Jennifer Zaspel cannot explain why she decided to stick her thumb in the moth bottle. Just wanted. She caught moths on a July night in the Russian Far East and caught a Calyptra, with brown curls on its wings that resemble dried leaves, in a plastic collection bottle. Of the 17 tropical species of calipra, eight were vampires. Males sometimes stray from their fruity diet, sinking their robust mouth jaws into mammals such as cattle, tapirs, and even elephants and humans to drink fresh blood.
But Zaspel believed that she was outside of the territory in which she could encounter the species of vampires. She caught C. thalictri, widely known in Switzerland, France and up to Japan as a strict fruit-eating.
Before rolling up the moth bottle, “I just put my thumb in it to see what she did,” says Zaspel. "She pierced my thumb and started eating me."
So much for eight vampires. Zaspel, an entomologist at the Milwaukee Public Museum, is still puzzled by the genetics of moths in two Russian locations she visited in 2006. Males will bite the researcher's finger if offered, but genetic studies show these moths are on the list of friendly species. At least they should.
The proboscis of Calyptra thalictri extracts blood from a scientist. For a long time it was believed that this moth feeds exclusively on fruits, because its proboscis is better adapted for punching plums than its thumb.
“I would compare it to a bee sting,” says Zaspel. For the benefit of science, one of Zaspel's colleagues voluntarily documented the experience, noting that the moth ate for 20 minutes. These bites definitely don't go unnoticed. These moths and other vampires risk their lives while feeding.
Interrupting occasional red breakfasts or trying to survive with blood alone is much more difficult than shown in the movies. Relatively few animals lead a similar lifestyle: some insects and other arthropods, some molluscs, some fish, sometimes birds, and, of course, three species of bats.
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Blood is not the easiest food to eat. The animal usually tries to absorb as much food as possible at a time. But with such heroic volumes, blood can be toxic. That said, bloody food alone is not enough, as it lacks some of the basic nutrients. With this lifestyle, the intestines have a special physiology. Modern tools in genetics and molecular biology reveal hidden specializations required for blood feeding, and at the same time brutal practices that sometimes go to the extreme, such as transferring blood from moth to moth. While many of these biological adaptations will never match the power of immortal vampires, in some ways they can be considered super powers.
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To understand the risks that real vampires take, imagine an animal that weighs 35 million times yours. Now try to bite him. Strong enough to bleed.
Obviously, it will go berserk. "You can easily be killed by a host," says molecular insect physiologist Pedro Oliveira of the Federal University of Rio de Janeiro. A multiplier of 35 million is applied to a 2 milligram mosquito attacking a 70 kilogram person.
Finding such a giant source of blood is not easy. “If we go into the forest, there will be hundreds of meters of distance between the vertebrate hosts, and hundreds of meters will be like kilometers for us,” says Oliveira. The tiny vampire then needs to find a capillary to bite through, just a few millimeters below the surface of the skin. In the case of humans, only about 10% of the skin is suitable.
The blood-sucking professional, the Rhodnius prolixus beetle, has enzymes in the intestines that keep the tyrosine in food from crystallizing and puncturing tissue.
Given the dangers and challenges faced by blood donors, “most of them try to minimize the number of visits,” says Oliveira. They drink fast and drink a lot. A young bloodsucking beetle, capable of spreading debilitating Chagas disease, drinks 10 times its weight in blood in just a few minutes.
To tie it to human physiology? Forget it. There are people who deliberately drink blood, and that's another story, but even small amounts by vampire standards - like blood swallowed through nosebleeds - can cause stomach upset, meaning diarrhea, says Thomas Gantz of David Geffen School of Medicine of University of California, Los Angeles. Fresh blood is difficult for the human intestine to digest and very little water is extracted from the blood and sent to the kidneys. Gantz compares blood to solutions that people drink to cleanse the digestive system, quickly and uncomfortably, for colonoscopy.
Ingredients that would be harmless in large quantities can be toxic with high blood intake. "The dose determines the poison," says Oliveira.
