June 18, 2013
Cyprus, the Mediterranean island nation just south of Turkey, took centuries to gain its independence. The Greeks, Assyrians, Egyptians, Persians, Romans, Ottomans, British and others all took their turns taking over the island, and each left their mark on the archeological record. But in a ruined chamber in a castle on the western corner of the island, it may be more apt to say the invaders left a smear.
In 1191, during the Third Crusade, King Richard I of England invaded Cyprus and ordered that a castle be built on the island’s western corner in order to defend the harbor there. Called Saranda Kolones, the castle’s name refers to its many monolithic columns. But in typical tumultuous Cyprus fashion, the medieval castle was only used for thirty years before it was destroyed by an earthquake. By then, King Richard had sold Cyprus to Guy de Lusignan, the King of Jerusalem. Lusignan and his successors had other plans for expanding the island. The wrecked port was abandoned and the castle never rebuilt.
As castles go, Saranda Kolones had a pretty poor run. But two University of Cambridge researchers recently realized that, precisely thanks to the castle’s short use, a priceless treasure had been left behind in the Saranda Kolones’ bowels. One of the centuries-old castle latrines (read: ancient toilet), they found, was still full of dried-up poo. That feces, they thought, could provide valuable insight into what kind of parasites plagued the former residents’ guts. And because only 30 years’ worth of waste clogged the ancient sewage system, those parasites could provide specific insight into what ailed medieval crusaders. The researchers rolled up their sleeves and collected samples from the dessicated cesspool.
To rehydrate the ancient night soil, the team placed one gram of their sample into a chemical liquid solution. They used micro sieves, or tiny strainers to separate parasite eggs from the digested remains of the crusaders’ meals. They created 20 slides, and peeked into their microscopes to see what creatures the soldiers may have left behind.
The samples revealed 118 “lemon-shaped” Trichuris trichiura eggs–a type of roundworm commonly called the whipworm–as well as 1,179 Ascaris lumbricoides, or giant roundworm, eggs. A control sample of non-toilet soil they tested did not contain any parasite eggs, confirming that the eggs did indeed come from the toilet, they report in the International Journal of Paleopathology.
The study of ancient parasites, whether through old bones that reveal leprosy-causing pathogens or dried up leaves that elucidate the cause of the Irish potato famine, is a thriving field. In this case, the long-dead parasite eggs were pooped out by the crusaders using the toilet years ago. These species reproduce within human bodies, and go on to infect new hosts through egg-contaminated soil or food delivered courtesy of the host.
Heavy infection with either of these worms was no picnic. The authors write, first of giant roundworms:
The mature female then starts to lay about 200,000 eggs per day that can be fertile or unfertile if no male worms are present. Although a mild infection with roundworms is mostly asymptomatic, heavy burdens with Ascaris can cause intestinal blockage and abdominal pain in adults. Because children are less able to tolerate parasites that compete with them for nutrients in their diet, heavy infection with roundworms can cause nutritional impairment, vitamin deficiencies, anaemia and growth retardation.
And of whipworms:
When the females reach maturity they can release 2000–10,000 eggs per day. As with roundworm a heavy worm burden may contribute to malnutrition, stunted growth in childhood and sometimes mechanical damage of the intestinal mucosa, diarrhoea and prolapsed rectum.
The presence of these worms, the authors write, attests to the poor hygienic conditions the castle residents likely practiced and put up with. “Poor hygiene with dirty hands, contamination of the food and water supplies with faecal material, inadequate disposal of the faecal material, and consumption of unwashed vegetables fertilized with human faeces are some of the means through which roundworms and whipworms are spread.”
The worms also could have jeopardized the health of their hosts, especially during years of famine when both parasite and human competed for scarce nutrients from meals few and far between. Previous studies found that between 15 to 20 percent of nobles and the clergy died from malnutrition and infectious disease during the crusades. Although death records for poor soldiers are not available, the authors think it’s safe to assume that malnutrition probably hit the lower-ranking crusaders even harder.
“It is quite likely that a heavy load of intestinal parasites in soldiers on crusade expeditions and in castles undergoing long sieges would have predisposed to death from malnutrition,” they write. “This clearly has implications for our understanding of health and disease on mediaeval military expeditions such as the crusades.”
Before contemporary readers breathe a sign of relief that these parasites infested the guts of people living more than 800 years ago, it’s important to note that the giant roundworm infests an estimated one-sixth of all humans living today. As the authors write, “In modern times A. lumbricoides and T. trichiura are two of the most common and widespread intestinal parasites.” Other parasites continue to plague human populations worldwide, especially in developing countries. Who knows what the archaeologists of the future will find in the scum of your latrine?
