by Matt Simon
To the naked eye, the blast looks simple. Poke a velvet worm and there’s suddenly slime on your fingers. But slow the squirt down and the majesty of the velvet worm glue gun becomes clear. Each of the cannons is oscillating, waving horizontally to create a stream that looks like a sine wave. Yet that isn’t a muscular action. It’s simply a trick of physics: Just as a garden hose left to its own devices at full blast will flop around, so, too, do the velvet worm’s guns, as many as sixty times a second. And so the two streams will cross over each other, creating more of a shotgun blast than a precise shot, to hit prey as far as eight inches away.
Once the glue coats the victim, it immediately coagulates. The prey is doomed, and struggling only helps ensnare it more. Never one to be rushed, the velvet worm approaches slowly. It crawls up on top of the victim and searches for a good spot to drive its blades into—maybe the less-armored joint of a cricket would be nice—and injects a saliva that begins breaking down the thing’s insides. At its leisure, the worm gobbles up the glue that’s lying around going to waste, sucks the juices out of the prey, eats the odd limb here and there, and then shuffles on.
Perhaps the most enthralling and methodical (in a good way) experiments with such velvet worm hunts come from two biologists who set up shop in Trinidad in the 1980s. They worked with a species that prefers to get nice and close to its victims, and they recorded its tactics in great detail. The velvet worm would begin by sneaking up on the prey and gently probing it with the antennae, often quite thoroughly, and somehow without raising suspicion. When it was satisfied with its choice, it would blast its goo at the victim, so rapidly that the “emission of glue was undetectable, but the prey would suddenly appear covered in a network of beaded threads of glue.” Usually one blast sufficed, but if the prey struggled, the worm would hit it with up to thirty additional blasts, many of them aimed at the limbs, and in the case of spiders, at the fangs. Once the prey was subdued, the velvet worm injected its saliva and spent as long as an hour consuming the threads around the corpse. Finally turning its attention to the meal itself, the hunter took perhaps another ten hours eating the quarry.
About that glue. The researchers found that the stored glue made up an average of 11 percent of the velvet worm’s body mass. An impressive figure, but those reserves can quickly run out, especially when the velvet worm is tackling bigger targets. And that’s a dangerous prospect when you consider that it takes weeks for the worm to fully replenish the reserves, during which time it may not be able to hunt as effectively or defend itself from its own enemies, which it aims to slow down with glue strikes. What the researchers found, though, is that the velvet worm tailors the amount of glue it fires based on the size of its prey, using as much as 80 percent of its reserves to tackle its biggest prey, like large crickets.
SPIT-TAKE
Sharpshooting isn’t the territory of just terrestrial hunters. Archerfish target insects crawling along trees above flooded mangrove forests, spitting high-speed jets of water to knock them off their perches. That’s no small feat, considering the fish has to correct both for the fact that light bends when it hits water, making the insect appear where it isn’t, and that gravity tugs on the jet, making it more of an arch than a straight shot.
More impressive still, the jet speeds up as it approaches the target, which would seem to, well, defy the laws of physics. The trick here is that the archerfish spits so the rear of the stream is traveling faster than the front. The jet turns into blobs, and when the faster blobs at the back reach those at the front, they form a larger blob that’s traveling at a higher speed. Really, it’s more like firing a rocket than an arrow, so I guess we should call them rocketfish instead of archerfish. Wouldn’t want it to go to their heads, though.
Think of it as an investment. It seems counterintuitive, but going after small prey is a risk for the velvet worm. If it ends up blowing through too much glue trapping the tiny thing, that’s a crummy investment, because the energy it gains from eating the prey can’t offset the lost material, which requires energy to produce. Accordingly, in the Trinidad experiments velvet worms preferred larger prey over their smaller counterparts. Such a big meal justified the expense of glue. But the hunter can’t risk going too big. The largest prey could well escape, making off with the glue the worm would normally consume and recycle. So if food is plentiful, the predator aims for victims somewhere in the middle, not too small to be a waste of glue, and not too big to abscond with that precious resource.
