Why It's Nearly Impossible to Castrate a Hippo

Chances are you've never wondered how difficult it is to remove the testes of a hippopotamus. Other people have been thinking hard about it, though, because in fact it's almost impossible.

Before sitting down to emasculate a common hippopotamus, Hippopotamus amphibius, it would be reasonable to ask why. They're a threatened species, so usually conservationists try to make more baby hippos—not fewer. But in zoos, hippos turn out to be prolific baby-makers. Females can live for 40 years and may birth 25 calves in that time. This would be great news in the wild, but zookeepers don't always have someplace to store a new two-ton animal.

Male hippos can also be aggressive toward each other, at least while they have all their man parts. For both of these reasons, zoos may want to have their male hippos fixed. But there are a few factors working against them, explains a new paper in the journal Theriogenology (that's reproductive science for vets) by an international group of authors.

The first challenge is that hippopotamuses hide their genitals. The testes are inside the body, instead of outside in a scrotum. (Other mammals in the internal-testes club, since you asked, include the armadillo, sloth, whale, and platypus.) This makes the hippo's testes totally invisible from the outside. Combined with a penis that the paper's authors describe as "discreet," it means it's hard to tell males from females at a distance.

Another problem is that testes aren't in the same place from one hippo to the next, and they may "retract" even farther during surgery. Hippopotamuses are also difficult to safely put to sleep. "In the past, hippopotamus anesthesia has been fraught with serious complications," the authors explain.

After moving past the anesthesia problem (they used an apparently safer blend of drugs, delivered via a dart to the hippo's ear), the researchers turned to the anatomical problems. Their answer was ultrasound. Once they had positioned the animal, they used ultrasound imaging to find the testes—then used it again after cutting into the hippo, if the testis they were looking for had scooted farther away from them.

Even after finding the sneaky organs, the procedure wasn't simple. The depth of the testes' hiding places varied by as much as 16 inches from one hippo to the next. Everything had to be done deep inside the animal's body, making it hard to see what was going on. "Grasping the testicle with forceps proved laborious" in most of the animals, the authors write. They also mention using a "two-handed technique" and "moderate traction." The whole hour-and-a-half procedure, based on a method for castrating horses, is described in detail for anyone who wants to try it themselves.

All ten hippos in the study were successfully castrated, though one died shortly afterward, following a complication from a unknown pre-existing condition. Over the next six months, the authors checked in with the zoos housing the hippos to see whether their behavior or interaction with other animals had changed. There were four cases where zoos wanted their hippos fixed to ease aggression between males; in all four, the problem seemed better. (One zoo, though, reported that castrated males were harassed more by females.) Overall, the authors think their technique will help zoos take better care of their hippos.

The final challenge to hippopotamus surgery—what should be a challenge, anyway—is that the animals spend most of their time in a pool of water packed with feces. The animals in the study lowered their stitched-up bellies into this infectious slurry as soon as they had a chance. Yet all of them healed from surgery without trouble. Hippos in general seem to be especially good healers, the authors write.

A possible explanation for the animals' healing superpower is the "red sweat" or "blood sweat" that oozes from their skin. It's not really sweat and it doesn't contain blood, though it is red. The pigments in this skin secretion have been found to absorb UV light, making the "sweat" a potential sunscreen. The pigments can also keep bacteria from growing. So a built-in antibiotic may be what keeps hippos from getting infections after they tussle and bite each other (or after meddling vets come and cut out their manhood). However the red sweat works, it shows that a hippo's secrets don't end with the location of his testicles.


Images: Charlesjsharp (via Wikimedia Commons); drawings by Eva Polsterer (from Walzer et al.).

Walzer C, Petit T, Stalder GL, Horowitz I, Saragusty J, & Hermes R (2013). Surgical castration of the male common hippopotamus (Hippopotamus amphibius). Theriogenology PMID: 24246424

Leaping Land Fish Has Perfect Camouflage, Is Not a Hoax

You might never spot them if not for the jumping. On the coast of Guam, Pacific leaping blennies blend in perfectly with the rocks they live on, their limbless bodies maintaining a sleek profile. But the creatures give themselves away when they coil their tails to one side and shoot like a spring from rock to rock. These unsettling animals are fish that live on land. How they pull it off could give us hints about the evolution of our first earthbound ancestors.

Terry Ord, an evolutionary ecologist at the University of New South Wales, calls the Pacific leaping blenny "an extraordinary animal." It lives its adult life out of water, hopping between rocks and breathing through its skin as well as gills. It relies on splashes from waves to stay wet, but it rarely—or never—goes for a swim.

Even though the coast of Guam teems with leaping blennies, Ord says, "we know surprisingly little about this land fish." Ord and his graduate student Courtney Morgans investigated one mysterious feature: the fish's conveniently rock-like coloration. Without being so well camouflaged, could the blennies have ever made their first leap onto land?

Morgans and Ord traveled around the periphery of Guam and visited five different blenny populations. At each site, they took photographs of the fish and their background rocks. (The blennies aren't always stone-colored; during courtship, males darken to a charcoal hue while females fade nearly to white. Both sexes can flash a bright-red fin on their backs that they normally keep hidden. But the researchers kept a close eye on their subjects during the experiment to make sure they didn't change colors.)

Computer analysis of the photos showed that the blennies' normal skin color is a perfect match to the rocks they live on. Some birds use UV light, which the researchers didn't analyze, to find their prey. But for most of the hungry lizards and crabs patrolling Guam, the blennies should blend right in to the rocks.

To find out how well this camouflage really protects leaping blennies, Morgans and Ord set up 70 fake fish as bait. They molded plasticine blenny bodies with realistic coloration and anchored them to spots around the island with fishing line. Some fake blennies sat on the rocks, while others were on the sand, where they don't blend in as well.

After three days, Morgans and Ord returned to their fake fish. If the props were nicked, punctured, or had bites taken out of them, the scientists assumed predators had come by. They saw that predators attacked blennies on the sand much more often than those on the rocks.

So their coloration seems to be crucial to the leaping blennies' survival on shore. The scientists think that in this regard, the fish may have just been lucky. When they compared the Pacific leaping blenny to 12 closely related blenny species, they found that all the relatives have similar coloration. (Some of these relatives also spend time out of water, but the Pacific leaping blenny is the only one to live on land full-time.) If the ancestor to all these species had the same rocky skin color, then it was well prepared to wriggle out of the ocean and start a new life on land.