June 12, 2013
Visit a sunny pond in a meadow, park or zoo and you’ll likely see turtles basking on logs and small lizards hanging out on warm rocks. If you’re in the south, you may even spot an alligator lazing on a bright patch of shore.
Ectotherms (better known as cold-blooded animals) such as these reptiles have to shuttle back and forth between shade and sun in order to manually regulate their body temperature. Insects, fish, amphibians and reptiles all do it. Now, new research suggests that these animals begin their temperature-regulating tasks much earlier than previously thought–while they are embryos encased in their eggs.
Previously, researchers thought of developing embryos as cut off from the outside world. But back in 2011, researchers found that Chinese soft-shelled turtle embryos could move between warmer or cooler patches in their eggs, though they lacked any feet at such an early stage of development. Some of the same Chinese and Australian researchers who published that original finding decided to investigate further to see just how deliberate these movements are.
“Do reptile embryos move away from dangerously high temperatures as well as towards warm temperatures?” the team, writing in the journal Biology Letters, wondered. “And is such embryonic movement due to active thermoregulation, or (more simply) to passive embryonic repositioning caused by local heat-induced changes in viscosity of fluids within the egg?”
In other words, are unborn reptiles purposefully moving from one spot to another within their eggs, much like an adult animal does? The team decided to investigate these questions by experimenting on turtle embryos. They incubated 125 eggs from Chinese three-keeled pond turtles. They randomly assigned each of the eggs to one of five temperature groups: constant temperature, hot on top/cool on the bottom, or at a range of heats directed towards one end of the egg.
When they began the experiment, most embryos sat in the middle of their eggs. A week after exposing them to the different temperature groups, the team again measured the baby turtles’ positioning within the eggs. At the 10-day mark, the researchers again measured the turtles’ positions, and then injected half of the eggs with a poison that euthanized those developing embryos. Finally, after another week, they took one last measurement of the developing turtles and euthanized turtles.
The turtles within the eggs held at constant temperature or those that were in the “warm on the top/cool on the bottom” group tended not to shift around in their eggs, the researchers found. Those belonging to the groups that experienced warm temperatures only on one end of their egg, however, did move around. They gravitated towards warm conditions (84-86°F), but if things heated up too extremely (91°F), they edged towards the cooler side of their egg. Crucially, the embryos that the researchers euthanized stopped moving after receiving the dose of poison. This shows that the embryos themselves, not some passive physical process, are doing the shifting.
The turtle embryos, the researchers note, behave much like adult reptiles do when thermoregulating their bodies. They warm up and cool down by moving toward or away from heat sources. For species like turtles, temperature during development plays an important part of determining the embryo’s sex. Turtle nests, which are buried in the sand, often experience a range of different temperatures, so embryos could be playing a role in determining their own gender, edging towards the cooler side of the egg if they feel like becoming a male, or the warmer side if they’re more female-inclined, the authors write.
June 10, 2013
The smell of pungent urine may make humans wrinkle their noses, but white-tailed deer don’t mind it. In winter months, they crowd together in northern Michigan–sometimes 100 animals per square mile–and pee all over everything. All of that urine, it turns out, does more than just create an excess of yellow snow. It directly impacts the ability of plants the deer depend on for survival to grow, meaning the animals may be peeing themselves out of their own winter havens.
Researchers typically think of deer’s impact on the environment in terms of the plants they eat. Usually, the animals “simplify” those plant communities with their munching–in other words they eat up all the plants, so only the heartiest species can survive. But it seems the story may be a bit more complicated than that. Though their nitrogen-rich urine–and, to some extent, their feces–they are increasing the complexity of plant communities by helping a multitude of species flourish–perhaps to their own detriment.
For wildlife managers whose job it is to ensure the forest can support deer well into the future, this is a significant consideration. “It’s important to keep ecological context in mind when discussing deer habitat sustainability,” said Bryan Murray, a doctoral candidate in environmental science at Michigan Technical University, in an email.
Murray and colleagues arrived at these findings after performing experiments with deer living in Michigan’s upper peninsula. Long, bitter winters can dump around 250 inches of snow in the region, so deer survival depends upon finding enough to eat and keeping warm in the frozen landscape. Areas of the forest that contain a mix of trees such as eastern hemlock, northern white cedar and balsam fir provide shelter from the wind and some snowfall with their broad, strong branches and bushy needles. Researchers refer to these deer hot-spots as “deeryards.”
