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- September 6, 2010
- 08:29 AM
- 1,990 views
Ocean of Pseudoscience: Sharks DO get cancer!
by Christie Wilcox in Observations of a Nerd
The sea is a dark and often mysterious place, and it's no wonder that the fear and fascination with the marine world has led to more than a few inaccurate claims. The crew over at Southern Fried Science have decided that this week is all about busting pseudoscience and the myths that surround our ocean realm. As it turns out, I'd posted about one of these before. So here, in honor of Ocean of Pseudoscience week, is a repost busting the myth that sharks don't get cancer.
There are a lot of myths out there about the marine world, but by far the one that bothers me the most is the notion that sharks don't get cancer. This simply untrue statement has led to the slaughter of millions of sharks via the industry for shark cartilage pills, which are sold to desperate cancer patients under the false pretense that they can help reduce or cure their illness. Read the rest of this post... | Read the comments on this post...... Read more »
Brem H, & Folkman J. (1975) Inhibition of tumor angiogenesis mediated by cartilage. . J Exp Med, 427-439. DOI: 10.1084/jem.141.2.427
Langer R, & et al. (1976) Isolations of a cartilage factor that inhibits tumor neovascularization. Science, 70-72. DOI: 10.1126/science.935859
Lee A, & Langer R. (1983) Shark cartilage contains inhibitors of tumor angiogenesis. Science, 1185-1187. DOI: 10.1126/science.6193581
Luer CA, & Luer WH. (1982) Acute and chronic exposure of nurse sharks to aflatoxin B1. Federal Proceedings, 925. info:/
Horsman MR, Alsner J, & Overgaard J. (1998) The effect of shark cartilage extracts on the growth and metastatic spread of the SCCVII carcinoma. Acta oncologica (Stockholm, Sweden), 37(5), 441-5. PMID: 9831372
Miller DR, Anderson GT, Stark JJ, Granick JL, & Richardson D. (1998) Phase I/II trial of the safety and efficacy of shark cartilage in the treatment of advanced cancer. Journal of clinical oncology : official journal of the American Society of Clinical Oncology, 16(11), 3649-55. PMID: 9817287
Loprinzi CL, Levitt R, Barton DL, Sloan JA, Atherton PJ, Smith DJ, Dakhil SR, Moore DF Jr, Krook JE, Rowland KM Jr.... (2005) Evaluation of shark cartilage in patients with advanced cancer: a North Central Cancer Treatment Group trial. Cancer, 104(1), 176-82. PMID: 15912493
Lu C, Lee JJ, Komaki R, Herbst RS, Feng L, Evans WK, Choy H, Desjardins P, Esparaz BT, Truong MT.... (2010) Chemoradiotherapy with or without AE-941 in stage III non-small cell lung cancer: a randomized phase III trial. Journal of the National Cancer Institute, 102(12), 859-65. PMID: 20505152
Vickers, A. (2004) Alternative cancer cures: "unproven" or "disproven"?. CA: A Cancer Journal For Clinicians, 110-118. DOI: 10.3322/canjclin.54.2.110
Ostrander GK, Cheng KC, Wolf JC, & Wolfe MJ. (2004) Shark cartilage, cancer and the growing threat of pseudoscience. Cancer research, 64(23), 8485-91. PMID: 15574750
- August 24, 2009
- 05:19 PM
- 1,690 views
This Week's Sci-Fi Worthy Parasite: Leishmania spp.
by Christie Wilcox in Observations of a Nerd
Ah, the joys of a tropical getaway. There's warm, clear waters, soft, sandy beaches, and of course, a whole ton of amazing parasites waiting to gorge on your delicious flesh.Anyone who has traveled out of the US has been told horror stories of the disgusting creatures that await them. Take a nice trip to Brazil for some sightseeing, for example, and you might find yourself at the mercy of a small, intracellular protozoan parasite of the genus Leishmania. There are many species of Leishmania living all over the world, from Saudi Arabia to Texas. No one's entirely sure how the parasites ended up in such diverse locations, or where they originated, but wherever there are sand flies, there is Leishmania. Like many parasites, it has a fairly complicated life, full of developmental stages and alternate hosts. Here's a good explanatory figure:Leishmania is a fascinating parasite because it actively lives in our immune cells. First it must be injested by a sand fly, which feeds on human blood like a mosquito. Once inside the fly, it changes form and creates a very strange substance called "promastigote secretory gel." The gel serves a very important purpose - it blockades the gut of the sand fly. For the fly to feed during its next meal, it must throw up this gel, which, conveniently, carries the parasites into the human host. There, the parasites wriggle their way inside our macrophages and reproduce. In short, they takes our best anti-parasite weaponry and turn them into comfy homes. How it does this has been a question of scientists for years.What we have found is that first, the parasite does a fantastic job of playing dead. It tends to live inside apoptitic immune cells and use the fact that the immune system doesn't eat them right away to grow and reproduce in peace. But how do they get into cells in the first place? The most up to date research might just have some clues as to the amazing slight of hand pulled by the protozoans to get inside our immune cells. In a new paper published in PLoS Pathogens, researchers found that the strange gel used to transport the parasites into the human host does more than just aid transmission between fly and blood. Firstly, it attracts far more immune activity than the bite does, and in doing so, gives the parasite a wide variety of cell targets. But the gel does even more - it changes the immune cells' behavior. Instead of creating death-inducing nitrous oxide, the macrophages produce other compounds that the parasites can feed on. Once in our cells, Leishmania is hard to get rid of. The parasite causes a disease referred to as Leishmaniasis. There are three different types of leishmaniasis: cutaneous, visceral and mucocutaneous. In all cases, the parasite causes tissue damage, often in the form of ulcers or sores. In cutaneous or mucocutaneous forms, these sores are on the surface, and though disgusting, tend to clear up without too much danger to the person. Mucocutaneous is the worse of the two, though, as it leads to infections on the face and terrible disfigurement.But the disfigurement is nothing compared to the dangers of visceral leishmaniasis. It is the second-largest parasitic killer in the world (only topped by another protozoan parasite: malaria), responsible for about 500,000 cases each year worldwide, with around 10% proving fatal. What happens is that the parasite doesn't stay in the skin. It travels to the internal organs - the liver, spleen and bone marrow - and lives in the cells there. Infection can seem like many other illnesses at first; fever, weight loss, fatigue, anemia and enlargement of the liver and spleen are all signs of visceral leishmaniasis. The parasite itself rarely kills its host, but in living in immune cells, it opens the person up to secondary infections like pneumonia, tuberculosis, or bacterial infections. In a way, it is very similar to AIDS, depressing the immune system enough that even a common cold can be fatal. And if that's not enough to worry about, treatment can have an unfortunate side effect - pushing the parasite to the surface, causing disfiguring ulcers that are more pervasive than the cutaneous form of infection.Like so many other parasites, we have yet to find a way to vaccinate or prevent infection with Leishmania except for avoiding the bites of sand flies. As anyone who has tried to avoid mosquitoes knows, this is a hard thing to do, if not impossible, for people living where flies do.As for science fiction-worthiness, how's this: some suggest that Leishmania might have did in the dinosaurs. Researchers have successfully found ancient parasites in amber-preserved insects. There are even books on dino parasites. How could these little creatures have wreaked so much havoc? Well, some argue, they were new and invasive back then, and the reptiles didn't have the opportunity to evolve immune defenses. Massive outbreaks causing devastating population decreases and even localized extinctions could have seriously hindered dinosaur species. So it's possible that parasitic overrun might just have contributed to the fall of the great reptiles. Of course, other factors were also in play, but perhaps the parasites gave the final blow which kept dinosaurs from adapting to changing environments.Rogers, M., Kropf, P., Choi, B., Dillon, R., Podinovskaia, M., Bates, P., & Müller, I. (2009). Proteophosophoglycans Regurgitated by Leishmania-Infected Sand Flies Target the L-Arginine Metabolism of Host Macrophages to Promote Parasite Survival PLoS Pathogens, 5 (8) DOI: 10.1371/journal.ppat.1000555Poinar Jr, G. (2007). Early Cretaceous trypanosomatids associated with fossil sand fly larvae in Burmese amber Memórias do Instituto Oswaldo Cruz, 102 (5) DOI: 10.1590/S0074-02762007005000070
... Read more »
Rogers, M., Kropf, P., Choi, B., Dillon, R., Podinovskaia, M., Bates, P., & Müller, I. (2009) Proteophosophoglycans Regurgitated by Leishmania-Infected Sand Flies Target the L-Arginine Metabolism of Host Macrophages to Promote Parasite Survival. PLoS Pathogens, 5(8). DOI: 10.1371/journal.ppat.1000555
Poinar Jr, G. (2007) Early Cretaceous trypanosomatids associated with fossil sand fly larvae in Burmese amber. Memórias do Instituto Oswaldo Cruz, 102(5). DOI: 10.1590/S0074-02762007005000070
- May 4, 2009
- 10:39 PM
- 1,646 views
Climate change won't cause the largest spread of dengue fever - we will.
