An Integrated View of Trade-offs between Immunity and Sexual Signalling." BioEssays 29.5 (2007): 427-30.
4) Shykoff, Jacqui A., and Alex Widmer. "Parasites and Carotenoid-based Signal Intensity: How General Should the Relationship Be?" Naturwissenschaften 83.3 (1996): 113-21.
5) Zuk, M. Riddled with Life: Friendly Worms, Ladybug Sex, and the Parasites That Make Us Who We Are. Orlando: Harcourt, 2007. pp 180-206.

Sunday, April 6, 2014

Fighting Water Parasites

What’s up with water anyways?


Life Cycle of Cryptosporidiosis
 The CDC reported an outbreak of Cryptosporidiosis in Sweden in 2010. The disease is caused by a parasite known as Cryptosporidium hominis, and, like most of the other water born parasites, causes chronic intestinal disease. The diseases caused by these parasites are characterized mainly by diarrhea, but can be accompanied by other symptoms including stomach pains (1). Water borne parasites that cause intestinal diseases are usually transmitted through the fecal oral route. The parasites have two forms: cysts and trophozoites, with the cysts being the infectious particles located in the fecal matter. The outbreak in Sweden can be traced back to fecal contamination, which was determined by tests that yielded abnormally high levels of E. Coli in the raw water supply (1). The usual microbial barriers of ozonation, a process that destroys microorganism through the infusion of ozone (6), and chlormination, a process in which ammonia is added to drinking water that already has chlorine added to disinfect (7), both proved infective in this case due to the resistance of the cysts (5). The Swedish added UV water disinfecting systems to help clean the water and prevent another outbreak in the future. It seems that in industrial nations it is more practical to try and prevent the limited contamination that could occur but the costs to install systems to monitor for the cysts seems impractical (1).

 Avoiding Parasites in First World Areas 

Don't Do It! 

 There are a few simple tips provided by the CDC to help prevent the prevalence parasites as well as to prevent infection. The first is do not use water that you are swimming in as a restroom because most of the water borne parasites can be transmitted in this manner. Next, do not swallow or ingest the water that you are swimming in, just in case someone could not quite make it to the restroom. The final tip is to use nose plugs when entering water that might be contaminated just to help further prevent infection (2).


Third World Problems


Children getting water 
 While such contaminations can occur in industrialized nations that have access to clean water most of the time it is the nations that do not have clean water that have a higher prevalence of infection by these parasites. This becomes especially hazardous for children, elderly, and other immune compromised individuals, who suffer from dehydration and even death caused by diarrhea. With out proper plumbing and water treatment facilities it is extremely difficult to reduce the fecal-oral contamination that promotes the spread of these diseases. Efforts are being made to find ways to inexpensively purify the water in these nations. Two ways that have been uniformly promoted are the use of Aquatabs, or the use filters to help rid the water of the disease causing cysts, not just for the residence of theses nations but also for those who visit them (3). Aquatabs are water purification tablets, which have specific tablet requirements based on the volume of water to ensure that the water is clean. The tablets work by using the ingredient Dichloroisocyanurate, and recommend that you mix thoroughly and then wait thirty minutes before drinking the water. Also, they advise that the water be filtered first if the water is opaque or cloudy (4).



 UNICEF

As we all know UNICEF is an organization that works in several ways to aid nations in need. One of their latest initiatives is to try and provide clean drinking water to children that are in need, as children are extremely susceptible to water borne parasites (11). Not to mention the consequences of them getting sick put them behind in school and the problems seem to cascade from there. The new initiative is called TAP. Essentially TAP is a challenge to those of us who are fortunate enough to have cell phones to restrain from using them for the betterment of children in need. For every 10 minutes a person goes with out using his/her phone a day of drinking water is provided for a child  in need. To take the challenge just access UNICEFTAPPROJECT.ORG from your cell phone and stay off of it (11)!Please enjoy the videos that show some of the other efforts that UNICEEF has made to provide clean drinking water for nations that have the highest incidence on intestinal disease. 


Conclusion 

While theses intestinal parasites and the diseases they cause may not seem like that big of a deal the truth is they are. Diarrhea is still one of the leading causes of death in the world and can keep children that desperately need an education out of school for weeks. Even if you don’t care about the children or people in other places you are not as safe as you think. Many of these parasitic cysts are resistant the chemicals currently used in water treatment plants, and are not filtered out by the filters used, which mean an outbreak could happen in your town or city. The more we work to help decrease the incidence of these diseases around the world the safer everyone else will be. All it takes is one fecal-oral contamination to start an outbreak.