The researchers decided to investigate how deer may be impacting the environment during those times of winter crowding. They fenced off three patches of forest to prevent deer from visiting those areas, then compared those deer-free sections with three other patches where that animals continued to congregate. Over the course of the year, they found that the deer significantly influenced the types of plants that grew in those patches, thanks to the nitrogen they excreted in their urine and feces.
Or, in sciencey-speak: “Our results suggest that browsing ungulates affect spatial patterns of herb-layer cover and diversity through the excretion of nitrogenous wastes in small, discrete patches,” lead author Murray and his colleagues report in the journal Ecology.
How, exactly, do the deer influence what grows in their vicinity? During the winter, the high concentration of deer in specific areas mean that the soil underfoot becomes saturated with pee. Nitrogen from the deer’s wastes builds up in the soil, and when spring arrives, the chemical acts like fertilizer, encouraging the growth of some nitrogen-loving plants, including hardwood seedlings. If this pattern repeats itself over a number of years, the conifer-filled deeryards may disappear, replaced by different types of trees that may not do as good of a job blocking wind or catching snow.
In the past, fewer deer congregated in this area of the upper peninsula, but logging and development are forcing more deer to crowd into smaller and less favorable spaces with smaller numbers of viable deeryards. This creates a potentially vicious cycle of crowding “where deer fertilize the soil, plant productivity increases, more deer are attracted to the habitat, fertilizing the soil, and so on,” Murray says.
So it seems that the deer themselves could wind up playing a part in their own undoing by wetting their winter beds.
May 30, 2013
Think of an ecosystem as a Jenga pillar. Each piece–microbes, birds, trees, insects, animals, fungi–comes together to form the larger, intertwined structure. Maybe you can knock out a Jenga block or two, but tamper with those components enough and the system will collapse. As ecologists well know, small changes in the environment–cutting down a few patches of forest, causing a local species to go extinct–can create cascading and potentially disastrous effects on the broader environment.
Like a teetering Jenga tower, predicting which of those changes will most significantly reverberate in the complex natural world is nearly impossible. So we wait to see the consequences. Today, an international team of researchers just identified a pointed example of one such fatal tinkering. In Brazil’s damaged Atlantic forest, the absence of large birds has caused seeds to shrink and become weaker, in turn threatening the forest’s future.
The story began more than a century ago, they found. Local people began hacking away at the Atlantic forest, which once covered more than 400,000 square miles of Brazil’s coast. Agricultural and livestock fields, as well as growing urban centers, divided swaths of jungle, creating isolated patches of green. By the time people realized there was value in keeping the forest around, nearly 90 percent of it had been lost. Much of what remains today occurs in isolated, random pockets, though those patches still represent some of the world’s most biodiverse forests.
When a forest becomes divided, like the Atlantic forest did, wildlife often loses its ability to disperse from one patch of trees to another. Larger species may not be able to survive in some of the smaller, resource-scarce patches, and hunters can more easily track down animals if they’re confined to a smaller area. This turned out to be the case for some large birds that once made their home throughout the Atlantic forest, including toucans and toucanets–prized for their brilliant plumage, the birds are a favorite of hunters.
Significantly, these birds’ big beaks–which open up more than half an inch, on average–make them key players in distributing larger seeds throughout the jungle. Smaller birds can’t swallow or fit those big seeds into their beaks, meaning the toucans and toucanets carry nearly sole responsibility for regenerating the jungle with new seedlings of several plant species.
The authors of this new study, published in Science, compared the size of more than 9,000 seeds from 22 palm plant populations–a major tree type in the Atlantic forest, several species of which are threatened. Some of the seeds came from robust patches of forest with lots of large birds, while others came from smaller patches where those birds have long been missing. In those smaller patches, they found, seeds of palm plants were significantly smaller.
The researchers also used statistical models to independently evaluate 13 different environmental variables, including soil type and climate, to find out whether they could have driven the size difference seen in the seeds instead. None of the other factors could explain the difference, suggesting birds–the primary transport mechanism for large seeds–as the most likely culprit. Additional genetic analyses indicated that, in the smaller forest patches, seeds most likely began shrinking about 100 years ago, or right around the time that coffee and sugar cane plantations began to boom. Human activities a century ago, the authors conclude, likely drove a rapid evolutionary change in the forest palms’ seed size.
