Why Animal Genitals Are Important to Science

Did you know that male black widow spiders have corkscrew-shaped genitals? Or that barnacle penises are up to eight times the length of barnacle bodies? Or that echidnas have frankly horrifying four-headed dangly bits?

If you’ve been following scientists on Twitter in the past week or so, you probably do. That’s because biologists have gone wild posting junk shots of their research subjects, from meerkats to cheetahs to some truly bizarre ants. The #JunkOff hashtag took off last week, and not entirely for sophomoric reasons: Animal genitalia are actually a major window into how evolution works.

“It all goes back to the basis of animal behavior and evolution,” said Anne Hilborn, a doctoral student at Virginia Tech and cheetah researcher who launched #JunkOff and helped start the warmer-and-fuzzier follow-up hashtag, #CuteOff.

Wild junk

As #JunkOff illustrates, the world of genitals is … diverse. And maybe a little scary. But really, let’s focus on the diversity. [The 9 Weirdest Animal Penises]

Alligators, for example, have enormous, permanently erect penises made of connective tissue called collagen. Instead of inflating with blood like most mammalian penises, the alligator penis pops out of the cloaca (the alligator all-purpose genital and waste opening) with the help of rubber-bandlike tendons and muscles. And, yes, there is video.

Even creepier are the detachable genitalia of the male orb-web spider (Nephilengys malabarensis). The “palps,” or sperm-transferring organs, of these spiders stay attached to the female when mating is done, in part so they can keep working if the female spider decides to chow down on her mating partner — these spiders are sexual cannibals. Similarly, black widow males leave the tips of their corkscrew genitalia inside the female. Leaving genitals behind may save spiders energy in the long run. [Animal Sex: 7 Tales of Naughty Acts in the Wild]

Even paleontologists got into the #JunkOff fun, tweeting pictures of dire-wolf penis bones that were preserved in the La Brea Tar Pits in Los Angeles. Yes, many mammal penises have actual bones, also known as baculums. Dogs have them, as do chimpanzees, bears and walruses. (Chimps also have penis spines, a feature that humans — fortunately? — have lost.)

And let’s not give females’ short shrift: Many mammalian females have an analogous genital bone, the baubellum, which sits below the clitoris. This bone, also called the os clitoridis exists in many rodents, as well as bats and some primates. Perhaps the craziest clitoris out there belongs to hyenas, which is about 7 inches (18 cm) long and looks almost like a penis. Female hyenas give birth through it.

“It’s one of my favorite ice-breaking conversation topics at parties when I don’t know what to say,” Hilborn said.

(R)evolutionary genitalia

If the eyes are the windows to the soul, the junk is the window to evolution. Genitalia are important because they’re front and center in sexual selection — and that means that private parts are thought to evolve faster than other body parts.

Very closely related species often have dramatically different genitals, biologist Julia Klaczko, who researches lizard genitalia at the University of Campinas in Brazil, told Live Science in January. Klaczko and her team measured the rate of evolution in lizard hemipenes, the penis-equivalents for snakes and lizards. They then compared the rate of hemipene change with the rate of change in lizard limb length and throat flaps called dewlaps.

They found that male genitalia evolve six times faster than limbs or dewlaps, explaining the large diversity seen in lizard hemipenes. It’s possible that females are picky about penises, so males are constantly evolving new, better options. Or perhaps the penis evolution is an example of an evolutionary arms race, in which males and females both evolve genitals in an effort to gain the most control over fertilization.

That sort of arms race is apparent in ducks. Many species sport long, corkscrew-shaped penises. Females, in turn, have corkscrew vaginas. But the vaginas spiral in the opposite direction as the penises, making it harder for sexually aggressive males to fertilize a female against her will. (And male ducks can get very aggressive. Just ask the discoverer of dead gay duck sex.)

Certain beetles, too, appear to be involved in a genital race — one that leads to the differentiation of new species. Some species of tiny seed beetles have truly intimidating male genitals studded with more than 100 spikes. As male beetles evolve more spikes, researchers found, females evolve tougher genitals to survive mating. This arms race is costly, leading to fewer offspring in species with spikier junk.

