Carnivorous Fungi Set Traps for Unsuspecting Nematodes

Posted on April 30, 2014 by Saad Ali Akhtar

Contributed by Saad A. Akhtar

Fungi and Nematodes

Whenever people take the time out of their day to wonder about some of the awesome things living in the vast glory of nature, they generally think of every creature except fungi and nematodes. Observant readers will realize my post concerns fungi and nematodes.

Don’t look at me like that. Those were great opening lines.

But wait, don’t leave! I’m here to talk about interesting fungi and the nematodes that they eat! Yes, the fungi I’m talking about eat living, breathing nematodes, and they do so by laying out traps. I promise they’re really cool!

In fact, Bill learns how cool fungi are when he finds himself in a pit of lava moments after he mocks them.

(Note that the picture above can be enlarged by clicking on it.)

Fungi of the species Arthrobotrys oligospora normally get their grub by taking in nutrients from dead organic material just like other, typical species of fungi. However, when the fungi find that there is little nitrogen in their environment, they gain the ability to detect the concentration of ascaroside secreted from the nematodes into the soil. By the way, ascaroside is a molecule that regulates development and behavior in nematodes. In other words, the fungi can eavesdrop on chemical communication held among their nematode prey. Yes, I know what you’re thinking and you’re absolutely right…

“Indeed, the majority of our employees are carnivorous fungi. Why do you ask?” – an NSA spokesperson

Then, when the fungi find a nematode, they decide to eat those juicy, wriggling worms instead of sucking up nutrients from the soil.

“But how do immobile fungi catch something that can move?,” asks one hypothetical reader. Well, dear reader, the fungi create adhesive networks in response to the amount of nematodes they detect in the soil. You can think of these networks as spider webs in that they stick to prey and prevent them from moving.

Yeah, like we needed any other creature that acted like these things.

An Evolutionary Misconception

Now, you may be thinking that the ability to detect nematodes is something that fungi can obtain throughout their lifetime. However, this notion is incorrect as only a population of individuals can change over time, not an individual itself. In other words, evolution occurs over time in a population and is not instantaneous.

What I’m really trying to say is that living things aren’t Pokémon.

A conceivable example disproving this misconception would involve a population of fungi containing carnivorous and non-carnivorous fungi. The carnivorous fungi would be able to obtain food when nutrients in the soil are scarce, while the non-carnivorous fungi would not be able to do so and end up dying during those difficult times. Thus, there would be more carnivorous fungi that could pass on their genes and produce carnivorous offspring. Over time, the fungal population would consist mostly of carnivorous fungi rather than non-carnivorous fungi. As you can see from this example, the fungal population evolved and became carnivorous as a whole while individual non-carnivorous fungi did not suddenly gain the ability to become carnivorous. If you think about it a little bit, this conclusion really does make a lot of sense.

Um, sorry to shatter your worldview.

Coevolution

A rather important topic that this system touches on is coevolution. Coevolution is where two populations from different species influence the evolution of the other population. For instance, the A. oligospora fungi population is able to detect a certain form of ascaroside but if the nematode population evolves to secrete another kind of ascaroside molecule, the fungal population could also evolve in response to that change. Thus, the fungi and nematode populations coevolve. Note studied have not tested whether the nematode and fungi populations were actually evolving in response to one another, but researchers have considered it to be a real possibility.

See, I told you guys I had interesting stuff to say!

I even have a complimentary dog picture for you all on your way out! Isn’t life great or what?

For more information, see:

Hsueh, Y., Mahanti, P., Schroeder, F.C., & P.W. Sternberg. 2013. Nematode-trapping fungi eavesdrop on nematode pheromones. Curr. Biol. 23(1): 83-86.

All images with exception of the second image are listed as free to reuse by Google. The second image is original artwork by the author.

From Lakes to Oceans: Speciation of Sockeye Salmon and Other Fishes

Posted on April 30, 2014 by Heng Cheng

Contributed by Heng Cheng

When you go to a zoo, an aquarium, or a botanical garden, you may wonder how nature created countless species. In fact, nature did not “create” species—species arose from a common ancestor through a process called speciation. Speciation can occur through a number of mechanisms. Among these, one mechanism that is widely seen is that populations of the same species diverge from one another because they use different resources in the environment. We called this ecological speciation. We are going to focus on ecological speciation here. Fishes in postglacial lakes provide excellent examples of how the use of different parts of the environment can lead to reproduction isolation then ultimately, speciation.