It’s easy to forget that out there in nature choices like these are a matter of life and death. I don’t imagine you’ve had to make the decision recently whether or not walking to the corner store would use up more energy than you’d get from the six-pack you’d bring home (forgive me, I’m nearing my deadline, and am familiar with such pursuits), but nature scoffs at a waste of energy. It’s why alligators laze around so much, and why being a glacially slow snail makes sense. Plants aren’t about to get up and flee from you, so there’s no sense in being speedy and burning all that energy.
It makes sense, that is, unless you’re a snail that craves meat. Then you’re going to need one hell of a solution to get by.
Geography Cone Snail
PROBLEM: Snails also aren’t celebrated for their speed.
SOLUTION: To capture fish, the cone snail drugs them first by releasing chemicals into the water, before strolling up and enveloping the prey with its balloonlike mouth.
Out on an island in the Great Barrier Reef in the year 1935, a man picked up a Conus geographus, or geography cone snail. Holding it in his palm, he proceeded to scrape off the thin cuticle covering the shell. This, however, did not suit the snail, which fired its venomous harpoon into the man’s palm. And so began the numbness. Ten minutes later, the man’s lips had gone stiff, and after another ten minutes his vision went double. A half hour after the sting, his legs were paralyzed, before he slipped into a coma. In four more hours, he was dead.
Strangely enough, just three years prior to the incident, another man, this one on an island off of Africa, made the same mistake, holding a snail and scraping it with his knife. Following the inevitable sting, his entire body went into paralysis. Luckily someone got him to a doctor, who treated the victim and recommended “that he should be given general massage in addition.” I’m not a betting man, but I’m reasonably confident the massage didn’t play much of a part in his eventual recovery. But then again, it probably didn’t hurt either.
LET’S GET ONE THING STRAIGHT ABOUT SNAILS
Between the giant African land snail and the cone snail, you may be getting a picture of snails as being maleficent. They’re not. Mostly because . . . they’re snails. There are hapless snails out there, for instance, that ingest the eggs of a certain parasitic worm via bird droppings. These eggs hatch and invade their host’s eyestalks, greatly swelling them. Then the multicolored worm puts on a little dance to look an awful lot like a squirming caterpillar while mind-controlling the snail out into the open, where birds pluck out its parasite-packed eyes. Inside the bird, the worm breeds and produces eggs, which the bird poops out, which the next snail scarfs down. So while this poor snail is out gobbling up turds and having birds eat its eyes, the cone snail is dispatching humans who so much as scrape its shell. Doesn’t seem like a fair deal, really.
You may already be familiar with cone snails. They are, after all, some of the most venomous creatures on Earth, propelling toxic harpoons into fish so quickly that the strike is all but invisible to the naked eye. But the geography cone snail belongs to a relatively obscure group among them called the net hunters. They don’t just approach a fish and fire a venomous harpoon into it. They go for entire schools of fish, and they take their sweet time with it, sedating the victims with a cloud of toxins and strolling in for the kill. Because while other hunters have the luxury of speed, the net-hunting snails have hungry mouths attached to sluggish bodies. Their solution to holding on to their pre
y isn’t brawn, but a brutal, sophisticated mix of both chemical and ballistic warfare.
Something weird happens when a geography cone snail approaches a school of fish. Well, a couple weird things happen. First, the fish don’t seem to give a hoot. They’re aloof, lolling there wide-eyed. They don’t even seem to give a hoot when the snail expands its huge mouth like a fleshy hot air balloon. Slowly the mouth envelops several clueless fish, until the snail at last fires a harpoon into each victim, paralyzing it almost instantly. The mouth balloon shrinks, and the fish go quietly into death.
Which would seem like a silly thing to be so relaxed about. But it turns out that the fish are under a kind of spell: The geography cone snail has evolved to deploy insulin as a chemical weapon. By releasing massive amounts of the hormone into the water, the snail makes its prey’s blood sugar levels plummet. Hypoglycemic shock sets in. The fish grow sluggish and confused as their nervous systems glitch. In effect, they’re hypnotized, conscious yet locked up, like you or me suffering a fit of sleep paralysis. But what’s even weirder is that insulin in an invertebrate like a geography cone snail and insulin in a vertebrate like a fish are chemically distinct. Yet in addition to producing invertebrate insulin for its own body, the snail has evolved fishlike insulin that it has weaponized to overload its prey.
