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Meet the Flashing, Toxic Disco Clam

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You can tell just by looking at Ctenoides ales that this is not the kind of bivalve you'd find in your clam chowder. This reddish-orange mollusk, which makes its home in clusters in the caves and crevices of Indo-Pacific coral reefs, creates flashing light shows so bright that they can be seen without artificial light—hence its common name, the disco clam. Scientists weren't quite sure why, or how, the mollusks flashed; they thought it might be bioluminescence, a chemical reaction that creates light within an animal. But recent research, conducted by University of California, Berkeley graduate student Lindsey Dougherty and scientists from Duke University and the University of Queensland, Brisbane, Australia, shows that there's something a little more complicated going on.

Dougherty used a number of high tech tools—including a transmission electron microscope, a spectrometer, an energy dispersive x-ray spectroscope, and high speed video—to examine the clam mantle lip, and found that the flashes are created not by bioluminescence but by a double layer of specialized tissues. The inside of the clam's lip is packed with spheres of silica that make the tissue reflective to light, like a mirror (or a disco ball!); on the other side of the lip, where no silica balls are present, light is absorbed. When the clams rapidly roll and unroll the tissues—typically at a rate of two times a second—it creates the appearance of flashing. Dougherty could find no other bivalves that have evolved this mechanism; the question is, why do they need it?

Dougherty and her team had a few hypotheses about why the clams flash. Examining the clams' eyes under a microscope showed that, although they have 40 tiny eyes, their eyesight is probably too weak to see displays from other clams, ruling out flashing for the purposes of finding a mate. "We did not find much chemical or visual attraction to one another, and research into their eyes suggests they may not be able to perceive the flashing in one another," Dougherty told LiveScience. But the other two hypotheses had more promise: Flashing to attract prey and repel predators.

To test the prey hypothesis, the scientists released phytoplankton into the tank in their lab. When the clams sensed the prey, their flashing increased. Though some plankton are attracted to light, it's unclear if this is true for the disco clam's prey, and researchers plan to study this question further in the field.

Natural predators of the disco clam include octopuses, mantis shrimp, and some species of snails. But for their first test of the predator hypothesis, scientists used a different kind of foe: A styrofoam lid, which they moved over the clams as if a predator was looming. The clams' flashing went from a rate of 1.5 times a second to 2.5 times a second when they sensed the lid. 

Next, they unleashed an actual predator in the tank. Odontodactylus scyllarus, the peacock or harlequin mantis shrimp, uses its claws—which can deliver 160 pounds of force—to break open clams and other prey. The shrimp attacked the clam a few times, each time retreating from it and, eventually, going into what seemed to be a catatonic state (and then it got a little frisky with the mollusk). "They're very aggressive critters, and to have a clam open and flashing, and the mantis shrimp not attacking, is very weird," Dougherty told LiveScience. "That is very strange behavior [for the mantis shrimp]."

In both experiments, the researchers found high levels of sulfur in the water; Dougherty thinks the clams might be producing an acidic mucus in its tentacles that repels predators. "If you're flashing and saying, 'I'm distasteful; don't eat me,' that's one thing, but you have to sort of back it up," she said.

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Ethan Miller/Getty Images
Look Up! The Orionid Meteor Shower Peaks This Weekend
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Ethan Miller/Getty Images

October is always a great month for skywatching. If you missed the Draconids, the first meteor shower of the month, don't despair: the Orionids peak this weekend. It should be an especially stunning show this year, as the Moon will offer virtually no interference. If you've ever wanted to get into skywatching, this is your chance.

The Orionids is the second of two meteor showers caused by the debris field left by the comet Halley. (The other is the Eta Aquarids, which appear in May.) The showers are named for the constellation Orion, from which they seem to originate.

All the stars are lining up (so to speak) for this show. First, it's on the weekend, which means you can stay up late without feeling the burn at work the next day. Tonight, October 20, you'll be able to spot many meteors, and the shower peaks just after midnight tomorrow, October 21, leading into Sunday morning. Make a late-night picnic of the occasion, because it takes about an hour for your eyes to adjust to the darkness. Bring a blanket and a bottle of wine, lay out and take in the open skies, and let nature do the rest.

Second, the Moon, which was new only yesterday, is but a sliver in the evening sky, lacking the wattage to wash out the sky or conceal the faintest of meteors. If your skies are clear and light pollution low, this year you should be able to catch about 20 meteors an hour, which isn't a bad way to spend a date night.

If clouds interfere with your Orionids experience, don't fret. There will be two more meteor showers in November and the greatest of them all in December: the Geminids.

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11-Year-Old Creates a Better Way to Test for Lead in Water
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In the wake of the water crisis in Flint, Michigan, a Colorado middle schooler has invented a better way to test lead levels in water, as The Cut reports.

Gitanjali Rao, an 11-year-old seventh grader in Lone Tree, Colorado just won the 2017 Discovery Education 3M Young Scientist Challenge, taking home $25,000 for the water-quality testing device she invented, called Tethys.

Rao was inspired to create the device after watching Flint's water crisis unfold over the last few years. In 2014, after the city of Flint cut costs by switching water sources used for its tap water and failed to treat it properly, lead levels in the city's water skyrocketed. By 2015, researchers testing the water found that 40 percent of homes in the city had elevated lead levels in their water, and recommended the state declare Flint's water unsafe for drinking or cooking. In December of that year, the city declared a state of emergency. Researchers have found that the lead-poisoned water resulted in a "horrifyingly large" impact on fetal death rates as well as leading to a Legionnaires' disease outbreak that killed 12 people.

A close-up of the Tethys device

Rao's parents are engineers, and she watched them as they tried to test the lead in their own house, experiencing firsthand how complicated it could be. She spotted news of a cutting-edge technology for detecting hazardous substances on MIT's engineering department website (which she checks regularly just to see "if there's anything new," as ABC News reports) then set to work creating Tethys. The device works with carbon nanotube sensors to detect lead levels faster than other current techniques, sending the results to a smartphone app.

As one of 10 finalists for the Young Scientist Challenge, Rao spent the summer working with a 3M scientist to refine her device, then presented the prototype to a panel of judges from 3M and schools across the country.

The contamination crisis in Flint is still ongoing, and Rao's invention could have a significant impact. In March 2017, Flint officials cautioned that it could be as long as two more years until the city's tap water will be safe enough to drink without filtering. The state of Michigan now plans to replace water pipes leading to 18,000 households by 2020. Until then, residents using water filters could use a device like Tethys to make sure the water they're drinking is safe. Rao plans to put most of the $25,000 prize money back into her project with the hopes of making the device commercially available.

[h/t The Cut]

All images by Andy King, courtesy of the Discovery Education 3M Young Scientist Challenge.


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