About 15000 years ago, lakes formed after ice disappeared over the northern part of North America and Eurasia. These lakes were mainly freshwater lakes. Some lakes connected to the ocean, which provided the opportunity for some fishes to go to the ocean. However, fish had different degrees of salt-tolerance–not all the fish were able to live in high salt concentrated ocean water. Only salt-tolerant fish were able to get to the ocean. From this point, fish utilized different habitats. Some used fresh water and some used salted water. This happened in the yummy sockeye salmon. One kind of sockeye salmon, anadromous sockeye salmon, spend their first two years in the lakes then swim to the ocean. In the ocean, they grow into a very big size. Another kind, kokanee salmon, stay in the lakes forever and remain a much smaller size. These two kinds of sockeye salmon are genetically distinct. DNA analyses demonstrate that kokanee salmon evolved from anadromous salmon. This sockeye salmon speciation was an example of sympatric speciation. They lived in the same place but they did not mate with each other.

Another example of ecological speciation can been seen in the European whitefish (Coregonus lavaretus) in Scandinavian lakes. Similar to the sockeye salmon, whitefish utilize different areas of the lakes that were ecologically different. To the extreme, some lakes have up to five ecologically different areas. As a result, whitefishes in these lakes developed into five different species: they have different sizes, consume different resources, and have different spawning sites and times, which lead to reproductive isolation, just like the sockeye salmon.

To read more, see:

Schluter, Dolph. 1996. Ecological Speciation in Postglacial Fishes. Philosophical Transaction of The Royal Society B.Biological Sciences 351(1341): 807-814.

Fahlman, Johan. 2014. Size selective predation of pike on whitefish: The effects on resource polymorphism in Scandinavian whitefish populations. Umeå University. 13p.

The Plight of the Gummy Bears

Posted on April 30, 2014 by Joshua Lee

by Adrian Kinkead, Taara Rangan, Tiffany Liao, and Joshua Lee

The Basics of Gummy Bear Selection

Natural selection is a force that acts upon life on Earth, and works in tandem with evolution to produce fitter populations in a given environment. We often think of evolution as a linear phenomenon, but it is more accurate to think of it as a branching tree of trial and error. The idea that a structured process of adaptation is appealing to us; it imposes an attractive order on the natural world. But the challenges of survival are also arbitrary, meaning the strongest and the fastest don’t always have the advantage in the face of a novel threat.

Imagine a population of gummy bears, living together on their red planet.

Against this red background, the red bears are not easily seen to the eyes of the predators, but the other bears are not so lucky. Even though the red bears aren’t stronger, smarter, or faster than the others, selective pressures are random, meaning those attributes aren’t always relevant. It would follow that the majority of bears who were able to survive predation would be red.

However, life is always changing. Imagine that this red planet suddenly turned green as a forest sprang up overnight. Now, the red bears are very visible to predators. Shown no mercy, the red bear population would be easily reduced, while the green bears (who had clashed with the surface of their red planet) could blend instead.

It is easy to see natural selection as this locomotor that operates outside of the human world, but we are just as malleable to natural selection as any other species on Earth. For example, researchers at the Research Center for High Altitude Medicine found that Tibetans carry a mutation that allows them to thrive in elevations that would be burdensome on humans of other populations. When foreigners visit the summit of Mt. Everest, they must pace their elevation to allow for their blood cell count to increase in order to make up for the lower oxygen availability at that elevation. However, the observed blood cell count in Sherpas and the Tibetans remained at a baseline level. Furthermore, the study revealed that no difference in tissue oxygen concentration was observed either, despite the Sherpas and Tibetans being significantly stronger at those elevations. Researchers observed significantly higher levels of EPAS1 expression, and while the mechanism for its function is not known, they were able to confirm that this mutation accounts for the difference in physiological traits in the Tibetans and Sherpas (Simonson, et al.).