That doesn't mean the transition was easy. Blennies also had to evolve a way to breathe air through their skin, like frogs do. Their tail-jumping trick is helpful too, letting the legless fish propel themselves through their habitat. "Obviously moving about on land is critical," Ord says. (You can watch them leaping in the video below, from his lab's YouTube channel.)

Ord says this freak-show fish actually has a lot to tell us about evolution. For one thing, it demonstrates the kinds of adaptations an animal can make after it transitions to a new home. It also speaks to our own ancestry. "In the late Devonian, fish made the first transition onto land, and from that event evolved all of the land vertebrates we now have in the world," he says. The land fish represent a "snapshot of one of the most important evolutionary events in our history." Our ancestors may have looked equally ridiculous as they floundered on land—but like the leaping blenny, they were going places.




Image: Courtney Morgans, UNSW

Courtney L. Morgans, & Terry J. Ord (2013). Natural selection in novel environments: predation selects for background matching in the body colour of a land fish. Animal Behaviour DOI: 10.1016/j.anbehav.2013.09.027

Beetles Show There Is Such Thing as a Free Lunch, and It's a Weapon Attached to Your Face

If the rhinoceros beetle were the size of an actual rhinoceros, its horn could be 16 feet long. Male beetles grow this gargantuan face-fork so they can win mates (why else?). And even though evolutionary science would predict that the beetle pays a price for this appendage, it seems to come absolutely free.

Males of many animal species wear showy accessories: antlers on deer, long tails on birds. Growing one of these accessories often comes at a cost. For example, energy spent growing one large body part may leave another body part smaller, as seems to be the case with the dung beetle's horns. Or the showy feature may make the animal more vulnerable, as in the Bahamas mosquitofish, which grows a large sperm-delivery organ to impress females but then can't swim away as quickly when chased by predators. Females benefit from being choosy, because males that can afford to spend resources on a fancy headpiece or tail demonstrate that they're hardy or have good genes.

Erin McCullough, a PhD student at the University of Montana, Missoula, and her advisor, Douglas Emlen, have been putting rhinoceros beetles through the wringer to try and find the cost they pay for their giant horns. Individual males grow horns of widely varying sizes. In the Japanese rhinoceros beetle, Trypoxylus dichotomus, horns range from a stubby 7 millimeters to a towering 32. In other species, the largest horns are 10 times the length of the smallest ones.

In a previous paper, the researchers showed that larger horns—somehow—don't hurt the rhinoceros beetle's ability to fly. Now, they measured the horns of T. dichotomus beetles and compared their size to the insects' legs, wings, eyes, and genitalia. They also tested the strength of the beetles' immune systems. And by marking beetles with paint, releasing them outdoors, and recapturing them later from the same area, the researchers assessed whether larger horns make a beetle more likely to die.

The result was a big goose egg. Nothing. If you're a rhinoceros beetle, there is apparently no trade-off to growing the biggest horn you can.

So why aren't all horns huge? Males with larger bodies are able to grow disproportionately longer horns than smaller beetles; Emlen found in an earlier study that this is tied to the beetles' insulin levels. "Males that have poor nutrition and therefore have low levels of circulating insulin simply can’t produce big horns," McCullough explains.

Still, if big horns are so great, evolution might favor males who can use their good nutrition to grow ever-larger appendages. Why is there any limit on the size of the horn? "I think the primary reason...is because they are weapons that are continuously tested in combat," McCullough says. Male rhinoceros beetles use their horns to fight each other for the best territory on tree trunks and branches. Grappling over sap-rich sites, they wield their horns like pitchforks to pry rivals loose. "So it doesn’t benefit a male at all to have a horn that’s so large that he can’t use it properly," she says.

McCullough is currently testing that idea by measuring the force needed to pry a male beetle from a tree and comparing it to the force needed to snap the beetle's horn. She thinks longer horns are at more risk of breaking, and that this may be what limits their size.

The reason rhinoceros beetles escape paying for their horns might be that they're functional, and not merely a decoration. When birds pay a price for a showy tail, it ensures that only the genetically strongest birds can give the best display to females. If unhealthy birds could cheat and grow fancy tails at no cost, females would no longer benefit from favoring good tails—so they'd stop paying attention at all, and males would stop bothering. But because there's a cost, the system works. In the case of the rhinoceros beetle, McCullough and Emlen believe cheaters are weeded out because they can't fight with their oversize horns. This means the flashy gear comes for free—as long as the beetle knows how to use it.


Erin L. McCullough, & Douglas J. Emlen (2013). Evaluating the costs of a sexually selected weapon: big horns at a small price. Animal Behaviour DOI: 10.1016/j.anbehav.2013.08.017

Image: McCullough & Emlen.

World's Ugliest Fish Jam Each Other's Mating Calls

Perhaps understandably, the male toadfish doesn't rely on his looks to attract females. He uses a bellowing, foghorn-like call to lure the ladies instead. But he'd better beware of his neighbors—nearby toadfish, a scientist has discovered, use short grunts to stealthily jam each other's signals.

In the spring, at the start of breeding season, male oyster toadfish nestle into rocks and debris on shallow seafloors in the western Atlantic. From his hidden nest, the male sends out his tuba blasts. A female who hears something she likes comes to the nest and glues down her eggs. Then she leaves the homely male to fertilize the eggs and guard the young till they're grown.

The breeding season stretches to the beginning of fall, and during this time male oyster toadfish have been observed grunting as often as 200 times an hour. When sending out their signature mating calls, neighboring males alternate with each other so as to be heard more clearly. But more often, they make quick little grunts that do overlap with others' calls.

To find out why toadfish interrupt each other like this, biologist Allen Mensinger of the University of Minnesota, Duluth, gathered a small group of male toadfish in an artificial pond. The pond was lined with underwater microphones to capture the fishes' calls. Bricks and concrete slabs were stacked into simple shelters on the bottom of the pond. After a couple days in their new home, the oysterfish agreeably moved into their "nests" and started calling out for females. (Those, however, were lacking.)

Each toadfish that Mensigner recorded had a distinct "fundamental frequency" (the lowest note it produced) to its mating call. In other words, each fish called with its own voice. But out of the thousands of recorded toadfish sounds that Mensigner analyzed, the majority were short grunts that interrupted other fishes' calls. And when a grunt overlapped with another toadfish's mating call, that call's fundamental frequency—its voice—was altered.

