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5 Real-Life Zombies

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Wikimedia Commons

While I wouldn’t hold my breath waiting for the dead to rise from their graves, there are still plenty of zombies roaming the Earth. Some of them are in the waters where we swim (not unlike this guy), and many more of them are right underneath our feet.

To get a leg (or six) up in a world that’s red in tooth and claw, some animals have struck upon a peculiar strategy: bending other critters to their will like VooDoo zombie masters and using them as homes, hosts, food or labor. Here are just a few of nature’s zombies and the parasite masters that control them. They’re coming to get you Barbara…

1. Fungus Among Us

When a spore of Ophiocordyceps unilateralis meets an ant, things get very weird and very bad for the ant very quickly. The spore germinates and enters the ant’s body through holes in its exoskeleton. The fungus then starts to grow inside the ant’s body, absorbing soft tissue while leaving vital organs intact, for the ant must remain alive and fully functional for a while longer to be of real use to the fungus.

When O. unilateralis reaches the autumn of its short life and is ready to sporulate and make way for a new generation, its long, branching filaments grow into the ant’s brain. The fungus produces chemicals that poison the ant’s brain and cause it to become transportation to the fungus’ birthing ground—and its own hearse. The ant, no longer in control of its own body, leaves its colony, climbs a plant, and clamps its mandibles around a leaf at the top, fastening it to its grave. There, new life springs into the world, right out of the ant’s head. Now out in the open, the fruiting bodies of the fungus mature and burst, releasing clusters of spore capsules into the air. As they descend, these capsules explode, spreading spores like confetti over the ground. The spores  infect other ants, continuing the fungus’ bizarre life cycle. The whole ordeal, from one infection to the next, can take as little as two weeks.

2. What a Web It Weaves

Thwack

Normally, the web of an orb weaver spider is where bugs meet their untimely death and become spider snacks. Using an arsenal of toxins and mind-altering chemicals, though, the parasitic wasp Hymenoepimecis argyraphaga turns the spider into a slave and a meal, and its web into a safe haven. The female wasp paralyzes the spider with a sting and then lays her egg on its abdomen. When the egg hatches, the larva lives on the spider and sucks hemolymph (kind of the arthropod version of blood) from its body for nourishment.

A few weeks later, the larva is ready to move on to the next stage of its life cycle, and injects the spider with a chemical (as yet unidentified) that alters its behavior. The next time the zombie spider builds a web, it repeats the first few steps over and over again instead of going through all the regular steps, resulting in a web that’s just a few heavily-reinforced anchor threads and a small center section. Then the spider crawls to the center of the web and sits there complacently. The larva molts, kills the only companion it has ever known, sucks any remaining useful bits out from its corpse, and discards it. Then it builds its cocoon on a web custom-built for the job. A few weeks later, the adult wasp emerges and flies away, and the cycle starts over.

3. Roach Motel

Like H. Argyaphaga, the Emerald Cockroach (or Jewel) Wasp is free-living as an adult, but starts life inside a host. As their name suggests, these wasps use cockroaches as living nurseries for their little bundles of joy. When a female wasp is ready to lay her eggs, she swoops in, lands on a roach’s back and plunges her stinger into its midsection. The roach’s legs buckle and it tumbles to the ground, unable to flee or fight back for a short while. This buys the wasp time to play brain surgeon. She slides her stinger through the roach’s head and into its brain, slowly probing until she hits just the right spot. The venom she releases this time doesn’t paralyze the roach; it can move its legs again, but not of its own accord. When the momma wasp grasps its antennae and starts moving, it follows her like an obedient puppy. She leads the roach to her burrow, where she lays her egg on its abdomen and then leaves. All the roach can do is sit and wait. Soon the egg hatches and the larva emerges. It chews into the roach’s abdomen and wriggles inside, where it lives for a week, devouring the roach’s organs the whole while. It forms a pupa and emerges as a full-grown adult a few weeks later, bursting forth from the roach and leaving it buried in the burrow.

4. The Bodyguard

Last wasp, we promise (there are just so many!). The females of the genus Glyptapanteles lay scores of eggs inside caterpillars, and the larva squirm out a short time later to spin their cocoons. It seems like the caterpillar gets off a little easier than those poor roaches and spiders, but its work isn’t done yet. A few of the larva actually stay behind inside the caterpillar and give up their chance to pupate and mature, for the good of their siblings. They take control of their host’s body, and force it to stand guard over the cocoons. The caterpillar waits motionless, unless a potential predator comes too close to the pupae, in which case it thrashes violently at the visitor to drive it away. By the time the adult wasps emerge, the caterpillar, which hasn’t eaten during its guard duty, dies from starvation.

5. Watery Grave

The parasitic hairworm grows up on land—specifically, inside a grasshopper or a cricket—but is aquatic as an adult. To make the transition to water, it forces its host to take it for a swim. The worm pumps the insect full of proteins (which may mimic ones that the host produces on its own) that sabotage its central nervous system and compels it to leap into the nearest body of water. The host drowns and the adult worm, three to four times longer than the corpse it once called home, wriggles out and swims away in search of a mate. The babies they make will infest the water until they're guzzled down by a host they can call their own.

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Big Questions
Why Do Small Dogs Live Longer Than Large Dogs?
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Why do small dogs live longer than large dogs?

Adriana Heguy:

The issue of body size and lifespan is a fascinating topic in biology. It’s strange that across species, at least in mammals, large-bodied animals live longer than small-sized animals. For example, elephants live a lot longer than mice. The theory is that
bigger animals have slower metabolisms than small animals, and that faster metabolisms result in more accumulation of free radicals that damage tissue and DNA. But this doesn't always hold for all animals and the “rate of living” theory is not widely accepted. What we cannot clearly understand remains fascinating.

