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

Found: A Rotten-Smell Button in the Brain

Window or aisle? Hamburger or hot dog? Bouquet of flowers or rotting flesh? Not all your preferences are up to you—some have been hammered into your genes by evolution.

If you're an average human, you avoid the smell of decay. It signals unsafe food and the threat of infection or disease. Other animals run toward the stench of a stale carcass, maybe because they're flies and it signals a place to lay their eggs.

Whether they love it or hate it, animals identify the scent of rot from two signature molecules. German doctor Ludwig Brieger discovered these molecules in the late 1900s; in English, they're rather cutely named "cadaverine" and "putrescine." Bacteria create the two culprits by breaking down down amino acids in animal bodies. Not solely the sign of a rotting carcass, cadaverine and putrescine also show up in urine and bad breath.

Despite the importance of these smells (or avoiding these smells) in animals' lives, no one had found receptors for these molecules—that is, the locks to which the molecules are keys. Scent receptors are attached to one end of a neuron inside the nose (or whichever body part an animal smells with); when a certain chemical wafts up the nose and latches onto the receptor, a signal travels along the neuron to the brain at the other end. Researchers at the University of Cologne in Germany and Harvard University think they've found one of those receptors for rot.

The authors, led by the University of Cologne's Ashiq Hussain, studied zebrafish, which are commonly used to model the sense of smell in vertebrates. First they checked to make sure zebrafish respond to the smell of decay. When they put putrescine and cadaverine into a tank, zebrafish swam to the other end, showing they feel the same way we do about these smells. When the authors plugged the zebrafishes' little nostrils with glue, the fish were no longer bothered by the odor.

The researchers searched for a receptor in a family of proteins called TAARs (trace amine-associated receptors). Related receptors in rodents are thought to detect other unpleasant odors that come from living things. Zebrafish make 112 different kinds of these receptors, but the molecules that attach to them hadn't been found yet.

After testing 93 smelly chemicals on representative zebrafish TAARs, the authors found a match: cadaverine turns on a receptor called TAAR13c. But could the receptor detect cadaverine in real life, and not only when it was dripped on in purified form by a scientist? To test it, the researchers used an extract of dead fish. When exposed to liquid made from a recently deceased zebrafish, the receptors didn't respond. Liquid from a week-old, rotten fish carcass, though, easily activated the receptor—even when diluted to 1 part in 1,000.

Finding a receptor for cadaverine means scientists now understand a little bit more about how the vertebrate brain responds to awful smells. The receptor protein itself "will not be similar in humans, because mammals do not have close relatives of this zebrafish receptor," says Sigrun Korsching, the paper's senior author. Still, she adds, "There are very few cases where you can show activation of a single receptor leads to a behavioral response." Studying how the zebrafish's neurons respond to cadaverine could lead to a better understanding of how animals process all kinds of odors, whether they enjoy them or not.

Image: by Bill Gracey (via Flickr)

Ashiq Hussain, Luis R. Saraiva, David M. Ferrero, Gaurav Ahuja, Venkatesh S. Krishna, Stephen D. Liberles, & Sigrun I. Korsching (2013). High-affinity olfactory receptor for the death-associated odor cadaverine. PNAS DOI: 10.1073/pnas.1318596110

Note: This post has been edited from an earlier version.

Schrödinger's Turtle: How Observing Ocean Animals Can Harm Them

We rely on roving ocean creatures to fetch us all kinds of data we couldn't get otherwise. Carrying cameras or GPS units or sensors glued to their bodies, marine animals collect data for human scientists about the health of ocean ecosystems or how their own species migrate. Yet lugging our equipment through the sea may be harder for these creatures than we realize. By tagging them, we might be slowing down or even harming the same species we're trying to preserve.

When scientists tag birds, the authors of a new paper in the journal Methods in Ecology and Evolution explain, they follow the "five percent rule": any transmitters they attach to a bird must be less than five percent of its body mass. This ensures the animal can still take off and fly without trouble. But underwater, heaviness doesn't matter as much. Everything gets a boost from buoyancy. What matters more, the authors say, is drag.