by Christie Wilcox in Observations of a Nerd
Of course, the climate change won't help, either. At least that is the claim of a new study published in PLoS Neglected Tropical Diseases. The researchers used computer models using ecological modelling ("GARP") to project the distribution of dengue fever's carrier, the mosquito Aedes aegypti, under today's climate and under climate change scenarios for 2030 and 2050 given published temperature...
[...]... Read more »
Beebe, N., Cooper, R., Mottram, P., & Sweeney, A. (2009) Australia's Dengue Risk Driven by Human Adaptation to Climate Change. PLoS Neglected Tropical Diseases, 3(5). DOI: 10.1371/journal.pntd.0000429
- May 27, 2009
- 09:00 AM
- 1,608 views
Like Taking Candy From A Baby
by Christie Wilcox in Observations of a Nerd
...err..well, not exactly. But it is a much easier way for a 45 ton sperm whale to get a quick bite to eat. This amazing footage of sperm whales (Physeter macrocephalus) shaking cod fishing lines 108 m deep off the coast of Sitka, Alaska, is the first ever of sperm whales feeding - albeit not on its usual prey, the massive squids of the deep sea. Most of the time, sperm whales dive to a staggering 900 to 2600 feet (that's up to half a mile or so deep) to catch their meals. At such depths, with no light and such a wide expanse, filming feeding is nigh impossible. But we do know that eating the massive, deep-sea squid is no piece of cake - scars on the heads of the whales tell tales of arduous battles between predator and prey. It's no wonder, then, that some sperm whales have found an easier route to food, thanks, begrudgingly I'm sure, to cod fishermen off Alaska. The long lines of black cod (Anoplopoma fimbria) just waiting to be plucked are a tempting target for a lazy but quick-witted sperm whale. This video captures this incredible feeding behavior, long thought to exist but never before shown.But the video does much more than just show how sperm whales steal the fishermen's catch. It reveals fascinating details about sperm whale echolocation and bioacoustics. What we do know about marine mammal sound production and function is most often from studies shallower species. The trouble is, sperm whales are unique when it comes to head anatomy. Unlike other odontocete species, they don't have a "melon" structure (in yellow). Instead, they have two triangular sacs, one atop the other. The lower sac, referred to as "junk", is filled with a very dense oil and is likely derived from the melon. But the upper sac is unlike any other melon. It's filled with a lighter, waxy substance called "spermaceti". While this strange two-sac complex seems to have functions in diving and fighting, it's also presumed to play a large role in sperm whale acoustics, as it replaces the melon found in other, similar whales.Previously, recordings of sounds had been correlated to total body length that was estimated when the animal surfaced. From these data, scientists had come up with two different equations that estimate sperm whale body length from what is called the "inter-pulse interval" (IPI), or the time between clicks. But no studies were able to compare the size of the whale, its IPI and the size of its spermaceti organ and junk sac, as the sizes of these organs wasn't directly measured at the same time as the length and sounds. Other studies have tried to model how the spermaceti and junk organs relate to sound, finding equations which estimate their length based on the distance between an initial and a full sound of a click, presumed to relate to how the sound bounces off and around the two sacs.The video, caught by scientists from Scripps and the University of Alaska, was used to examine the relationship between sperm whale's anatomy and the sound it produces in a paper published in The Journal of the Acoustical Society of America. Because the hungry thief was oriented perpendicularly to the camera as it contacted the longline and scientists knew how far away it was from the camera, they were able to estimate the total length of the whale as well as the size of its spermaceti organ. They wanted to compare the sizes with the sounds produced to see if they matched what scientists had previously predicted.The real-time audio and video gave the scientists a unique opportunity to see if models of acoustic creation, made from examinations of dead whales and recorded sounds without direct video to compare to, were accurate. By comparing the actual sizes with the predicted sizes based on the sounds produced, the researchers were able to see how well the current model of sound production in sperm whales actually describes reality. They found that when it comes to body length, the models which utilize sound to estimate length are spot on. The animal's body length was estimated to be between 13 and 16 meters by both sound models using two IPI choices, which fell well within range of the roughly 15 m estimate given by four anatomical models: two which utlize the snout, one using the distance from the blowhole to the eye and one based on the size of the teeth. But the acoustic models were not nearly as accurate when it came to the sound-related organs, the spermaceti and the junk. By sound alone, the researchers estimated the spermaceti to be about 5.5 m long, but this number is a good 2.1 m longer than the visual estimate. The acoustics also estimated the junk to be close to 3.1 m long - which is odd, considering the 5.5 m estimate for the spermaceti. Biologically, that difference is too large - the two organs are always much more similar in length. Combined, what these data mean is that while IPI can be used to determine a sperm whale's size, the assumption that the sound the animal produces can be used to determine the length of the spermaceti organ is off. This, in turn, means that the way in which we think sound travels and propagates from a sperm whale's head may be off as well, and that there's something going on that scientists are missing about how the sperm whale produces and receives sound. So a simple, neat behavioral video has opened the door to a much better understanding of sperm whale anatomy and acoustics. Mathias, D., Thode, A., Straley, J., & Folkert, K. (2009). Relationship between sperm whale (Physeter macrocephalus) click structure and size derived from videocamera images of a depredating whale (sperm whale prey acquisition) The Journal of the Acoustical Society of America, 125 (5) DOI: 10.1121/1.3097758... Read more »
Mathias, D., Thode, A., Straley, J., & Folkert, K. (2009) Relationship between sperm whale (Physeter macrocephalus) click structure and size derived from videocamera images of a depredating whale (sperm whale prey acquisition). The Journal of the Acoustical Society of America, 125(5), 3444. DOI: 10.1121/1.3097758
- February 5, 2009
- 12:48 PM
- 1,607 views
A new link in the chain of whale evolution
by Christie Wilcox in Observations of a Nerd
Paleontologists have found a new fossil of a whale ancestor - and its announced just after I finish watching my preview DVD of Nat Geo's Morphed on whale evolution. I smell fate.Anyhow, the new whale predecessor was unveiled in a PLoS One article this week. Donned "Maiacetus inuus", the species is described from two adult fossil finds, and reveals even more about whales evolved.Maiacetus inuus is a new species of Protocetid whale, roughly 2.6 m long and dated to be about 47.5 million years old. Like other Protocetids, Maiacetus' limbs are relatively short and pelvic girdles provide a direct connection to the vertebral column...Ok, I know, I might as well be speaking gibberish. Let's go back a step.Whales, once upon a time, began as land mammals. The earliest definitive ancestor is Pakicetus, which, if you look at the image, really looks nothing like a whale at all. It more closely resembles some small hyena-like creature, though it's got hoofed feet like an ungulate, making more like some carnivorous antelope. The only thing, in fact, which makes it a "whale" is its ears - there's a bone that's only found in the Cetaceans (whales - you'll get it).This small, meat-eating wolf-cow somehow (technically, there's a bit of an argument on this) led to a group of animals known as the Ambulocetids and Remingtonocetids. These