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Gauthier via Wikimedia Commons // CC BY-SA 3.0
Gauthier via Wikimedia Commons // CC BY-SA 3.0

Darwin’s Obsession With Barnacle Penises Makes a Lot of Sense Now

Gauthier via Wikimedia Commons // CC BY-SA 3.0
Gauthier via Wikimedia Commons // CC BY-SA 3.0

Barnacle penises are amazing. That’s not a direct quote from Charles Darwin, but it might as well have been; the naturalist was obsessed with the little crustaceans’ very large members. Now scientists say he missed out on one of the best barnacle facts: Many species can change the shape and size of their penises to suit their environment. A report of the findings was published in the journal Integrative & Comparative Biology

Relative to its body size, the barnacle has the largest penis in the animal kingdom. This is, of course, not just some hilarious joke by Mother Nature—the length is necessary in order for these sessile (non-moving) animals to reach one another. Barnacles grow in colonies clamped to rocks, piers, boats, and sometimes large animals like whales. They feed by extending little feathery sensory appendages called cirri into the water to catch plankton. 

In their resting state, barnacles are simultaneous hermaphrodites, meaning that they have both male and female parts. In many species, mating season begins when one barnacle’s egg glands begin to swell, rendering it “functionally female.” That barnacle releases chemicals into the water that tell its neighbors that it’s time to get busy. In response, they become “functional males,” unfurling their long, flexible penises into the water like party horns, questing for the right opening.   

For obvious reasons, these bizarre sexual adaptations fascinated Darwin. The naturalist devoted seven years of his life to studying barnacles, in the process compiling descriptions of the “probosciform” (elephant trunk–like) penises of hundreds of species. (We are not making this up.) 

A small sample of Darwin's barnacle collection. Image credit: FunkMonk via Wikimedia Commons // CC BY 3.0

Darwin was determined to learn all he possibly could about the animals, their anatomy, and their behavior. When he got wind that a friend of a friend had been lucky enough to see barnacle sex in action, he wrote a pretty intense letter, peppering his contact with questions. An excerpt:

Was the probosciformed penis inserted into more than one individual? For about how long [and how many] times was it inserted? Was it inserted deeply & at which end of valves? Especially did the recipient individual continue during the times exerting its cirri? Did it keep its opercula valves widely open for the reception of the organ? I am anxious to know whether this recipient was a willing agent or adulterer. or whether it was a case of rape by act. If the recipient was in full vigour, I think it wd be impossible to insert anything without its consent. Were the specimens under water at times? 

Who was the observer that I might check his authority. 

We told you he was obsessed. But he was far from the only one. Darwin’s love of (and thorough notes on) the lumpy little animals left a scientific legacy that continues to this day. Marine biologists J. Matthew Hoch and Daniel T. Schenk of Nova Southeastern University and Quest University’s Christopher J. Neufeld have spent years studying barnacles. They collected their research—and the findings of others—in the recent review paper, and they came to some very interesting conclusions. 

Barnacle reproductive organs. Image credit: J. Matthew Hoch, Nova Southeastern University

“We know that barnacles are robust in their ability to overcome environmental challenges and to mate successfully,” they write. Sometimes they do that by stretching their penises, making them thicker, or changing their shape altogether. “In the most extreme circumstances,” they say, “it degenerates and is shed during the first post-mating molt and is re-grown for the next mating season." 

These animals are “so robust” in their sexual prowess, the authors say, that in one case a barnacle with two penises was still able to mate successfully.

“As barnacle biologists,” they write, “we understand and identify with Darwin’s excitement about barnacle reproduction and look forward to new knowledge generated through the modern-day comparative approach that has yielded so many new insights.”

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Slow Motion Is the Only Way to Appreciate a Chameleon’s Lightning-Fast Tongue
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From the unusual way they walk, to their ability to change color, the evolutionary adaptations of chameleons are pretty bizarre, and some of them remain mysterious even to scientists. Their super-powered tongues, for instance, can dart out so quickly that the movement can barely be seen with the naked eye. But modern high-speed cameras have enabled researchers at the University of South Dakota to observe this appendage at work like never before. The video below, shared over at The Kid Should See This, includes some of that groundbreaking footage, and it's pretty amazing to watch.

Shooting at 3000 frames per second, the camera was able to capture every split-second aspect of the chameleon's tongue strike. Slowed down, the video allows you to see how every component of the process works in harmony: First, muscles in the lizard’s tongue contract like the string of a bow. Then, when that tension is released, the bony base of the tongue shoots forward, pushing the sticky, elastic part toward the chameleon’s prey.

According to Christopher Anderson, one of the scientists who conducted the high-speed camera research, larger chameleons can catapult their tongues forward at distances of one to two times their body length. For smaller chameleons, this distance can reach up to two and a half times their body length. “Small chameleons need to be able to eat more food for their body size than large chameleons,” he tells bioGraphic in the video, “and so by being able to project their tongues proportionately further than these large species, they basically are opening up additional feeding opportunities to themselves that they wouldn’t have if they had a shorter tongue.”

To see one of nature’s greatest hunting tools in action, check out the full video below.

[h/t The Kid Should See This]

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There May Be an Ancient Reason Why Your Dog Eats Poop
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Dogs aren't known for their picky taste in food, but some pups go beyond the normal trash hunting and start rooting around in poop, whether it be their own or a friend's. Just why dogs exhibit this behavior is a scientific mystery. Only some dogs do it, and researchers aren't quite sure where the impulse comes from. But if your dog is a poop eater, it's nearly impossible to steer them away from their favorite feces.

A new study in the journal Veterinary Medicine and Science, spotted by The Washington Post, presents a new theory for what scientists call "canine conspecific coprophagy," or dogs eating dog poop.

In online surveys about domestic dogs' poop-eating habits completed by thousands of pet owners, the researchers found no link between eating poop and a dog's sex, house training, compulsive behavior, or the style of mothering they received as puppies. However, they did find one common link between the poop eaters. Most tended to eat only poop that was less than two days old. According to their data, 85 percent of poop-eaters only go for the fresh stuff.

That timeline is important because it tracks with the lifespan of parasites. And this led the researchers to the following hypothesis: that eating poop is a holdover behavior from domestic dogs' ancestors, who may have had a decent reason to tuck into their friends' poop.

Since their poop has a high chance of containing intestinal parasites, wolves poop far from their dens. But if a sick wolf doesn't quite make it out of the den in time, they might do their business too close to home. A healthier wolf might eat this poop, but the parasite eggs wouldn't have hatched within the first day or two of the feces being dropped. Thus, the healthy wolf would carry the risk of infection away from the den, depositing the eggs they had consumed away in their own, subsequent bowel movements at an appropriate distance before the eggs had the chance to hatch into larvae and transmit the parasite to the pack.

Domestic dogs may just be enacting this behavior instinctively—only for them, there isn't as much danger of them picking up a parasite at home. However, the theory isn't foolproof. The surveys also found that so-called "greedy eaters" were more likely to eat feces than dogs who aren't quite so intense about food. So yes, it could still be about a poop-loving palate.

But really, it's much more pleasant to think about the behavior as a parasite-protection measure than our best pals foraging for a delicious fecal snack. 

[h/t The Washington Post]

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