To study how drag from tags affects marine animals, NOAA scientist T. Todd Jones and his coauthors put turtles into a wind tunnel. They chose turtles because they're popular—more than 50 published studies per year involve sticking some kind of device to a turtle. Some sea turtle species migrate across entire oceans, so they may carry these devices for hundreds or thousands of miles. And most are endangered.

Instead of propping up live endangered animals inside their wind tunnel, the researchers built fiberglass models. These were casts of 11 types of turtle bodies, minus the front flippers, made from frozen or stuffed carcasses. (The carcasses themselves were too heavy to mount in the wind tunnel.) The researchers also compared a fiberglass cast to a real turtle carcass in water, to make sure the shell materials themselves didn't cause different amounts of drag.

Turtles, of course, don't fly. "Air and water are both fluids," Jones explains; by matching the Reynolds number—a measurement representing turbulence—of the wind to that of water, the scientists could simulate a swimming turtle. Wind speeds of 8 to 20 meters per second corresponded to turtle swimming speeds of 0.5 to 1.3 meters per second.

Attaching seven different kinds of tags to their fake turtles, the researchers saw that most devices increased drag on adult turtles by 5% or less. With a young turtle and a bulky tag, though, it's possible to double the normal drag on the animal. The authors provide charts that other scientists can use to estimate how much drag they're adding to a turtle, based on the animal's size and species as well as the size and shape of their equipment.

It's nearly impossible to tell how tagging equipment affects animals in real life, thanks to a Schrödinger's-turtle paradox: we can't follow the long-term activities of ocean animals that aren't tagged in some way, so we can only compare tagged animals to other tagged animals. However, Jones worries that putting a lot of extra drag—or even a little extra drag—on an animal like a sea turtle could be harmful. These species may burn through every last bit of their energy as they make long-distance migrations, so any extra burden could hurt their odds of surviving and reproducing. (The added brake on their swimming speed might also make them more vulnerable to predators.)

"By following our guidelines, researchers can minimize the drag effects to their study organism," Jones says. This should help keep animals as safe as possible, and keep scientists' results in line with natural conditions for the animals. "However," Jones adds, "sometimes the guidelines will suggest that a certain tag simply should not be used on a particular animal."

Since sea turtles sometimes carry barnacles on their shells, which also add drag, Jones recommends that researchers take the time to pry off a few barnacles while they're gluing on equipment. That way they can make up for some of the extra burden on the turtle, and perhaps alleviate their own guilt about replacing one pest with another.


T. Todd Jones, Kyle S. Van Houtan, Brian L. Bostrom, Peter Ostafichuk, JonMikkelsen, EmreTezcan, Michael Carey, Brittany Imlach, & Jeffrey A. Seminoff (2013). Calculating the ecological impacts of animal-borne instruments on aquatic organisms. Methods in Ecology and Evolution DOI: 10.1111/2041-210X.12109

Images: top, USGS/photo by Kristen Hart; middle, T. Todd Jones.

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

Fish Evolve Stabbier Genitals When Predators Are Near

Like sock garters and homburg hats, the equipment used by our great-grandparents doesn't always cut it for later generations. Certain male fish have evolved differently shaped genitals depending on what other fish share their caves. Attracting females, though, doesn't seem to be as important as not getting eaten.

Most fish reproduce simply by scattering a lot of of eggs and sperm around their environment. But a few types of fish are "livebearers": their eggs are fertilized and hatched inside the female's body, then come swimming out as fully formed miniature fish. Many sharks bear live young. So does Gambusia hubbsi, the Bahamas mosquitofish.

The main difficulty of reproducing this way—at least, the main difficulty from a male perspective—is getting the sperm inside the female's body. You can't just leave it around the ocean and hope for the best. Males in the mosquitofish's family solve this problem with an organ called a gonopodium. The body part's overall size is subject to a couple of different evolutionary pressures: Females of some species prefer a larger gonopodium. But carrying around the bigger organ slows males down when they're trying to escape predators.

