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What Are Loofahs Made Of?

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Bath time, spa experiences, and even common household chores just wouldn't be the same without the humble sponge. Sponges, mostly from class Demospongiae, have been sold commercially as cleansing aids for thousands of years, and have also been used as water filters, padding for soldiers’ helmets, and for painting and decorating. (The brightly-colored pad hanging out by your kitchen sink right now is, of course, a synthetic design modeled after nature's handy tool.)

Although natural loofahs resemble their bathroom counterparts, they're actually about as unrelated as it’s possible to be. The loofah you scrub with is a dried-out tropical or subtropical gourd belonging to genus Luffa (most often either species L. aegyptiaca or L. acutangula). And while no one is completely sure where it originated—as W.M. Porterfield wrote in a 1955 Economic Botany article: "[c]ultivation of the sponge gourd is of such ancient origin that it is impossible to determine whether the original home was in Africa or Asia” [PDF]— a study in 1990 indicated that it was probably first cultivated in India. These plants—which look a bit like giant cucumbers—grow year-round in almost any tropical climate and places that have warm seasons, so long as there is plenty of moisture and no risk of frost.

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Like sponges, the fibrous dried luffa has likely been used in Egypt and Asia for up to a couple thousand years. But its biggest boost as a cleansing tool began in the early 1890s, when Japan started cultivating commercial luffa crops for international export. (Prior to that, luffas were mostly used when a thorough household scrubbing was in order.) Word spread about the exfoliating item just as bathing suits and hemlines began retreating in the late 19th and early 20th centuries, according to The New York Times Magazine, which left many women with newfound anxiety about the smoothness of their skin. Inventions like the Improved Bathing Mitten, patented in 1889 by Judson S. Snyder of Brooklyn, New York, transformed the large gourds into easier-to-handle versions. By 1893, “no one seemed able to agree on how to spell the name of that sponge, but it inspired such a craze [that one] expected to see ‘a ‘loafer,’ ‘luphar,’ a ‘loopa’ or a ‘loofah’ in every wash basin the land,'” according to that same New York Times Magazine article.

But cleaning isn't all they're good for. According to Porterfield, commercial cultivation of the plant in the 1890s also let luffas fill a wide range of industrial roles. Before the second World War, over half of imported luffa goards were used in filters (chiefly in the Navy) for everything from steam to diesel engines. They also found use as water filters, industrial scourers, and even surgical tools. After wartime conflict drove Western powers to start sourcing their luffa shipments elsewhere, the dried veggies continued to prove useful through the mid-20th century as an effective sound-proofing material for tanks, helmets, and certain kinds of buildings.

When man-made materials began taking over many industrial roles in the 20th century, the noble luffa was mostly returned to its role as a cleaning tool—and, of course, a popular food, one that easily stands in for cucumbers or summer squash while it’s still immature. The vine is so easy to grow that it has been floated as a candidate for a profitable, sustainable crop to help drive economic and agricultural development here in the U.S. as well as countries like Paraguay [PDF]. Because they’re so resilient, luffa vines can be easily grown by amateur gardeners in much of the country (apart from the upper Midwest and New England), so feel free to take a whack at rearing this useful gourd—just make sure that any luffas that find a place in your bathroom don’t end up being a farm for bacteria themselves.

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Animals
These Strange Sea Spiders Breathe Through Their Legs
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Sylke Rohrlach, Wikimedia Commons // CC BY-SA 2.0

We know that humans breathe through their lungs and fish breathe through their gills—but where exactly does that leave sea spiders?

Though they might appear to share much in common with land spiders, sea spiders are not actually arachnids. And, by extension, they don't circulate blood and oxygen the way you'd expect them to, either.

A new study from Current Biology found that these leggy sea dwellers (marine arthropods of the class Pycnogonida) use their external skeleton to take in oxygen. Or, more specifically: They use their legs. The sea spider contracts its legs—which contain its guts—to pump oxygen through its body.

Somehow, these sea spiders hardly take the cake for Strangest Spider Alive (especially because they're not actually spiders); check out, for instance, our round-up of the 10 strangest spiders, and watch the video from National Geographic below:

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science
Scientists Study the Starling Invasion Unleashed on America by a Shakespeare Fan

On a warm spring day, the lawn outside the American Museum of Natural History in Manhattan gleams with European starlings. Their iridescent feathers reflect shades of green and indigo—colors that fade to dowdy brown in both sexes after the breeding season. Over the past year, high school students from different parts of the city came to this patch of grass for inspiration. "There are two trees at the corner I always tell them to look at," Julia Zichello, senior manager at the Sackler Educational Lab at the AMNH, recalls to Mental Floss. "There are holes in the trees where the starlings live, so I was always telling them to keep an eye out."

Zichello is one of several scientists leading the museum's Science Research Mentoring Program, or SRMP. After completing a year of after-school science classes at the AMNH, New York City high school students can apply to join ongoing research projects being conducted at the institution. In a recent session, Zichello collaborated with four upperclassmen from local schools to continue her work on the genetic diversity of starlings.

Before researching birds, Zichello earned her Ph.D. in primate genetics and evolution. The two subjects are more alike than they seem: Like humans, starlings in North America can be traced back to a small parent population that exploded in a relatively short amount of time. From a starting population of just 100 birds in New York City, starlings have grown into a 200-million strong flock found across North America.

