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Fish Markets: Cooperation and Competition in the Undersea "Economy"

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You probably know that hermit crabs live in shells. What you might not know is that really nice shells to call home are a scarce commodity, and hermit crabs consequently have some pretty cool ways of optimizing the ways they acquire and occupy their shells.

A study of the purple-clawed hermit crabs (Coenobita clypeatus) on an island off the Belizean coast reveals that the crabs fill shells using "vacancy chains"—social structures through which vacancies in certain resources propagate through a population, like the ways humans fill jobs and apartments.

Synchronous and Asynchronous Vacancy Chains

The hermit crabs were observed to use two types of vacancy chain: synchronous and asynchronous. An asynchronous chain is when one crab moves into a new, empty shell and abandons its old one to be found by another crab, which abandons its own for another crab to find, etc. With this type of chain, shell switching is sequential and the crabs experience little to no interference or competition. They have the opportunity to investigate any vacant shells they find and can directly compare their current shell with a new shell by switching back and forth between the two. It's sort of like when you look at apartments that have just been moved out of and are available immediately or in the near future. If you take one of those apartments, someone else can check out and move into yours, someone else will move into theirs, etc., in an orderly fashion.

Synchronous vacancy chains are more social and much more interesting. They start off with "waiters," crabs that hang around a shell that's too big for them, and wait for a bigger crab to come along so that if the big crab moves in to the vacant shell, the waiter can grab their more appropriately-sized hand-me-down shell. (The researchers note that the decision to wait, and how long to wait, based on previous experience, provides some evidence that the crabs are smarter than we thought.)

As a crowd gathers—a crowd always gathers, but no one knows how; the researchers think the waiters may use vocal or chemical signals to draw attention to the vacancy—the crabs queue up by size, from largest to smallest. Once the largest crab switches into the vacant shell, each crab climbs into a new shell as it's vacated by the slightly larger crab ahead of it, quickly shuffling vacancies (literally) down the chain. A similar type of chain happens in college towns across America every fall. Students spend months "lining up" by finding apartments, packing and labeling boxes, and then—BAM!—a few thousand kids move in and out of apartments in one day.

Here's a synchronous chain in action.

The Undersea Service Industry

Moving away from real estate and into the service industry, animals still behave kind of like humans. They partner with other animals that provide the high-quality goods and services, cheat each other, and then threaten to take their business elsewhere in order to get what they want.

"Cleaner fish," which remove dead skin and parasites from other fish in a mutually beneficial relationship (they get a meal, and the other fish get groomed), have been known to make their "clients" wait for service and cheat them by feeding on healthy tissue or mucous instead of parasites. Clients don't have many options for ensuring good service. They can't demand their mucous back or complain to the Better Business Bureau. What they can do is go get cleaned somewhere else.

A study by a University of California, Santa Barbara biologist found that individuals of one type of cleaner fish near French Polynesia, the luestreak cleaner wrasse, have to compete for access to their preferred clients, the ornate butterfly fish. This competition gives clients with easy access to multiple "cleaner stations" - areas where the cleaner fish hang out and do their thing - the ability to get better service from cleaners, who apparently are cued to the fact that their customers can easily take their business elsewhere and are discouraged from cheating them.

This story originally appeared in a different format on Matt's website.

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Penn Vet Working Dog Center
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Stones, Bones, and Wrecks
New Program Trains Dogs to Sniff Out Art Smugglers
Penn Vet Working Dog Center
Penn Vet Working Dog Center

Soon, the dogs you see sniffing out contraband at airports may not be searching for drugs or smuggled Spanish ham. They might be looking for stolen treasures.

K-9 Artifact Finders, a new collaboration between New Hampshire-based cultural heritage law firm Red Arch and the University of Pennsylvania, is training dogs to root out stolen antiquities looted from archaeological sites and museums. The dogs would be stopping them at borders before the items can be sold elsewhere on the black market.

The illegal antiquities trade nets more than $3 billion per year around the world, and trafficking hits countries dealing with ongoing conflict, like Syria and Iraq today, particularly hard. By one estimate, around half a million artifacts were stolen from museums and archaeological sites throughout Iraq between 2003 and 2005 alone. (Famously, the craft-supply chain Hobby Lobby was fined $3 million in 2017 for buying thousands of ancient artifacts looted from Iraq.) In Syria, the Islamic State has been known to loot and sell ancient artifacts including statues, jewelry, and art to fund its operations.

But the problem spans across the world. Between 2007 and 2016, U.S. Customs and Border Control discovered more than 7800 cultural artifacts in the U.S. looted from 30 different countries.