Justa Heinen-Kay and R. Brian Langerhans at North Carolina State University were curious about just one part of the gonopodium. The tip is tiny but weapon-like: about one millimeter long, it carries bony hooks, spines, and teeth. It's not big enough slow males down while swimming, or visible enough for females to judge it. Yet the authors wondered whether other evolutionary pressures might be acting on this spiky little body part.

The researchers collected mosquitofish from water-filled, vertical caves in the Bahamas called blue holes. Certain populations of mosquitofish live in caves that also contain their predator Gobiomorus dormitor, the bigmouth sleeper. Other populations live with few predators, and can swim and mate—a process that may or may not involve female cooperation—without the threat of being eaten.

Comparing mosquitofish from 10 caves with predatory bigmouth sleepers and 12 caves without them, Heinen-Kay and Langerhans saw that the fish had evolved different genital shapes. Male mosquitofish that lived with a lot of predators had longer tips on their gonopodia, and those tips were more densely covered in bony bits.

This sturdier, stabbier tip may help a male to work more quickly and efficiently, whether or not the female wants him to. The authors speculate that when predators are nearby and time is short, this genital shape is an advantage. Bony hooks "may serve as holdfast devices," and a longer shape might get sperm farther inside the female while pushing out anything competitors have left behind. But in caves without predators, they add delicately, "males may rely more on cooperation and less on genital shape."

However it helps, modifying the shape of their genitals must be a powerful tool for mosquitofish. Over and over again, fish populations living with predators have evolved in the same way. It's a trend that's here to stay—despite what their ancestors might think.


J. L. HEINEN-KAY, & R. B. LANGERHANS (2013). Predation-associated divergence of male genital morphology in a livebearing fish. Journal of Evolutionary Biology DOI: 10.1111/jeb.12229

Image: Heinen-Kay and Langerhans.

Elusive Marine Mammal Uses Interspecies Buddy System

What ocean mammal is a rare bird but not a lone wolf? Meet the false killer whale. You're not likely to ever spot one in the wild, but if you do, it won't be alone. These animals prefer to travel with a crowd—not just of their own species, but also including their closest companion, the bottlenose dolphin.

False killer whales are so named because the look a little like killer whales, or orcas.* Yet unlike their showy namesake, false killer whales are rarely encountered by humans. In most places where we know they live, it's only because they've turned up stranded on the shores. We don't even know whether they migrate with the seasons.

We do know that the whales are social, and that they sometimes pal around with other species. Jochen Zaeschmar, a master's student at Massey University in New Zealand, has been rescuing and studying false killer whales and other species since 2000. This summer he published a paper reporting that false killer whales sometimes partner with bottlenose dolphins to hunt. On two occasions, researchers had come across large groups of the whales and dolphins apparently working together to round up fish. They blew bursts of bubbles to herd their prey into one helpless crowd, then feasted.

For Zaeschmar's latest study, he and other researchers gathered up records of false killer whale sightings along the northeast coast of New Zealand between 1995 and 2012. It was a total of just 47 encounters—on one whale-watch boat, false killer whale sightings happened on less than half of one percent of trips.

The observations of whales and dolphins hunting together had been no (ahem) fluke. When false killer whales were seen, bottlenose dolphins were by their side "virtually all the time," Zaeschmar says—in 43 out of the 47 sightings.

"Increasing the size of your group...increases the chances of finding food," Zaeschmar explains. The prey fish hunted by these mammals are plentiful, but spread out. Working together could help the hunters find their prey, he says, and "once they do find it there won't be any competition, because there is enough for everyone."

It's also possible, Zaeschmar notes, that one species is just taking advantage of the other's superior hunting skill. The dolphins and whales seem to be working in a true partnership. But "it's difficult to really prove it."