were much more like modern otters - they were clearly semi-aquatic, but also definitely relied on freshwater and land. Their nasal openings are on the top of the snout, like in land mammals, they had legs adapted for swimming, and bone tests of one fossil find, the crocodile-looking Ambulocetus, found residues distinctive of fresh water, meaning they hadn't yet moved into the oceans. Finally we get to the Protocetids. The protocetids were more aquatic than their predecessors, finally marine, though they still utilized the land. It's in this group where the hind legs begin to dwindle, that they develop underwater hearing, some begin to have tail flukes, and generally start looking more like whales by the end (like Protocetus, on the left). They still have limbs that, while good for swimming, are able to bear weight. And we arrive at Maiacetus - somewhere in the middle of the Protocetids.In the case of Maiacetus, the proportions of the limbs and long 'fingers and toes' would have made it clumsy on land, much like a seal, so it was probably mostly aquatic. The male had 20% larger canines than the female. Large canines are usually found in male mammals that use these teeth for threat displays and fighting, so it's possible that these were used like that, though little is known about mating behavior even in living marine mammals, and the size difference between the female and male was small, so they could have lived in mixed-sex groups. The most iteresting part, though, isn't the two adult skeletons that were found. The female was pregnant. The baby's skeleton is still inside its mother's! The fetus was well-developed and looked much like its mother and had a full set of teeth, meaning it was likely "precocious", or relatively mature and mobile from the moment of birth, like modern baby dolphins and whales. It is positioned head downward, like a human baby. There's only one problem with that - in living cetaceans, all babies are born tail first, not head first. This works well in aquatic species, because it makes sure that the baby doesn't try to take a breath before its mother can get it to the surface. So the head down posture of the fetus suggests that Maiacetus gave birth on land, not in the water.This means that at one point during their evolution, whales may have filled a niche similar to modern seals and sea lions. Or, perhaps, that one day modern seals and sea lions might become fully aquatic. Anyhow, finding a pregnant fossil is an incredibly rare and lucky find, and in my opinion, awesome one. Be sure to check out the article - it's got some great images and some really interesting information. I swear, I need to become a paleontologist!Philip D. Gingerich, Munir ul-Haq, Wighart von Koenigswald, William J. Sanders, B. Holly Smith, Iyad S. Zalmout (2009). New Protocetid Whale from the Middle Eocene of Pakistan: Birth on Land, Precocial Development, and Sexual Dimorphism PLoS ONE, 4 (2) DOI: 10.1371/journal.pone.0004366trackback to the article... Read more »
Philip D. Gingerich, Munir ul-Haq, Wighart von Koenigswald, William J. Sanders, B. Holly Smith, & Iyad S. Zalmout. (2009) New Protocetid Whale from the Middle Eocene of Pakistan: Birth on Land, Precocial Development, and Sexual Dimorphism. PLoS ONE, 4(2). DOI: 10.1371/journal.pone.0004366
- April 17, 2009
- 11:41 AM
- 1,547 views
Hawaiian monk seals give inbred a whole new meaning
by Christie Wilcox in Observations of a Nerd
Cheetahs are thought of as unfortunate examples of how genetics can be devastating. After a population bottleneck 10,000 years ago 1, cheetahs have become so closely related that it's said you can use skin grafts from any two individuals without rejection. To put that in perspective, your own immediate family is probably too genetically distinct to do that for you. But cheetahs look like they're in great shape compared to Hawaiian Monk Seals, new research from the University of Hawaii has found.
Hawaiian monk seals (Monachus schauinslandi) were known to the native Hawaiians as...
There's more... go to my site to read the rest!... Read more »
Schultz, J., Baker, J., Toonen, R., & Bowen, B. (2008) Extremely Low Genetic Diversity in the Endangered Hawaiian Monk Seal (Monachus schauinslandi). Journal of Heredity, 100(1), 25-33. DOI: 10.1093/jhered/esn077
- February 15, 2009
- 10:35 AM
- 1,511 views
Darwin's Degenerates - Evolution's Finest
by Christie Wilcox in Observations of a Nerd
If I ask you what group of organisms is an exhibition of evolution at its finest, what would you say? Most people, I think, would say human beings, or at least apex predators. After all, we have staggering intellect compared to our prey items and clearly dominate the planet, eat what we will, etc. Not only that, we're insanely complex. Ask some scientists, and they might give you any number of answers. Cockroaches are likely to exist long after we do, as are rodents, so maybe they get the title. Or, being scientists, they might be biased to whatever organism they study. Maybe algae and plants, as the sustenance for all other life. But all of you, in my humble opinion, are wrong. That is, unless you choose parasites.It's ok if you don't believe me yet. Darwin wouldn't have, either. He and his contemporaries viewed parasites as degenerates who, at best, violated the progressive nature of evolution. Even in The Origin of Species, Darwin refers to parasites as regressive instead of progressive. But truly, no group of species is a better choice for evolution's finest.Soybean Nematode and EggFirst off, let's talk numbers. Parasitism is the most popular lifestyle on earth - over 40% of all known species are parasitic, and the number of parasitic species rises daily1. Sure, you might say, but they tend to be small. In that case, let's talk biomass - weight, just to be clear. One group of parasites, the flukes, have been found to be equal in weight to fish in estuarine habitats, and three to nine times the weight of the top predators, the birds - estimates which are thought to be conservative for the earth as a whole2. Though they're largely ignored when we study food webs, they've been estimated to be involved in over 75% of inter-species interactions1. Clearly, by the numbers, they are the most prolific and successful organisms on earth.But even that is not why I would argue they are evolution's finest. They, more than any other group out there, both exhibit extreme evolutionary adaptations and spur them onward in other species. Toxoplasma gondiiNo matter how complex or how impressive any other species may be, it has parasites. We do - lots, actually. Every species we might hold as a masterpiece of evolutionary complexity cannot out maneuver their parasites. Not one. Even parasites, marvelous as some are, have parasites - like a crazy russian doll. They have evolved amazing abilities to survive host defense systems, manipulate host behavior and boost heir own reproductive success. They've even been implicated in major cultural differences in people. It turns out that a rat parasite, Toxoplasma gondii, needs to be eaten by a cat to complete its lifestyle. Somehow it developed a trick to make rats unafraid of cat smells. When it accidentally ends up in people, it does the same kind of mind-altering, making people more guilty and insecure, even more frugal, mild-tempered, and complacent3. Other parasites do far more intricate manipulations of behavior, turning males into females, creating walking zombies, even forcing suicide. If parasites can not only break into and survive the most complex assortments of systems available, even with modern medicine fighting against them, and manipulate those complex organisms to slave to their bidding, how can we not credit them as masters at what they do?left: Malaria and red blood cells. © Prof David Fergusonright: Haemonchus contortus.But even more impressively, I would argue, is that no other group has so dramatically impacted how other species have evolved. They don't just affect their hosts immune systems, either. If you read much into evolutionary theory, you realize it's riddled with parasites. Why are some birds very colorful? Oh, because if they've got a lot of parasites they can't be, so it's a signal of a healthy male4. Why are we attracted to