Remove water from the blood and get 90% protein. Oliveira faced the danger of this protein while researching the genetics of one of the American beetles, Rhodnius prolixus, in his laboratory. This teardrop-shaped beetle, with a body tapering towards the head, hides in crevices indoors or outdoors. At night, male and female beetles are looking for people, their pets or other mammals for a blood meal. This beetle is extremely secretive and, unlike the vampire moths, does not awaken its prey when bitten. Unlike mosquitoes, whose bites transmit pathogens through saliva, this beetle transmits Chagas disease parasites through excrement that it leaves on the host.
Of all the amino acids found in this large serving of the drink, tyrosine alone has a large array of enzymes ready to break it down in the stomach of a beetle, scientists showed in 2014. Finding enzymes that break down tyrosine in the gut is "a little weird," Oliveira says. In mammals, the liver and kidneys are the only organs with tyrosine-degrading enzymes. Again, most mammals don't flood their guts with protein alone.
When the researchers turned off the beetle's tyrosine-breaking abilities, either genetically or by chemically blocking enzymes, the beetles died after lunch. Oliveira and colleagues wrote about this in Current Biology in 2016. Some of the dead beetles showed that tyrosine crystals pierced the intestines and splashed its contents into the body cavity. This discovery, the scientists noted, could one day give molecular biologists their own medicine that would serve to kill vampires.
Bloodsucking in arthropods has developed independently several times (up to 21), but more often than not, vampires had to solve the same problems with various quirks of biochemistry. However, tyrosine detoxification could be a problem that many bloodlines have tackled in an unusually similar way, Oliveira said.
The first weapon strikes to turn off general chemistry are compounds that inhibit the HPPD enzyme. The enzyme stops the breakdown of tyrosine, and not only in the aforementioned beetles. When tested, the method was safe for dairy beetles and mealy worms.
Bad blood
Tyrosine is just one of the nutrients that become toxic through volume. In the real world, the ability of vampires to excrete waste is much more important than some kind of fictional power to lift trucks.
Nephrologist Jonas Axelsson of the Karolinska Institute in Stockholm and his colleagues are studying kidney function in vampire bats compared to their sibling species living on fruit or nectar. A human diet typically includes 50 to 120 grams of protein per day, but if fed like a vampire bat, the human equivalent would be 6,000 grams of protein per day for a 70-pound body. This protein overdose means that these bats have a concentration of protein in protein-metabolic waste products such as urea, which will instantly lead to kidney failure in humans.
But the vampire mice are fine. Their kidneys are the same size as those of other bats. Vampire mice devote more space to the long tubules that reabsorb nutrients from freshly prepared urine, he notes.
Most of the protein in the blood is hemoglobin, an iron-containing miracle molecule that carries oxygen throughout the body and helps vertebrates grow big and fat. However, the rapid digestion of this amount of hemoglobin can release a potentially toxic dose of iron into the bloodstream. A healthy person can make their doctor happy with an iron concentration in the blood of the order of 127 micrograms per 100 milliliters. However, concentrations 200 times higher do not appear to harm the larval species of lamprey. The larvae take iron in the process of eating whatever they find. As the sea lampreys (Petromyzon marinus) mature, they develop pitiless rows of teeth, which they pierce and suck blood from other fish. At the same time, the concentration of iron in the blood falls - to about 10 times the level of healthy for humans.
But even worse than blood-sucking sea lampreys is the secretion that prevents the victim's blood from clotting.
Lampreys first adhere to the skin, which resembles a "moisturized sucker on the face," says lamprey specialist and biologist Margaret Docker of the University of Manitoba in Winnipeg, Canada. As part of an experiment, she allowed a blood-sucking silver lamprey (Ichthyomyzon unicuspis) to bite her cheekbone. They are found in lakes and streams in North America. Only half of the world's 38 species of lampreys suck blood.
Lampreys capture prey well. Some do not disengage even when driving up waterfalls or dams. It is extremely rare that a fish has time to drop a lamprey before it grabs its teeth on its tongue or oral disc and releases its anticoagulants.
Lampreys could have become parasites at the very beginning of vertebrate history, and therefore they had to develop their vampiric tendencies for a long time. Some 360 million-year-old Devonian fossils, dating back to well before the heyday of the dinosaurs, exhibit an oral disc with 14 evenly spaced teeth, seemingly ready to suck blood.