Either way, hunting was happening during less than half of the mixed-species encounters. Yet the animals—anywhere from dozens to hundreds of them at a time—behaved like a single group. There must be some other reason they seek each other's company. "Social factors might play a role," the authors write. Staying in large groups might also help the animals keep an eye out for their own predators, which include (real) killer whales.

The researchers were able to identify some individual animals using distinctive marks and scars on their bodies, such as bites from cookie-cutter sharks (named for the shape of the bite they take out of their victims). Spotting certain animals over and over, the scientists could build a rough map of the animals' social structure. They found that "long-term associations exist between the two species," Zaeschmar says, "with some of the same dolphins observed together with the same whales [over] at least 5 years and 650 kilometers."

"These associations appear to be stable," he says. The two species stick together, whether they're ruthlessly rounding up prey or surprising a boatful of very lucky humans.

*Technically, both the false killer whale and the real killer whale are types of dolphins. But just because marine biologists like to make their lives difficult doesn't mean we have to, so I refer to the false killer whale here as a "whale."

Images: (top) Mazdak Radjainia, (bottom) David Hall.

JOCHEN R. ZAESCHMAR, INGRID N. VISSER, DAGMAR FERTL, SARAH L. DWYER, ANNA M. MEISSNER, JOANNE HALLIDAY, JO BERGHAN, DAVID DONNELLY, & KAREN A. STOCKIN (2013). Occurrence of false killer whales (Pseudorca crassidens) and their association with common bottlenose dolphins (Tursiops truncatus) off northeastern New Zealand. Marine Mammal Science DOI: 10.1111/mms.12065

Jochen R. Zaeschmar, Sarah L. Dwyer, & Karen A. Stockin (2013). Rare observations of false killer whales (Pseudorca crassidens) cooperatively feeding with common bottlenose dolphins (Tursiops truncatus) in the Hauraki Gulf, New Zealand. Marine Mammal Science DOI: 10.1111/j.1748-7692.2012.00582.x

For Diguise, Female Squid Turn On Fake Testes

The best way to stay out of trouble, if you're a shimmery, color-changing little squid, might be to paint on some pretend testes. Scientists have found that certain female squid can switch on and off a body pattern that makes them look male. They use a never-before-seen cell type to do it, and it may be all for the sake of keeping the actual testes owners far away.

The opalescent inshore squid, Doryteuthis opalescens, lives in the Eastern Pacific and is one of the main species caught for food in the United States. So you'd think someone would have noticed its trick before. But the animals shift their colors all the time, and no one seems to have paid much attention to a certain bright stripe particular to females.

Daniel DeMartini, a graduate student at the University of California, Santa Barbara, "observed the female squid rapidly switching the stripe on and off," says his advisor, Daniel Morse. He decided to gather a few hundred D. opalescens squid in laboratory tanks and watch them work.

DeMartini found that females can opt to turn on a bright white stripe on their mantles, highlighted by a line of iridescence on both sides. This happens to look pretty similar to a male squid's testis, which—in his less colorful moments—is visible as a long white shape inside his transparent body.

The authors speculate that female squid might use this stripe as a disguise when they want to avoid harassment by males. "In this species of squid, mating occurs in dense assemblages of animals, with the females subject to repeated bouts of mating by multiple males," Morse says. By switching on her white stripe and mimicking a male, a lady squid might be able to fend off some of these mating attempts, protecting both herself and any fertilized eggs she's carrying.

Morse is less excited about this act of deception, though, than he is about the cells that squid use to pull it off. Within the white stripe region, specialized cells hold proteins called reflectins inside many spherical packages. These proteins start out colorless. Upon receiving a signal from the brain, the packages shrink into dense blobs. The varying sizes of the blobs make them reflect all different wavelengths of light, so that the cells as a whole appear bright white. It's the same way we humans make white paint, Morse says: small, dense particles of titanium dioxide are suspended in the liquid, and the combination of different-sized particles ensures all light waves are reflected at once.