When the birds disappear, the larger seeds do not get distributed throughout the forest. Only the smaller ones wind up in new plots of earth, which in turn sprout into more trees that produce smaller seeds. Gradually, the forest becomes dominated by smaller seed-producing trees.
Shrinking seed size is no small detail for forest palms. The larger the seed, the more nutrients that are packed in to give the seedling the best possible chances of survival in the tough jungle ecosystem. Prior research has found that forest palms that began life as smaller seeds are smaller on average after a year of growth than those that came from larger seeds, meaning that the runty plants are more likely to lose out to competition with other species. Smaller seeds are also more prone to drying out. Given that climate models predict hotter temperatures and longer periods of drought for South America in the coming years, this could be a serious problem for smaller-seeded forest palms’ survival.
If palms start dying out throughout the Atlantic forest, researchers have no idea what will happen to the tens of thousands of species that take shelter in the ecological web the plants help to maintain–a web that includes more than 11,000 threatened plants and animals. For those smaller jungle patches, the authors speculate, the choices long-dead humans made may lead to complete collapse of some of the world’s most diverse sections of rainforest. Like a real-life game of Jenga, those birds could prove to be the key piece that causes the entire jungle system to fall down.
May 23, 2013
Most people consider saving the Amazon rainforest a noble goal, but nothing comes without a cost. Cut down a rainforest, and the planet loses untold biodiversity along with ecosystem services like carbon dioxide absorption. Conserve that tract of forest, however, and risk facilitating malaria outbreaks in local communities, a recent study finds.
Nearly half of malaria deaths in the Americas occur in Brazil, and of those nearly all originate from the Amazon. Yet few conservationists consider the forest’s role in spreading that disease. Those researchers who do take malaria into account disagree on what role forest cover plays in its transmission.
Some think that living near a cleared patch of forest–which may be pockmarked with ditches that mosquitoes love to breed in–increase malaria incidence. Others find the opposite–that living near an intact forest fringe brings the highest risk for malaria. Still more find that close proximity to forests decrease malaria risk because the mosquitoes that carry the disease are kept in check through competition with mosquitoes that don’t carry the disease. Most of the studies conducted in the past only focused on small patches of land, however.
To get to the bottom of how rainforests contribute to malaria risk, two Duke University researchers collected 1.3 million positive malaria tests from a period of four-and-a-half years, and ranging over an area of 4.5 million square kilometers in Brazil. Using satellite imagery, they added information about the local environment where each of the cases occurred and also took rainfall into account, because precipitation affects mosquitoes’ breeding cycles. Using statistical models, they analyzed how malaria incidences, the environment and deforestation interacted.
Their results starkly point towards the rainforest as the main culprit for malaria outbreaks. “We find overwhelming evidence that areas with higher forest cover tend to be associated with higher malaria incidence whereas no clear pattern could be found for deforestation rates,” the authors write in the journal PLoS One. People living near forest cover had a 25-fold greater chance of catching malaria than those living near recently cleared land. Men tended to catch malaria more often the women, implying that forest related jobs and activities–traditionally carried out by men–are to blame by putting people at greater risk for catching the disease. Finally, the authors found that people living next to protected areas suffered the highest malaria incidence of all.
Extrapolating these results, the authors calculated that, if the Brazilian government avoids just 10 percent of projected deforestation in the coming years, citizens living near those spared forests will contend with a 2-fold increase in malaria by 2050. “We note that our finding directly contradicts the growing body of literature that suggests that forest conservation can decrease disease burden,” they write.
The authors of the malaria study do not propose, however, that we should mow down the Amazon in order to obliterate malaria. “One possible interpretation of our findings is that we are promoting deforestation,” they write. “This is not the case.” Instead, they argue that conservation plans should include malaria mitigation strategies. This could include building more malaria detection and treatment facilities, handing out bed nets and spraying for mosquitoes.
This interaction between deforestation and disease outbreakis just one example of the way efforts to protect the environment can cause nature and humans to come into conflict. Around the world, other researchers have discovered that conservation efforts sometimes produce negative effects for local communities. Lyme disease–once all but obliterated–reemerged with a vengeance (pdf) in the northeastern U.S. when abandoned farmland was allowed to turn back into forest. Human-wildlife conflict–including elephants tearing up crops, tigers attacking livestock, and wolves wandering into people’s backyards–often comes to a head when a once-declining or locally extinct species makes a comeback due to conservation efforts.
“We believe there are undoubtedly numerous ecosystem services from pristine environments,” the PLoS One authors conclude. “However, ecosystem disservices also exist and need to be acknowledged.”