“Normally, we think of evolution being adaptive, with organisms becoming better and better adapted to their lifestyle,” study researcher Göran Arnqvist, a biologist at Uppsala University in Sweden, told Live Science in 2007. “Here we have an example of evolution that leads to something bad.”

In many cases, animals keep their private business private. In wild cheetahs, Hilborn said, a couple of males will pick out a female and hang around her for several days — not even leaving to hunt — until she’s ready to mate. Many mating buddies are brothers, but others are unrelated, Hilborn said, and it’s not clear how the female decides which cheetah she mates with.

Iguana Relative Shows How Lizards Spread Worldwide

An 80-million-year-old lizard discovered in southern Brazil has provided a surprising clue about how these reptiles evolved, and where they once lived, according to a new study.

Until now, researchers had found acrodontans only in the Old World, including Africa and Asia. (This is a type of lizard is called an iguanian that has teeth fused to the top of its jaws, a group that includes chameleons and bearded dragons.) But the newfound fossil, a partial lower jaw of a new species of acrodontan, shows that they lived in the New World much earlier than thought.

The fossil suggests that acrodontans managed to distribute themselves worldwide before the ancient supercontinent Pangaea broke up about 200 million years ago, the researchers said. [Image Gallery: 25 Amazing Ancient Beasts]

“This fossil is an 80-million-year-old specimen of an acrodontan in the New World,” study co-author Michael Caldwell, a biological sciences professor at the University of Alberta in Canada, said in a statement. “It’s a missing link in the sense of the paleobiogeography and possibly the origins of the group, so it’s pretty good evidence to suggest that back in the lower part of the Cretaceous, the southern part of Pangaea was still a kind of single continental chunk.”

The jaw, photographed from different angels, of Gueragama sulamerica.
Credit: Tiago Simoes and Adriano Kury

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Paleontologists discovered the fossil in the rock outcrops of desert that dates to the late Cretaceous in the Brazilian municipality of Cruzeiro do Oeste. The researchers named the new species Gueragama sulamericana — guera meaning “ancient” in native Brazilian; “agama” in reference to agamid, a family of iguanian lizards; and “sulamericana” meaning “from South America” in Portuguese.

The jaw is missing a few teeth, but has room for 18 of them, and the teeth almost uniformly increase in size from the front to the back of the mouth, the researchers found.

During the Late Cretaceous, G. sulamericana lived in an arid desert environment, although evidence of ancient wetlands suggests that water was available seasonably, the researchers said. G. sulamericana also had company. Other fossil findings, including “hundreds of bones” of the pterosaur species Caiuajara dobruskii, show that larger animals lived there, too, the researchers wrote in the study.

G. sulamericana may have lived in burrows to avoid extreme daytime heat, just as some modern lizards do today, the researchers added.

Surprise finding

Among living lizards, iguanians comprise one of the most diverse groups, with more than 1,700 species. Previous research has found that acrodontan iguanians dominated the Old World, and nonacrodontan iguanians (such as iguanas) dominated the New World, particularly the American South, Caldwell said.

The oldest known acrodontans are from the early to middle Jurassic period in present-day India. However, now researchers know that acrodontans had spread elsewhere in the world by the late Cretaceous, the researchers said.

“This Gueragama sulamericana fossil indicates that the group is old, that it’s probably southern Pangaean in its origin,” Caldwell said. “After the [Pangaean] breakup, the acrodontans and chameleon group dominated in the Old World, and the iguanid side arose out of this acrodontan lineage that was left alone on South America.”

Eventually, nonacrodontans replaced acrodontans in the Americas. But nonacrodontans remain as natives in the Old World, the researchers said.

“This is an Old World lizard in the New World at a time when we weren’t expecting to find it,” Caldwell said. “It answers a few questions about iguanid lizards and their origin.”