Earlier, the authors found reflectins in the same squid's color-changing cells. Instead of turning from transparent to white, these cells can move between many different colors. In this case, "the reflectins are packed in accordion-like folds or pleats in the cell membrane," Morse says. When the brain tells the proteins to clump together, the accordion folds close up—and depending how far they close, the cells will reflect different wavelengths of light, from red all the way to blue.

It's fitting that squid have ten arms, because this one seems to have a surprise up every sleeve. As to whether it's still hiding anything more surprising than fake testes, we'll have to wait and see.


Daniel G. DeMartini, Amitabh Ghoshal, Erica Pandolfi, Aaron T. Weaver, Mary Baum, & Daniel E. Morse (2013). Dynamic biophotonics: female squid exhibit sexually dimorphic tunable leucophores and iridocytes. Journal of Experimental Biology : 10.1242/​jeb.090415

Images: DeMartini et al. (Top: a close-up view of an iridescent stripe in a female.)

Fish Grow Big Fake Eyes When Predators Are Near

If you're a young, edible animal, a little flexibility about how you develop can save your behind. Or, if you're a damselfish, it can get a few bites taken out of your behind but ultimately save your life.

The damselfish Pomacentrus amboinensis lives on coral reefs in the western Pacific, where it spends its days nibbling algae and trying to avoid being swallowed. As juveniles, these small fish have a pronounced eyespot toward the back of their bodies—a cartoonish false eye drawn on the body, like you might see on a butterfly's wing. Normally, the eyespot fades as the fish matures.

Researchers from James Cook University in Australia and the University of Saskatchewan in Canada asked just how flexible damselfish are while those false eyes are fading away. Can fish opt to keep their false eyes in certain situations? And if they do, does this not-very-subtle disguise actually do anything to protect them?

The scientists raised damselfish in tanks divided into compartments. Some damselfish lived alongside a natural predator of theirs: Pseudochromis fuscus, the "dusky dottyback." Thanks to the special tanks' clear windows and shared water, the young damselfish could see and smell the predator all the time. Other damselfish were raised on their own, or in tanks shared with a harmless vegetarian fish.

After maturing for six weeks in their respective tanks, the fish showed some clear differences. Compared to the other fish, damselfish that had lived near predators had larger false eyes. And their real eyes—startlingly to the scientists—were actually smaller.

"I was very surprised by the result," says lead author Oona Lonnstedt, a PhD student at James Cook University. "It just goes to show the lengths small prey will go to minimize predator attention on their front end."

This assumes that the point of all this camouflaging—growing a big fake eye near your tail and minimizing the actual eyes on your face—is to focus predators' attention on the wrong end of your body. The researchers didn't test predatory fish to see which part of a damselfish they chomped down on. But they did put the damselfish from their experiment onto isolated reef patches in the wild to see how they fared.

Within two days, up to half of the control fish (those raised alone or with non-predators) had disappeared from the reefs, and were presumed eaten. Damselfish that had grown up in a tank with predators, though, radically outperformed the others. Four days after being released onto the reefs, 90% of them were still alive and well.

Their large eyespots and minimized eyes may have made predators chase their back end, where a bite isn't as fatal as one to the head. These fish had also grown up taller in the spine-to-belly dimension, which gives an added challenge to hunters limited by the size of their mouths (and may give the damselfish better bursts of speed too). In the lab, these fish were less active and spent more time hiding; their reticence may also have helped them survive in the wild.

There's a trade-off happening, Lonnstedt says. Damselfish that live with predators and grow large false eyes also have stunted eye growth, which probably impairs their vision. It's not bad enough, though, to keep them from avoiding predators on the reef. In the end, being flexible about how their bodies develop allows them to survive and swim another day.

Image: Lonnstedt et al. (The fish on top grew up in the predator tank.)