Mensinger thinks the grunts essentially jam the signals from the bellowing toadfish. In this way, interrupting toadfish might make their neighbors' carefully tuned calls less attractive to listening females.

The interrupting fish time their quick grunts to end before their neighbors' mating calls do. Mensinger thinks this protects the interrupters from being detected. Don't worry too much for the toadfish, though—despite their apparent gamesmanship, a few males managed to breed successfully when Mensinger threw some female fish into the artificial pond later in the season.

To hear the oyster toadfish in all his uninterrupted beauty, click here.


Image: by EricksonSmith (via Flickr)

Allen Mensinger (2013). Disruptive communication: Stealth signaling in the toadfish. Journal of Experimental Biology DOI: 10.1242/jeb.090316

Male Frogs Grip Mates with Pheromone-Injecting Thumb Spikes

There's nothing subtle about the wooing of European common frogs. Males grow spiny pads on their thumbs during the breeding season, the better to grip their mates. As if that weren't enough, the pads also seem to channel pheromones out of a frog's hands and straight into his female partner's body.

Frogs fertilize their eggs out in the open, so you might think there'd be no need for all this effort. Yet males of most frog species can be seen during the mating season "taking a piggyback ride" on their mates, as a group of scientists in Belgium euphemistically puts it. Technically called amplexus, the male-on-top position allows him to fertilize the eggs just as the female sends them out of her body.

In some frog and salamander species, males further ensure their success by temporarily growing tough, often spiky pads on their forearms or thumbs. Earlier research discovered glands of some sort sitting beneath these pads, but it wasn't clear what the glands did. So the scientists in Belgium decided to take a closer look at the hands of one such animal: Rana temporaria, the European common frog.

The scientists used micro-CT scanning to build a 3D image of a male frog's thumb pad. They saw that glands underneath the pad led to ducts, which traveled up through the pad to pores on its surface. It appeared that the grippy gloves donned by males for the mating season were also some sort of delivery system.

But what were they delivering? An analysis of proteins in the glands turned up a group of molecules the authors dubbed "amplexins." They're in the same family as certain proteins found in male mammals' reproductive organs, as well as a courtship pheromone in salamanders. In humans, proteins from this family help regulate how eggs and sperm interact.

Comparing thumb pads in the breeding season to shrunken-back thumb pads during the rest of the year, the scientists saw that amplexin production suddenly dropped off near the end of the breeding season. During the rest of the year, the frogs didn't make amplexins at all.

A male who's already got his hooks—literally—into his partner probably doesn't need to worry about courtship. But the authors speculate that amplexins in these frogs might be pheromones that speed up the mating process. Female frogs' chests are often scraped and scratched by their mates' spiny thumb pads, and this may be how a male delivers the pheromones to his partner: straight into her circulatory system.

Hey, it works for Cupid and his arrows. Female frogs, though, would probably give this system two thumbs down.


Image: by Erik Paterson (via Flickr)

Bert Willaert, Franky Bossuyt, Sunita Janssenswillen, Dominique Adriaens, Geert Baggerman, Severine Matthijs, Elin Pauwels, Paul Proost, Arent Raepsaet, Liliane Schoofs, Gwij Stegen, Dag Treer, Luc Van Hoorebeke, Wim Vandebergh, & Ines Van Bocxlaer (2013). Frog nuptial pads secrete mating season-specific proteins related to salamander pheromones Journal of Experimental Biology DOI: 10.1242/jeb.086363

12 Things I Found Exploring the California Seafloor (and You Can Too)

If for some reason you haven't been invited on a submersible ride-along, the next best thing is probably 340 miles' worth of raw video footage from the ocean floor.

The U.S. Geological Survey just released a whole mess of data from its California Seafloor Mapping Program. Together with many partners, it's working on building maps of the California coast that include seafloor depth, habitat type, and other geological features. There's also video footage from cameras towed a few feet above the seafloor, as well as 87,000 still photos taken at regular intervals.

At the project's website, visitors can explore an interactive map that's layered with whichever types of data interest them. I know somebody out there is into bathymetry, but I opted to explore the library of photos and videos. Below is a selection of things I spotted. 

The videos are kind of tedious but will reward the patient viewer with an occasional sea cucumber or alarmed fish. And the up-and-down bouncing of the camera as it travels over the seafloor might induce seasickness, so I'm guessing it's a realistic experience. If I ever get that invitation, I'll let you know.

Local color.

Cauliflower trees (disclaimer: I am not a marine biologist)...

...which the camera smashed into.

Scientists!

Crabs making friends with starfish.

An ex-starfish? Note the impression in the ground. Maybe it got friendly with the wrong arthropod.

Further evidence for my theory that at the bottom of the sea, everything is either terrifying...

...or shaped like a penis. (What? I edit a kids' science magazine. YOU try finding a photograph of a bone-eating worm that's appropriate for 12-year-olds. Go Google it right now. I'll wait.)

We crashed into the ground again. Maybe the little crabs that keep scurrying away from the camera have the right idea.

Fodder for the future BuzzFeed article "45 Ocean-Floor Animals That Are Totally Waving Hello."

And something incognito. Does anyone know what it is?

Golden, Nadine E., & Cochrane, Guy R. (2013). California Seafloor Mapping Program video and photograph portal U.S. Geological Survey data set : 10.5066F7J1015K

Images: Golden, Nadine E., and Cochrane, Guy R., 2013, California Seafloor Mapping Program video and photograph portal. U.S. Geological Survey data set, doi.10.5066F7J1015K

Decapitated Worms Regrow Heads with Memories Still Inside

How good are you at remembering something you learned two weeks earlier? What if during the intervening 14 days, your head was removed? One flatworm isn't bothered by this scenario. After growing back its entire head and brain, it picks off pretty much where it left off.

The planarian is a modest little flatworm, the kind of common microscope denizen you might find in a Gary Larson cartoon. What's remarkable about it is its ability to regenerate. The whole body can regrow, head to eyespots to tail, from even a tiny fragment of the original animal.