The study of the physiology of modern bloodsuckers received a powerful source of new data in 2013, when an international team of scientists deciphered a book with genetic instructions for sea lamprey. Docker hopes to reveal more detoxification tricks in lampreys, such as superoxide dismutase, which increases as liver iron levels rise in adult lampreys. At this stage, liver cells are similar to human cells when suffering from hemochromatosis. Another reason to study real vampires, if there aren't enough of them, is to uncover new secrets of human metabolic disease.
Not enough
In the blood can be catastrophically a lot of some things and catastrophically few others. “It's not easy for vampires to deal with this,” says microbiologist Rita Rio of West Virginia University in Morgantown.
She explains that there is not enough B vitamins in the blood. Animals need these substances as nutrients for a wide range of basic body processes such as gene regulation, cell signaling and amino acid breakdown. However, animals cannot make their own supplies. Any Ryo vampire flies get around this problem very cleverly.
“I've loved tsetse flies since I first learned about them,” she says. In sub-Saharan Africa, flies have “really cool biology,” she says, and it’s not their ability to spread parasites that put people to death.
Tsetse flies are similar to normal fat house flies, but are very different. Instead of laying many small eggs like a normal insect and hoping that some of the offspring are lucky, a female tsetse fly carries one offspring at a time. One egg appears in it and, as it grows, draws food from the "mammary" glands inside the mother. You can see how it becomes more and more gluttonous. Sometimes the mother gives offspring that is larger than her. And then the offspring by this time will have only a puppet stage, separating them from maturity. “As if I gave birth to a 12-year-old,” says Rio.
When a fly mom gives her baby a head start in life, she also gives him the infection that will be needed to incorporate the bloody diet into his diet. Each larva emerges with its own rod-shaped bacteria, Wigglesworthia. These bacteria consume B vitamins and thrive inside a special organ that grows inside the fly. The tsetse fly's version of this organ - a bacterioma - is like "a little donut around the digestive tract," Rio says.
The interaction between the fly and the microbes has attracted evolutionary biologists, as the genes of the bacteria and the host change over generations, sometimes destroying or creating strange functions, depending on the actions of one of the partners.
Low fat bats
Another disadvantage of blood is its low fat content, at least from the vampire bat's point of view. A small flying mammal can only carry 20-30% of its own weight as a load, so a small, fat-free snack will not be able to saturate a mouse for a long time. A typical vampire bat (Desmodusrotundus) can't survive three days without drinking blood, says evolutionary biologist Gerald Wilkinson of the University of Maryland at College Park. This is one of the forces pushing these mice to build social circulatory networks.
These sharp-toothed mammals belong to one of three species of bloodsucking bats, all of which are found in the warm latitudes of the western hemisphere. Wilkinson encountered the first wild D. rotundus he studied at a ranch in Costa Rica, where he "often took off and landed on the croup of a horse," he says. The mouse had a fleshy little nose, "like a pig," capable of sensing heat - this helps to determine where warm blood flows closest to the surface of the body. In general, getting blood "was not the most trivial thing for mice." Usually, the mouse spends half an hour looking for a spot, combing the horse's hair, if necessary, biting off a tiny piece of flesh and licking the wound, while urinating. The horse doesn't even wake up. Going back to the wound the next night is much easier than finding a new location. Wilkinson realized that the bat feeds on the same horse,despite the fact that the horse moves to another pasture.
According to Wilkinson, bat saliva has impressive anticoagulant properties. “I was bitten several times and the blood was difficult to stop,” he says. "People who were bitten woke up in a pool of blood - and often the blood goes long after the bat leaves."
Compared to other species of bats, the common vampire bat has almost superpowers: instead of flying, it just runs on the ground.
When a hungry bat cannot find food for the night, an experienced bloodsucker can take some blood from a more successful hunter. They position their faces one against the other, and "while one animal is stationary, the other licks," Wilkinson says.
In his first experiments with captive bats, he found animals willing to periodically share blood with hungry mice without any kind of relationship. For decades, scientists have debated whether it is fair to regard vampire bats as examples of natural altruists. Even in captivity, the vampire helps a starving relative.
Yes, being a vampire is difficult. Therefore, vampires help each other.
Ilya Khel