Vampires!

Photo by Alejandro Lunadei at Wikimedia.

A reposting of an original article from October 19, 2015

Vampire mythologies have been around for thousands of years, terrifying the young and old alike with stories of predatory bloodsuckers that feed on our life essences. You may not believe in vampires, but they are all around us. In fact, you may have some in the room with you right now! You just don’t notice them because they are not human, or even human-like.

Vampires feed on the blood of their victims in order to sustain their own lives. This phenomenon, called hematophagy, is more common than typically occurs to us at first. Just take mosquitoes and ticks as examples. Once we’ve opened our minds to the idea of bloodthirsty arthropods, we quickly think of many more: bedbugs, sandflies, blackflies, tsetse flies, assassin bugs, lice, mites, and fleas. In fact, nearly 14,000 arthropod species are hematophages. We can expand our thoughts now to worms (like leeches), fish (such as lampreys and candirús), some mammals (vampire bats), and even some birds (vampire finches, oxpeckers, and hood mockingbirds). We’ve been surrounded by vampires our whole lives, we just never sat up to take notice!

Hematophagous animals are not as scary as mythical vampires, in part because they don’t suck their victims dry – they just take a small blood meal to sustain their tiny bodies. Hematophagy is not, in itself, lethal. However, the process of exposing and taking the blood of many individuals transmits many deadly diseases, like malaria, rabies, dengue fever, West Nile virus, bubonic plague, encephalitis, and typhus.

Because blood feeders do not kill their meals, feeding can be even more dangerous for them than for traditional predators. As a result, many hematophagous animals have developed a similar toolkit. Many have mouthparts that are specialized to work as a needle or a razor and biochemicals in their saliva that work as anticoagulants and pain killers. Their primary skill, however, is their stealth: they can sneak up on you, eat their meal, and be home for bed before you even notice the itch.

Although a few species, like assassin bugs and vampire bats, are obligatory hematophages (only eat blood), most hematophages eat other foods as well. Somehow, Dracula is not quite so intimidating when you imagine him drinking his morning fruit juice, like many mosquitoes do.

Why drink blood in the first place? Blood is a body tissue like any other, and it contains a lot of protein and a variety of sugars, fats and minerals, just like meat. However, blood is mostly water, which means that a blood meal contains less protein and calories than the same weight of meat. Because you need to consume so much more to get enough protein and calories out of a meal, large animals and animals that generate their own body heat can't usually rely on blood meals alone. So much for human-like vampires that only live off the blood of their victims.

A deadly vampire spreading malaria. Photo by the CDC available at Wikimedia.

So true vampires are everywhere, but they are small, take small blood meals, don't generally kill their hosts, and often use blood to supplement their other meals. Not so scary any more, are they? ...Although, about 3.2 billion people (about half the world's population) are at risk of contracting the deadly disease, malaria, from these bloodsuckers... so maybe you aren't scared enough. Bwaa-haha!

Mind-Manipulating Slave-Making Ants!

A reposting of an article from October 10, 2012.

An entire colony enslaved by an alien species to care for their young. Slave rebellions quelled by mind manipulation. It sounds like science fiction, right? But it really happens!

Myrmoxenus ravouxi (called M. ravouxi for “short”) is a slave-making ant species in which the queen probably wears a chemical mask, matching the scent of a host species in order to invade their nest without detection. Once inside, she lays her eggs for the host species workers to care for. Armies of M. ravouxi workers then raid these host colonies to steel their brood to become future slave-laborers to serve the needs of the M. ravouxi colony.

A M. ravouxi queen throttling a host queen. Photo by Olivier Delattre.

Enslaved worker ants could rebel: They could destroy the parasite brood or at least not do a good job caring for them. But to selectively harm the parasite brood without harming their own nests’ brood, the host ants would have to be able to tell them apart. Ants learn the smell of their colony in their youth, so any ants born to an already-parasitized colony would likely not be able to tell apart parasite ants from their own species. But what about ants that were born to colonies before they were invaded?

Olivier Delattre, Nicolas Châline, Stéphane Chameron, Emmanuel Lecoutey, and Pierre Jaisson from the Laboratory of Experimental Ethology in France figured that compared to ant species that were never hosts to M. ravouxi colonies, ant species that were commonly hosts of M. ravouxi colonies would be better able to discriminate their own species’ brood from M. ravouxi brood. Host species may even be better at discriminating in general.

The researchers collected ant colonies from near Fontainebleau and Montpellier in France. They collected M. ravouxi colonies and colonies of a species that they commonly parasitize (but were not parasitized at the time): Temnothorax unifasciatus (called T. unifasciatus for “short”). The researchers also collected T. unifasciatus that were parasitized by M. ravouxi at the time. Additionally, they collected colonies of T. nylanderi and T. parvulus, two species that are never parasitized by M. ravouxi. (Sorry guys. All these species go by their scientific names. But really, that just makes them sound all the more mysterious, right?). The researchers took all their ant colonies back to the lab and housed them in specialized plastic boxes (i.e. scientific ant-farms).

On the day of the tests, the scientists removed a single pupa (kind of like an ant-toddler) from one nest and placed it into a different nest of the same species or back in its own nest. They did this for colonies of both non-host species and for colonies of host species T. unifasciatus that were not parasitized at the time. Then they counted how many times the workers bit the pupa (an aggressive behavior) or groomed the pupa (a caring behavior).

Workers from all three species bit the pupa that was not from their colony more than they bit their own colony’s pupa. But the T. unifasciatus (the host species) were even more aggressive to foreign pupa than the other species. And only the T. unifasciatus withheld grooming from the pupa that was not from their colony compared to the one that was from their colony. Although all three species seemed to be able to tell the difference between a pupa from their own nest versus one from another nest, only the species that is regularly enslaved by M. ravouxi decreased care to foreign young. So that is what these ants do when they are not enslaved. How do you think enslaved ants respond to their own species’ young compared to M. ravouxi young?

A 1975 cover of Galaxie/Bis, a French science
fiction magazine, by Philippe Legendre-Kvater.
Image from Wikimedia.