certain people? Because their immune genes are different from ours, giving our children the best chance to fight off the next generation of parasites. Almost everywhere you look, evolutionary changes are spurred on by parasites. It's even suggested that sex itself evolved as a response to parasites. It's a way of better shuffling our genes so that we have better odds at fighting off parasites. Leishmania amazonensisEven we, as "ideal" or "complex" as we are, owe much to parasites. Some even argue that we are worse off without them. The argument, as it goes, is that our immune system evolved in the presence of unkillable parasites, particularly the parasitic worms. These worms, or Helminths as they are called as a group, were too costly to try and eradicate. Attacking foreign invaders, after all, is energetically expensive, and always runs the risk of over-activating our immune system, leading to self-inflicted injuries and diseases. So the best strategy, instead, was to have an immune system that functioned optimally against other issues, like the fatal viruses or bacteria, despite the mostly benign worm infections5. Since worms secrete anti-inflammatory compounds to fight off our defenses, we were better off with systems that overcompensated for that. Now, since we have drugs which kill them off, our immune system is out of balance. Many cite the rising rates of auto-immune and inflammatory diseases like allergies, arthritis, irritable bowel, type 1 diabetes, and even cancer in developed nations as evidence that ridding ourselves of helminths has damaged our health6. They're backed up with multiple studies that show unexpected results, like that mice genetically predisposed to diabetes never develop it if infected with flukes at an early enough age.7Parasites are uniquely capable of out-evolving their hosts and adapting to whatever changes go on in them. Simply put, they evolve better. They change their genes faster and keep up with a barrage of host defense systems, often like it's effortless, spurring onward dramatic changes in other species. If Darwin had only known how amazingly complex the barriers these creatures have to overcome and the extent to which they have affected the species he'd encountered on his travels, he would not have labeled them "degenerates". As far as evolution is concerned, no group of species demonstrates it, causes it, and is so capable of it as the parasites. While disgusting or even cruel, they are truly evolutionary masterpieces. So while you may find them vile or detestable, you have to admit they're good at it. Can you really argue that some other group is more deserving of the title of Evolution's Finest?Cited:1. A. Dobson, K. D. Lafferty, A. M. Kuris, R. F. Hechinger, W. Jetz (2008). Colloquium Paper: Homage to Linnaeus: How many parasites? How many hosts? Proceedings of the National Academy of Sciences, 105 (Supplement_1), 11482-11489 DOI: 10.1073/pnas.08032321052. Armand M. Kuris, Ryan F. Hechinger, Jenny C. Shaw, Kathleen L. Whitney, Leopoldina Aguirre-Macedo, Charlie A. Boch, Andrew P. Dobson, Eleca J. Dunham, Brian L. Fredensborg, Todd C. Huspeni, Julio Lorda, Luzviminda Mababa, Frank T. Mancini, Adrienne B. Mora, Maria Pickering, Nadia L. Talhouk, Mark E. Torchin, Kevin D. Lafferty (2008). Ecosystem energetic implications of parasite and free-living biomass in three estuaries Nature, 454 (7203), 515-518 DOI: 10.1038/nature069703. Kevin D. Lafferty (2006). Can the common brain parasite, Toxoplasma gondii, influence human culture? Proceedings of the Royal Society B: Biological Sciences, 273 (1602), 2749-2755 DOI: 10.1098/rspb.2006.36414. Jesús Martínez-Padilla, François Mougeot, Lorenzo Pérez-Rodríguez, Gary R. Bortolotti (2007). Nematode parasites reduce carotenoid-based signalling in male red grouse Biology Letters, 3 (2), 161-164 DOI: 10.1098/rsbl.2006.05935. Joseph A. Jackson, Ida M. Friberg, Susan Little, Janette E. Bradley (2009). Review series on helminths, immune modulation and the hygiene hypothesis: Immunity against helminths and immunological phenomena in modern human populations: coevolutionary legacies? Immunology, 126 (1), 18-27 DOI: 10.1111/j.1365-2567.2008.03010.x6. Joel V. Weinstock, David E. Elliott (2009). Helminths and the IBD hygiene hypothesis Inflammatory Bowel Diseases, 15 (1), 128-133 DOI: 10.1002/ibd.206337. Anne Cooke (2009). Review series on helminths, immune modulation and the hygiene hypothesis: How might infection modulate the onset of type 1 diabetes? Immunology, 126 (1), 12-17 DOI: 10.1111/j.1365-2567.2008.03009.x... Read more »
A. Dobson, K. D. Lafferty, A. M. Kuris, R. F. Hechinger, & W. Jetz. (2008) Colloquium Paper: Homage to Linnaeus: How many parasites? How many hosts?. Proceedings of the National Academy of Sciences, 105(Supplement_1), 11482-11489. DOI: 10.1073/pnas.0803232105
Armand M. Kuris, Ryan F. Hechinger, Jenny C. Shaw, Kathleen L. Whitney, Leopoldina Aguirre-Macedo, Charlie A. Boch, Andrew P. Dobson, Eleca J. Dunham, Brian L. Fredensborg, Todd C. Huspeni.... (2008) Ecosystem energetic implications of parasite and free-living biomass in three estuaries. Nature, 454(7203), 515-518. DOI: 10.1038/nature06970
Kevin D. Lafferty. (2006) Can the common brain parasite, Toxoplasma gondii, influence human culture?. Proceedings of the Royal Society B: Biological Sciences, 273(1602), 2749-2755. DOI: 10.1098/rspb.2006.3641
Jesús Martínez-Padilla, François Mougeot, Lorenzo Pérez-Rodríguez, & Gary R. Bortolotti. (2007) Nematode parasites reduce carotenoid-based signalling in male red grouse. Biology Letters, 3(2), 161-164. DOI: 10.1098/rsbl.2006.0593
Joseph A. Jackson, Ida M. Friberg, Susan Little, & Janette E. Bradley. (2009) Review series on helminths, immune modulation and the hygiene hypothesis: Immunity against helminths and immunological phenomena in modern human populations: coevolutionary legacies?. Immunology, 126(1), 18-27. DOI: 10.1111/j.1365-2567.2008.03010.x
Joel V. Weinstock, & David E. Elliott. (2009) Helminths and the IBD hygiene hypothesis. Inflammatory Bowel Diseases, 15(1), 128-133. DOI: 10.1002/ibd.20633
Anne Cooke. (2009) Review series on helminths, immune modulation and the hygiene hypothesis: How might infection modulate the onset of type 1 diabetes?. Immunology, 126(1), 12-17. DOI: 10.1111/j.1365-2567.2008.03009.x
- January 6, 2009
- 09:11 AM
- 1,506 views
This Week's Sci-Fi Worthy Parasite
by Christie Wilcox in Observations of a Nerd
Many parasites alter their hosts behavior by small manipulations in the brain that go largely unnoticed by the host until its eaten by another. But not all use so much finesse. This week's parasite is probably the rudest as far as mechanisms go - luckily, their hosts are cockroaches, so we don't hold it against them.I'm talking about the Emerald Cockroach Wasp. As with many parasitic wasps, it needs to inject its eggs into the host to incubate. When the eggs hatch, they'll feed on the host, cocoon, and emerge adult wasps. But most parasitic wasps paralyze their hosts and drag the bodies somewhere to feed the soon-to-be-born young. Such forethought would be considerate compared to the behavior of the Emerald Cockroach Wasp.You see, the Emerald Cockroach Wasp is rather small compared to most parasitic wasps, and can't really "drag" its victim anywhere. Instead of paralyzing the cockroach, the wasp injects venom into its host cockroach which cause the insect to lose its front limbs (specifics, here). This causes the roach to bow head down, exposing its ganglion. The wasp then stings again, aiming for the brain. It was found in 2007 that the venom actually blocks the neurotransmitter octopamine. This effect is so precise that the cockroach's survival instincts are turned off, but its motor capabilities (like walking) are left unimpaired. After the initial paralysis is over and the roach has been essentially zombified, the wasp chews off parts of the roach's antennae and uses them like a leash to lead the roach to a burrow. It then fills the backside of the roach with eggs and seals them both in. The roach, still alive (as roaches can live for a long time without eating), simply rests with no desire to escape, until the larvae hatch. The larvae then begin eating the hosts organs, one by one in a systematic manner that keeps it alive the longest, so that the fresh fuel lasts long enough for the larvae to form a cocoon. Only then does the roach, in a totally wasted state, have the bliss of death.Interestingly enough, the Emerald Cockroach wasp was introduced to Hawaii as an attempt to biocontrol the cockroach population. Unfortunately, the wasps are highly territorial and need very few cockroaches to sustain themselves, so the attempt was ineffective.Anyhow, here's a little video I found of the behavior...For more info, check out the links embedded or this article: R GAL, F LIBERSAT (2008). A Parasitoid Wasp Manipulates the Drive for Walking of Its Cockroach Prey Current Biology, 18 (12), 877-882 DOI: 10.1016/j.cub.2008.04.076... Read more »