Tal Shomrat and Michael Levin at Tufts University built a computerized apparatus for training planarians. Back in the 1960s, an intriguing line of research had suggested that the worms might be able to retain memories after decapitation. But researchers had done their training and testing by hand, a cumbersome method that led to inconsistent results. ("The process of training worms by hand is very time-consuming," Levin says, probably understating it.) Ultimately, the topic was abandoned. Now, with a totally automated procedure, Shomrat and Levin hoped to study planarian memory with less error and greater numbers of worms.

First, their worms spent 10 days getting familiar with one kind of environment, either a regular petri dish or one with a rough floor. They were fed abundantly so that they'd learn a positive association with their home environment. Then, for testing, they were put in a rough-bottomed dish with a little spot of food in the center and a light shining on it. Planarians like to stick to the periphery, and they hate light, so they needed to overcome both aversions to get the food. As expected, worms that were more familiar with the rough dishes reached the food sooner, as measured by video tracking.

When the researchers tested the worms again 14 days later, they found that the worms trained on a rough-bottomed dish were still more comfortable with it than the other worms. This memory seemed to last for at least two weeks. Perfect—that's just enough time for a planarian to lose its head and grow it back.

The worms were relieved of their heads. The scientists made certain that no bit of brain survived. Then, after the worm stumps had painstakingly re-headed themselves, the planarians went back into the testing chamber.

The memory wasn't there right away. But Levin and Shomrat found that if they gave all the worms one quick training session before testing, worms who'd previously been familiarized with rough petri dishes reached the food significantly faster than the other worms. The training session "basically allowed the worms to refresh their memory of what they had learned before decapitation," Levin says. In other words, their memories had survived the loss and regrowth of their heads.

Levin doesn't know how to explain this. He says epigenetics may play a role—modifications to an organism's DNA that dial certain genes up or down—"but this alone doesn't begin to explain it."

It's a mystery, Levin says, how a chemical tweak somewhere outside of a worm's brain can later be translated into information, such as the knowledge that a bumpy environment means food is nearby. "We don't have an answer to this," he says. "What we do show evidence of is the remarkable fact that memory seems to be stored outside the brain."


Image: Shomrat and Levin.

Tal Shomrat, & Michael Levin (2013). An automated training paradigm reveals long-term memory in planaria and its persistence through head regeneration The Journal of Experimental Biology : 10.1242/​jeb.087809

Help Desk: Chastity Belts and Other FAQs

Hello!

I'm on vacation this week. With any luck, as you read this I will be lying in the shade with a book or having a hilarious misunderstanding with a non–English speaker. I will not be thinking about en-dashes, as I did just now. I will try not to think about beige liquid diets.

While I am away, please refer to these FAQs for any concerns you might have. They're not Frequently Asked Questions so much as Fairly Awkward Queries: search terms that, through some whim of a Google or Bing algorithm, brought people to this blog. I hope that their questions were answered eventually—or, at least, that they're enjoying their summers.

are cuckoo birds real
Yes, unlike the dragon dishwasher or manticore microwave, the cuckoo clock is an appliance based on a real animal. 

how to outsmart an 8 year old
Nineties Trivial Pursuit?

covered in bees 
If your hands are free to type, I have to think you're overstating the severity of the situation. At best you're sprinkled in bees.

a mutation of a lion and a monkey
I'm not sure about the lonkey, but you can see some other imaginary animal hybrids in this gallery at Wired. (I contributed the suggestion for the cuttlephant.)

chastity belt for 2 months
I'm sorry to hear about that.

been in a chastity belt for 9 months
Do you have any advice you'd share with a seven-months-earlier version of yourself?

chastity belt why on why now
I knew I'd regret this post.

fish adoption form
I've never tried this personally, but I'm pretty sure they just let you take them home from the store in a plastic bag.

orangutan tool use fish
Is the orangutan using the fish as a tool? Is the fish using the orangutan? Is this why you wanted to adopt it?

pretending to be paraplegic 

I'm going to stop you right there and say there HAS to be a better way to make your Match profile stand out.

i draw worms out of the ground
Maybe you could be a new X-Man? Like Storm, but Worm? Though in a different comic universe, if Robin is your sidekick, this could be distracting.

miniature poodle evolved
It was survival of the fittest in the Tundra of Purses, and once the miniature poodle had developed its portable stature and warm, hypoallergenic coat, it dominated its niche.

what do polar bears hate
Wild tundra poodles.

where baby point in female 
Um.

a real octopuses that tie you up
Ooh! This might be a good tactic to try on that 8-year-old.

unicorn horns photo 
I'm afraid I have some bad news.


Previously: Help Desk, Relationship Edition; 12 Days of Inkfish, Day 4: Help Desk

Image: Aryc Ogre (via Flickr)

"Fool Me Twice, Shame on ME," Says Sea Slug

"Simple" is often a compliment in the human world, used to describe low-fuss dinners or closet solutions. When scientists use "simple" to describe an animal, they mean something more like, "That sac of goo has no business acting clever." An especially simple creature—a sea slug—recently demonstrated that despite its humble resources, it can learn from experience and form new hunting strategies. Smaller goo sacs, beware.

Despite its squishy stature, the sea slug Pleurobranchaea californica is a killer. It roams the sea and swallows whatever appealing morsels are in its way. Being blind, it can't tell how tasty its prey looks—or doesn't.

It can't see, for example, the flashy coloration of the "Spanish shawl" nudibranch (Flabellina iodinea). If it could, it might guess that those bright pink and orange hues are a warning: Flabellina is not nice to eat. It steals stinging cells from its own prey (such as corals and anemones) and stores those stingers in its bristles.

Rhanor Gillette, a neuroscientist at the University of Illinois, Urbana-Champaign, observed that not only do Pleurobranchaea slugs spit out Spanish shawls, but they seem to remember and avoid the animals in the future. To study how well the predatory sea slugs learn their lesson after tasting Flabellina, he and graduate student Vanessa Noboa set up a meet-and-greet between the two species.

In tanks, the large, hungry sea slugs encountered the smaller nudibranchs. Researchers recorded how long it took for Pleurobranchaea to take a taste, then waited for the slugs to change their minds and turn away from their potential prey. (Here's a great video of a Pleurobranchaea attempting to Hoover up a Flabellina, then spitting the animal back out. While the big slug pivots away in disgust, the little one does its "Don't eat me" dance like nobody's watching, which is true.)