The researchers repeated the study using enslaved T. unifasciatus, placing either a pupa of their own species from a different nest or a M. ravouxi pupa in with their brood. Even though prior to M. ravouxi takeover the T. unifasciatus bit foreign pupa more than their own, after M. ravouxi takeover they didn’t bite foreign pupa of their own species or M. ravouxi pupa very much. Not only that, but they groomed the M. ravouxi pupa more than the pupa of their own species! Ah hah! Mind control!

This, my friends, is the kind of truth that science fiction is made from.

But how might this work? Ants born to an enslaved colony would be exposed to both their own odors and the M. ravouxi odors. Because ants learn the smell of their colony in the first few days after they emerge from their eggs, these enslaved ants would have a broader set of smells that they may perceive as being “within the family”. That would explain why the enslaved T. unifasciatus ants didn’t attack either the foreign-born T. unifasciatus or the M. ravouxi young, but it doesn’t explain why the enslaved ants provided more care to the M. ravouxi than they did to their own species. One possibility is that the M. ravouxi produce more or especially attractive odors to encourage the host workers to take care of them.

There is still more to learn about this system: How exactly may the M. ravouxi be hijacking the pheromonal systems of their host species? How are the host species protecting themselves from exploitation? I guess we’ll have to wait for the sequel.

Want to know more? Check this out:

Delattre, O., Chȃline, N., Chameron, S., Lecoutey, E., & Jaisson, P. (2012). Social parasite pressure affects brood discrimination of host species in Temnothorax ants Animal Behaviour, 84, 445-450 DOI: 10.1016/j.anbehav.2012.05.020

Drinking Beer Makes You More Attractive… To Mosquitoes

Summer is a time of backyard bar-b-ques, camping, baseball games, beer, and mosquitoes. Ugh, mosquitoes! Have you ever noticed that when a bunch of us are hanging out together outside, some of us get eaten alive by those pesky buggers while others are hardly touched at all? It turns out, differences in how much alcohol we have imbibed may be a factor.

An Anopheles gambiae mosquito ready for a meal. Photo by James D. Gathany
at the Public Health Image Library at Wikimedia Commons.

“No! Say it ain’t so!”

I hate to be the bearer of bad news, so I’ll let the scientific evidence speak for itself.

A research team from the French Research Institute for Development, including Thierry Lefèvre, Louis-Clément Gouagna, Eric Elguero, Didier Fontenille, François Renaud, Carlo Costantini, and Frédéric Thomas, and Kounbobr Roch Dabiré, from the Institute for Research in Health Sciences in Burkina Faso set out to test whether people were more attractive to female mosquitoes after drinking a beer compared to beforehand. They only tested females because only female mosquitoes bite, requiring extra protein for their eggs.

The researchers put groups of 50 hungry female mosquitoes into the end of a special Y-shaped maze that let them fly in the direction of one of two odors. At the end of one arm of the Y-maze was a fan, simply blowing outdoor air through a tent and into the apparatus. At the other end of the Y-maze was a fan blowing air through a tent past a shirtless man and into the apparatus. This shirtless man had either not had anything to drink recently, or had recently drunk either a liter of beer or a liter of water. Between the starting chamber and both ends of the arms of the Y-maze were traps that would capture mosquitoes that had chosen to head that direction (lucky for the shirtless men). The number of mosquitoes caught in both traps combined (compared to the total of 50 that was initially released) was called mosquito activation, and reflected how many mosquitoes were motivated to take off and fly upwind. The proportion of mosquitoes caught in the volunteer-bated trap compared to those caught in both traps combined was called mosquito orientation, and reflected the attractiveness of the volunteer’s odor compared to the control odor.

Image A shows the two tents: one in which the man-bait sat (having consumed beer or water), and the other with no one in it. Air from each tent blew threw a tube (seen in picture B) and then into the building, past the traps and into the downwind box, where the mosquito starting-line was located (seen in picture C). Photos from Lefèvre et al., 2010.

The mosquitoes significantly increased both activation and orientation in response to the beer-drinking volunteers, but not in response to the water-drinking volunteers. That is to say, that the smell of someone that has had a beer motivates more mosquitoes to actively pursue them, and makes them more of a focused target of the mosquitoes. The researchers believe there is an interaction between how our bodies naturally smell and how our bodies break down beer that increases the attractiveness of our odors to mosquitoes. People that were more attractive to mosquitoes before they drank were also more attractive to mosquitoes after they drank. But interestingly, people that were warmer or gave off more CO2 were not more attractive to mosquitoes.

You should know that this research is much more important than just being a drag on your summer bar-b-que. The particular mosquito species that these researchers studied was Anopheles gambiae, the primary vector for malaria in Africa. They did this study in Burkina Faso, a country in West Africa with a high rate of malaria, using a local beer called dolo. Dolo, a fermented sorghum beer with low (3%) alcohol content, is the most common alcoholic beverage in Burkina Faso. So if you are in a place with a high rate of malaria, knowing that you should take extra precautions against mosquitoes when you drink could be a life-saver.

Want to know more? Check this out:

Lefèvre, T., Gouagna, L.C., Dabiré, K.R., Elguero, E., Fontenille, D., Renaud, F., Costantini, C. and Thomas, F. (2010). Beer consumption increases human attractiveness to malaria mosquitoes. PloS one, 5(3), e9546.

True Blood: Vampires Among Us

A reposting of an article from October, 2012.

Who is your favorite vampire? Are you a fan of Edward Cullen, Bill Compton or Stefan Salvatore? Or do you prefer the classic Dracula, elegant Lestat, or butt-kicking Selene?

Vampires have fascinated us since the Middle Ages, when a hysteria of vampire sightings spread across Eastern Europe. We now know that many of these “vampires” were actually victims of diseases like tuberculosis or bubonic plague that cause bleeding in the lungs (and elsewhere), resulting in the disturbing effect of blood appearing at the lips. Add this attribute to the already poorly understood physiology of decomposing corpses and the cases in which people mistakenly buried alive got up and left their graves, and voila! Vampire mythology is born. So vampires don’t really exist… Or do they?