R GAL, & F LIBERSAT. (2008) A Parasitoid Wasp Manipulates the Drive for Walking of Its Cockroach Prey. Current Biology, 18(12), 877-882. DOI: 10.1016/j.cub.2008.04.076
- January 7, 2009
- 09:06 AM
- 1,462 views
Tetris good for more than wasting time
by Christie Wilcox in Observations of a Nerd
Ok, I simply had to post about this new study from PLoS ONE because my boyfriend, Barry, absolutely loves the game Tetris. Anyhow, new research has found that Tetris can help treat PTSD flashbacks, which is pretty cool for a really old, really simple video game.Read the rest of this post!Here's how it works. Your brain has limited resources and capacity. In other words, your brain can only process, remember and manage so much input at a time. When you see an image or perform a mental task, you have to put energy into it and resources. After witnessing a traumatic incident, part of your brain is allocating resources to that image, causing it to later reappear in flashbacks. So, hypothetically, if you could force that part of the brain to focus on something else, the flashbacks would lessen or completely stop.Of course, this is easier said than done. Finding the right activity which can act as a 'cognative vaccine' for such events is not easy. After all, it has to be involved and stimulating enough to warrant the brain power allocated to the stressful event. And anyone who has had even a glimpse of the kind of stressful event that can cause PTSD knows that "forgettting" the trauma and focusing on something else isn't that easy. Currently, vivid flashbacks are treated with psychiatry and drugs. However, the counseling often only occurs after a significant buildup of symptoms (like flashbacks) and the drugs don't just help rid you of flashbacks - they destroy your memory of the event all together. So if, say, you need to testify in court, you might have a problem. Some current methods of treatment have even been shown to worsen symptoms. Researchers from Oxford may have found a better way. They say that since flashbacks are sensory-perceptual, visuospatial mental images that tend to implant in memory somewhere between 1-6 hours after an event, you can disrupt them from ever forming by providing other sensory-perceptual, visuospatial mental images during that time. Their choice? Tetris.Tetris has been shown to occupy much of the same kind of memory that a flashback does. People even seem to 'relive' intense moments of Tetris play much later on - which, of course, I can totally vouch for. Who hasn't gone over and over 'if only I'd rotated that piece that way!'?So the researchers exposed people to a violent film depicting death and injury, then had them play Tetris or just sit there. Afterwards, they sat alone for 10 minutes, and reported any flashbacks to the film. Tetris, it turned out, significantly reduced the number of flashbacks. The subjects continued reporting flashbacks over a week long period, and the Tetris players continued to experience fewer flashbacks. Later, when subjects were tested on the film, both groups performed equally, so Tetris didn't impair voluntary memory of the trauma, just involuntary.Using this kind of 'cognitive vaccine' could reduce PTSD from all kinds of traumatic events, from fires to rape. Although, imagine, you walk out of a burning building, sit down, and the emergency worker hands you a DS to play for a few minutes before you're interviewed about the scene. It seems almost ridiculous, but it could really help a lot of people. Who'd have thought Tetris was so useful for anything other than wasting time?Emily A. Holmes, Ella L. James, Thomas Coode-Bate, Catherine Deeprose (2009). Can Playing the Computer Game “Tetris” Reduce the Build-Up of Flashbacks for Trauma? A Proposal from Cognitive Science PLoS ONE, 4 (1) DOI: 10.1371/journal.pone.0004153... Read more »
Emily A. Holmes, Ella L. James, Thomas Coode-Bate, & Catherine Deeprose. (2009) Can Playing the Computer Game “Tetris” Reduce the Build-Up of Flashbacks for Trauma? A Proposal from Cognitive Science. PLoS ONE, 4(1). DOI: 10.1371/journal.pone.0004153
- April 24, 2009
- 10:45 AM
- 1,454 views
Night owls - the energizer bunnies of society
by Christie Wilcox in Observations of a Nerd
I have to start work at 8 am every morning. I'm not sure exactly who decided that scientists should start early, but it seems to be a universal assumption. Throughout college my science classes were always first thing, and research efforts often seem to involve early morning work. But I've never really been a morning person. Last night is a great example: I had to clean up the house in preparation for Barry's brother coming to stay with us (which, with a dog and a cat and two messy people, is no small feat). We started when we got home and tackled room after room. As I looked up at the clock...
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Schmidt, C., Collette, F., Leclercq, Y., Sterpenich, V., Vandewalle, G., Berthomier, P., Berthomier, C., Phillips, C., Tinguely, G., Darsaud, A.... (2009) Homeostatic Sleep Pressure and Responses to Sustained Attention in the Suprachiasmatic Area. Science, 324(5926), 516-519. DOI: 10.1126/science.1167337
- April 22, 2009
- 01:03 PM
- 1,451 views
Are Conservation Efforts Harming Rare Species?
by Christie Wilcox in Observations of a Nerd
Since today is Earth Day, I've got all kinds of green, eco-friendly, conservation-type thoughts jumbling around in my head. I keep reading articles about how some rare alligator has a little hope or how some big rare fish got eaten, and thinking positively about the press surrounding our environment. All these daily, constant reminders about the status of species on the verge of collapse - this kind of awareness has got to be helping conserve those speices, right? But then I stumbled upon a PLoS ONE article that completely soured my mood.
Rarity of Tigers raises the value of their...
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Angulo, E., & Courchamp, F. (2009) Rare Species Are Valued Big Time. PLoS ONE, 4(4). DOI: 10.1371/journal.pone.0005215
- May 8, 2009
- 09:25 AM
- 1,431 views
Our effects are simple: the more people, the fewer fish
by Christie Wilcox in Observations of a Nerd
People are bad news for fish - yeah, we've known that for awhile. Just look at the decrease in size of catch off the Florida Keys from 1957 to the 1980s and 2007 (on right) and that conclusion is obvious. But, surprisingly, little research has been able to show how human populations affect a group of fish. Most studies focus on one type of fish or are contained to a small area because their...
[...]... Read more »
Stallings, C. (2009) Fishery-Independent Data Reveal Negative Effect of Human Population Density on Caribbean Predatory Fish Communities. PLoS ONE, 4(5). DOI: 10.1371/journal.pone.0005333
- March 30, 2009
- 09:47 AM
- 1,418 views
Biocontrol of Biocontrol?
by Christie Wilcox in Observations of a Nerd
One of the most controversial ideas in conservation is that of Biocontrol. The goal is to control invasive species or damaging pests by introducing predators/diseases/etc which kill them. Some attempts at biocontrol have been hugely successful. But others have been disastrous, like the introduction of Cane Toads.
Cane Toads (Bufo marinus) were introduced to a lot of places from 1840-1940 to attempt to control agricultural pests. Cane Toad extent
both native (blue)
and introduced (red)They were first unsuccessfully introduced into Jamaica to control the rat population. Then, a seemingly...