Gummy Bear Mimicry and Selection

But life isn’t just about colors. Imagine that a few of the bears developed a toxin in their bodies that cause painful stomachaches in their predators, and also produce a very bright red pigment. Predators would think twice before snatching up an easy catch of red bears and opt for other colors instead. Furthermore, the nonpoisonous red bears, despite being a duller red than their poisonous counterparts, also enjoy safety; their color is associated with discomfort and pain, causing the predators to ignore red bears altogether.

But the nonpoisonous gummy bears only receive such an advantage because the poisonous ones are so few and far between. If the poisonous ones become more numerous, predators would have an easy time of comparing the nonpoisonous red gummy bears to their brighter, redder counterparts. And so, the protection afforded to the nonpoisonous bears disappears. There may be a moment of hesitation, but predators will no doubt go back to preying on the hapless dull red gummy bears, leaving the poisonous ones alone.

This method of mimicry, known as Batesian mimicry, is not a perfect disguise however, as some predators can distinguish between dangerous and harmless prey. In a study conducted by researchers, Kraermer and Adams, they found that two salamander species, a model and mimic, would elude snake and mammal predators by color association alone. However, bird predators were able to distinguish between the palatable and toxic salamanders by their distinguishing patterns.

The organisms seen today are reflections of eons of environmental changes and selective pressures. Our DNA bears the markings and scars of cataclysmic events and relationships with other kinds of life around us. Natural selection explains the mechanism that allows organisms to evolve as a species. It acts on individuals to affect the whole, but it must be made clear that it does not evolve an individual specifically. It allows for the emergence of different attributes that can be passed on to future generations and define entire new species.

http://youtu.be/XS-pUWLtVe4

More resources on selection and mimicry can be found in:

Johnstone, Rufus A. “The Evolution of Inaccurate Mimics.” Nature 418.6897 (2002): 524-26.

Kraemer, Andrew C., and Dean C. Adams. “Predator Perception Of Batesian Mimicry And Conspicuousness In A Salamander.” Evolution 68.4 (2014): 1197-206.

Losos, Jonathan B., Thomas W. Schoener, and David A. Spiller. “Predator-induced Behaviour Shifts and Natural Selection in Field-experimental Lizard Populations.” Nature 432.7016 (2004): 505-08.

Morgans, Courtney L., and Terry J. Ord. “Natural Selection in Novel Environments: Predation Selects for Background Matching in the Body Colour of a Land Fish.” Animal Behaviour 86.6 (2013): 1241-249.

Skelhorn, J., and G. D. Ruxton. “Predators Are Less Likely to Misclassify Masquerading Prey When Their Models Are Present.” Biology Letters 6.5 (2010): 597-99. Print.

Simonson, T. S., Y. Yang, C. D. Huff, H. Yun, G. Qin, D. J. Witherspoon, Z. Bai, F. R. Lorenzo, J. Xing, L. B. Jorde, J. T. Prchal, and R. Ge. “Genetic Evidence for High-Altitude Adaptation in Tibet.” Science 329.5987 (2010): 72-75. Print.

Speed, Michael P., and Graeme D. Ruxton. “Imperfect Batesian Mimicry and the Conspicuousness Costs of Mimetic Resemblance.” The American Naturalist 176.1 (2010): E1-E14.

Are Humans Still Evolving?

Posted on April 29, 2014 by Kevin O'Neal Childress

Contributed By Kevin Childress, Ricardo Acevedo, and Crystal Seales

Can we be at the mercy of evolution?

A common misconception about evolution is that humans are no longer evolving. It’s very easy to think that because we seem to be the masters of the world around us, there is no need for the human species to be changing anymore. However, if we just look at some examples, we can see that humans are indeed not immune to the power of natural selection. For example, only certain human populations, mainly from pastoral/cow farming heritage, have the ability to digest milk at older ages. If you contrast those humans with humans from East Asia, you see that a large majority from East Asia cannot digest milk due to the lack of dairy in their ancestor’s diets. (For more information, see a recent post on lactase).

But let’s take a look at a more “drastic” example, the pygmy humans. They represent a population of humans around the world that have an unusually small body size that is well proportioned. They are found in certain African, Southeast Asian and South American populations, so they aren’t just an isolated group of people. The groups found in Central Africa are known to be the shortest humans on Earth! These pygmy populations tend to grow at a slower rate than other humans, and they normally stop growing at just 13 years old!