On the first day, this interaction happened five times. By the end, most of the Pleurobranchaea slugs were much slower to take a taste of the Spanish shawls, or were ignoring them altogether. Twenty-four hours later, the sea slugs were still reluctant to approach Flabellina. Even after 72 hours, they remembered what they'd learned. Gillette and Noboa report their results in the Journal of Experimental Biology.

Since the predatory slugs seem to sniff something in the water that makes them turn away, the researchers think the noxious Spanish shawls give off a distinctive warning odor.

Gillette says the sea slugs have a decent memory, considering their elementary nervous system. "In these experiments their memory is strong at 48 hours," he says, "and in unpublished work we've seen savings up to a week, so it's not bad." (Oddly, some slugs had to be removed from the experiment because they didn't mind the taste of the stinging Flabellina at all. They sucked it up just like any other food.)

Learning from an unpleasant taste experience, then using that memory to change one's hunting strategy, is "a real cognitive trait," Gillette says—in other words, a "goal-directed use of knowledge." The Pleurobranchaea slugs learned to avoid the smell of Flabellina, although they continued to eat a related, non-stinging species without hesitation.

Being able to change their feeding strategy is a good thing, since these slugs are generalists. Everything in the path of their oozing is a potential meal. "More specialized animals, say sea-slugs that may munch on a particular kind of sponge, may not need to employ such learning abilities," Gillette says. For a hunter like Pleurobranchaea, the decisions aren't so simple.


Noboa, V., & Gillette, R. (2013). Selective prey avoidance learning in the predatory sea-slug Pleurobranchaea californica Journal of Experimental Biology DOI: 10.1242/​jeb.079384

Image: Rhanor Gillette.

Squid's Daily Rhythms Are Controlled by Glowing Symbiotic Bacteria

At nightfall, the Hawaiian bobtail squid digs itself out of the sand and rises into the ocean water like a spaceship taking off. It switches on its cloaking device: glowing bacteria inside its body light up, disguising the squid's silhouette against the moonlight for any predators swimming below. As sleek a vehicle as it appears, though, the bobtail may not totally outrank its microscopic crewmembers. The bacteria seem to power a clock inside the squid's body that can't function without them.

Hiding during the day and hunting at night in shallow Pacific waters, Euprymna scolopes clearly has a working circadian clock. Researchers had noticed, though, that the squid's light organ—the specialized pocket inside its body that houses its bacterial helpers—seemed to have a rhythm of its own. The Vibrio fischeri bacteria give off fluctuating amounts of light throughout the day, for one thing. And the bacteria have their own daily rhythm of gene expression (when various genes are turned on or off), explains Margaret McFall-Ngai, a microbiologist at the University of Wisconsin, Madison.

McFall-Ngai and her coauthors looked for genes linked to circadian rhythms within the squid. They found two types of "cry" genes, which are known to control internal clocks throughout the animal and plant kingdoms. One gene had a daily cycle of activity in the squid's head—which is what you'd expect, since animals' main circadian clocks are in our brains. Other clocks can be elsewhere in the body, though, and this is what researchers found with the second cry gene. It was cycling only within the light organ.

Baby squid, which hadn't yet collected bacterial friends in their light organs, didn't show the same cycling. So it seemed that the bacteria themselves were driving the daily rhythms in the light organ. When the researchers let squid fill their light organs with defective, non-glowing bacteria, the cry gene still didn't cycle properly. This suggested that the glow of the bacteria was the crucial ingredient.

To test this idea, the scientists shone a blue light on the squid holding defective bacteria. Now they expressed just as much cry as the original squid.

McFall-Ngai explains that cryptochromes, the proteins made by cry genes, respond to blue light. Based on the light signals the cryptochromes receive, they turn other genes on or off. Cryptochromes in the squid's head respond to light from the sun to drive its daily rhythms, as in other animals and plants. Those in its light organ, though, respond to the light of its glowing bacterial companions.

The role of the bacterial clock isn't clear yet. "We don't know if the light organ rhythms control any other rhythms in the body," says McFall-Ngai. "But they certainly seem to be involved in controlling the rhythms of the organ itself." The squid controls the daily schedule of the bacteria, too: it jettisons most of its bacteria in the morning, and seems to keep them dimmed during the day by restricting their oxygen supply. At night, it gives the bacteria enough resources to glow at full strength—and that glow drives the clock within the light organ. "There seems to be a tit for tat," McFall-Ngai says. "The host and symbiont 'talk' to one another, controlling one another's biology."

The idea that bacteria can drive circadian rhythms inside their hosts is exciting to humans because we, too, are animals packed full of bacteria. Ours don't glow, but they do line our guts and participate in digesting our food. McFall-Ngai points out that scientists have found "profound circadian rhythms" within our gut tissues, both in their activity and in what genes they express.

Even though we're land-bound, non-glowing vertebrates, our bacteria could be powering circadian rhythms within our bodies just like the squid's. "We think it might be a very general phenomenon," McFall-Ngai says. Our microscopic passengers, that is, might be helping to steer the spaceship.


Heath-Heckman, E., Peyer, S., Whistler, C., Apicella, M., Goldman, W., & McFall-Ngai, M. (2013). Bacterial Bioluminescence Regulates Expression of a Host Cryptochrome Gene in the Squid-Vibrio Symbiosis mBio, 4 (2) DOI: 10.1128/mBio.00167-13

Image: Margaret McFall-Ngai

The Composer and the Cassowary: An Appreciation of Mistakes

High in a church balcony last weekend, waiting to perform a solo for Palm Sunday and trying not to panic, I thought about cars being hit with hammers. I'm not sure this is the kind of visualization recommended for singers. But sometimes genetics asserts itself.

A college biology professor once told my class that genetic mutation is like whacking a car with a hammer. You will almost never improve your car this way. More often, you'll damage it. If you're lucky the damage will be only superficial: a change in the silent portion of your genome, or maybe a few funny feathers.

The piece my choir was getting ready to sing, Gregorio Allegri's Miserere, has experienced some mutations in its own DNA over the centuries. Allegri composed the piece way back in the early 1600s, and after that it was sung exclusively during Holy Week at the Sistine Chapel. Even though people had to attend a 3 AM service in Rome to hear it, the Miserere became famous. The Vatican, wanting to keep the piece to itself, threatened excommunication for anyone who copied down the score.