Actually, there are many animals that feed on blood. So many in fact, that there is a scientific term for blood-eating, hematophagy. And why not? Blood is fluid tissue, chock full of nutritious proteins and lipids and a source of water to boot. And if you don’t kill your prey to feed, the food supply replenishes itself. Here are just some of these animal vampires living among us:

Vampire bat

A vampire bat smiles for the camera
from his Peruvian cave. Photo from Wikimedia.

Vampire bats are our most famous animal vampires, and the ones that most resemble our vampiric lore. There are three species of vampire bats that live from Mexico down through Argentina. Two of them, the hairy-legged and white-winged vampire bats, feed mostly on birds. The common vampire bat feeds more on mammals, like cows, horses, and the occasional human. Their razor sharp teeth cut a tiny incision in their victims and their anticoagulant saliva keeps the blood flowing. Like Dracula, vampire bats sleep by day and hunt by night. But these vampires are not loners like Dracula: They live in colonies of about 100 animals, and in hard times will share their blood-harvest and care for one another’s young.

Vampire finch

The Galapagos Islands are the famous home to numerous finch species, each one with a beak shape specially adapted to their preferred food source. For most of these finches, their food of choice is a type of seed or nut that is appropriately sized for their beak shape and strength. But the vampire finch (also called the sharp-beaked ground finch for obvious reasons) uses its long sharp beak to feed on blood. Their most common victims are their booby neighbors (named for less obvious reasons).

Candirú

A tiny candirú catfish (being measured in cm) strikes
terror into the souls of Amazonian fishermen.
Photo by Dr. Peter Henderson at PISCES
Conservation LTD. Photo at Wikimedia.

The tiny Amazonian candirú catfish is legendary for one documented case (and several undocumented ones) in which a candirú swam up a local man’s urine stream into his penis, where it attached to feed on his blood. Although terrifying, this is not typical candirú behavior. Actually, it was all just a misunderstanding. You see, candirú catfish do feed on blood, but they usually feed from the highly vascularized gills of other Amazonian fish. The gills of freshwater fish release high quantities of urea, a major component of urine. So to a hungry candirú, your pee smells an awful lot like a fish-gill blood dinner. Just another reason to not pee where you swim.

Lamprey

Notice the sharp-toothed sucker mouth of the river
lamprey. Photo by M. Buschmann at Wikimedia.

Lampreys are species of jawless fish. With their eel-like bodies and disc-shaped mouths filled with circles of razor-sharp teeth, they look like something from science fiction horror. Although some lamprey species are filter feeders, others latch onto the sides of other fish, boring into their flesh and feeding on their blood. Once attached, they can hitch a ride on their victim for days or even weeks.

Leech

A European medicinal leech.
Photo by H. Krisp at Wikimedia.

Leeches are the earthworm’s bloodsucking cousins. With three blade-like mouthparts, they slice into their victims, leaving a Y-shaped incision. They produce anticoagulants to prevent premature clotting of their bloodmeals, which can weigh up to five times as much as the leach itself. The bloodletting and anticoagulant abilities of leeches have led them to be used medicinally in ancient India and Greece as well as in modern medicine.

Female mosquito

A female mosquito getting her blood meal.
Photo by at Wikimedia.

Most of the time, mosquitos use their syringe-like mouthparts to feed on flower nectar. But when the female is ready to reproduce, she seeks out a blood meal to provide the additional protein she will need to produce and lay her eggs. Although their bites only cause minor itching, these lady vampires are truly something to be feared: They kill more people than any other animal due to the wide range of deadly diseases they spread.

There are many other examples of animals that feed on blood. But unlike their mythological counterparts, none of them come back from the dead to do so… Or do they?

Happy Halloween!

Want to know more? Check these out:

1. SCHLUTER, D., & GRANT, P.R. (1984). ECOLOGICAL CORRELATES OF MORPHOLOGICAL EVOLUTION IN A DARWINS FINCH, GEOSPIZA-DIFFICILIS EVOLUTION, 38 (4), 856-869

2. Francischetti, I. (2010). Platelet aggregation inhibitors from hematophagous animals Toxicon, 56 (7), 1130-1144 DOI: 10.1016/j.toxicon.2009.12.003

Mosquitoes Don’t Like Parasites Either (A Guest Post)

By Maranda Cardiel

A photograph of Culex pipiens, the species of mosquito that the researchers used
in their experiment. Source: David Barillet-Portal at Wikimedia Commons.

Everybody hates mosquitoes. They are annoying, persistent, and make us itch like crazy. Sometimes there are so many of them that we are afraid to go outside unless we want to risk getting covered in spots and scratching ourselves all over for the next week. And if that wasn’t enough, they can also carry dangerous diseases with the potential to kill us. However, just like us, mosquitoes don’t like to be bugged by parasites that can make them sick either. Research shows that they may even avoid interacting with hosts that might pass along parasites to them.

A group of researchers - Fabrice Lalubin, Pierre Bize, Juan van Rooyen, and Philippe Christe from the University of Lausanne in Switzerland and Olivier Glaizot from the Lausanne Museum of Zoology – wanted to see if mosquitoes would show a preference for feasting upon birds that were infected with malaria (a blood parasite) or uninfected birds. Mosquitoes find animals to snack on by sensing odors and carbon dioxide in the air that animals give off, along with using their senses of vision, hearing, and touch. In order to figure out if mosquitoes use these senses to specifically choose their unlucky victims, the researchers did an experiment with mosquitoes, malaria, and great tits (a type of bird with a funny name).

For their experiment, the researchers collected mosquito eggs that they hatched and raised in a lab. Only female mosquitoes suck blood, so only female mosquitoes were used in the experiment. The mosquitoes had never been exposed to birds before and were starved of sugar for one day to make sure that they would be hungry. The researchers also caught wild adult great tits, and they took small blood samples from each bird to test for malaria before and after the experiment.