So why are they short? Well, genetic testing has shown that these groups evolved separately from one another. Currently, many hypotheses are being investigated. The most recent one is that this is an adaptation that allows the pygmies to stop growing at an earlier age, and thus reproduce at a younger age. This is plausible because less resources are put into their growth, allowing for more energy to be available to reproduce at an earlier age. Understandably, however, the hypothesis is highly debated. Others believe that earlier reproduction times and a smaller body size evolved to compensate for a lack of food and resources in their environment. A shorter stature could also help the pygmies navigate their surroundings and regulate their body temperatures more efficiently.

These hypotheses are an attempt by researchers to explain why the pygmy populations differ physically from the rest of the human species. Even though evidence doesn’t support a specific hypothesis at this time, the current data illustrates that evolution is a force that will continue to influence our species.

Check out our video on the topic!

https://www.youtube.com/watch?v=oYWNP0o5f00

For more info, see :

Migliano, A. B., Romero, I. G., Metspalu, M., Leavesley, M., Pagani, L., Antao, T., & T Kivisild. 2013. Evolution of the Pygmy Phenotype: Evidence of Positive Selection from Genome-wide Scans in African, Asian, and Melanesian Pygmies. Human Biology 85, 251–284.

Becker, N. S.A., Verdu, P., Froment, A., Le Bomin, S., Pagezy, H., Bahuchet, S. & E Heyer. 2011. Indirect evidence for the genetic determination of short stature in African Pygmies. Am. J. Phys. Anthropol. 145: 390–401.

Simmons, R.E., & L. Scheepers. 1996. Winning by a Neck: Sexual selection in the evolution of giraffe. The American Naturalist. 148: 771-786.

Migliano, A.B., L. Vinicius, & M.M. Lahr. 2007. Life history trade-offs explain the evolution of human pygmies. Proceedings of the National Academy of Sciences of the United States of America 104.51: 20216–20219.

Meazza, C., Pagani, S., & M. Bozzola. 2011. The pigmy short stature enigma. Pediatric Endocrinology Reviews. 8: 394-399.

Human Impact on Altered Behavior and Evolution of Species

Posted on April 29, 2014 by Brad William Richardson

Contributed by Brad Richardson

A common misconception about evolution is that it is only a theory; however, it is a fact. A fact is a truth known by actual experience or observation. Darwin’s Theory of Evolution by Natural Selection on the other hand is a theory much like the theory of relativity or gravity; it is a broad explanation of a particular phenomena that is proposed based on multiple observations and can be used to make predictions.

Many believe the theory is not testable or observable and that if it is true, it only happens over a very long period of time. However, human intervention via our technological advances such as city building and industrialization has led to an altered environment that is changing at an extreme rate. Although this can have either negative or positive consequences for varying species, one positive consequence for the human species is that it is allowing us to get a much better understanding of the scope and specificity of how evolutionary mechanism works.

Because of this accelerated rate of technological advance by humans, others species are having to adapt and evolve at an equally fast rate. This allows us to get a unique glimpse of evolution happening before our eyes. One of the biggest culprits is of course the effect climate change is having on all species, including our own. Various animals are breeding earlier in the spring, becoming smaller to keep their body temperatures in balance, and even completely moving their ranges away from the equator to avoid the heat!

Many changes are also occurring at the microscopic level due to technological advances in medicine. Antibiotic resistant bacteria have evolved to increase their chances of survival. The bacteria evolve and reproduce at such a fast scale that “superbugs” even exist which evolve resistance to the antibiotics that are usually given as an alternative to regular antibiotics.

Changes are happening all around us, which makes the Theory of Evolution such an interesting topic to study because every day species are changing and adapting and providing “natural” observable data that further bolsters the legitimacy of the theory.

Take a look below at some examples of observable evolution!

https://www.youtube.com/watch?v=fioFFtvEXBw

For more information check out:

Candolin U, Nieminen A, Nyman J. 2014. Indirect effects of human-induced environmental change on offspring production mediated by behavioral responses. Oecologia. 174: 87-97.