The Science of Adorable What It Takes to Win CuteOff

Science Twitter has gone full squee. Biologists are tweeting pictures of their adorable research subjects in a #CuteOff, and the results are downright nom-able.

Baby elephants? Adorbs. Pert-nosed pikas? Too cute. Hummingbird nestlings? Heart-stopping. Meanwhile, #TeamHerpetology is making a strong showing with shots of baby sea turtles that fit in the palm of a hand, and #TeamEntomology is showing how sweet bugs can be.

“I don’t generally think of fish as cute, but there were some alarmingly cute fish,” said Anne Hilborn, a doctoral student and cheetah researcher at Virginia Tech who helped launch the hashtag.

While the #CuteOff may open eyes to wildlife conservation, it’s also an opportunity to look at what really makes people squee. What are the essential ingredients of cute? Based on the types of animals posted — and previous scientific research on adorableness — here are seven features that could help an animal win a cuteness contest. (This #CuteOff emerged on Twitter following a perhaps, ahem, more salacious animal contest, the #JunkOff.)

1. Big Eyes

Big eyes, full heart, can’t lose. It’s pretty clear that a wide pair of peepers pushes an animal high in the cuteness ratings. Whether it’s a puffer fish or a pygmy possum, many of the animals Tweeted in the #CuteOff are blessed in the eye department. Even plants are getting in on this action: Atmospheric scientist Brian DiNunno tweeted about the doll’s-eye plant (Actaea pachypoda), which has fruit that looks like a stalk full of googly eyes. (These eyes, however, can kill you — the berries contain toxins that can cause cardiac arrest in humans.)

Big eyes may be so alluring because they remind people of human babies. Huge eyes trigger a caregiving response in adult humans, research finds, as do other babylike features such as chubby cheeks, a protruding forehead, and a small nose and mouth. A 1979 study in the journal Infant Behavior and Development reported that even among babies, those with more infantile features were perceived as cuter. The baby-loving response appears to be deeply embedded, even in nonparents.

“Cute infants at all ages tend to have large foreheads, large eyes, small features and narrow faces below the eyes,” the researchers wrote in the 1979 paper. It’s not hard to see how animals with similar features can trip the brain’s cuteness detector.

2. Youth

Given that infantlike features prompt paroxysms of glee, it’s no surprise that baby animals were #CuteOff front-runners. Infant sooty mangabeys? Yes, please.

Humans respond to baby animal cuteness in the same way they respond to baby human cuteness, according to a 2013 study published in the journal Behavioural Processes. The researchers found that women were more sensitive to the appeal of infant animals than were men, and that people who had higher levels of empathy also found baby animals more heart-melting than did people with lower empathy levels.

This love of baby animals may have spilled over from the evolutionary drive to protect infants of one’s own species, the researchers wrote. But bonds with animals can also contribute to well-being, the researchers noted, so perhaps baby animal cuteness stands on its own two (or four) feet.

3. Tininess

If you can’t be a baby, at least stay the size of one. That seems to be one message of the #CuteOff, which featured a cascade of pictures of almost absurdly small creatures. [Photos: See the World’s Cutest Baby Wild Animals]

The link between smallness and cuteness isn’t as well established as the link between babylike features and cuteness. But the connection is certainly there. (Evidence: Buzzfeed has done a listicle.) Without research, it’s only possible to speculate. Perhaps small things simply remind people of babies. Or perhaps, as posited in a 2012 article by a museum studies professor in Insite Magazine, miniature things remind people of toys and give people a sense of power because they know they have control over something so small.

4. Being a mammal

#CuteOff was officially kicked off by herpetologists, who tweeted a picture of a teeny, tiny lizard and declared premature victory.

But it soon became clear that mammals were going to dominate the #CuteOff feed, much to the chagrin of scientists who study less-vaunted taxons.

“There was some talk about the inverts [invertebrates] and the fish joining up to challenge mammals, because mammals are always thought of as cute,” Hilborn said. “It was interesting to see biology rivalry and cooperation come out over Twitter.”