Next it was time to see if the mosquitoes would find some birds to be more appealing than others. A special Y-shaped wind tunnel allowed the mosquitoes to choose between the odors of two birds: one that was infected with the malaria parasite and one that was not. But don’t worry, the mosquitoes could not directly contact the birds. The researchers set up the lab so that it was completely dark to mimic the natural settings of when mosquitoes feed in the wild. This also meant that the mosquitoes were blind and could only choose a bird based on the chemicals in the air. Randomly-chosen pairs of birds and new mosquitoes were used for each round of the test.

A cartoon depicting the experiment setup. A hungry female mosquito hones in on the odors
of a healthy great tit and a great tit infected with malaria parasites. Source: Maranda Cardiel

The results of the study showed that the mosquitoes had a strong preference for birds that were not infected with the malaria parasite. This was true even when the researchers took into account the body sizes and sexes of the birds. Previous studies with different kinds of birds, mosquitoes, and malaria or malaria-like parasites have found similar results. The researchers think that this may be because the malaria parasite somehow causes changes in the chemical processes in the birds’ bodies that the mosquitoes can pick up on.

Infection with malaria might change what the birds smell like to the mosquitoes or how much carbon dioxide the birds give off. There is also evidence that birds who are more susceptible to malaria infections have a different odor than birds with stronger immune systems. But why should mosquitoes be picky and choose to bite healthy birds? They certainly don’t seem like they care whose blood they suck when they are swarming around us!

Previous research has shown that mosquitoes infected with malaria parasites have problems developing their eggs and can have trouble sucking up blood from their victims. Female mosquitoes use blood to nourish their eggs, so if they don’t drink as much blood, they will not be able to lay as many eggs. This means that female mosquitoes carrying malaria parasites are less likely to produce as many healthy offspring. Thus, it makes sense for female mosquitoes to want to avoid feeding on birds that are infected with malaria.

This probably has not changed your thoughts about mosquitoes. They are still a nuisance that we all squish - or at least attempt to squish - upon sight. It might be ironic, but mosquitoes don’t like to have parasites bothering them either. Even though we hate them, maybe now you can find some solace in mosquitoes finding you attractive. It might be a sign that you are actually healthier than your peers.


Source:

Lalubin, F., Bize, P., van Rooyen, J., Christe, P., & Glaizot, O. (2012). Potential evidence of parasite avoidance in an avian malarial vector Animal Behaviour, 84 (3), 539-545 DOI: 10.1016/j.anbehav.2012.06.004

Vampires!

Photo by Alejandro Lunadei at Wikimedia.

Vampire mythologies have been around for thousands of years, terrifying the young and old alike with stories of predatory bloodsuckers that feed on our life essences. You may not believe in vampires, but they are all around us. In fact, you may have some in the room with you right now! You just don’t notice them because they are not human, or even human-like.

Vampires feed on the blood of their victims in order to sustain their own lives. This phenomenon, called hematophagy, is more common than typically occurs to us at first. Just take mosquitoes and ticks as examples. Once we’ve opened our minds to the idea of bloodthirsty arthropods, we quickly think of many more: bedbugs, sandflies, blackflies, tsetse flies, assassin bugs, lice, mites, and fleas. In fact, nearly 14,000 arthropod species are hematophages. We can expand our thoughts now to worms (like leeches), fish (such as lampreys and candirús), some mammals (vampire bats), and even some birds (vampire finches, oxpeckers, and hood mockingbirds). We’ve been surrounded by vampires our whole lives, we just never sat up to take notice!

Hematophagous animals are not as scary as mythical vampires, in part because they don’t suck their victims dry – they just take a small blood meal to sustain their tiny bodies. Hematophagy is not, in itself, lethal. However, the process of exposing and taking the blood of many individuals transmits many deadly diseases, like malaria, rabies, dengue fever, West Nile virus, bubonic plague, encephalitis, and typhus.

Because blood feeders do not kill their meals, feeding can be even more dangerous for them than for traditional predators. As a result, many hematophagous animals have developed a similar toolkit. Many have mouthparts that are specialized to work as a needle or a razor and biochemicals in their saliva that work as anticoagulants and pain killers. Their primary skill, however, is their stealth: they can sneak up on you, eat their meal, and be home for bed before you even notice the itch.

Although a few species, like assassin bugs and vampire bats, are obligatory hematophages (only eat blood), most hematophages eat other foods as well. Somehow, Dracula is not quite so intimidating when you imagine him drinking his morning fruit juice, like many mosquitoes do.

Why drink blood in the first place? Blood is a body tissue like any other, and it contains a lot of protein and a variety of sugars, fats and minerals, just like meat. However, blood is mostly water, which means that a blood meal contains less protein and calories than the same weight of meat. Because you need to consume so much more to get enough protein and calories out of a meal, large animals and animals that generate their own body heat can't usually rely on blood meals alone. So much for human-like vampires that only live off the blood of their victims.

A deadly vampire spreading malaria. Photo by the CDC available at Wikimedia.

So true vampires are everywhere, but they are small, take small blood meals, don't generally kill their hosts, and often use blood to supplement their other meals. Not so scary any more, are they? ...Although, about 3.2 billion people (about half the world's population) are at risk of contracting the deadly disease, malaria, from these bloodsuckers... so maybe you aren't scared enough. Bwaa-haha!

How Fungus Makes Ant Zombies

"Ants biting the underside of leaves as a result of infection
by O. unilateralis. The top panel shows the whole leaf with
the dense surrounding vegetation in the background and the
lower panel shows a close up view of dead ant attached to
a leaf vein. The stroma of the fungus emerges from the back
of the ant's head and the perithecia, from which spores are
produced, grows from one side of this stroma, hence the
species epithet. The photograph has been rotated
to aid visualization." Image and caption by David P. Hughes
and Maj-Britt Pontoppidan at Wikimedia Commons.