Lönnstedt OM, McCormick MI, & Chivers DP (2013). Predator-induced changes in the growth of eyes and false eyespots. Scientific reports, 3 PMID: 23887772

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

Why a Lost Baby Seal May Soon Be at Your Doorstep

Every host knows when you run out of ice, the party's over. For young seals surviving on ice floes, the festivities are breaking up sooner than they used to. That sends vulnerable youngsters into the ocean before they're ready—maybe to end up stranded on a beach near you.

To keep their young from becoming drifting bait in a predator-filled ocean, female harp seals give birth on top of winter sea ice. The pups stay on the ice, undercover in a coat of white fur, until they're old enough to survive in the ocean. Then they shed their white coats, dive in, and begin migrating with the rest of their population.

Harp seals live in two main populations, one on either side of the northern Atlantic. From the population on this side of the pond, increasing numbers of seals have been showing up stranded along the U.S. coast, from Maine all the way down to North Carolina. Researchers at Duke University looked for patterns in these strandings—more than 3,000 over the past two decades.

Not too surprisingly, there was a clear relationship between strandings and the amount of sea ice. Years with more ice had fewer strandings. In years with less ice, when melting floes might force pups into the water before they're ready, strandings went up.

The same trend didn't apply to adults, however. Strandings of adult harp seals weren't linked to the amount of sea ice in that year. But in all years, the majority of stranded seals were pups. That means fluctuations in sea ice have the strongest effect on young harp seals.

The researchers also saw that males were more likely to strand than females. This may be due to what they call a "tendency to wander" among males. Brianne Soulen, one of the paper's lead authors, adds that because adult females need to spend more energy on things like pregnancy, they're less likely to stray from safe feeding grounds.

Genetic factors may also be at work. Soulen says they found slightly less genetic diversity among males, which in theory could make them more susceptible to disease or other factors. No matter the reason, if a harp seal does wind up on the shore of your local beach, it's likely to be a baby boy. Get blue balloons.

In the most recent years included in the study, 2009 and 2010, the usual pattern didn't hold up. The year 2010 was bad for ice, but didn't have a lot of strandings. However, Soulen doesn't see this as reason for optimism. An earlier study saw harp seals changing their migratory behavior in response to shifting ice cover; they may simply be stranding someplace else now, where they're not counted. Or the population as a whole may have dropped dramatically.

It matters, of course, because the ice is running out everywhere. Despite year-to-year fluctuation, the authors write, ice cover in the North Atlantic is disappearing at up to 6% per decade. And Soulen says what's happening with the harp seals provides a big hint about the state of other marine mammals. "Harp seals are a good representative species of the effects of ice changes." The hooded seal population in the western North Atlantic, for example, has declined by 90% since the 1940s, as ice there has steadily disappeared.

When sea ice is gone, there's no one who can dash out for more. The party may not be over quite yet, but it's getting pretty lame.


Image: courtesy of the International Fund for Animal Welfare

Brianne K. Soulen, Kristina Cammen, Thomas F. Schultz, & David W. Johnston (2013). Factors Affecting Harp Seal (Pagophilus groenlandicus) Strandings in the Northwest Atlantic PLOS ONE DOI: 10.1371/journal.pone.0068779

"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.

Whale Turns Down Its Hearing When Expecting Loud Sounds

We can knit sweaters for oiled penguins, but it's harder to protect whales and dolphins from the harm of having us as neighbors. Loud underwater sounds from activities like sonar and drilling may damage these animals' hearing and even lead to mass strandings. Though we can't chase cetaceans around with homemade earmuffs, we might be able to teach them to tune us out.

Like squinting or letting one's pupil shrink in bright light, some animals can adjust how sensitive their ears are. When we're making loud noises, humans reflexively squeeze the muscles of the middle ear to dampen our hearing. Some bats do the same thing while echolocating.