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Georgia Ward-Fear, & et al. (2009) Maladaptive traits in invasive species: in Australia, cane toads are more vulnerable to predatory ants than are native frogs. Functional Ecology. DOI: 10.1111/j.1365-2435.2009.01556.x
- June 7, 2009
- 06:02 PM
- 1,408 views
Conservtives more easily disgusted
by Christie Wilcox in Observations of a Nerd
Our emotions are strongly tied to our morals. We're more likely to think something is wrong if it repulses us, even if we can't describe exactly why or how it is wrong. For example, most people would disapprove of consensual adult incest between siblings, but few would be able to articulate exactly why it is 'wrong.' This is very different from moral beliefs deduced from reasoning. These moral intuitions, which are highly motivated by emotional response or learned associations, are quick and require little supporting evidence in the person's mind.Since emotions affect our morals, it easily follows that they affect our political beliefs. Two studies from Cornell University explored this relationship between disgust and politics and found a very interesting result: conservatives, particularly those that are conservative with respect to social issues like abortion and gay marriage, are more easily disgusted.Why do humans feel disgust in the first place? Many scientists believe it evolved as a way of avoiding disease or unhealthy things - rotting fruit, feces and urine, wounds oozing puss, etc. Our bodies naturally react with revulsion to things that carry disease, parasites, or risks to our health. Disgust is ubiquitous in people. All people show a very specific face when feeling disgust, and can readily identify that same face in others: a raised the upper lip and wrinkle the nose, for example. Feeling disgust and seeing it in others is hard-wired into our brains: people with Huntington's, a neurodegenerative disorder, cannot tell when others are disgusted and do not show disgust when presented with something revolting.So why do some of us feel disgust towards things that are not imminent health threats? No one's really sure. The assumption is that somehow our morals got tied into a much more primitive system (that of disgust). It's a phenomenon called preadaptation, where something that evolves for one purpose is later used for another. Think of feathers, for example. Many scientists believe that feathers evolved for displays or disguise, and only later were utilized in flight.Issues like gay marriage and abortion are heavily rooted in moral beliefs. So researchers from Cornell University wanted to know how disgust related to those political views. What they found was that conservatives, in general, are more easily grossed out and repulsed by things.To understand the link fbetween disgust and politics, Cornell researchers performed a few experiments. First things first, they wanted to show how the human face responds when disgusted. In the first study, published in Science, they gave participants foul drinks and had them view photographs of uncleanliness and contamination-related disgust stimuli, including feces, injuries, insects, etc. In both cases, participants responded with the clear, well-known face of disgust. They then had the participants play a game where they were treated unfairly to see if a moral situation provoked that disgusted facial expression. Sure enough, the same snarled lip expression occurred (Left). They even asked the participants afterward about their feelings, and offers that were rated as more disgusting were significantly associated with more activation of the levator labii region.But the researcher's didn't stop there. In another paper, published in the journal Emotion, the researchers further probed the relationship between disgust and morality. This time they had participants take the Disgust Sensitivity Scale (DSS), a psychological measure which quantifies a person's sensitivity to a variety of forms of disgust from core disgust (feces, etc) to blood and gore, and even unusual sexual practices (like incest). They then compared this to the participants self-reported religious affiliation and political views. High sensitivity to disgust significantly predicted conservative views on topics like abortion and gay marriage, a connection not explained by religious affiliation. The same was not true for other non-disgust related issues like affirmative action, labor unions or gun control.Even still, the researchers weren't done. Self reported data has its own flaws and faults - mostly, people lie or don't always represent themselves as they really are. So to test the connection between disgust and morality implicitly, the researchers designed a unique experiment (PDF). They had participants look at a scene. In it, a director appears to be encouraging two men or a man and a woman to kiss in public. They then took measures of disgust sensitivity. When asked if there was anything wrong with two men or straight couple kissing, the participants mostly said no. But when asked if the director intentionally encouraged the couples to kiss, those who were more sensitive to disgust were more likely to view the director's action as intentional when encouraging the gay couple - but NOT when encouraging the straight couple. This implicitly showed a bias against gay kissing even when the participants self reported as non-biased - a bias tied to their sensitivity to disgust in general.In short, conservatives, especially those who are conservative on disgust-driven moral initiatives like gay marriage or abortion, are more easily disgusted. Since disgust is, at least in part, rooted to genetics, its possible that a part of our political views are literally determined in our genes. The question is, how tied to our instinctive disgust system is this moral disgust? After all, it is the instinctive disgust which is in our genetics. A review of the article published in Science makes this note: Unfairness and other moral violations may directly affect the disgust output system, after processing by some other evaluation system, or these violations might simply activate the verbal label "disgust," which would then activate the disgust output system. The outcome of either route would include the facial expression of disgust. This means that while the data is convincing in tying disgust to political views, it doesn't say whether this disgust is innate, like repugnance of dirty toilets, or learned through our environments and merely hitchhiking on the disgust system. It's possible that the disgust shown and felt on moral issues comes from the word disgust being used to describe it, not from an inner sense of revulsion or morality. But if it is rooted deeper, it's entirely possible that our genes help determine our political views, even before we understand what a liberal or a conservative is. Even without cultural influences, it is likely that those who are easily grossed out or squeamish are more likely to be conservative on moral issues. Which makes sense, too, when we look at current moral stances. Many liberal viewpoints stress a logical understanding of the issue and a general "if it doesn't hurt another person, it's ok" attitude towards behaviors. Conservatives, on the other hand, press upon people to follow their instincts. Leon Kass, a noted conservative bioethicist, has argued for what he calls "the wisdom of repugnance" - that our natural aversion to something is evidence of its evil or wrongness. This different approach to defining 'right' and 'wrong' is at the center of disagreements between the two parties. I think research like this fascinating because it probes deep into our understanding of why we feel the way we do. So often we spend so much time focusing on why one animal does this or why another does that we forget that we, too, are animals. We neglect that, as complex as our intellect may be in comparison, we still are shaped by our genes and our environments. And I think understanding is key, especially when it comes to politics. If we cannot understand why people feel how they do, we can never truly decide what is right or wrong for our society and ourselves.Citations:1.... Read more »
Chapman, H., Kim, D., Susskind, J., & Anderson, A. (2009) In Bad Taste: Evidence for the Oral Origins of Moral Disgust. Science, 323(5918), 1222-1226. DOI: 10.1126/science.1165565
Inbar, Y., Pizarro, D., & Bloom, P. (2008) Conservatives are more easily disgusted than liberals. Cognition , 23(4), 714-725. DOI: 10.1080/02699930802110007
Inbar, Y., Pizarro, D., Knobe, J., & Bloom, P. (2009) Disgust sensitivity predicts intuitive disapproval of gays. Emotion, 9(3), 435-439. DOI: 10.1037/a0015960
Rozin, P., Haidt, J., & Fincher, K. (2009) PSYCHOLOGY: From Oral to Moral. Science, 323(5918), 1179-1180. DOI: 10.1126/science.1170492
- July 9, 2009
- 03:31 AM
- 1,407 views
Sex ed just got a little more complicated
by Christie Wilcox in Observations of a Nerd
It's amazing how the field of stem cell research has advanced so much in such a short amount of time. Today, just a little over a decade after the first stem cell line was produced, scientists announced another breakthrough - turning stem cells into sperm.In a paper published in the journal Stem Cells And Development (PDF), british scientists from England’s Newcastle University detail a technique for turning stem cells with male chromosomes into reproductive germline cells and prompt them to divide into sperm.Like non-stem derived sperm, the in vitro versions have 1/2 the amount of genetic material of a regular cell, have a head and a tail, and are capable of swimming and activating an egg for fertilization.And, interestingly enough, they were only able to produce them with male-derived cells. Female stem cells could begin the process, but stopped at an early stage, suggesting that genes on the Y chromosome are absolutely essential for sperm development.While this step is a huge one, it's important to note that these sperm are not the same as the normal, mature sperm which are created in the testes, and cannot be used to produce fertilized embryos and offspring. There are other external structural differences which make these man-made sperm unable to act like normal sperm. So while it's an amazing discovery, it isn't a cure for male impotency - yet. The sperm do, however, give us valuable insights into the origins of sperm and perhaps the underlying causes of infertility. The team is now trying the same trick using skin cells of infertile men and studying the differences between how those sperm and their embryo-derived ones develop, with the hopes of understanding more about the root causes of infertility. These studies may lead to new treatments for infertility, although at the moment, British law forbids the implantation of such sperm into humans, and any lab-grown embryos (if they could get the sperm to successfully fertilize an egg) can only be grown for 14 days, at which point they must be destroyed. Even if a cure for impotence isn't in the near future, this new technique allows us to speed up nature's clock and see sperm development in a way that we have never been able to before. In the human body, it takes 15 years for the cells which develop into sperm-producing cells to develop and mature before they produce sperm - a process we have never been able to witness step-by-step. Now, it takes only 3 months, granting scientists the unique opportunity to learn even more about human development.Nayernia, K., Lee, J., Lako, M., Armstrong, L., Herbert, M., Li, M., Engel, W., Elliott, D., Stojkovic, M., Parrington, J., Murdoch, A., Strachan, T., & Zhang, X. (2009). In Vitro Derivation of Human Sperm from Embryonic Stem Cells Stem Cells and Development DOI: 10.1089/scd.2009.0063... Read more »
Nayernia, K., Lee, J., Lako, M., Armstrong, L., Herbert, M., Li, M., Engel, W., Elliott, D., Stojkovic, M., Parrington, J.... (2009) In Vitro Derivation of Human Sperm from Embryonic Stem Cells. Stem Cells and Development, 2147483647. DOI: 10.1089/scd.2009.0063
- September 17, 2009
- 04:44 PM
- 1,400 views
White-Eyes Killing Off Native Birds In Hawaii
by Christie Wilcox in Observations of a Nerd