Janssens L, Khuong DV, Debecker S, Bervoets L, Stoks R. 2014. Local adaptation and the potential effects of a contaminant on predator avoidance and antipredator responses under global warming: a space-for-time substitution approach. Evolutionary Applications. 7: 421-430.

Sol D, Lapiedra O, Ganzalez-Lagos C. 2013. Behavioural adjustments for a life in the city. Animal Behaviour. 85: 1101-1112.

Nemeth Z, Bonier F, MacDougall-Shackleton SA. 2013. Coping with uncertainty: integrating physiology, behavior, and evolutionary ecology in a changing world. Integrative and Comparative Biology. 53: 960-964.

Martin J, Lopez P. 2013. Effects of global warming on sensory ecology of rock lizards increased temperatures alter the efficacy of sexual chemical signals. Functional Ecology. 27: 1332-1340.

Miranda AC, Schielzeth H, Sonntag T, Partecke J. 2013. Urbanization and its effects on personality traits: a result of microevolution or phenotypic plasticity?. Global Change Biology. 19: 2634-2644.

Evolution in Influenza

Posted on April 29, 2014 by Runako Alexis Aranha-Minnis

Contributed by Runako Aranha-Minnis

Evolution is not only limited to the organisms we are able to see with the naked eye. Viruses like influenza are able to evolve, and this can be very dangerous to human populations. Though it is true that influenza is not the danger that it once was, it still can not be ignored. Viral resistance to treatment can lead to many deaths globally, especially during flu seasons. During these times, doctors usually see a rise in cases of viruses resistant to the treatments available at the time. One type of resistance that influenza can develop is Oseltamivir resistance. Oseltamivir is an important antiviral defense against the flu. It is found in drugs like Tamiflu, and can be rendered ineffective if resistance is developed.

Influenza and its neuraminidase

The DNA change that in the virus that occurs is related to the neuraminidase enzyme activity. The enzyme cleaves salicylic acid moieties that can be bound by the viral hemagglutinin. In essence the enzyme’s job is to help release newly formed viral particles. Imagine the enzyme as little Pac-Men just going about and eating the connections of new virus particles to let them spread. Oseltamivir works by inhibiting the activity of the neuraminidase enzyme. This limits the infectiousness of the virus.

Resistance requires changes in the DNA of the virus. Mutations, changes in the DNA, can change genes, often leading to changes in the organism. For Oseltamivir resistance, a point mutation, the change of a single base of DNA, is all that is necessary. A change in the genes leads to a change in the amino acids produced. This change in the amino acids is just one amino acid at the 274th spot in the chain leads to a change in the activity of the virus. This line of reasoning is why the mutation is called H274Y.

The H274Y mutation that gives influenza resistance usually does not spread through the population. In early clinical tests, the mutation meant the virus was unaffected by oseltamivir, but had associated decreased viral fitness. So even though viruses with resistance would be selected for, their lower chance of survivability because of the mutation meant it did not matter. The influenza virus is able to evolve with Oseltamivir only when an associated mutation occurs. These associated mutations that allow oseltamivir resistance to keep going are permissive mutations. More recently, permissive mutations have arisen that allow influenza to be resistant to Oseltamivir without losing any fitness. Imagine a population of influenza like a game of “Where is Waldo?”:

No permissive mutations. In the absence of permissive mutations, all viruses, including Waldo, die.

With permissive mutations. If Waldo has a permissive mutation, he survives to reproduce and the whole populations becomes Waldos because all other viruses died.

Waldo in the first cartoon has H274Y with no permissive mutations. Without permissive mutations, there is no evolution under treatment. After treatment, the viruses are killed. There are no viruses left so the picture goes black. In the second cartoon, With permissive mutations, there is evolution for Waldo and a new viral population arises. This population only has Waldo because only Waldo has the H274Y mutation that conferred resistance.