"Generally speaking, mammals have evolved mechanisms to protect their auditory systems from self-produced intense sounds," write Paul Nachtigall of the University of Hawaii and Alexander Supin of the Russian Academy of Sciences. In 2008, the pair showed that a false killer whale (Pseudorca crassidens) could adjust its hearing while it echolocated. So they set out to see whether the species could also dial down its hearing in response to sounds made by someone else.

They taught their whale (a female, originally caught in the wild and now thought to be 30 or 40 years old) that hearing a quiet warning sound meant a louder sound was coming soon. The subject wore suction-cup electrodes on her head during the experiment. Waiting at an underwater listening station, she first heard a series of tones while the electrodes measured which ones her ears responded to. Then, a variable amount of time later, she heard a sudden loud sound (170 decibels).

Over hundreds of trials,* the researchers saw that the whale learned to anticipate the loud sound. If it came within 35 seconds of the warning sound starting, the whale was able to desensitize her ears before it played. (With a longer delay, her response wasn't as strong.) The authors report their results in the Journal of Experimental Biology.

Nachtigall can't say how a whale turns down its hearing. "No one knows for sure how the cetacean middle ear works," he says. Whales don't have eardrums like humans or other land animals, he says, because the sounds they hear must travel through tissue instead of air. So his whale subject probably doesn't squeeze her ear muscles to dampen sound, as a human or bat would. He speculates that it's more likely a top-down control from the brain.

However she does it, the whale can make her ears less sensitive when she knows a loud sound is coming soon. The biggest decrease in her hearing sensitivity was about 13 decibels. That's "about what your hearing changes if you stick your fingers in your ears," Nachtigall says. If you—or the whale—are trying to protect your hearing from a loud noise, he says, "That helps. This would help."

When humans must make a racket underwater, it's possible that we could help whales and other animals by making quieter warning sounds beforehand. This could teach the animals to anticipate the sound and "plug" their ears.

Since he's only studied one animal so far, Nachtigall doesn't know how the abilities of other marine mammals to desensitize their ears compare. "To ask whether [warning sounds] would prevent whale hearing damage is sort of like asking whether ear plugs would prevent deafness in people who work next to jet engines," he says. "I believe the possibility is great, but there are more questions to be answered."

Image: by MichiKimmig (Flickr)

Nachtigall, P., & Supin, A. (2013). A false killer whale reduces its hearing sensitivity when a loud sound is preceded by a warning Journal of Experimental Biology DOI: 10.1242/​jeb.085068

*If you're wondering how one convinces a whale to participate in so many trials, the answer is "fish reinforcement."

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

New Journal Celebrates Animal Stalking

Christmas arrived early this year for people who love animals carrying transmitters around. A new open-access journal called Animal Biotelemetry launched this week, and it promises to bring new tales of mind-blowing bird migrations and seals that study climate change (without exactly having volunteered for the job). Also, sharks.

Published by BioMed Central, the journal will include all kinds of research having to do with biological data gathered by instruments attached to animals. This is a field that's been expanding as the technologies themselves shrink. A few decades ago, scientists were limited to studying the movements of giant land animals such as bears or elk—because transmitters and battery packs were too bulky to comfortably attach to other creatures. Now, miniaturized electronics (aided by GPS satellites) mean that even lightweight birds can carry tracking devices.

Editor A. Peter Klimley describes the history of the field in an introduction to the journal. Klimley himself is a professor and shark guy at the University of California, Davis. His biography claims that he "is known to have held his breath while diving up to 100m deep in order to hand-tag hammerhead sharks with a dart gun." In case "biotelemetry" didn't sound exciting to you.

To mark the occasion, here are some earlier posts involving animals carrying transmitters around, since I am one of the aforementioned people who love them.

Monitoring from Space Shows Even This Giant Crab Can Navigate Better than You

Climate-Studying Seals Bring Back Happy News

This Penguin: An Unexpected Journey


Klimley, A. (2013). Why publish Animal Biotelemetry? Animal Biotelemetry, 1 (1) DOI: 10.1186/2050-3385-1-1

Image: by MEOP Norway North

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