As secrets and life forms tend to do, though, the music leaked out. In the late 18th century, a certain precocious teenager with the last name of Mozart spent Holy Week in Rome with his father. After hearing the Miserere at the Sistine Chapel, young Wolfgang sat down and transcribed the whole thing from memory. He returned for a second performance to double-check his work. From there, the score got into the hands of a music historian who published it.

If the music had really been genetic material, Mozart would have been DNA polymerase, a molecular machine that copies DNA. The polymerase molecule grasps a DNA strand and crawls along, letter by letter, building a matching strand as it goes.

Like Mozart, the enzyme is good at what it does. It proofreads. But sometimes it slips up: A single letter of DNA might be swapped for another one. A section of the code might be flipped backward. One or more letters might be inserted or deleted. (Even one letter lost or gained can cause a major change, since the DNA code is read in three-letter words. In English, imagine losing a letter from the sentence "SHE ATE THE RED BUG" and ending up with "SEA TET HER EDB UG." Some words are still there, but the meaning of the sentence is destroyed.)

Even if DNA polymerase is performing well, damage to the genome can come from outside sources such as UV radiation. But a large fraction of your DNA seems to do nothing at all. If a mutation happens here, you won't know the difference. If a slip-up creates a synonymous change in a gene—the code allows for some words to be spelled in multiple ways—you'll also be fine. And if the mutation does something horrible, it will remove you from the gene pool.

Evolution doesn't care much about any of this. It only notices the rare constructive strokes of the hammer, and it only sees them if they happen in the cells that will become your sperm and eggs (called the "germ line"). If you have DNA damage in the skin of your back from too much tanning, you can't pass it on to your children.

Back when Allegri's Miserere was being sung in the Sistine Chapel, the choirs were made up of men and boys. In choirs like mine, women sing the alto and soprano parts. But that's only a superficial mutation; we singers are the flesh of the piece.

The germ line mutation came in the 19th century. Someone who copied the piece apparently made a mistake, shifting a whole repeated section up by a fourth. What started out as a normal soprano solo now rocketed all the way to a high C, a preposterous note that humans are almost never asked to sing.*

Natural selection didn't weed out this mutation. Once the change had happened and been passed to new generations of the musical score, it stayed in place—even after the error was discovered. We continue to sing the mutated piece because, simply, it's awesome this way. Here's a video. You'll know when the boy soprano hits the high C: it's the note you hear through the bones of your spine instead of your ears.

It's not an overstatement to say that what happened to Allegri's music represents the whole history of life on Earth. Every new development has come from a mistake, small or egregious, that was allowed to stick around for one reason or another. Life started as tiny blobs, then whoops—heads! Legs! Oops again—tulips! Uncorrected errors became tree bark, snail shells, lungs, fur, resistance to antibiotics. Inching along mistake by mistake, life forms developed the machinery to make blood, slime, deadly venom, and spider silk.

Some living things have come together so elegantly that they bring an audience to its feet. There are racing cheetahs, swooping owls, orchids that mimic bees. But even the giant, gut-colored flower that stinks like a corpse to attract flies is a success in its family line. The cassowary is a bird that made so many mistakes, it traded the ability to fly for tree-trunk legs and a head with a sail on top. Even the cassowary, though, is doing something right. Errors become the high notes.

Postscript: My choir director turns out to have a son who, at age three, actually took a hammer to the family car while it was in the garage. The car was not improved. 

Images: Top, cassowary from The New Student's Reference Work and Gregorio Allegri, both via Wikimedia Commons. Bottom, cassowary by Peter Nijenhuis via Flickr.

*Plot clarification, in case anybody is worrying about me up there in the loft: this is not the part I sang.

Play Along as Sub Discovers Sunken Whale Bones Crawling with New Life Forms

Forget a needle in a haystack. For that search you'd be allowed light and air—and when you held the needle in your hand at last, it wouldn't be unrecognizably coated in bone-eating worms. Looking for whale skeletons on the ocean floor is such an impossible task that no one sets out to do it on purpose. The most recent find, lying near Antarctica and crawling with previously unseen species, was a very happy accident.

A dead whale that sinks all the way to the ocean floor is called a "whale fall," kind of like "windfall," which it is. The corpse is a massive sack of food dropped from above into a barren landscape. It feeds generation upon generation of life: first the scavengers that pick it clean, then other creatures that chew the bones into scaffolding and bacteria that churn out sulfides, and then a host of animals that feed on these chemicals directly or indirectly.

The same types of animals live at hydrothermal vents and cold seeps, where they consume sulfides and other chemicals seeping out of the earth. Whale falls may act as stepping stones for these species to migrate from one undersea chimney to the next. Even though they haven't seen many sunken skeletons up close, scientists have deduced this with the help of experiments such as dropping wood piles into the ocean and leaving them there.

When the members of a UK-funded research expedition came across the latest whale fall, they were piloting a remotely operated vehicle (ROV) more than 1,440 meters under the sea. "We were at the end of a very long ROV survey," says graduate student Diva Amon, "and had already gone an hour over our allocated time on the seafloor." Then, she says, "we spotted a row of curious white blocks in the distance."

Investigating more closely, the team realized that the blocks were spine bones. They were looking at a whale skeleton covered in deep-sea animals. "We all realized that this was only the sixth natural whale fall to be seen, and the first in the Antarctic," Amon says. "Everyone was thrilled."

In this video, you can watch from the eyes of the ROV as it pans across the find. The camera moves from the whale's skull to its vertebrae, which are lined up like a string of enormous marshmallows. Then it zooms in to see the lush jungle of life sprouting from each bone. Around 50 seconds in, you'll get a cephalopod surprise (is there a better kind?).

The fronds you see waving from the vertebrae are the tail ends of bone-eating worms called Osedax, which Amon calls "remarkable." Tucked in between them are the shells of limpets. When the camera pans down to a fellow who looks like a rubbery sock (a sipunculan worm), you might spot tiny crustaceans scurrying across the bone in the background. Did you see the worm whisk itself into hiding when the squid jetted by? You should probably watch again to be sure.

If the pale denizens of this skeleton look weird to you, they were weird to the scientists back at sea level too. The creatures at the whale fall included nine species that had never been seen before. "Every time one explores the deep sea, there is a very large chance of finding a new species," Amon says.