For Further Reading:

Jesse D. Bloom, Lizhi Ian Gong, David Baltimore. 2010. Permissive Secondary Mutations Enable the Evolution of Influenza Oseltamivir Resistance Science. 328: 1272-1275

Nicholas Renzette, Daniel R. Caffrey, Konstantin B. Zeldovich, Ping Liu, Glen R. Gallagher, Daniel Aiello, Alyssa J. Porter, Evelyn A. Kurt-Jones, Daniel N. Bolon, Yu-Ping Poh, Jeffrey D. Jensen, Celia A. Schiffer, Timothy F. Kowalik, Robert W. Finberg, Jennifer P. Wang. 2013. Evolution of the Influenza A Virus Genome during Development of Oseltamivir Resistance In Vitro 88: 272-281

The Sad History of HIV and its Persistence against Drug Therapy

Posted on April 28, 2014 by Oliver Ting

Contributed by Oliver Ting, Jackson Fritz and Milan Patel

According to a report from the World Health Organization, human immunodeficiency virus (HIV) infected about 2.7 million new people in 2010 alone. Broken down, HIV destroys the immune system in humans, allowing opportunistic diseases to come in and kill the patient. HIV spreads through bodily fluid from person to person. Once inside a patient, HIV targets certain cells within the immune system called T-cells. HIV forces these cells to create new copies of the virus and destroys the T-cells in the process. As the virus grows exponentially, the immune system loses its ability to fight other diseases, leading to acquired immune deficiency virus (AIDS).

HIV cannot be cured. The main problem in creating a drug that treats HIV is that the virus is constantly changing. HIV is a retrovirus, meaning it uses RNA and then converts that into DNA when it infects cells. Retroviruses use an enzyme called reverse transcriptase to do this. However, unlike DNA enzymes, this enzyme cannot proofread itself, allowing more mutations (changes in the genetic code) to occur. This causes the virus to produce a base mismatch roughly every 10, 000–30, 000 bases during the replication. This differs significantly from regular viruses that typically have a range of one base mismatch per one million to one billion base pairs. When these base mutations occur in specific regions of the HIV DNA, new types or subtypes of the virus can be created. HIV builds up drug resistance because a drug that was effective for a previous variation of HIV may not be effective against a new variant of the virus. In addition, the virus builds cross-resistance, and becomes resistant to multiple types of HIV drugs within the same class. This further limits the number of drugs that can be used to treat the virus.

HIV is a prime example of evolution in action. HIV’s high rate of DNA mutation creates many variants. When HIV is selected against through antiviral drugs, certain variants survive that are resistant to the drug. These drug-resistant strains of HIV survive to reproduce and can be transmitted to other individuals. This constantly changing HIV population produces a substantial obstacle in trying to treat and eradicate the virus. Continued research is required to combat this evolving virus and improve the quality of life of those affected by HIV and AIDS.

Inspired by Radiolab “Patient Zero”, a fascinating tale about how HIV began, where it came from, and who “Patient 0” may have been. The podcast further reinforces how the virus has been able to combat so many challenges to its existence as well as it has.

Superbugs: The Evolution of Gonorrhea

Posted on April 28, 2014 by Kari Camille Tyler

Contributed by Nyasia Jones, Chris Richardson and Kari Tyler

https://www.youtube.com/watch?v=AesE046gtQs

A common misconception regarding evolution it that it is slow, and because it is slow, humans are not influencing it. This is completely false. Humans have and are continuing to make major changes that are not only influencing the course of our own evolution, but are also influencing the evolution of other species we interact with. Especially in medicine, human advancement is occurring at an amazing pace and thus allowing us to witness evolution in response to our actions.

Over the past century, the use of antibiotics to treat bacterial pathogens has become a widespread practice. Starting around 1930, medical practitioners began discovering several drugs that successfully rid patients of a particular bacterial pathogen Neisseria gonorrhoeae. The first successful therapy was administration of a class of chemicals called sulfonamides. For years, treatment with sulfonamides proved successful in patient after patient until about the mid-1940s when reports of N. gonorrhoeae resistance to sulfonamides increased. Fortunately, at this time, the “miracle drug” penicillin was found to be highly effective at bacterial treatment and become the number one treatment option. After ten to fifteen years though, low doses of penicillin were no longer as effective, and by the 1980s strains with high-level penicillin resistance had emerged.

So what happened with both penicillin and the sulfonamides? Nothing.

But something did happen to the N. gonorrhoeae. They evolved.

Sequential chromosomal mutations allowed some bacteria to incur resistance to penicillin. With penicillin treatment, the bacteria with resistance survived while those without it did not. The resistant individuals reproduced thereby creating a new generation of bacteria in which all individuals were penicillin resistant. This, my friends, is evolution.