Introduced and invasive species are a hot topic in ecology. Even when brought in for good reason, introduced species can have unforeseen negative impacts on the environment and the species around them. Take Cane Toads, for example. They were introduced to Australia to control a particular bug, but ended up eating everything they could fit in their mouths, especially native, endangered species. Or look at the mongoose, brought to Hawaii to control rat populations. While it does enjoy the invasive rodents, it also feeds on the eggs of native birds, decimating their populations. Now, there's another species to add to the list of dangerous invasives: The Japanese White-Eye.Japanese white-eyes (Zosterops japonicus) are really, really cute little birds (see me with one on the R). At just under 5 inches with bright green feathers and a yellow throat, the white-eye is a colorful and attractive bird. It's name comes from the distinctive white ring around its eyes. You'll find them all over the Hawaiian Islands where they were introduced intentionally in the 1929 to control bug populations. Populations have grown exponentially since, devouring bugs and nectar wherever the white-eyes can survive. Since they're cute, few people have thought twice about the invasion of this pretty little bird. The federal fish and wildlife commission here doesn't think they're a problem, and has even revoked the permits of scientists studying the bird's effects. But, a paper soon to be published in Current Biology begs to differ.You see, there were already nectar-feeders in Hawaii before the white-eye was introduced. These native honeycreepers, like the Akepa and the Amakihi (on L), are a little larger and breed slower than the white-eye. But what's worse for them is that the white-eye didn't come alone. It brought with it parasites like avian malaria that the native species had never encountered before. The sickness and competition for food have taken their toll. Since the arrival of the white-eye, native Hawaiian bird populations have plummeted.That's what Dr. Lenny Freed and Dr. Rebecca Cann have shown using 20 years of mark and recapture data in the federal preserve Hakalau on the big island of Hawaii. The birds were caught using mist nets and all kinds of data was taken for each bird - weight, morphological measurements, age, sex, parasitic infections, and more. The data revealed that over the years, where the white-eyes flourished, the overall survival of juvenile native birds has dropped. Specifically, the native species are being out competed for food resources, leading to signals of malnourishment. The bill length and overall size of the native species has decreased dramatically. "Just as there are permanent effects of stunted growth in human children, there are permanent effects in adult birds," explains Dr. Rebecca Cann from the University of Hawaii at Manoa. "Birds cannot use their shorter bills to feed efficiently for themselves or when feeding their young. Stunted birds have higher death rates than normal size birds. The Japanese white-eye is causing this problem for native Hawaiian birds by depleting the food available for growth, survival, and breeding." Where the white-eyes have yet to invade or are in low numbers, the native honeycreepers are healthier, with larger bills and higher survival rates. In the end, the data suggested that white-eyes are most likely responsible for the decline of 7 of 8 native forest birds in a major portion of the Hakalau refuge. While there are other threats like malaria and parasitoids, the fact that juvenile birds fared well wherever white-eyes are not is pretty damning. Another paper, out of the same lab in Hawaii, has shown that decreased food availability is altering sex ratios of the native Akepa (PDF), leading to too few females - another way in which the competition for food with the white-eye is dooming native Hawaiian bird species.The white-eye is yet another example of how invasive species can severely damage the communities they take over. And despite how many biocontrol methods have failed horribly, nations and scientists continue to consider them viable options to control pest species. It's a tangled web we weave when we add or subtract species from an ecosystem - we shouldn't do it so lightly. Leonard A. Freed, & Rebecca L. Cann (2009). Negative Effects of an Introduced Bird Species on Growth and Survival in a Native Bird Community Current BiologyLeonard A. Freed, Rebecca L. Cann, & Karl Diller (2009). Sexual dimorphism and the evolution of seasonal variation in sex allocation in the Hawaii akepa Evolutionary Ecology Research, 11, 731-757
... Read more »
Leonard A. Freed, & Rebecca L. Cann. (2009) Negative Effects of an Introduced Bird Species on Growth and Survival in a Native Bird Community. Current Biology. info:/
- October 8, 2009
- 08:07 PM
- 1,398 views
Women to stop liking Sean Connery?
by Christie Wilcox in Observations of a Nerd
Boyish good looks - the next generation of sexy?I couldn't help but notice that a new study has come out about the behavioral effects of hormonal contraception. It's all over the science news sites. With titles ranging from the conservative "Pill May Change Attraction" to the bolder "Taking the pill for past 40 years 'has put women off masculine men'"and "The pill 'gives women a taste for boyish men like Zac Efron'," this new publication has swept the media outlets by storm. This idea that birth control might have behavioral side effects isn't new, even I've mentioned this before, as a side note on another study's findings. But the strong tone and conclusions in this review paper seem to have caught the media's attention, causing Grizzly Adams impersonators everywhere to fear that they're soon to be cast out of their lovers' bedrooms in favor of DiCaprio-esque alternatives.Calm down, manly men. It's just like how the media always starts raving about how scientists have found a "missing link" every time there's a new fossil species identified - mention sex or relationships in a paper, and it's bound to get noticed. And just like the constant "missing link" hype, the whirlwhind response to this paper is unfounded and ridiculous.Don't get me wrong - I love a good paper about behavior and hormones. But a non-systematic review paper has a lot of holes in it, and this one is no exception.In the paper, the authors state that "there is emerging evidence that the use of the pill by women can disrupt: (i) the variation in mate preferences across their menstrual cycle; (ii) their attractiveness to men; and (iii) their ability to compete with normally cycling women for access to mates" and that there are "consequences of pill-induced choice of otherwise less-preferred partners for relationship satisfaction, durability and, ultimately, reproductive outcomes."Let me start by explaining the paper's premise. It's somewhat established scientifically that certain traits that women find attractive - like "manliness" - can vary over the menstrual cycle. When a woman is most fertile, she's more strongly attracted to more masculine men. There's some suggestion that this is because while she may not be able to marry the sexiest, most genetically spectacular man alive, she can sleep with him behind her mate's back when she's highly fertile and get a genetically fantastic kid while still keeping the loser hubby around to take care of him. In turn, scientists have shown that women are sexiest to men when they're most fertile - the theory being that if men sleep with a woman when she is most likely to get pregnant, then they're most likely to pass on their genes. All of these shifts in attractiveness are completely unconscious, so we don't know that we're changing how we see each other over a monthly cycle.The Culprit?Hormonal birth controls change the hormones in a woman's cycle. They convince her body that she's pregnant, thus preventing her from going through ovulation-induced changes into that 'high fertility' state. Logically following, this change in hormones might shift how she views men and how men view her, because she's never entering that body phase where all this change in attraction occurs. Then, the paper's authors conclude, it's likely that the women taking the pill are shifting society's opinion of men, steering towards less masculinity. They're changing the rules, making feminine men more attractive and thus more likely to mate, which they say could have drastic consequences. Since manly men are supposed to contain the 'better' genes, a shift in mate choice could have reproductive repercussions. As one of the co-authors, Dr Virpi Lumma, is quoted as saying: "The ultimate outstanding evolutionary question concerns whether the use of oral contraceptives when making mating decisions can have long-term consequences on the ability of couples to reproduce." Even on the small scale, they warn that birth control might be dooming relationships, because women are likely to be off birth control before a relationship, then meet someone, and go on it. Beforehand, the women had 'high fertility' attractions, but after, their tastes change. Even if it's not dooming the masses, it could be a major contributing factor to the rising divorce rate and general relationship woes.It sounds very logical, but there are gaping holes that the journalists and even the study authors completely ignore.Firstly, it's important to point out that this is a non-systemic review. A non-systemic review is one that doesn't describe the methods used to choose the papers which are included in it. The authors say that 75% of the studies performed in the past decade support their conclusions. But how did they choose the 72 studies included in their review? How exhaustive was their search? Without explaining these methods, it's entirely possible that the review is biased, focusing on research which supports the writers' preformed conclusion. Small, non-random samples aren't fit mathematically to be expanded to populationsBut even assuming that the choices were comprehensive when it comes to the literature, there are flaws in those, too. Most of these studies have incredibly low, non-random sample sizes (i.e. Furthermore, when comparing women who are on the pill to those who are not, the treatment group the women are in isn't double blind or random. The two groups are self selected - aka women who are on the pill already versus those that aren't. There is no control, no group that takes a placebo or, at least, goes from not taking the pill to taking it (with one exception - kind of. I'll explain in a minute). No clinical studies into side effects - like those done on various pharmaceuticals - would be tolerated without these kinds of controls. It goes back to the underlying scientific question of the chicken or the egg. It's possible that taking birth control affects one's mate preferences. It's also possible that those with certain mate preferences are more interested in taking birth control, particularly those interested in the pill over other contraceptive methods like condoms. The studies examined in this review lack the power and structure to determine the difference. After all, studies have shown that there are differences in contraceptive use between political, religious, and age groups. Is it not entirely likely that underlying factor might stimulate a woman to be attracted to 'boyish' men and take birth control, like her religious preferences? The only study covered in the review which did, at least, compare women before and after taking the pill, did not randomly select women for each group. The women elected to take the pill or not, which means it does not rule out all of these issues.Furthermore, among their logical conclusions, the authors suggest that taking the pill after starting a relationship may affect relationship satisfaction because a woman might change her mind about what she finds attractive. Call me a scientist, but can I have some data? This one ought to be easy to look at! Why speculate so broadly without any kind of data to back it up?The authors do note that their conclusions are 'speculative,' but it seems the mainstream media has overlooked this portion of the paper. The majority of their conclusions are evolutionary speculations, not scientifically supported theories. And there is danger in trying to see everything from an evolutionary perspective. Evolution is a complex combination of selection, random change, and genetic shifts. Don't panic, Jackie.Your rugged good looks won'tkeep women fro... Read more »
Alexandra Alvergne, & Virpi Lummaa. (2009) Does the contraceptive pill alter mate choice in humans?. Trends in Ecology and Evolution. info:/10.1016/j.tree.2009.08.003
- May 28, 2009
- 09:00 AM
- 1,385 views
Size does matter!