The parasitic fungus, Ophiocordyceps unilateralis sensu latu (O. unilateralis, for short), infects the brains of Carpenter ants, turning them into zombies that live and die for the sole purpose of helping the fungus thrive and reproduce. Under the influence of the fungus, zombie Carpenter ants leave their nests at an odd yet specific time, move randomly and convulsively, and climb up the north side of a plant to almost exactly 25 cm, where they bite the leaf vein. Once they bite the leaf, the muscles of their mandibles (mouth parts) deteriorate, causing lockjaw and fixing the ant victim in place while its legs kick and twitch. After a few hours, the movement stops as the fungus kills the ant, continues to grow throughout the victim's head, and then sprouts out of the back of the head. The fungus anchors itself to the plant and releases antimicrobial chemicals to protect itself and grows fruiting bodies from the ant's head to release its spores, spawning the next generation of fungus. O. unilateralis has been known to infect and wipe out entire Carpenter ant colonies, leaving dense aerial graveyards of ant carcasses in its wake.

Today at Accumulating Glitches, I talk about new research that has used genetic techniques to determine how this parasitic fungus takes over the minds of its ant victims. Check it out here.

And to learn more, check this out:

de Bekker, C., Ohm, R.A., Loreto, R.G., Sebastian, A., Albert, I., Merrow, M., Brachmann, A. and Hughes, D.P. Gene expression during zombie ant biting behavior reflects the complexity underlying fungal parasitic behavioral manipulation, BMC Genomics, 16:620, 1-23 (2015). DOI 10.1186/s12864-015-1812-x.

Real Zombie-Making Parasites Among Us

The mummified cat and the rat in the crypt of Christ Church in Dublin.
Photo by Adrian Grycuk at Wikimedia Commons.

The Happening, M. Night Shyamalan’s worst panned movie of all time, is a science fiction thriller about people going into a mysterious trance and committing suicide as a result of other mind-hacking species. One of the leading criticisms raised against this movie is the ridiculousness of the premise. One species can’t cause another to willingly commit suicide! …Or can they?

Toxoplasma gondii (we’ll call it T. gondii) is a protozoan parasite that has developed just such mind-hacking abilities! As far as we can tell, T. gondii only reproduces in the digestive tract of cat species, where it lays fertile eggs that are pooped out into the environment. From there, T. gondii eggs can contaminate any number of things that are consumed by other animals, such as rodents, birds, or even humans. When cats eat prey animals that are infected with T. gondii, another generation of parasites is now positioned to reproduce and the cycle continues.

However, prey animals can be pretty good at avoiding cats, in part by avoiding the smell of cats. This is a problem for the reproductive plans of T. gondii. The tiny protozoan has responded to this problem with remarkable biological sophistication: They alter the behavior of their rodent hosts so that the infected rodents find the smell of cat urine so irresistible that they run straight towards their predators! Now, researchers have found that T. gondii-infected rats don’t only like the smell of cat urine, but they even prefer the smell of wild cat urine over the smell of urine of weaker domesticated cats.

A rat checks out odor-soaked papers
in a Y-shaped apparatus. Image from
Kaushik, et al. (2014) in
Integrative and Comparative Biology.

Maya Kaushik, Sarah Knowles and Joanne Webster at the School of Public Heath at the Imperial College of London compared the responses of rats that were either infected with T. gondii or not to urine produced by domestic cats or wild cats. To do this, they put infected or uninfected rats into a Y-shaped apparatus. For each trial, tissue paper soaked in domestic cat urine or wild cat (cheetah or puma) urine was placed in two of the three arms and nothing was placed in the third arm. The researchers then measured how much time the rats spent in each of the three arms and how much they moved.

As expected, the T. gondii-infected rats avoided the cat-urine-soaked arms less than the uninfected rats did. Furthermore, when presented with a choice between arms with wild cat urine versus domestic cat urine, the infected rats (but not the uninfected rats) preferred the smell of the predatory wild cats over the domestic cats! Infected rats also moved more slowly around the wild cat urine compared to domestic cat urine, as if just begging any wild cats that may be around to eat them. It appears that T. gondii have developed a mechanism to turn rats into mindless zombies that practically run into the mouths of the nearest, most vicious cat they can find.

These mind-hacked rat-zombies may not be the only victims of T. gondii. People (particularly those that change their kitties’ litter boxes) can also become infected with the parasite. Some estimates suggest that nearly one-third of all people are already infected! Furthermore, people that test positive for T. gondii infection find the smell of cat urine more attractive than people who test negative! Although we are not likely to run to be eaten by our house-bound kitties, we may be more likely to change the litter box (or get more cats and become a crazy cat lady). So it looks like many of us are mind-hacked zombies too!

Want to know more? Check this out:

Kaushik, M., Knowles, S., & Webster, J. (2014). What Makes a Feline Fatal in Toxoplasma gondii's Fatal Feline Attraction? Infected Rats Choose Wild Cats Integrative and Comparative Biology, 54 (2), 118-128 DOI: 10.1093/icb/icu060

We Are Each A Community



Lactobacillus (the purple rod-shaped things)
is a common bacterial species in reproductive
tracts. Image by Janice Carr from the
CDC at Wikimedia Commons.

In our world of antibacterial soaps, we have learned that bacteria are evil, dirty, sickness-causing agents to be eliminated at all costs. Although some bacteria can cause sickness, bacteria in general are actually a critical component of animal bodies. A human body has ten times as many bacterial cells as human cells and a hundred times as many bacterial genes as human genes, and this pattern is likely true for most animals. We animals have bacterial communities living on our skin, fur, feathers, scales and exoskeletons. We have bacteria in our guts, respiratory systems and reproductive tracts. And bacteria live in glands that are specialized for grooming or scent communication. These bacteria play critical roles not just in how our bodies work, but also in how we behave.

This week at Accumulating Glitches I talk about how all animals (including ourselves) include a community of microbes, such as bacteria. Even more amazing is that many of these bacteria are critical for our health and behavior. Check it out here.

And to learn more, check this out:

Archie, E.A., & Theis, K.R. (2011). Animal behaviour meets microbial ecology Animal Behaviour, 82, 425-436 DOI: 10.1016/j.anbehav.2011.05.029

With a Fish in Your Pooper, Things Are Never Super (A Guest Post)

By Brittanie Delorit


You’ve probably heard of relationships between animals before: fish hitching a ride with a shark, clown fish hanging out in their anemones, or barnacles clinging to the fins of whales as they go for a swim; These are all unique in their own way. But have you ever heard of a fish living in the butt of another animal?