Unlike the billions and billions of years it took to create modern-day humans, this evolution took less than a century to change these N. gonorrhoeae bacteria into “superbugs” which are becoming increasingly harder to treat. And it doesn’t stop there. N. gonorrhoeae has also become resistant to more recent treatment options, such as tetracycline and fluoroquinolones. Now, with less and less success to current methods of treatment, namely cefixime and ceftriaxone, scientists are worried history will repeat itself and strains of N. gonnorhoeae with complete cefixime and ceftriaxone resistance will emerge. With dwindling options for treatment, N. gonorrhoeae resistance and that of other superbugs remains a major problem in the fields of medicine and epidemiology.

So are humans influencing evolution? N. gonorrhoeae tell us, loud and clear: yes!

For more information:

Anderson, M. T., & Seifert, H. S. (2011). Neisseria gonorrhoeae and humans perform an evolutionary LINE dance. Mobile Genetic Elements, 1(1), 85-87.

Mavroidi, A., Tzelepi, E., Siatravani, E., Godoy, D., Miriagou, V., & Spratt, B. G. (2011). Analysis of emergence of Quinolone-resistant gonococci in Greece by combined use of Neisseria gonorrhoeae multiantigen sequence typing and multilocus sequence typing. Journal of Clinical Microbiology, 49(4), 1196-1201.

Unemo, M., & Shafer, W. M. (2011). Antibiotic resistance in Neisseria gonorrhoeae: Origin, evolution, and lessons learned for the future. Annals of the New York Academy of Sciences, 1230(1), E19-E28.

Forget Harry Potter… Check Out the Bobtail Squid’s Invisibility Cloak!

Aside

Contributed by Kelly Costopoulos, Taylor Werkema, and Nina Zook.

One of the most spectacular biological phenomena is an organism’s ability to luminesce. The light can be produced through chemical reactions in specific cells and even, in more rare cases, through a symbiotic relationship of an organism and unique bacteria. An extraordinary example of this is the cooperative relationship between the Bobtail squid and the bacteria Vibrio fisheri.

The Bobtail squid lives in the coastal waters off the Pacific Ocean and some parts of the Indian Ocean. During the day the squid buries itself in the sand and at night it comes out to hunt. The squid mimics the moonlight by using luminescent V. fischeri and eliminates its shadow on the ocean floor below to avoid predators. It’s nature’s own invisibility cloak!

This incredible act starts every morning when free living bacteria in the water are taken up by special light organs in the squid’s mantle. There, they are nourished by special cells that promote the growth of only V. fischeri, all other competitors are actively selected against. Once the bacteria population reaches a certain density, the bacteria produce light. The squid has the ability to control the intensity of light through specialized filters to match the moon’s light exactly. When the sun comes up in the morning, the squid expels the bacteria in a process known as venting, and the cycle starts over.

The video above gives a graphical representation of how the squid uses its invisibility cloak. As the moon comes out, the squid becomes luminescent and its shadow on the ocean floor disappears. This hides the squid from predators below.

The bobtail squid is only one of many squid species in the sepiolid family with V. fischeri symbionts. How did such an intricate symbiosis evolve in these squid species? Because both organisms can be easily cultured and raised in the laboratory setting, researchers can do evolutionary studies to shed light on how and why the sepiolid squid-V. fischeri system has evolved. Researchers have determined the relatedness between similar squid species and the relatedness of their symbiotic bacteria. Interestingly, the bacterial tree lines up with the squid tree, indicating that the squid and bacteria of each symbiotic pair have coevolved. This means that as squid species diverged from one another, so did their native bacteria such that the bacteria became more host-specific.

Evolutionary studies have also helped us understand how bacteria compete to establish symbiosis with the their squid hosts. Experimental competition, or raising a squid in the presence of two different bacteria, has shown that a squid’s native bacterial symbiont will outcompete nonnative strains. Further, the more closely related the nonnative strain is to the native bacteria, the more competitive it will be in inhabiting the squid’s light organ. Thus, the evolutionary history of sepiolid squid species and their unique symbionts is one of fidelity and preference for the native strain with whom the squid has evolved intimately over time.