Dr. Julia Zichello
Dr. Julia Zichello
©AMNH

The story of New York City's starlings began in March 1890. Central Park was just a few decades old, and the city was looking for ways to beautify it. Pharmaceutical manufacturer Eugene Schieffelin came up with the idea of filling the park with every bird mentioned in the works of William Shakespeare. This was long before naturalists coined the phrase "invasive species" to describe the plants and animals introduced to foreign ecosystems (usually by humans) where their presence often had disastrous consequences. Non-native species were viewed as a natural resource that could boost the aesthetic and cultural value of whatever new place they called home. There was even an entire organization called the American Acclimatization Society that was dedicated to shipping European flora and fauna to the New World. Schieffelin was an active member.

He chose the starling as the first bird to release in the city. It's easy to miss its literary appearance: The Bard referenced it exactly once in all his writings. In the first act of Henry IV: Part One, the King forbids his knight Hotspur from mentioning the name of Hotspur's imprisoned brother Mortimer to him. The knight schemes his way around this, saying, "I'll have a starling shall be taught to speak nothing but 'Mortimer,' and give it him to keep his anger still in motion."

Nearly three centuries after those words were first published, Schieffelin lugged 60 imported starlings to Central Park and freed them from their cages. The following year, he let loose a second of batch of 40 birds to support the fledgling population.

It wasn't immediately clear if the species would adapt to its new environment. Not every bird transplanted from Europe did: The skylark, the song thrush, and the bullfinch had all been subjects of American integration efforts that failed to take off. The Acclimatization Society had even attempted to foster a starling population in the States 15 years prior to Schieffelin's project with no luck.

Then, shortly after the second flock was released, the first sign of hope appeared. A nesting pair was spotted, not in the park the birds were meant to occupy, but across the street in the eaves of the American Museum of Natural History.

Schieffelin never got around to introducing more of Shakespeare's birds to Central Park, but the sole species in his experiment thrived. His legacy has since spread beyond Manhattan and into every corner of the continent.

The 200 million descendants of those first 100 starlings are what Zichello and her students made the focus of their research. Over the 2016-2017 school year, the group met for two hours twice a week at the same museum where that first nest was discovered. A quick stroll around the building reveals that many of Schieffelin's birds didn't travel far. But those that ventured off the island eventually spawned populations as far north as Alaska and as far south as Mexico. By sampling genetic data from starlings collected around the United States, the researchers hoped to identify how birds from various regions differed from their parent population in New York, if they differed at all.

Four student researchers at the American Museum of Natural History
Valerie Tam, KaiXin Chen, Angela Lobel and Jade Thompson (pictured left to right)
(©AMNH/R. Mickens)

There are two main reasons that North American starlings are appealing study subjects. The first has to do with the founder effect. This occurs when a small group of individual specimens breaks off from the greater population, resulting in a loss of genetic diversity. Because the group of imported American starlings ballooned to such great numbers in a short amount of time, it would make sense for the genetic variation to remain low. That's what Zichello's team set out to investigate. "In my mind, it feels like a little accidental evolutionary experiment," she says.

The second reason is their impact as an invasive species. Like many animals thrown into environments where they don't belong, starlings have become a nuisance. They compete with native birds for resources, tear through farmers' crops, and spread disease through droppings. What's most concerning is the threat they pose to aircraft. In 1960, a plane flying from Boston sucked a thick flock of starlings called a murmuration into three of its four engines. The resulting crash killed 62 people and remains the deadliest bird-related plane accident to date.

Today airports cull starlings on the premises to avoid similar tragedies. Most of the birds are disposed of, but some specimens are sent to institutions like AMNH. Whenever a delivery of dead birds arrived, it was the students' responsibility to prep them for DNA analysis. "Some of them were injured, and some of their skulls were damaged," Valerie Tam, a senior at NEST+m High School in Manhattan, tells Mental Floss. "Some were shot, so we had to sew their insides back in."

Before enrolling in SRMP, most of the students' experiences with science were limited to their high school classrooms. At the museum they had the chance to see the subject's dirty side. "It's really different from what I learned from textbooks. Usually books only show you the theory and the conclusion, but this project made me experience going through the process," says Kai Chen, also a senior at NEST+m.

After analyzing data from specimens in the lab, an online database, and the research of previous SRMP students, the group's hypothesis was proven correct: Starlings in North America do lack the genetic diversity of their European cousins. With so little time to adapt to their new surroundings, the variation between two starlings living on opposite coasts could be less than that between the two birds that shared a nest at the Natural History Museum 130 years ago.

Students label samples in the lab.
Valerie Tam, Jade Thompson, KaiXin Chen and Angela Lobel (pictured left to right) label samples with Dr. Julia Zichello.
©AMNH/C. Chesek

Seeing how one species responds to bottlenecking and rapid expansion can provide important insight into species facing similar conditions. "There are other populations that are the same way, so I think this data can help [scientists],” Art and Design High School senior Jade Thompson says. But the students didn't need to think too broadly to understand why the animal was worth studying. "They do affect cities when they're searching for shelter," Academy of American Studies junior Angela Lobel says. “They can dig into buildings and damage them, so they're relevant to our actual homes as well.”

The four students presented their findings at the museum's student research colloquium—an annual event where participants across SRMP are invited to share their work from the year. Following their graduation from the program, the four young women will either be returning to high school or attending college for the first time.

Zichello, meanwhile, will continue where she left off with a new batch of students in the fall. Next season she hopes to expand her scope by analyzing older specimens in the museum's collections and obtaining bird DNA samples from England, the country the New York City starlings came from. Though the direction of the research may shift, she wants the subject to remain the same. "I really want [students] to experience the whole organism—something that's living around them, not just DNA from a species in a far-away place." she says. "I want to give them the picture that evolution is happening all around us, even in urban environments that they may not expect."

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