by Christie Wilcox in Observations of a Nerd
When I interned at Florida Aquarium I had the pleasure of working with two screech owls. Sure, there were bigger, more impressive looking raptors that I could hold and show people, but those pint-sized versions were my favorite. It wasn't just that they were small (though that totally helped). It was that when you'd go to take them out of their cage to walk around with, they would puff up and try to act all big an menacing - which, frankly, just made them look like giant brown cotton balls.What the birds were aiming to do was make themselves look bigger and more important. All kinds of animals have similar tricks to improve their size, which in turn reflects on their status. Whether it be to scare off rivals for their territory or impress the ladies, in the animal kingdom, size does matter. And humans, the hairless apes that we are, are no different.It's long been known that size is associated with status. After all, we "look up" to people of power and authority. Taller people are more likely to be leaders, attract mates, be healthy, live long and be more intelligent. Just think of the quintessential ideal or model male and female - neither is anywhere near average height. Even where height seems less important, like in generally shorter cultures, overall size is still big. Sumo wrestlers, for example, are considered to be high status individuals, and the kings and upper class of Polynesian cultures flaunted their wealth with their waistlines. It's uncertain whether the bias exists because of some genetic link between size and admirable traits or if being tall or large is like colorful plumage in birds - attractive because it puts the person in danger or is energetically costly, thus impossible for unhealthy, unfit people to achieve. But what is certain is that bigger is better.What's even more interesting is that perception of size is strongly linked to status. That's what a very interesting study, published in PLoS ONE, has shown experimentally. Not only did people think taller-looking people were higher status, they thought that those who displayed higher status traits were taller and heavier.To probe the relationship between status and size, the researchers from Georgetown University and the NIH used a set of experiments which asked participants to guess the relative dominance, age, height and weight of actors in photos. The actors were manipulated into different poses, one which portrayed a high, authoritative status, one which portrayed a low, submissive status and one which was neutral. Poses were also either sitting or standing or in between. High status poses included lowered brows, open body postures, eye contact and outward-directed gestures like pointing, whereas the submissive poses had raised brows, averted eyes, closed postures and self-directed gestures like touching one's own body. Some of the photos were altered to make the actor look larger by making other objects in the photo smaller.What they found was that, unanimously across the board, people that looked taller were perceived as more dominant. Even the same actor in the exact same pose, with simply a change in the background to make him look shorter, looked less dominant. But even more amazingly, the status implied by the posture an actor took, whether sitting or standing, affected how tall they appeared to the participants. Actors in authoritative status poses were judged to be on average an inch taller and 5 lbs heavier than when they were in submissive ones, whether sitting or standing.Part of the effect, the researchers found, is due to silhouettes. When we're in certain poses, we look like we take up more space - literally. By analyzing the pixels in a 2d manner of different poses, the researchers found that we, in effect, are larger when we're in dominant positions. As the authors explain, "Although the targets' actual size did not vary across poses, in the sense that their actual height and weight were unchanged, the targets' apparent size in the two-dimensional plane visible to a perceiver varied significantly."This is the first study which has shown that these status cues, like open or closed posture, directly impact perceived size. The authors speculate that like other animals, we, too, have evolved behaviors which change the appearance of our size as ways of gaining or losing status in a situation. These cues are picked up by low-level perceptual processes, not by higher order rational thought, but have a big impact on how we see a situation or judge a person. While we can't actually make ourselves taller or heavier, we can make ourselves appear to be so, and by doing so, affect how other perceive us. Though hopefully we're a bit more effective in our efforts than those little screech owls were - I definitely wasn't scared one bit by their tough guy acts. Marsh, A., Yu, H., Schechter, J., & Blair, R. (2009). Larger than Life: Humans' Nonverbal Status Cues Alter Perceived Size PLoS ONE, 4 (5) DOI: 10.1371/journal.pone.0005707... Read more »
Marsh, A., Yu, H., Schechter, J., & Blair, R. (2009) Larger than Life: Humans' Nonverbal Status Cues Alter Perceived Size. PLoS ONE, 4(5). DOI: 10.1371/journal.pone.0005707
- March 26, 2009
- 11:19 AM
- 1,378 views
Self-healing car paint? Ok, I'm in.
by Christie Wilcox in Observations of a Nerd
Who hasn't walked to their car after getting groceries or the like and suddenly found a nice, large scratch where you're fairly sure there wasn't one before? Then you think do you spend $50 on some random infomercial product claiming to fix scratches of every color, get the thing repainted, or just live with it? In my case, of course, the third is the obvious option. What can I say? I'm cheap, and my car is instantly recognizable for its terrible paint job (let me tell you, black + Florida weather = bad idea).
But what if my car's paint could fix itself? That would be worth dropping a huge...
There's more... go to my site to read the rest!... Read more »
Ghosh, B., & Urban, M. (2009) Self-Repairing Oxetane-Substituted Chitosan Polyurethane Networks. Science, 323(5920), 1458-1460. DOI: 10.1126/science.1167391
- March 31, 2009
- 03:38 PM
- 1,345 views
This Week's Sci-Fi Worthy Parasite
by Christie Wilcox in Observations of a Nerd
So you're sitting there, reading the paper, when you notice your head's a bit itchy. Dry skin? Maybe. Irritated scalp? It's possible. Of course it could be something far more sinister...
It could be every parent and school teacher's worst nightmare: Lice.
Lice, the kind that is the bane of elementary schools everywhere, are a kind of wingless insect. They're members of the order Phthiraptera, which is classically broken into two groups, the chewing lice and the sucking lice - the latter is where our lovely head louse, Pediculus humanus, belongs.
Why did I pick the measly little louse for...
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Shao, R., Kirkness, E.F., & Barker, S.C. (2009) The single mitochondrial chromosome typical of animals has evolved into 18 minichromosomes in the human body louse, Pediculus humanus. Genome Research. DOI: 10.1101/gr.083188.108.
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