by Becky Crew
Not surprisingly, these sinister little freeloaders are prone to bizarre sex lives, too. Not much is known about the sexual behavior of tongue-eating isopods because they are extremely rare, but scientists believe that a juvenile attaches itself to the gills of a fish to begin the process of becoming sexually mature, causing it to morph into the male form. As the young male isopod develops, reaching up to 0.4 inches in length, it can morph again into the female form. If a male cannot find himself a female to mate with—which they’ll also do on the gills of a fish—he will simply change sexes and mate with the more available sex.
Now, Weeverfish, this situation can go either way, depending on how well you treat your new houseguest. It’s your isopod, you can do whatever you want with it, but if you want my advice, you should probably make the most of things because that isopod isn’t going anywhere in a hurry. I’m sure he’d be more than happy to pay a little for his keep in return for you not swishing a mouthful of nails around him like you did when he ate too much of your breakfast that one time.
You know that cute lady weeverfish whom you like but you’re always too shy to talk to? Well, your isopod will probably think she’s gross because he has very complicated sexual preferences, so you guys could totally do the old, “Why don’t you tell me what to say to the boy/girl I like because you’re so eloquent and/or suave and I’m so stupid and/or shy and s/he will totally fall in love with me, thinking I’m the eloquent and/or suave one?” thing. It’ll be so much easier than when most awkward lovers try it because your isopod won’t have to hide in a clump of nearby seaweed or behind a bookshelf and try to whisper to you over an unreasonable distance. What a great team you could make!
On the other hand, you could be a whiny bitch about the whole situation and every time you run into someone and they ask you how you are, you’re like, “An isopod replaced my tongue. How do you think I am?” Isopods have feelings too, Weeverfish, and you don’t want yours to get upset, because one day you could be in the photocopying room with that woman from Accounts who’s dating your boss and your isopod will be like, “Hey, do you have time to look at an important report I’ve just drafted … in my pants?” through your gills.
Who needs a job anyway, right, Weeverfish?
The Master Deceiver
ASSASSIN BUG
(Stenolemus bituberus)
“No, you can’t be something else when you grow up. You’re not called a plumber bug, are you?”
IF YOU’RE GOING TO hunt the ultimate predators—spiders—you really have to know what you’re doing. Along with bedbugs and aphids, assassin bugs fall into the “true bugs” category Hemiptera, a group based on the way mouthparts are arranged. In the assassin bug’s case, this arrangement involves a needlelike proboscis: an elongated feeding tube separated into two barrels, one for injecting special anticoagulating saliva, and the other for siphoning blood and liquefied insides from its prey. But before it can siphon anything from said prey, the assassin bug has to figure out how to catch it.
In 2011, researchers from Macquarie University in Sydney examined the predatory behavior of Stenolemus bituberus, a local species of assassin bug known to feed exclusively on spiders and spider eggs. “Assassin bugs in general have some pretty bizarre behaviors, and we originally had the suggestion that Stenolemus assassin bugs have interesting predatory strategies from the field observations of a closely related species,” says one of the team, biologist Anne Wignall.
Not all species in the assassin bug family are spider killers, or araneophages. Only those within the Stenolemus genus have demonstrated this behavior, according to Wignall. Their success lies in the fact that web-building spiders have very basic eyesight; their main sensory system is based on detecting vibrations. So whether the assassin bug decides to sneak up on a spider, or lure a spider toward it, it does not need to worry too much about being spotted, plus it can use the spider’s reliance on reading vibrations against it.
First publishing in Animal Behaviour, the researchers reported that if an assassin bug decides to use what they called the stalking method, it will sneak up on a spider in its own web using irregular, bouncing movements while skillfully severing and stretching the silk threads between them, just like a Portia spider (see previous section, “The Spider-Eating Spider”). When the researchers pointed an electric fan at the web during this process, recreating the effect of strong winds, the assassin bugs were found to step more often and more continuously toward their prey, suggesting that they knew their movements were being masked by the vibrations caused by the “wind.” So it would seem that together with the vibrations created by its cryptic movements, the assassin bug knows how to exploit periods of environmental disturbance, creating a “smokescreen” effect to cover its tracks.