A Thelenota ananas sea cucumber
(one of the species used in this study).
Photo by Leonard Low at Wikimedia.

The sea cucumber, an echinoderm (along with sea urchins and sea stars), is found in shallow, sandy areas in all the world’s oceans. They eat by gulping in sand through their mouth, extracting decaying organic matter through their digestive tract and then excreting all of the unused matter from their anus. As if the way they eat isn’t strange enough, even more strange is the fact that sea cucumbers breathe using their anus. The sea cucumber gulps in water through its anus taking the oxygen out of the water… and that’s where the pearlfish come in, literally!

Several undergraduate scientists, Brooke Luciano, Ashleigh Lyman, Selena McMillian, and Abby Nickels, from the University of California in Santa Cruz, were on a Marine Ecology field course in French Polynesia. As part of their semester abroad, they wanted to study the interactions of pearlfish and their host, the sea cucumber. They focused their study on four main questions: 1) Is there competition to find a host?, 2) Is the pearlfish host specific and do they return to their original host after leaving?, 3) When the pearlfish finds a host are association cues present between the two?, and 4) Is the pearlfish nocturnally active?

To find results to their five hypotheses, studies were conducted. Two species of sea cucumbers were collected from sites outside of Opunohu Bay on the island of Moorea in French Polynesia. To remove the pearlfish from the sea cucumbers, the cucumbers were placed in a shallow, oxygen depleted container of water.

To answer the first question (Is there competition to find a host?), the pearlfish and the sea cucumber it inhabited were both tagged and observed to see if any fighting occurred between pearlfish. They also recorded if and when a pearlfish chose a different host to inhabit. Once they observed an incident of two male pearlfish fighting to the death inside a sea cucumber and resorting to cannibalism inside the cucumber. They also saw a pearlfish eating its way out of the sea cucumber it was inhabiting.

  It's reported that most pearlfish enter tail-first, like in this video. 

But cases of pearlfish entering head-first have been reported.

To answer the second question (Is the pearlfish host specific and do they return to their original host after leaving?), the pearlfish were tagged and then placed into a tank with multiple sea cucumbers including their present host. They then observed which cucumber they chose to inhabit, if they returned to it, and for how long. Conducting these studies concluded that no selectivity was found while observing the fish; most fish inhabited the first cucumber they came across even if it wasn’t theirs.

To answer the third question (When the pearlfish finds a host are association cues present between the two?), observations of the fish interacting with a potential host were recorded. Pearlfish smelling the length of their potential host was observed before actually entering the anus of the cucumber were recorded. The pearlfish were also observed listening along the sides of the cucumber, checking for another pearlfish already inside, and after checking, the pearlfish performed a type of knocking around the anus, encouraging its entrance into the body cavity of the cucumber. The sea cumber needs to open its anus to allow entrance for the pearlfish.

To answer the fourth question (Is the pearlfish nocturnally active?), night observations were done. But observations done at night showed no nocturnal behavior. This is strange because in the wild it has been observed that pearlfish live in the cucumber during the day, using them for protection, and then emerge at night to feed and scavenge. The reason no nocturnal behavior was observed in this study is thought to be because the pearlfish were under stress.

The relationship between pearlfishes and their sea cucumber hosts is one of the more intriguing cases of parasitism in the fish world. So if you happen to be a sea cucumber, make sure to hold your breath the next time you see a pearlfish swimming your way!


Article:
Luciano, B., Lyman, A., McMillian, S., Nickels., A. 2002. The symbiotic relationship between Sea cucumbers (Holothuriidae) and Pearlfish (Carapidae). A project of the Marine Ecology Field Quarter at the University of California, Santa Cruz, pgs 1-8. Available online: http://bio.classes.ucsc.edu/bio162/Previous%20Class%20Material/Moorea%202002/Readings/cucumbers.pdf

Welcome Home to Wood Tick Acres!

Early last spring I was offered a new job and embarked on a search for a new home. We found a beautiful property: wooded acreage with a trout stream and spring-fed pond, all in a reasonable commuting distance. The potential of this forest sanctuary glistened even under feet of spring snow.

When we returned in the rains of early summer to collect our keys and move in, we found that the thaw had revealed our forest sanctuary to be a mosquito-infested swampy wetland, complete with this welcome sign:

 Ticks? In a wetland? You wouldn’t think ticks would do so well in the water… But think again.

Ticks, like spiders, are arachnids. They’re known for feeding on the blood of other animals, but in reality, they only do so three times in their life (once in each life stage). Between those three blood meals, they can live for months or even years without feeding. Their extremely low energy metabolism (only about 10% that of insects and spiders), waterproof “skin”, and cold hardiness give them the ability to hunker down and ride out a range of weather conditions. And anyone who has tried swimming or doing laundry as a means of getting rid of ticks knows they can withstand those pressures too.

Photo of ticks
in a jar by
Laura Fielden-Rechav.

Researchers Laura Fielden-Rechav, Lisa Knolhoff, Susan Villarreal and Philip Ryan from Truman State University tested how long wood ticks (also known as dog ticks) could survive while submerged in water. They did this by placing ticks in water-filled jars for up to three weeks. Every day they removed a few ticks from the jars and placed them on a piece of paper to see if they recovered. Amazingly, the ticks survived underwater for 11 days on average and some lasted as long as 15 days!

If ticks can live underwater for nearly two weeks, this suggests that either 1) they are holding their breath and do not need much oxygen or 2) they can somehow get oxygen out of the water. The researchers tested this by having another set of ticks in water-filled jars, but this water had less oxygen in it. These ticks survived underwater for only 7 days on average, which shows us that the ticks are getting and using oxygen from the water.