Humans are mammals, of course, so perhaps it’s no surprise that people are drawn to other fuzzy species. Which brings us to our next winning feature …

5. Fur

#TeamEntomology made a strong #CuteOff showing by showcasing species with features not normally associated with insects. The teddy bear ant (Tetramorium pulcherrimum) is a forest dweller in Africa that has what looks like a fine dusting of fur all along its back.

Fuzzy bees, moths and flies also made a showing. To explain the appeal of fuzz, let’s get wildly Freudian and blame mothers. Bear with us: In the 1950s, psychologist Harry Harlow did a series of famous experiments in which monkeys were “raised” by food-bearing “wire mothers” (really, wire frames with monkeylike faces) and terry cloth surrogates, which didn’t dispense food. Even though the wire mothers provided sustenance, the baby monkeys always snuggled back up with their terry-cloth “moms” when not nursing. The studies were groundbreaking, introducing the notion of psychological attachment not based simply on nourishment.

What can we take away from Harlow’s work? Primates really like cuddly things. Is it too much of a stretch to say that a furry ant might trip those same brain circuits?

Yes, you say? Oh, hush. Look, a fuzzy teen bee:

6. Smiling faces

Let’s bring our cute-related theorizing back to solid ground. You know what’s cute? Dolphins. You know why? They always look like they’re smiling.

Smiles make people more approachable, research finds. People also judge a smiling person as more likeable and smarter than a nonsmiling person, reported a 1982 paper in The Journal of Social Psychology.

The appeal of smiles clearly extends to animal faces, a fact that #TeamHerpetology exploited to good effect. Frogs, snakes and lizards may lack fur, but they can plaster on some adorable grins.

 

Animal scientists identify mutations that led to pigs that lack immune systems

Animal science researchers at Iowa State University have identified a pair of genetic mutations that cause immune deficiencies in pigs that make them uniquely good models for testing potential medical therapies for people.

The discovery of the mutations will pave the way for researchers to further develop a genetic line of pigs with severe combined immunodeficiency (SCID) at Iowa State and to improve husbandry and management practices for the pigs.

Christopher Tuggle, an animal science professor, said pigs born with SCID make ideal models for studying vaccines, potential cancer treatments and stem cell therapies for human medicine. That’s because their deficient immune systems can’t reject cells introduced experimentally.

“The pig is known to be an excellent model for human biology due to its similar size, physiology and genetic make-up,” Tuggle said. “This shows it has high potential as a model for many areas of testing in regenerative medicine, a new medical specialty that repairs disease instead of treating symptoms.”

Tuggle was part of a research team that published findings recently in the Journal of Immunology, a peer-reviewed academic publication, identifying two genetic mutations in pigs that lead to offspring with SCID. The editors of the journal highlighted the publication for its importance.

In collaboration with researchers at Kansas State University, ISU scientists first identified pigs with SCID around four years ago as part of an ongoing study of feed efficiency in pork production and the impact of infectious disease. The project, led by animal scientist Jack Dekkers, did not set out to breed a line of pigs with SCID, but the researchers quickly realized their value when some pigs did not show an immune response when exposed to a viral disease.

The National Institutes of Health awarded the researchers a $2.5 million grant earlier this year to improve management practices for the SCID pigs, which require a range of special considerations.

“A major challenge now is to figure out how to raise these pigs in extremely clean environments,” Tuggle said. “Our new NIH-funded project aims to meet that challenge, as well as improve upon the existing model.”

The project has attracted the interest of medical researchers across the country who want to test new regenerative therapies, Tuggle said. The SCID pigs hold particular promise for gauging the ability of stem cell-derived therapies to repair damaged tissues.

Tuggle said scientists are working on methods to use someone’s own stem cells to help heart attack victims, but mice with SCID are unreliable models for testing such advances. The SCID pigs might have a role to play in developing such therapies, he said.

“The data from pigs is likely much more accurate for predicting what stem cell derivatives will do in humans,” he said.