Another study published that year by the team identified a second hunting technique: luring. When luring, the assassin bug will deliberately make short, low-frequency vibrations on the web to reveal its location and draw the spider toward it. The researchers watched as the assassin bugs cleverly plucked at the silk threads to emulate the twitching, panicked movements of ensnared prey for up to twenty minutes, tricking the spider into thinking it was about to get a meal. The results, published in Proceedings of the Royal Society B, revealed that the spiders’ reactions to the assassin bugs’ luring behavior practically mirrored their reactions to actual snared prey. The spiders would turn, pause, and approach the assassin bugs 65 percent of the time, and turn but not approach the assassin bugs in the remaining 35 percent of cases. The spiders would never approach the assassin bugs aggressively, which indicated that they had indeed been fooled. “Assassin bugs … tend to make low-frequency, irregular, low-amplitude vibrations. It sounds somewhat like prey in the web when struggling,” says Wignall. “Picture a fly caught in the web, with its body in contact with the silk, rather than just the tarsi [or ‘feet’] pulling, stretching, and tapping the silk. The vibrations assassin bugs generate are thought to mimic small or tired prey.”
Wignall adds that when an assassin bug draws close enough to a spider, it will do something remarkable—it will begin gently tapping on the spider’s leg with its antennae before slowly moving the taps along the abdomen to the cephalothorax, or head. While distracting the spider in this manner, the assassin bug will raise its head above the spider so it can stab down into it with those dagger-sharp mouthparts. “Whether luring or stalking, assassin bugs will always tap the spider at least a few times before stabbing it. This behavior is truly bizarre, as you would expect the spider at this stage to be alerted to the assassin bug’s presence and either attack or run away,” says Wignall. “We can see during hunts that the assassin bug actually makes contact with the spider’s body with their antennae (and sometimes the spider will even move slightly in response to the assassin bug’s touch). We still aren’t sure what the function is, though we’re working on it!”
Killer Cone Snail
GEOGRAPHIC CONE
(Conus geographus)
YOU’VE BEEN STUNG BY something in the ocean and now you’re paralyzed. Nine hours later you’re still so incapacitated that you can’t stand up. And that’s if you’re very lucky. The worst part of this scenario is not that something in the ocean just almost killed you—it’s that the something in the ocean that just almost killed you was a snail. Sure, it’s one of the most dangerous snails in the world, but it’s still just a snail and that’s why your friends are laughing at you.
Armed with a cocktail of the most potent neurotoxins on Earth, the extremely rare geographic cone holds its own in an ocean full of weaponized fish, rays, and eels, having reportedly killed around thirty people so far in recorded history. There is no antivenom available and you have a 30 percent chance of being killed if stung. It may seem like a rather extreme weapon for a lowly snail to have, but when you move like a snail does, you need something to snare yourself a meal.
In 1932, British surgeon, pathologist, bacteriologist, and tropical shellfish expert Louis Hermitte reported
that a patient of his had been stung by a geographic cone snail in the Seychelles Islands, where he was practicing at the time. This was the first such case reported from the Indian Ocean. After dissecting the snail, Hermitte discovered a radular tooth—a hollow harpoonlike structure—on the end of its extendable proboscis, a tubular appendage attached to the head that extends several times longer than the snail itself. A closer look led Hermitte to find that the snail also had a coiled venom duct to deliver venom to the radular tooth for injecting into unsuspecting fish. Researchers have suggested that in order to get their prey close enough to inject them, geographic cone snails release paralyzing chemicals into the surrounding water and then swallow them whole using a specialized billowy expanse of tissue. Once ensconced, the prey is stuck with a venomous harpoon so it can be devoured. This technique is so effective, it can bring down prey large enough to sustain the geographic cone for several days.