But there are still more toxins at work here to sedate the snail’s prey, forming a complex mixture that biologist Baldomero Olivera, an expert on cone snail venom, calls the nirvana cabal. (“Nirvana” is pretty self-explanatory, and “cabal” because, according to Olivera, the various substances in the mixture work together to overwhelm the fish, just as a cabal of humans would do to a government.) The geography cone snail has additional peptides that further sedate the fish, quieting their nervous systems. In fact, researchers have used one of these peptides in clinical trials to treat epilepsy, which stems from abnormal levels of electrical activity in the brain.
So the geography cone snail has hypnotized and drawn several fish into its mouth, but it has to pull one last trigger. Attached to its venom gland is a cache of around twenty harpoons, which are in fact modified teeth. It’ll fire one into a dazed fish, load another harpoon, and fire that into the next, right on down the line. It’s a massacre. Dosed with enough venom, known as a motor cabal, to kill an adult human, the fish’s neurons short-circuit as their muscles shut down. Death probably comes from asphyxiation, since fish have to be able to pump water through their gills in order to breathe.
THE WEAPON OF CHOICE? INSULIN . . . ALLEGEDLY
The cone snail may have been the first to weaponize insulin, but it isn’t the last. In the 1980s, news of an apparent poisoning gripped the crummy clique of East Coast ultrarich people, and the weapon was supposedly insulin. A maid found the socialite Martha von Bülow, who was hypoglycemic, moaning in a locked bathroom. Yet Martha’s husband, Claus von Bülow, refused to call for help. Tests would show a high level of insulin in Martha’s system.
A year later, Martha was found unconscious, but this time she slipped into a coma from which she would never recover. Afterward, an investigator scouring the mansion found hypodermic needles that yielded traces of a sedative and insulin. Claus was arrested, tried, and convicted of trying to kill Martha, but later won his freedom on appeal. Martha died almost three decades after the incident, taking with her the secret of her undoing.
Now, the geography cone snail’s more well-known cousins, the so-called hook-and-line cone snails, hunt in a different way by harpooning just a single fish, and therefore they deploy different toxins. In this group, when the harpoon spears the prey, the first toxins that go to work are a group aptly named the lightning cabal (there are lots and lots of chemicals working in concert here, in some species as many as two hundred, and each species has its own unique mix). This messes with a fish’s neurons like the motor cabal does, but instead of short-circuiting them, it overloads them so they fire constantly. The fish is essentially Tasered, seizing up and twitching uncontrollably. The motor cabal takes longer to kick in, thus the lightning immobilizes the fish so the snail can reel it in, followed by the delayed effects of the second cabal, which put the prey down for good. Yet a net hunter like the geography cone snail has no need for that regimen. By pre-sedating schools of fish before it even makes contact, the snail can envelop them without a fight. Plus, if the snail hits the prey with the lightning cabal at the harpooning, it’d have a spazzing school of fish in its mouth, potentially leading to injury. It has them right where it wants them, no Tasering necessary.
It all adds up to a dizzyingly sophisticated and powerful weapon, evolved over generation after generation. So remember, no scraping snails with pocketknives. Unless you were looking for a doctor-mandated massage—then be my guest.
Lamprey
PROBLEM: Fish don’t take too kindly to traumatic parasitization.
SOLUTION: The lamprey has evolved to look like the desert pit monster that ate Boba Fett in Star Wars: It suctions on to its thrashing victim with a disklike mouth packed with dozens of hooked teeth and will often drill right down to the bone.
Raining frogs is one thing, but raining toothy tubes of flesh is a different anomaly entirely. It was June 2015, and the Alaska Department of Fish and Game was getting “calls about arctic lamprey found in strange locations” around Fairbanks. Someone had discovered the eel-like fish, with its fearsome suction-cup mouth it uses to suck the blood out of other fish, in a parking lot—hardly its natural habitat. Another lamprey materialized on a lawn. And two others around town. Yet there had been no reports of waterspouts, that classic generator of raining aquatic beings. But the Fish and Game folks had a solid clue. V-shaped bruises ran along the lampreys’ bodies: gull bites. Maybe there happened to be a lot of lampreys in a nearby river at the time. And maybe gulls like lampreys. And maybe sometimes gulls drop lampreys in midair. And thus does it appear to rain bloodsucking fish on the Golden Heart City of Fairbanks, Alaska.