DNA analysis showed that the skeleton, nearly 11 meters long, once belonged to a minke whale. The types of creatures now living on it were similar to those at other whale falls. Based on these life forms and the state of the bones, scientists could tell that the whale fall has become a sulfur-rich environment. It houses the same animals that inhabit deep-sea vents and cold seeps, and it may be helping those creatures migrate across the ocean floor. "One species of limpet that was found on the whale bones was also found on nearby hydrothermal vents," Amon says.

The researchers couldn't tell whether the skeleton had been in its resting place for a few years or for several decades. Either way, they left this rare needle right where they found it.


Amon, D., Glover, A., Wiklund, H., Marsh, L., Linse, K., Rogers, A., & Copley, J. (2013). The discovery of a natural whale fall in the Antarctic deep sea Deep Sea Research Part II: Topical Studies in Oceanography DOI: 10.1016/j.dsr2.2013.01.028

Images: Whale vertebrae photo and video (c) UK Natural Environment Research Council ChEsSo Consortium; deep-sea creatures (c) Natural History Museum.

Baby Cuttlefish Are Cute, Colorblind Killers

The business end of a cuttlefish is no place a small crustacean wants to be. Cuttlefish are hunters who creep around in camouflage—virtually indistinguishable from a gray patch of gravel or a branching green seaweed—then lash out with their tentacles, turning a passing shrimp into shrimp toast. Oh, and they're colorblind. Despite this apparent handicap, though, learning to hunt doesn't take a lifetime. Baby cuttlefish figure it out almost as soon as they hatch.

"Newly hatched cuttlefish are mini adults," says Anne-Sophie Darmaillacq of the Université de Caen Basse-Normandie in France. They behave similarly to full-grown cuttlefish, that is, and look like toy versions of their parents. Yet those grownups are long gone. "Parents die after the spawning season," Darmaillacq says. Since cuttlefish are born as orphans, they have to be able to look after themselves right away.

For this reason, Darmaillacq and her coauthors wondered how the eyesight of junior cephalopods compares to that of their adult relatives. To find out how quickly a just-hatched cuttlefish's eyes get up to speed, they collected eggs of the cuttlefish Sepia officinalis off the coast of France. (The genus name describes a cuttlefish's brown ink, not its many-colored body.)

 Zero to 30 days after hatching in the lab, the tots were tested in a carousel-like device. While a cuttlefish sat stationary at the center, a cylindrical screen with vertical stripes rotated around it at various speeds. Animals that were able to distinguish the stripes spinning by would follow them with their eyes, or by rotating their whole bodies. One set of test screens had black, white and gray stripes. Another had stripes that produced different polarizations of light.

Human eyeballs don't distinguish light polarization, which is when light waves all wiggle in the same orientation as they travel, as after passing through a filter. Bees and some other animals can see this polarization and use it to navigate. Cuttlefish, too, can see light polarization, and scientists are familiar with the architecture in a cuttlefish's retina that allows this. But Darmaillacq says the ability hadn't been studied as much in young cuttlefish.

The tests in the striped carousel showed that cuttlefish who had just hatched were already great at tracking black, white and gray stripes, and got even better over their first 30 days of life. They also started life with some skill at seeing stripes of light polarization, and improved as they aged.

Watching stripes spin is less important than knowing when to pounce on a passing meal, though. In a second set of experiments, the researchers showed young cuttlefish two types of prey trapped inside glass tubes and waited to see which the cuttlefish would attack. One prey was mysid shrimp, which hide by being transparent—but they're much easier to spot if you can see light polarization. The other prey was crabs, which both cuttlefish and humans can see without the help of polarized light.

In a regular glass tube, cuttlefish eagerly attacked all the prey. But in a tube covered with a plastic film that hid light polarization, cuttlefish were more reluctant to attack the shrimp. As they grew older, they got faster at spotting all their victims, but they still didn't like to attack transparent prey unless they could see the polarized light coming off their bodies.

Darmaillacq says newly hatched cuttlefish seem to already have the cognitive skills that make a good hunter, such as learning, attention, and decision making. Her experiments also show that cuttlefish can see light polarization soon after hatching, and that skill helps them find transparent prey and decide when to pounce.

The cuttlefish's colorblindness is a deficit that's almost impossible to believe once you've watched this camouflage master in action. Darmaillacq says the ability to see light polarization may make up for the cuttlefish's missing color vision.

Polarized light helps young cuttlefish spot some of their favorite transparent snacks, which would otherwise be hidden. Additionally, "Wavelengths vary a lot depending on the depth [of the water]," Darmaillacq says. "Light polarization does not." In other words, colors can lie in the ocean, but polarization tells the truth. This means cuttlefish can see well enough that their prey—like the fish in this video from the New England Aquarium—never see them coming.




Cartron, L., Dickel, L., Shashar, N., & Darmaillacq, A. (2013). Maturation of polarization and luminance contrast sensitivities in cuttlefish (Sepia officinalis) Journal of Experimental Biology DOI: 10.1242/jeb.080390

Image: Leonard Clifford (Flickr)

Video: New England Aquarium

Aphids Always Land on Their Feet

Pea aphids are even better at "stop, drop and roll" than elementary-schoolers. When a threatening ladybug or grazing deer approaches the stem where an aphid is sucking sap, it lets go and plummets toward the ground. By holding its limbs in just the right way, though, the insect can tumble into an upright position before sticking the landing.

The ground is a dangerous place for a small wingless animal, so it might help a falling pea aphid (Acyrthosiphon pisum) to hit it running. Or, better yet, to land feet-first on a lower leaf and never reach the ground at all. A group of scientists in Israel subjected pea aphids to predator scares, bouncing falls, and amputations to investigate their cat-like maneuvering.

In one experiment, the researchers placed a ladybug onto a fava bean plant where aphids were feeding. They covered the ground below with petroleum jelly so the insects would be caught however they landed.

As the ladybug crawled up the plant, alarmed aphids dropped to the ground. Falling from 20 centimeters, nearly every aphid landed right side up—"like a defenestrated cat," the authors note cheerfully.

If a live aphid is like a cat, a dead one is closer to buttered toast. The team used tweezers to drop upside-down aphids from 35 centimeters up. Some aphids started out alive and well; others were dead. The third (and least fortunate) group of aphids were still alive but had their limbs and antennae removed with a razor blade. Among the living, limbed aphids, 95 percent landed upright. Only about half of the dead aphids did, though. The number was even lower for the limbless group, reduced to flipping through the air like sesame seeds.