But now if we look at within a given species, lifespan and body size are inversely correlated. This is definitively the case for dogs and mice, and it has been proposed that this is the case for humans, too. Why would this be? A possible explanation is that larger dogs (or mice, or people) grow faster than their smaller counterparts because they reach a larger size in more or less the same time, and that faster growth could be correlated with higher cancer rates.

We do not have a clear understanding of why growing faster leads to accelerated aging. But it seems that it is an accelerated rate of aging, or senescence, that causes larger dogs to have shorter lifespans than little dogs.

The figure above is from Ageing: It’s a Dog’s Life. The data is from 32 breeds. Note that the inverse correlation is pretty good, however some large dog breeds, at around 40 to 50 kg (or about 88 to 110 pounds), live 12 or 13 years in average while some other dog breeds of equal body size live only eight or nine years on average. This is due to dogs being a special case, as they were artificially bred by humans to select for looks or behavior and not necessarily health, and that considerable inbreeding was necessary to produce “purebred” dogs. For example, boxers are big dogs, but their higher cancer rates may result in a shorter lifespan. However, the really giant breeds all consistently live eight to nine years on average. So there is something going on besides simple breeding quirks that led to bad genetics and ill health. Something more general.

A few years ago, a large study [PDF] was published using mortality data from thousands of dogs across 74 breeds, testing three hypotheses: Large dogs may die younger than small dogs because of (1) an earlier onset of senescence, (2) a higher minimum mortality hazard, or (3) an increased rate of aging. The conclusion from their study is that aging starts more or less at the same age in small and large breeds, but large breeds age faster. We do not have a clear understanding of the underlying mechanism for faster aging in dogs. It seems that when we selected for large body size, we selected for faster aging as well. But we do not know all the genetic components of this. We know that there are at least three genes that determine large body size in dogs: IRS4 and IGSF1, involved in thyroid hormone pathways which affect growth, and ACSL4, involved in muscle growth, and back fat thickness.

But how this accelerates aging is still speculation. More studies are needed, but dogs seem to be a great model to study the evolution of body size and its relationship to aging.

This post originally appeared on Quora. Click here to view.

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Big Questions
Should You Keep Your Pets Indoors During the Solar Eclipse?
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By now, you probably know what you’ll be doing on August 21, when a total solar eclipse makes its way across the continental United States. You’ve had your safety glasses ready since January (and have confirmed that they’ll actually protect your retinas), you’ve picked out the perfect vantage point in your area for the best view, and you’ve memorized Nikon’s tips for how to take pictures of this rare celestial phenomenon. Still, it feels like you’re forgetting something … and it’s probably the thing that's been right under your nose, and sitting on your lap, the whole time: your pets.

Even if you’ve never witnessed a solar eclipse, you undoubtedly know that you’re never supposed to look directly at the sun during one. But what about your four-legged family members? Shouldn’t Fido be fitted with a pair of eclipse glasses before he heads out for his daily walk? Could Princess Kitty be in danger of having her peepers singed if she’s lounging on her favorite windowsill? While, like humans, looking directly at the sun during a solar eclipse does pose the potential of doing harm to a pet’s eyes, it’s unlikely that the thought would even occur to the little ball of fluff.

“It’s no different than any other day,” Angela Speck, co-chair of the AAS National Solar Eclipse Task Force, explained during a NASA briefing in June. “On a normal day, your pets don’t try to look at the sun and therefore don’t damage their eyes, so on this day they’re not going to do it either. It is not a concern, letting them outside. All that’s happened is we’ve blocked out the sun, it’s not more dangerous. So I think that people who have pets want to think about that. I’m not going to worry about my cat.”

Dr. Jessica Vogelsang, a veterinarian, author, and founder of pawcurious, echoed Speck’s statement, but allowed that there’s no such thing as being too cautious. “It’s hard for me to criticize such a well-meaning warning, because there’s really no harm in following the advice to keep pets inside during the eclipse,” Vogelsang told Snopes. “It’s better to be too cautious than not cautious enough. But in the interest of offering a realistic risk assessment, the likelihood of a pet ruining their eyes the same way a human would during an eclipse is much lower—not because the damage would be any less were they to stare at the sun, but because, from a behavior standpoint, dogs and cats just don’t have any interest in doing so. We tend to extrapolate a lot of things from people to pets that just doesn’t bear out, and this is one of them.

“I’ve seen lots of warnings from the astronomy community and the human medical community about the theoretical dangers of pets and eclipses, but I’m not sure if any of them really know animal behavior all that well," Vogelsang continued. "It’s not like there’s a big outcry from the wildlife community to go chase down coyotes and hawks and bears and give them goggles either. While we in the veterinary community absolutely appreciate people being concerned about their pets’ wellbeing, this is a non-issue for us.”

The bigger issue, according to several experts, would be with pets who are already sensitive to Mother Nature. "If you have the sort of pet that's normally sensitive to shifts in the weather, they might be disturbed by just the whole vibe because the temperature will drop and the sky will get dark,” Melanie Monteiro, a pet safety expert and author of The Safe-Dog Handbook: A Complete Guide to Protecting Your Pooch, Indoors and Out, told TODAY.

“If [your pets] have learned some association with it getting darker, they will show that behavior or at a minimum they get confused because the timeframe does not correspond,” Dr. Carlo Siracusa of Penn Vet Hospital told CBS Philly. “You might put the blinds down, but not exactly when the dark is coming but when it is still light.” 

While Monteiro again reasserts that, "Dogs and cats don't normally look up into the sun, so you don't need to get any special eye protection for your pets,” she says that it’s never a bad idea to take some extra precautions. So if you’re headed out to an eclipse viewing party, why not do your pets a favor and leave them at home. They won’t even know what they’re missing.

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