 References
 1. http://wwwnc.cdc.gov/eid/article/20/4/pdfs/12-1415.pdf
2. http://www.cdc.gov/healthywater/swimming/protection/steps-healthy-swimming.html
3. http://globalhydration.com/resources/waterbone-disease
 4. http://www.aquatabs.com
5. http://water.epa.gov/learn/kids/drinkingwater/disinfection.cfm
 6. http://www.ntmwd.com/ozonation.html
 7. http://www.amwater.com/ilaw/water-quality-&-stewardship/chloramination-faq.html#q1
8. https://www.youtube.com/watch?v=vtLHcd3fDTk
 9. https://www.youtube.com/watch?v=QGpyD1maXqc
10. http://tap.unicefusa.org
11. http://d22r54gnmuhwmk.cloudfront.net/photos/1/tn/rg/gltnrGMwxHUtHpp-556x313-noPad.jpg 12. http://articles.waterdesalinationplants.com/wp-content/uploads/2011/11/children-dirty-water_jpg.jpeg
13. http://www.cdc.gov/parasites/images/crypto/cryptosporidium_lifecycle.gif

Friday, April 4, 2014



This Ain't A Scene, It's An Evo-Lutionary Arms Race 

The Cold War Heats Up1

 It's 1947 in post World War 2 Germany; Russia tightens its grip upon Berlin and blockades its former Allies from East Berlin.2 Tension rises between the Russians and allies. America announces the Marshall Plan, offering support to a recovering Europe, starting with reviving the industries of Germany. Stalin responds by extending the reach of his power by creating the Eastern Bloc, a coalition of communist states in Europe that was led by the USSR, to prevent America from buying influence in Europe.3 The Cold War Begins; America is pitted against their former ally, the USSR, in a dash for power. With expanding the missile gaps, a race for space, and a number of heated stand-offs, the arms race of the Cold War was in full effect.4  This was one of the biggest stalemates in world history, lasting for years and changing the USSR and America to a completely different countries by its end. Through all but its threats, secrets, and world changing effects, it still pales in comparison to a larger, grander war, one involving virtually every being on the planet. Slowly changing them, evolving them over time into greater adapted animals, yet still keeping them in an evolutionary deadlock with their opponents. I'm talking about the arms race that is co-evolution. 

 Co-evolution? More like Co-re-EVIL-ution? Right?

Huh? Huh? Am I right? Am I right?5
 Horrible puns aside, co-evolution, the evolutionary arms race is a deadlock between predator and prey, each one trying to gain an evolutionary advantage over the other. Take the relation between the cheetah and gazelle for example. The cheetah, a predator adapted for stealthy and speed, against it a gazelle would be easy prey, if it were not for the gazelle’s own adaptations. Where cheetahs are designed for encountering prey, gazelles are designed for avoiding dangers.6 They are agile, have quick reflexes, and are fast, though not as fast as a cheetah. It seems as though the two are locked in a stalemate, but even with all their adaptations some gazelle fail to escape the feline speedsters, and it is this tip towards the one side of the scale that will stoke the fires of the evolutionary arms race. Over the years, as the weaker gazelles become prey to the cheetahs and the stronger, better adapted members survive, you begin to see a slow change in the population, maybe faster gazelles that can jump higher, run faster and farther, far enough to escape being fancy feast for a ferocious feline. This small advance now puts cheetahs at a disadvantage, and puts the task of developing better adaptations upon them.6 Through all this, though, the two continue to reach a constant balance. 

"Crouching Gazelle, Flipping Cheetah"7
 The Red Queen and The Race Of Our Lives

The cheetah becomes faster, the gazelle jumps higher. If this continues their adaptations will only grow bigger. In a million years we may have gazelles leaping through trees as if it were a kung-fu movie and cheetahs with claws so big, they can cut a tree down in one swipe. A constant progression, only to reach the same relation as before; there is a hypothesis for this type of co-evolution, appropriately named “The Red Queen Hypothesis.”6  “Now here, you see, it takes all the running you can do to keep in the same place,” says the Red Queen to Alice.8 This is seen in many animals of the animal kingdom, such as the cheetah/gazelle relationship, but also between us humans and one of our most influential predators, parasites. Their need to use us as a host is so great that we developed sex in order to try and fend them off, to some success.9 But even though we developed new weapons and defenses and combined our DNA to strengthen the next generation against them, they retaliated with their own set of adaptations.9,10 Better camouflage, new infection methods, hiding themselves from our immune systems all keep these microscopic predators a constant and relevant threat to us. If it were not for our human ingenuity creating medicines to help eliminate them, our position in this evolutionary arms race would put us far from grabbing gold. As it now stands right now, we're barely bronze.
Red Queen11