A yellow Lab sniffs a metal cage designed to train dogs on scent detection.
Penn Vet Working Dog Center

K-9 Artifact Finders is the brainchild of Rick St. Hilaire, the executive director of Red Arch. His non-profit firm researches cultural heritage property law and preservation policy, including studying archaeological site looting and antiquities trafficking. Back in 2015, St. Hilaire was reading an article about a working dog trained to sniff out electronics that was able to find USB drives, SD cards, and other data storage devices. He wondered, if dogs could be trained to identify the scents of inorganic materials that make up electronics, could they be trained to sniff out ancient pottery?

To find out, St. Hilaire tells Mental Floss, he contacted the Penn Vet Working Dog Center, a research and training center for detection dogs. In December 2017, Red Arch, the Working Dog Center, and the Penn Museum (which is providing the artifacts to train the dogs) launched K-9 Artifact Finders, and in late January 2018, the five dogs selected for the project began their training, starting with learning the distinct smell of ancient pottery.

“Our theory is, it is a porous material that’s going to have a lot more odor than, say, a metal,” says Cindy Otto, the executive director of the Penn Vet Working Dog Center and the project’s principal investigator.

As you might imagine, museum curators may not be keen on exposing fragile ancient materials to four Labrador retrievers and a German shepherd, and the Working Dog Center didn’t want to take any risks with the Penn Museum’s priceless artifacts. So instead of letting the dogs have free rein to sniff the materials themselves, the project is using cotton balls. The researchers seal the artifacts (broken shards of Syrian pottery) in airtight bags with a cotton ball for 72 hours, then ask the dogs to find the cotton balls in the lab. They’re being trained to disregard the smell of the cotton ball itself, the smell of the bag it was stored in, and ideally, the smell of modern-day pottery, eventually being able to zero in on the smell that distinguishes ancient pottery specifically.

A dog looks out over the metal "pinhweel" training mechanism.
Penn Vet Working Dog Center

“The dogs are responding well,” Otto tells Mental Floss, explaining that the training program is at the stage of "exposing them to the odor and having them recognize it.”

The dogs involved in the project were chosen for their calm-but-curious demeanors and sensitive noses (one also works as a drug-detection dog when she’s not training on pottery). They had to be motivated enough to want to hunt down the cotton balls, but not aggressive or easily distracted.

Right now, the dogs train three days a week, and will continue to work on their pottery-detection skills for the first stage of the project, which the researchers expect will last for the next nine months. Depending on how the first phase of the training goes, the researchers hope to be able to then take the dogs out into the field to see if they can find the odor of ancient pottery in real-life situations, like in suitcases, rather than in a laboratory setting. Eventually, they also hope to train the dogs on other types of objects, and perhaps even pinpoint the chemical signatures that make artifacts smell distinct.

Pottery-sniffing dogs won’t be showing up at airport customs or on shipping docks soon, but one day, they could be as common as drug-sniffing canines. If dogs can detect low blood sugar or find a tiny USB drive hidden in a house, surely they can figure out if you’re smuggling a sculpture made thousands of years ago in your suitcase.

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Medicine
New Cancer-Fighting Nanobots Can Track Down Tumors and Cut Off Their Blood Supply
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iStock

Scientists have developed a new way to cut off the blood flow to cancerous tumors, causing them to eventually shrivel up and die. As Business Insider reports, the new treatment uses a design inspired by origami to infiltrate crucial blood vessels while leaving the rest of the body unharmed.

A team of molecular chemists from Arizona State University and the Chinese Academy of Sciences describe their method in the journal Nature Biotechnology. First, they constructed robots that are 1000 times smaller than a human hair from strands of DNA. These tiny devices contain enzymes called thrombin that encourage blood clotting, and they're rolled up tightly enough to keep the substance contained.

Next, researchers injected the robots into the bloodstreams of mice and small pigs sick with different types of cancer. The DNA sought the tumor in the body while leaving healthy cells alone. The robot knew when it reached the tumor and responded by unfurling and releasing the thrombin into the blood vessel that fed it. A clot started to form, eventually blocking off the tumor's blood supply and causing the cancerous tissues to die.

The treatment has been tested on dozen of animals with breast, lung, skin, and ovarian cancers. In mice, the average life expectancy doubled, and in three of the skin cancer cases tumors regressed completely.

Researchers are optimistic about the therapy's effectiveness on cancers throughout the body. There's not much variation between the blood vessels that supply tumors, whether they're in an ovary in or a prostate. So if triggering a blood clot causes one type of tumor to waste away, the same method holds promise for other cancers.

But before the scientists think too far ahead, they'll need to test the treatments on human patients. Nanobots have been an appealing cancer-fighting option to researchers for years. If effective, the machines can target cancer at the microscopic level without causing harm to healthy cells. But if something goes wrong, the bots could end up attacking the wrong tissue and leave the patient worse off. Study co-author Hao Yan believes this latest method may be the one that gets it right. He said in a statement, "I think we are much closer to real, practical medical applications of the technology."

[h/t Business Insider]

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