Of the 700 species of cone snail, the geographic cone is the most deadly. The venom used by cone snails is made up of active components called conopeptides—compounds consisting of 12–30 amino acids linked in a chain. According to Filipino-American chemist Baldomero Olivera, who has studied cone snail venom for over three decades, there are roughly 100–200 different conopeptides per species. This means that the composition of the venom differs between species, and even different individuals of the same species. Olivera says a shot of venom from a geographic cone is equivalent to eating a badly prepared piece of Japanese puffer fish while getting bitten by a cobra.
Olivera began his research by injecting the venom of the geographic cone into the abdomens of mice; they were immediately paralyzed each time. But in its original form, the geographic cone venom did not behave any differently from other known toxins, so Olivera lost interest. Then in 1975, a nineteen-year-old undergraduate student named Craig Clark from the University of Utah had the idea of taking isolated conopeptides from the venom and injecting them directly into the mice’s central nervous systems. The results were stunning, says Olivera. The mice would display completely different symptoms depending on which conopeptide Olivera and Clark injected, including shaking, sleeping, scratching, becoming sluggish, or convulsing. One of the peptides would even provoke different reactions depending on the age of the mouse receiving the venom. For example, a newborn mouse would immediately fall asleep, while a mature mouse would be worked into an uncontrollable frenzy. It was the bizarre effects of the conopeptides that prompted Olivera to consider that perhaps they had some kind of pharmaceutical potential.
Olivera found that each conopeptide worked by targeting a different type of molecule in the victim. He found that a great many of the molecules targeted were the types that control the flow of calcium, sodium, and potassium in and out of the cell. If you shut down these channels, as this venom does, messages between the brain and muscles cannot be delivered, which leads to shock and paralysis. Being able to home in on specific types of molecules made the cone snail toxins, or “conotoxins,” ideal for medical research, because the ability to block calcium channels through the body can help patients with high blood pressure. What made conotoxins perfect for this is that they only seem to block the calcium channels in nerve cells, not those in the heart or other tissues, so side effects due to this treatment were limited.
Since Olivera’s work, pharmaceutical companies have used conotoxins in treatments for an array of disorders such as epilepsy, cardiovascular disease, neurological disorders, and pain. In mid-2010, a team of Australian researchers reported that the venom of the marine cone snail (Conus victoriae), a species found in the waters of Western Australia and the Northern Territory, has potential as a painkilling medication. Based on their analysis of the marine cone snail’s conotoxin, the team, led by chemist David Craik from the University of Queensland, synthesized an imitation conotoxin, added a few extra amino acids, and manufactured a painkilling pill that is many times more powerful than morphine. The team is hoping that this painkiller will completely revolutionize how scientists manage chronic and terminal pain in the future.
What a hero to little garden snails everywhere. Right now, dozens of snail fairy tales are being rewritten, because finally there’s a snail that can do more than just move at the proverbial pace of itself.
So where snail-Rapunzel traditionally spent her entire life in the tower, reading, watching TV, making pesto, new Rapunzel would be rescued by a handsome geographic cone who launches his radular tooth up into her window like a grappling hook.
Where snail-Gretel traditionally shoves the snail-witch into the oven to save herself and snail-Hansel, new Hansel and Gretel will use their radular teeth to intimidate the snail-witch into building them a gingerbread mansion with a tennis court and Olympic-size pool.
New Snow White will be like, “You call this poison? Let me teach you a little something about poison, stepmother”; new Goldilocks will be like “All of these are pretty good. Three more bowls, slave bears!”; and new Three Little Pigs would be like, “Really, wolf? You’re going to try to eat us? It’s your funeral, dude.”