On the other side of North America, in the Great Lakes, the lamprey isn’t a mere parking-lot oddity. Here, it’s an invasive menace that has devastated populations of native fish: At one point in the twentieth century, the lamprey crashed the fishery in the Great Lakes to 2 percent of its normal catch. These days, eradication efforts have brought the invasive beast under some measure of control, but no realistic human being is expecting to rout the lamprey entirely. With so many tributaries connected to the lakes, cash-strapped officials can hope only for suppression, not outright defeat.
This story begins 360 million years ago with the earliest known lamprey fossil, which looked a lot like modern varieties. That number is, simply put, ridiculous. Life complex enough to be recognizable to us as life has been around for 570 million years, while the first mammals showed up around 200 million years ago. Yet the lamprey has survived largely unchanged, through all kinds of mass extinctions, for almost 400 million years. (As it happens, the lamprey’s only close relative is our friend the hagfish, a similarly ancient species. And indeed the two share a lot of characteristics, including a skeleton of cartilage instead of bone.)
WHO ARE YOU CALLING A FOSSIL?
You’ll hear the phrase “living fossil ” tossed at the lamprey and any number of other ancient species, but that language is problematic. It implies that the 360-million-year-old lamprey fossil is identical to the lampreys that swim Earth’s waters today, and that’s an impossibility. The lampreys didn’t survive for this long, over so many catastrophic events and climate changes and introductions of new predators and extinctions of potential prey, by being immutable. “Living fossils” may look like they’ve gone unchanged, but subtle variations over evolutionary time have allowed them to roll with the punches, as it were—if you could consider something like an asteroid hitting your planet right in the face as a “punch.”
Some of these species attach to their host and sip a bit of blood, while the flesh eaters among them go further, gouging out plugs of meat and
leaving their victims with gaping wounds, and likely death by blood loss or infection. For their exploits both types of lampreys are equipped with a mouth known as an oral disk, which is loaded with dozens upon dozens of hooked, fanglike teeth that help their owner get a purchase on a victim (aided by special structures along the disk’s edge that form a suction). Like a shark’s teeth, these are replaceable—highly replaceable: The vampiric species that’s invaded the Great Lakes, the sea lamprey, may replace its teeth as many as thirty times in two years.
What sets the bloodsuckers and flesh eaters apart, though, is something called a piston, which fires in and out of the center of the oral disk. A piston is like a tongue, only made out of teeth: one tooth that flicks vertically and two others that flick horizontally, creating a complex rasping mechanism. In bloodsuckers, that vertically firing tooth in the piston is shaped like a W to scrape away flesh and draw blood—these species also secrete an anticoagulant to ensure that blood flows freely—while in flesh eaters the tooth is more of a U shape that gouges out chunks of flesh (think of the former shape as sandpaper and the latter as a chisel). The whole mess is astonishingly effective. In the Great Lakes a single sea lamprey can kill forty pounds of fish in a year. At times, only one in seven fish here will survive a lamprey attack, and the fishery is suffering for it.
Really, though, it’s our own fault. You may be wondering by now what business a sea lamprey would have conquering freshwater lakes. But they have every right to be here. Sea lampreys begin their lives in freshwater streams, biding their time as harmless larvae for up to seven years. During that stage, their mouths are just squishy holes, with which they grab planktonic creatures floating by. When they mature, they head out to sea to parasitize fish, but return to the streams to spawn (interestingly, the larvae guide adults back from the sea to optimal spawning grounds by releasing pheromones). Thus, capable of living in freshwater, the parasitic adult sea lamprey jumped at the opportunity to invade the lakes when in the early twentieth century engineers deepened a canal that bypassed Niagara Falls, the natural barrier keeping the lampreys out. The floodgates opened, and the Great Lakes haven’t been the same since.