For more on the squid-vibrio system, check out:

McFall-Ngai, M. 2008. Hawaiian bobtail squid. Current Biology : CB, 18(22), R1043–4.

Nishiguchi, M.K., Ruby, E.G., & McFall-Ngai, M.J. 1998. Competitive dominance among strains of luminous bacteria provides an unusual form of evidence for parallel evolution in sepiolid squid-vibrio symbioses. Applied and Environmental Microbiology 64(9): 3209-3213.

O’Brien, Miles, and Marsha Walton. “Glowing Squid.” National Science Foundation. The National Science Foundation, 22 Nov. 2010. Web. 28 Apr. 2014.

Learning in Lizards

Posted on April 28, 2014 by edlake

Contributed by Elsa Lake

You may have heard about the relative intelligence of some animals, such as dolphins or chimpanzees. However, other animals are not just mechanistic beings. They too have individual variation, including variation in intelligence. An Australian lizard named the Eastern Water Skink (Eulamprus quoyii) was tested for variation in spatial learning performance. An enclosure was set up with a “safe” refuge and an “unsafe” refuge. The lizards were scared around the enclosure until they entered the “safe” refuge. If they entered the “unsafe” refuge, then the refuge was lifted and scaring the lizard resumed.The spatial learning task given to the lizards was learned by twice as many males as females.

Nature presents different challenges to males and females; males are more successful at passing on their genes if they mate with as many different females as possible, and females are more successful if they select males with the highest quality genes to mate with. It is suggested that males have more spatial challenges, such as location of rival males, to deal with, so males would be better at spatial tasks overall.

A “Boldness” Experiment. One refuge was designated the “hot” refuge, and the other the “cold” refuge. Lizards prefer the “hot” refuge because they are cold blooded, and need the external heat to warm up their bodies and get energy, similar to a person who wants to bask in the sun at the beach! However, in the experiment, the lizards were scared off the basking refuge into the “cold” refuge. Researchers measured the time it took for the lizards to return to their basking sites. “Bold” lizards were determined to be those that quickly returned to the basking site, and “shy” lizards took a long time to do so.

The learning task was also more likely to be learned in lizards who were shown to be either very bold or shy, but not likely in lizards with behavior somewhere in between the two extremes. It is suggested that the males in this species of lizard may have evolved so that these two different personalities serve different roles. Territorial lizards are known to actively defend against other males, while “floater” lizards travel from territory to territory in search of mates. These two strategies may be employed by “bold” and “shy” lizards, respectively, while a lizard with a personality in the middle cannot utilize either strategy effectively.

It’s amazing to see how evolution hasn’t caused all Eastern Water Skinks to be the same. There is individual variation in them, just like there is variation in our own personalities. This variation in personality causes us to have different interests, work different jobs, and in general live our lives differently, just as it has caused the male skinks to use different strategies for finding mates. Animals aren’t as different from us as one might think!

See the below papers for more information:

Carazo, P., Noble, D. W. A., Chandrasoma, D., & Whiting, M. J. 2014. Sex and boldness explain individual differences in spatial learning in a lizard. Proceedings of the Royal Society B: Biological Sciences, 281(1782).

Chittka, L., Skorupski, P., & Raine, N. E. 2009. Speed–accuracy tradeoffs in animal decision making. Trends in Ecology & Evolution, 24(7), 400-407.

Noble, D. W. A., Carazo, P., & Whiting, M. J. 2012. Learning outdoors: male lizards show flexible spatial learning under semi-natural conditions. Biology Letters, 8(6), 946-948.

Sih, A., & Del Giudice, M. 2012. Linking behavioural syndromes and cognition: a behavioural ecology perspective. Philosophical Transactions of the Royal Society B: Biological Sciences, 367(1603), 2762-2772.

Stapley, J., & Keogh, J. S. 2004. Exploratory and antipredator behaviours differ between territorial and nonterritorial male lizards. Animal Behaviour, 68(4), 841-846.

Titulaer, M., van Oers, K., & Naguib, M. 2012. Personality affects learning performance in difficult tasks in a sex-dependent way. Animal Behaviour, 83(3), 723-730.

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evolution and evolutionary biologists in the natural world

Monthly Archives: April 2014