The Mystery of the Sawfish’s Saw
SAWFISH
(Pristidae family)
LOOKING AT A SAWFISH, with its long, tooth-encrusted snout, it’s hard to believe that the use of such a distinctive appendage has remained a mystery for so long. But catching one of these critically endangered animals in the act has been near impossible, so scientists have assumed that the sawfish, like every other jawed marine vertebrate with an elongated rostrum, or “beak,” adheres to the rule that you use it to either sense or manipulate your prey. It’s one or the other, scientists said, you can’t have it both ways, and they had multiple examples of this occurring in other marine animals to back this up. The primitive, sad-looking paddlefish uses its extended, spatula-shaped rostrum to tune in to the electrical signals that give away the location of its prey, while members of the billfish group, including swordfish, sailfish, and marlin, instead use their slender, spearlike rostrums to physically stun their prey. And sturgeons, which sport a relatively modest but electroreceptive rostrum, use theirs to rifle through the seabed, sucking up any prey they locate.
The term “sawfish” describes seven species of ray that live in marine, estuarine, or freshwater environments, four of which are native to Australian waters. Their bodies are sharklike and they typically grow to be around 23 feet long. Along each side of the sawfish’s rostrum, toothlike projections called rostral teeth poke out of a great number of sockets, giving the animal a unique and intimidating appearance that sets it apart from other rays and the cartilaginous fish known as skates. While not considered a danger to humans, anecdotal evidence of sawfish using their saws as a defense mechanism includes an Australian man being chopped in half by one, and dugongs who drifted too close being attacked in Indian waters.
Oddly enough, until recently, only one—a smalltooth sawfish (Pristis pectinata)—had been observed using its saw to actively hunt prey, and this was in a controlled setting more than fifty years ago. Because sawfish are so rare and their trade restricted to conservation purposes only, for years no one had properly studied the function of the saw. It wasn’t until vertebrate biologist Barbara Wueringer from the University of Queensland published her PhD thesis in 2010 that we began to get some understanding of how they work, beyond being useful for raking through substrate on the seafloor.
By examining four species of sawfish from northern Australia, Wueringer discovered that the sawfish’s saw is packed with thousands of sensory organs called ampullary pores that can detect the subtle electrical fields given off by moving organisms. The ampullary pores turned out to be more densely packed on the upper side of the saw, which suggests that sawfish are able to detect prey even in low-visibility waters using the whole three-dimensional space above it. This can cover a lot of ground if you’re a green sawfish (Pristis zijsron), whose saw can grow up to 5 feet long. The result of Wueringer’s initial study meant that sawfish were slotted into the group o
f jawed fish that used their rostrums for detecting prey, because at this stage, substantial evidence for hunting did not exist. So just like the enigmatic hagfish, says Wueringer, sawfish gained the reputation of being “sluggish bottom dwellers.”
All of this changed when Wueringer got the chance to study a young, wild, longtooth sawfish (Pristis microdon) that had been accidentally caught by a fishing company and was on its way to an aquarium. Hidden cameras were installed in the sawfish’s temporary tank to observe what it would do when fed chunks of tuna and mullet. When pieces of fish landed on the floor of the tank, the sawfish used its saw to pin them down and eat them, and Wueringer suggested that in the wild this mode of saw use would be particularly useful for manipulating spiny fish into a safe position for eating. When the fish pieces were floating through the tank water, the sawfish would slash back and forth at them, managing multiple swipes per second, to impale them on its rostrum teeth.
To confirm that this species was able not only to manipulate its prey, but also to detect it using its saw, Wueringer suspended electric dipoles—devices that mimic the electrical signals that surround moving prey—in the water and on the tank floor. Just as the different movements of the fish pieces, or “prey,” prompted different aggressive responses from the sawfish, the different sources of the electrical fields brought about different detection responses from the sawfish. “Dipoles located on the substrate evoked predominately a biting response and sometimes ‘wiggle’ (a slight lateral movement of the head),” Wueringer reported in a 2012 issue of Current Biology. “Dipoles suspended in the water column evoked repositioning behaviors and ‘saw in water’ and ‘wiggle’, but never a biting response.”