1 http://www.designer-daily.com/examples-of-american-cold-war-propaganda-2918
2 Miller, Roger Gene (2000). To Save a City: The Berlin Airlift, 1948–1949. Texas A&M University Press. ISBN 0-89096-967-1
3 http://eastgermany.info/plans.htm
4 http://www.coldwar.org/index.asp
5 http://fozmeadows.files.wordpress.com/2013/06/snappy-snake.png
6 Zuk, M. Riddled with Life: Friendly Worms, Ladybug Sex, and the Parasites That Make Us Who We Are. Orlando: Harcourt, 2007.
7 icanhasgif.com
8 Carroll, Lewis, and Ralph Steadman. Through the Looking Glass. New York: C. N. Potter; Distributed by Crown, 1973.
9 Kurtz,Joachim.Sex, parasites and resistance – an evolutionary approach. Zoology. 106, (4) 2003: 327–339.
10 Hillis, Daniel, W. Co-evolving parasites improve simulated evolution as an optimization procedure. Physica D: Nonlinear Phenomena. 42 (1–3) 1990: 228–234.
11 http://www.visembryo.com/story170.html

Thursday, April 3, 2014

Sexual Selection


 I Like Bright Feathers and I Cannot Lie

Wouldn’t it be a wonderful world if the boys were the ones who had the responsibility of wooing over a girl? Today it seems like girls are the ones who are expected to dress up, do their makeup every morning, and stay “bikini ready” just for the guys. I wish it were the other way around sometimes…It would be nice to just roll out of bed, wear my pajamas to class, and gain 20 pounds without anyone batting an eye. But wouldn’t it be even better if you did all these things ladies, and the boys just couldn’t get enough of you? This is the case in most animals, including birds. The male birds go to extreme lengths to mate with a female. They undergo selective pressures to get the chance to mate with a female[1]. Sexual selection causes the males to grow colored and ornate feathers to attract the females[1].

Dress to Impress [2]

Color-O-Meter

When thinking of ornately feathered birds, the peacock comes to my mind instantly. Look at that difference between the male and the female! Who knew that boys could look so much better than their female counterparts? For this blog post, I am going to take a few steps back and shed some more light on why so many male birds are prettier than the females. Charles Darwin developed a theory that explains this occurrence [3]. He proposed that the traits that increase survival in a species are favored by natural selection. On the other hand, traits that help a male win over females are influenced by sexual selection. Sexual selection is the cause of the brilliant feathers on a male peacock, the fiery red of a cardinal, and the red or orange on the crown of a house finch.
Male and Female Peacock [4]

The Special One

So why are the males the more colorful of the 2 sexes? This is because it is the MALES job to attract the female. The female can pick and choose over whichever male bird she fancies. That must be nice… You may be asking yourself why do bright colors or long feathers seem attractive to the females. Why don’t they just choose any ole bird? This is because the females know that the most attractive bird is most likely the healthiest and will pass on the “best” genes to her future offspring[3].
Birds of Paradise [5]

Walk the Walk and Talk the Talk

Bright lengthy feathers aren’t the only things female birds are after. They want a man that can be a great singer and exhibits a specific behavior they deem attractive. An interesting example of this is in the bowerbird species. The males create elaborate bowers (structures of various sizes) and decorate them to attract the females. Each bowerbird has a specific taste, and the male’s decoration displays their “personality”. Some like the shiny beetle wings, while other male bowerbirds may choose flowers or berries. The females drop by to check out the bowers and if they are impressed, the males get to copulate with the female[6].

Follow this link for a peak into the lives of a bowerbird mating ritual!http://video.nationalgeographic.com/video/weirdest-bowerbird

 
Male Bowerbird with decorated bower [7]

You Are the Only Exception

In some instances, the female bird can be more colorful and ornate than the males of the same species. In these species the males incubate and care for the young while the females fight over territory and mates. We understand that the more competitive of the two sexes tends to be the more brightly colored[3].

Conclusion

In many species of birds, males go through daily routines of prepping for the females whether that is arranging their feathers or testing their vocal chords. It is interesting to see the many ways sexual selection plays out in bird species. Males spend much of their time and energy growing out beautiful feathers, singing for hours, and “dancing” in some instances. If you are a man and think your girl expects too much of you, then remember that she never made you build a bower with aluminum cans, fungi, and leaves before the first date.