So how do air-breathing ticks get oxygen from water? Ticks, like most insects and many spiders, have a breathing system called a tracheal system. This is a system of branching gas-filled tubes that provide each cell in the body with access to the environmental gas and the oxygen it contains. The tracheal system connects with the environment through openings in the body wall called spiracles. This is a great system for breathing air, but not for breathing water. So many water-breathing insects have developed an additional system called a plastron. A plastron is typically a region of the body near the spiracles that has lots of tiny water-repelling hairs that trap air around the opening of the animal’s breathing system. As the animal uses up its body’s oxygen, the oxygen levels in this trapped air space decline and oxygen then diffuses from the water around the animal into this trapped air space. Once the oxygen in the plastron air space is restored, the animal can breathe it with its air-breathing tracheal system. It works kinda like a perpetually refilling oxygen tank for SCUBA divers (if something so cool even existed).

The picture on the left shows a wood tick under the microscope. Notice the large spiracles behind the hind legs. If you don't see them there, check out the red spots on the sketch on the right. Images by Laura Fielden-Rechav.

The researchers were curious whether wood ticks have a plastron system to help them survive underwater for long periods of time. Ticks have two spiracles located behind their hind legs (which means they breathe with their rear end, not with their face – This is why they can bury their face into another animal to eat a blood meal without suffocating). The researchers wanted to test if these spiracles may each have a plastron. A plastron system relies on water surface tension that is generated by the water-repelling hairs, so if you do something that reduces this surface tension, it should block a plastron from being able to function. Rubbing alcohol breaks surface tension. So the researchers submerged three different groups of ticks in water: one group was just submerged as-is; a second group had one spiracle wetted with alcohol before they were submerged in water; and a third group had both spiracles wetted with alcohol before they were submerged in water. The group with no alcohol on either spiracle lived several days longer than either of the groups with alcohol.

When the researchers looked at the ticks under a high-powered microscope, they did not see little hairs that are typical of plastrons, but they did see lots of pores that open into structured pockets of airspace. This structure could produce the surface tension needed for a plastron system to work. So based on their evidence that ticks with spiracles wetted with alcohol don’t live as long in water and the microscope images showing these air pockets, it looks like air-breathing wood ticks can survive for long periods of time underwater by breathing with a unique plastron system never before seen in another species.

Before you get too grossed out the next time you pull a tick off your dog, take a minute to appreciate the incredible ability of this hardy critter.

Want to know more? Check this out:

Fielden, L.J., Knolhoff, L.M., Villarreal, S.M., & Ryan, P. (2011). Underwater survival in the dog tick Dermacentor variabilis (Acari:Ixodidae) Journal of Insect Physiology, 57, 21-26 DOI: 10.1016/j.jinsphys.2010.08.009

True Blood: Vampires Among Us

Who is your favorite vampire? Are you a fan of Edward Cullen, Bill Compton or Stefan Salvatore? Or do you prefer the classic Dracula, elegant Lestat, or butt-kicking Selene?

Vampires have fascinated us since the Middle Ages, when a hysteria of vampire sightings spread across Eastern Europe. We now know that many of these “vampires” were actually victims of diseases like tuberculosis or bubonic plague that cause bleeding in the lungs (and elsewhere), resulting in the disturbing effect of blood appearing at the lips. Add this attribute to the already poorly understood physiology of decomposing corpses and the cases in which people mistakenly buried alive got up and left their graves, and voila! Vampire mythology is born. So vampires don’t really exist… Or do they?

Actually, there are many animals that feed on blood. So many in fact, that there is a scientific term for blood-eating, hematophagy. And why not? Blood is fluid tissue, chock full of nutritious proteins and lipids and a source of water to boot. And if you don’t kill your prey to feed, the food supply replenishes itself. Here are just some of these animal vampires living among us:

Vampire bat

A vampire bat smiles for the camera
from his Peruvian cave. Photo from Wikimedia.

Vampire bats are our most famous animal vampires, and the ones that most resemble our vampiric lore. There are three species of vampire bats that live from Mexico down through Argentina. Two of them, the hairy-legged and white-winged vampire bats, feed mostly on birds. The common vampire bat feeds more on mammals, like cows, horses, and the occasional human. Their razor sharp teeth cut a tiny incision in their victims and their anticoagulant saliva keeps the blood flowing. Like Dracula, vampire bats sleep by day and hunt by night. But these vampires are not loners like Dracula: They live in colonies of about 100 animals, and in hard times will share their blood-harvest and care for one another’s young.

Vampire finch

The Galapagos Islands are the famous home to numerous finch species, each one with a beak shape specially adapted to their preferred food source. For most of these finches, their food of choice is a type of seed or nut that is appropriately sized for their beak shape and strength. But the vampire finch (also called the sharp-beaked ground finch for obvious reasons) uses its long sharp beak to feed on blood. Their most common victims are their booby neighbors (named for less obvious reasons).

Candirú

A tiny candirú catfish (being measured in cm) strikes
terror into the souls of Amazonian fishermen.
Photo by Dr. Peter Henderson at PISCES
Conservation LTD. Photo at Wikimedia.

The tiny Amazonian candirú catfish is legendary for one documented case (and several undocumented ones) in which a candirú swam up a local man’s urine stream into his penis, where it attached to feed on his blood. Although terrifying, this is not typical candirú behavior. Actually, it was all just a misunderstanding. You see, candirú catfish do feed on blood, but they usually feed from the highly vascularized gills of other Amazonian fish. As we saw last week, the gills of freshwater fish release high quantities of urea, a major component of urine. So to a hungry candirú, your pee smells an awful lot like a fish-gill blood dinner. Just another reason to not pee where you swim.

Lamprey

Notice the sharp-toothed sucker mouth of the river
lamprey. Photo by M. Buschmann at Wikimedia.

Lampreys are species of jawless fish. With their eel-like bodies and disc-shaped mouths filled with circles of razor-sharp teeth, they look like something from science fiction horror. Although some lamprey species are filter feeders, others latch onto the sides of other fish, boring into their flesh and feeding on their blood. Once attached, they can hitch a ride on their victim for days or even weeks.

Leech

A European medicinal leech.
Photo by H. Krisp at Wikimedia.