High-speed photography and mathematical modeling revealed the secret of the pea aphid. After letting go of a plant, it stretches its antennae forward and reaches its hind legs back and up. Then it freezes.

This position, the researchers discovered, it only aerodynamically stable when right side up. Holding its appendages stiffly in position like a skydiver, the falling insect will tumble until it's belly-down. Then it stays that way until it lands, the authors report in Current Biology.

"I was surprised and impressed by the simplicity of the righting mechanism," says Gal Ribak, a biologist at the Israel Institute of Technology and one of the lead authors. To land upright, the aphids only need to assume the right pose and stay that way. "All the rest is taken care of with the help of air resistance and gravity."

To see whether falling upright helped aphids land on a safe leaf, instead of going all the way to the groung, the researchers dropped insects directly over leaves. Those that were feet-first when they hit a leaf were able to stick the landing about half the time. When turned the wrong way, though, the aphids were guaranteed to bounce off the leaf and into danger.

The real danger in the lab, of course, came not from predators on the ground but from the scientists, who now snipped the ends off the aphids' legs to see if sticky pads there were helping them land. Once their wounds stopped oozing, the insects took another trip through the air. This time only 1 out of 20 caught the leaf.

Ribak studies animal locomotion within the university's department of aerospace engineering. That's because pea aphids, with their aerodynamical tricks, may have something to contribute to aircraft design. The species is also known for apparently capturing energy directly from the sun, something that's usually impossible if you're not a plant. Technologically, when it comes to these falling insects, we may never catch up.


Ribak, G., Gish, M., Weihs, D., & Inbar, M. (2013). Adaptive aerial righting during the escape dropping of wingless pea aphids Current Biology, 23 (3) DOI: 10.1016/j.cub.2012.12.010

Image: Ribak et al. (see the whole video here!)

When a Queen Dies, Wasps Know Who's Next in Line (and Next, and Next)

This post originally appeared in August 2012. Inkfish will return to its regularly scheduled wacky animals next week. 

The office of postmaster general to the United States used to come with a perk totally unrelated to mail. In the unlikely event that an accident wiped out the president, vice president, and every member of their cabinet, the postmaster general would become the leader of the country.

In reality, the line of succession has never gotten beyond the vice president. But there are 16 people lined up behind the VP to take over (a list that no longer includes the postmaster general and now culminates, less quaintly, with the secretary of homeland security). In the United Kingdom, the order of succession to the throne winds bafflingly through a giant family tree of princes, dukes, viscounts, and so on.

Wasps of the species Ropalidia marginata never have to argue about titles or families: when the queen dies or disappears, the other wasps in the colony unanimously agree on who her successor is. And if that queen disappears too, they know who comes after her. Though the ordering system is invisible to human eyes, the wasps adhere strictly to their line of succession and follow it all the way down (if necessary) to their equivalent of the postmaster general.

Alok Bang and Raghavendra Gadagkar, researchers at the Indian Institute of Science in Bangalore, have been determinedly assassinating wasp queens to try to figure out how the R. marginata system works. Until the researchers get to her, each nest's queen lives a peaceful life. She doesn't bother anyone, and no one bothers her as she pumps out new generations of fertilized eggs.

The queen's quiet lifestyle, like that of most royalty, is in stark contrast to the lifestyle of her subjects. All around their docile ruler, worker wasps live in continuous violence. Gadagkar says the wasps chase, bite, and "nibble" one another, pin each other in place by holding body parts in their mouths, and crash down on each other from above. These displays of aggression don't usually injure the wasps, but maintain a hierarchy of dominance among them.

When the peaceful queen dies, or is plucked from the nest by interfering scientists, things get shaken up. One worker wasp—and only one—suddenly becomes hyperaggressive. Within minutes of the queen disappearing, this worker begins attacking the wasps around her at 10 or even 100 times her usual frequency, Gadagkar says. She distributes her attacks evenly among anyone nearby, and no one fights back. It's all a show to announce that this wasp is the heir to the throne.

Over the following week or so, the heir's aggression dies down and her ovaries develop. She becomes another peace-loving, egg-laying machine.

The researchers believe that this successor is chosen somehow before the original queen disappears. Even though she's outwardly identical to the other wasps in the nest, she's predestined to be second in line to the throne. "The fact that there is invariably one and only one individual who becomes hyperaggressive" is one clue, Gadagkar says. That no one challenges this hyperaggressive individual is an even stronger clue. And in previous studies, the researchers have shown that the heir isn't simply the first wasp to get the news of the queen's death. The successor seems to know who she is ahead of time, and the other wasps know and respect it too.

If that weren't impressive enough, Bang and Gadagkar have now found that when they remove the first heir, a second one steps up just as quickly. In a new paper in PNAS, the authors say they've discovered a succession of at least five potential queens.

Each of these new queens jumps into action as soon as a the previous queen disappears, attacking any workers around her. Again, only one wasp steps forward, and no one challenges her. Within several days, this new queen starts laying her own eggs and maintaining the colony. In an entire nest of 20 or 30 individuals, the researchers say, there's no reason to believe the succession doesn't continue—maybe down to the very last wasp.

Having an agreed-upon order of succession makes sense for insects living in small colonies like R. marginata, the authors say. Unlike in a large honeybee colony, where queens are determined from birth and workers know they'll never lay their own eggs, workers in the termite colony actually have a shot at reproducing. Knowing where they are in the queen queue could help them decide whether to stay in their original nest or move out to start a nest of their own.

Even if it makes perfect sense for the wasps to have an orderly system of succession in place, that doesn't explain how on Earth they figure it out.

"That is the million-dollar question we are working on!" Gadagkar says. The researchers found that older wasps were more likely to be the immediate heirs to the throne, but the order doesn't go strictly by age. It also doesn't have anything to do with the dominance hierarchy in the nest.

"Perhaps it is something very subtle, related to the internal physiology of the wasp, that the wasps themselves can detect and which we have not yet discovered," Gadagkar says. Like obscure duchesses and earls, the wasps know their place in line—indecipherable as it may be to the rest of us—and wait for their day to step forward.

Alok Bang, & Raghavendra Gadagkar (2012). Reproductive queue without overt conflict in the primitively eusocial wasp Ropalidia marginata PNAS : 10.1073/pnas.1212698109

Image: Abhadra/Wikipedia