 References


 

Tuesday, April 1, 2014

Evolutionary Medicine: Darwin's Heel

Today [8]

It is a sunny 75 degrees outside, however the only things I can think about right now are Tylenol, Nyquil and my bed. Despite having a plethora of things to achieve today, my body decided to call it quits for the day, closing up my throat in between hoicks of phlegm while plaguing me with a headache and a desire for unnecessary sleep. I would tell you just how hot I am, but at the risk of sounding like a 65 year old chain smoker I will leave it to the thermometer. Oh great, it says 100.8 degrees. Now I have a fever, too? While these may be the common symptoms of the flu, my body may just be trying to tell me something…




Darwinian Medicine


Is this what we have become? [5]
We live in a busy and sometimes stressful world; therefore it is not surprising that any time we feel even slightly under the weather, we immediately attempt to treat the symptoms so that we may be able to return to our day to day lives as quickly as possible. No harm, no foul, right? Well it as it turns out…not always. Evolutionary medicine (also termed Darwinian medicine) is a relatively new medical practice that looks to our evolutionary history for answers to questions such as; why and how do we get certain maladies? and how can we help to prevent illnesses in the first place [1]? An interesting example given by Dr. Marlene Zuk in Riddled with Life is the ever-increasing problem of obesity. Zuk argues that we are chemically designed to keep on weight due to the chemical leptin. When stores are low, the mind tricks the body into thinking that it is starving and hence triggers hunger and immediately begins to store fat. Furthermore, our bodies may crave foods that are high in calorie content not because of flawed self-restraint, but rather as an evolutionary adaption to efficiently gain energy from as little food as possible. In a hunter-gatherer society where food was scarce and starvation a real threat, it makes sense that the body would need a backup plan for storing fat, and not one for shaving it off [1,2].


Why Am I so Hot?


Dipsosaurus dorsalis [6]
Looking at the process of natural selection to help explain the relationship between the body and disease (rather than seeing disease as a threat to an otherwise flawless body) allows physicians to infer when the body’s response to an illness may in fact be beneficial and not a side effect caused by the pathogen itself. Most people instinctively know that the fever is an indicator that something is wrong with the body. However, proponents of evolutionary medicine argue that getting a fever is the body’s response to infection, and that it may actually increase the production of cytokines to increase immunity [1]. Studies by the University of Michigan reveal that the lizard Dipsosaurus dorsalis is an ectotherm that actively seeks the hotter areas of a room when infected with sodium salicylate. What is even more astounding is that the lizards that were exposed to higher temperatures recovered faster from infection [3]. Though we are endotherms who produce our own heat and do not rely on external sources to warm our bodies up, these results can indeed be transferred to mammals as we do not change our behavior but our metabolism to overcome illness. Taking medication to reduce a fever can therefore put you at risk of silencing a helpful mechanism and therefore having a slower recovery.


What About the Other Symptoms?


Limit the spread of influenza by covering your mouth [7]
It is most important when applying evolutionary medicine to ask whether the symptom is the body’s defense or the pathogen’s offence. For example, the respiratory tract is lined with mucus that traps dirt and pollen. When the body recognizes an unusually high dose of pathogen, the body responds by producing extra mucus to prevent the invader from entering the body. If too much is produced and not expelled, the airways are stimulated and a cough results, expelling the excess mucus from the airways and keeping the lungs safe from contact [4]. However, coughing releases infected particles in the mucus and saliva which increases spread of the pathogen to other victims. Friend or Foe? While a tingling throat and fever may be annoying pre-cursors of the flu, we must realize that the cost of responding to a false positive is far less than the cost of not responding to a false negative [1]. This means that at any sign of an intruder, the body is ready for attack because it does not want to risk holding fire in case of ambush attack. So how do we know whether to treat symptoms or not? Essentially, the goal of evolutionary medicine is to discover without a doubt where the symptoms are coming from. As for me, I am going to make myself a cup of tea and crawl back in to bed.

Goodnight!

[1] http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1071402/
[2] Zuk, M. Riddled with Life: Friendly Worms, Ladybug Sex, and the Parasites That Make Us Who We Are. Orlando: Harvest, 2008. Print.
[3] http://jp.physoc.org/content/279/1/187.full.pdf
[4] http://www.adclinic.com/2012/04/cough-causes-and-tips/#.UztAtsJOXmQ
[5] www.zmescience.com
[6] www.wildherps.com
[7] http://www.theguardian.com/society/2010/dec/23/flu-surge-doctors-virus-children
[8] acurlygirlallthedaysofmylife.blogspot.com