Leeches are the earthworm’s bloodsucking cousins. With three blade-like mouthparts, they slice into their victims, leaving a Y-shaped incision. They produce anticoagulants to prevent premature clotting of their bloodmeals, which can weigh up to five times as much as the leach itself. The bloodletting and anticoagulant abilities of leeches have led them to be used medicinally in ancient India and Greece as well as in modern medicine.

Female mosquito

A female mosquito getting her blood meal.
Photo by at Wikimedia.

Most of the time, mosquitos use their syringe-like mouthparts to feed on flower nectar. But when the female is ready to reproduce, she seeks out a blood meal to provide the additional protein she will need to produce and lay her eggs. Although their bites only cause minor itching, these lady vampires are truly something to be feared: They kill more people than any other animal due to the wide range of deadly diseases they spread.

There are many other examples of animals that feed on blood. But unlike their mythological counterparts, none of them come back from the dead to do so… Or do they?

Happy Halloween!

Want to know more? Check these out:

1. SCHLUTER, D., & GRANT, P.R. (1984). ECOLOGICAL CORRELATES OF MORPHOLOGICAL EVOLUTION IN A DARWINS FINCH, GEOSPIZA-DIFFICILIS EVOLUTION, 38 (4), 856-869

2. Francischetti, I. (2010). Platelet aggregation inhibitors from hematophagous animals Toxicon, 56 (7), 1130-1144 DOI: 10.1016/j.toxicon.2009.12.003

Mind-Manipulating Slave-Making Ants!

An entire colony enslaved by an alien species to care for their young. Slave rebellions quelled by mind manipulation. It sounds like science fiction, right? But it really happens!

Myrmoxenus ravouxi (called M. ravouxi for “short”) is a slave-making ant species in which the queen probably wears a chemical mask, matching the scent of a host species in order to invade their nest without detection. Once inside, she lays her eggs for the host species workers to care for. Armies of M. ravouxi workers then raid these host colonies to steel their brood to become future slave-laborers to serve the needs of the M. ravouxi colony.

A M. ravouxi queen throttling a host queen. Photo by Olivier Delattre.

Enslaved worker ants could rebel: They could destroy the parasite brood or at least not do a good job caring for them. But to selectively harm the parasite brood without harming their own nests’ brood, the host ants would have to be able to tell them apart. Ants learn the smell of their colony in their youth, so any ants born to an already-parasitized colony would likely not be able to tell apart parasite ants from their own species. But what about ants that were born to colonies before they were invaded?

Olivier Delattre, Nicolas Châline, Stéphane Chameron, Emmanuel Lecoutey, and Pierre Jaisson from the Laboratory of Experimental Ethology in France figured that compared to ant species that were never hosts to M. ravouxi colonies, ant species that were commonly hosts of M. ravouxi colonies would be better able to discriminate their own species’ brood from M. ravouxi brood. Host species may even be better at discriminating in general.

The researchers collected ant colonies from near Fontainebleau and Montpellier in France. They collected M. ravouxi colonies and colonies of a species that they commonly parasitize (but were not parasitized at the time): Temnothorax unifasciatus (called T. unifasciatus for “short”). The researchers also collected T. unifasciatus that were parasitized by M. ravouxi at the time. Additionally, they collected colonies of T. nylanderi and T. parvulus, two species that are never parasitized by M. ravouxi. (Sorry guys. All these species go by their scientific names. But really, that just makes them sound all the more mysterious, right?). The researchers took all their ant colonies back to the lab and housed them in specialized plastic boxes (i.e. scientific ant-farms).

On the day of the tests, the scientists removed a single pupa (kind of like an ant-toddler) from one nest and placed it into a different nest of the same species or back in its own nest. They did this for colonies of both non-host species and for colonies of host species T. unifasciatus that were not parasitized at the time. Then they counted how many times the workers bit the pupa (an aggressive behavior) or groomed the pupa (a caring behavior).

Workers from all three species bit the pupa that was not from their colony more than they bit their own colony’s pupa. But the T. unifasciatus (the host species) were even more aggressive to foreign pupa than the other species. And only the T. unifasciatus withheld grooming from the pupa that was not from their colony compared to the one that was from their colony. Although all three species seemed to be able to tell the difference between a pupa from their own nest versus one from another nest, only the species that is regularly enslaved by M. ravouxi decreased care to foreign young. So that is what these ants do when they are not enslaved. How do you think enslaved ants respond to their own species’ young compared to M. ravouxi young?

A 1975 cover of Galaxie/Bis, a
French science fiction magazine,
by Philippe Legendre-Kvater.
Image from Wikimedia.

The researchers repeated the study using enslaved T. unifasciatus, placing either a pupa of their own species from a different nest or a M. ravouxi pupa in with their brood. Even though prior to M. ravouxi takeover the T. unifasciatus bit foreign pupa more than their own, after M. ravouxi takeover they didn’t bite foreign pupa of their own species or M. ravouxi pupa very much. Not only that, but they groomed the M. ravouxi pupa more than the pupa of their own species! Ah hah! Mind control!

This, my friends, is the kind of truth that science fiction is made from.

But how might this work? Ants born to an enslaved colony would be exposed to both their own odors and the M. ravouxi odors. Because ants learn the smell of their colony in the first few days after they emerge from their eggs, these enslaved ants would have a broader set of smells that they may perceive as being “within the family”. That would explain why the enslaved T. unifasciatus ants didn’t attack either the foreign-born T. unifasciatus or the M. ravouxi young, but it doesn’t explain why the enslaved ants provided more care to the M. ravouxi than they did to their own species. One possibility is that the M. ravouxi produce more or especially attractive odors to encourage the host workers to take care of them.

There is still more to learn about this system: How exactly may the M. ravouxi be hijacking the pheromonal systems of their host species? How are the host species protecting themselves from exploitation? I guess we’ll have to wait for the sequel.

Want to know more? Check this out:

Delattre, O., Chȃline, N., Chameron, S., Lecoutey, E., & Jaisson, P. (2012). Social parasite pressure affects brood discrimination of host species in Temnothorax ants Animal Behaviour, 84, 445-450 DOI: 10.1016/j.anbehav.2012.05.020