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Clams Are Giving Each Other Cancer

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The clams are dying. Since at least the 1970s, soft-shell clams (Mya arenaria) from Canada to Maryland have been plagued with a mysterious disease. This month, researchers announced that they’d finally identified the disease: clam leukemia.

Clam leukemia?!

Clams are simple creatures. They don’t have legs, or brains, or faces. But they do have hearts, and those hearts pump hemolymph (the clam version of blood) throughout their bodies. It’s in this hemolymph that the cancer has taken hold.

For years, scientists suspected that the clam-killing disease was caused by a virus. Then a team of researchers specializing in microbiology, cancer, and marine biology examined the clams’ DNA.

What they found inspired more questions than answers. The clams had cancer—and it was contagious.

Nearly all cancers are a one-shot deal, and can’t be passed from one animal to another. Until recently, there were only two known contagious cancers in the world. One is a dog STD called Canine Transmissible Venereal Tumor. The other is Devil Facial Tumor Disease, which is transmitted when one Tasmanian devil bites another one on the face.

But clams aren’t humping, and since they don’t have faces, they’re definitely not biting each other. How, then, is the cancer passed from one clam to the next? The researchers aren’t totally sure, but they think that the cancer cells may be released into the water. Clams are filter feeders, sucking up liters of water every hour. If a few clam-cer cells happened to be in the neighborhood, they could easily find themselves a new home.

Nobody knows how one clam’s leukemia could become contagious. So where did those free-floating cancer cells come from? To find out, the scientists sequenced cancer cells from clams all up and down the East Coast. Yet again, the answer was mind-boggling: the genes were all identical, which means that every clam’s cancer had all come from a single, original host. That’s one unfortunate clam—which got cancer more than 40 years ago. That clam’s cancer cells scooted off into the ocean, where they found another host, whose cancer cells eventually scooted off into the ocean … and now it’s 2015. The cancer has traveled hundreds of miles, and we’ve got a whole lot of sick clams.

And it may not just be clams. Mussels, oysters, and cockles are all afflicted with similarly mysterious illnesses. As long as people want to eat shellfish, these researchers will have jobs.

Thankfully, only clams can get clam-cer. Eating seafood and swimming in the ocean are still safe for humans. As safe as they’ve ever been, anyway.

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History
The Queen of Code: Remembering Grace Hopper
By Lynn Gilbert, CC BY-SA 4.0, Wikimedia Commons

Grace Hopper was a computing pioneer. She coined the term "computer bug" after finding a moth stuck inside Harvard's Mark II computer in 1947 (which in turn led to the term "debug," meaning solving problems in computer code). She did the foundational work that led to the COBOL programming language, used in mission-critical computing systems for decades (including today). She worked in World War II using very early computers to help end the war. When she retired from the U.S. Navy at age 79, she was the oldest active-duty commissioned officer in the service. Hopper, who was born on this day in 1906, is a hero of computing and a brilliant role model, but not many people know her story.

In this short documentary from FiveThirtyEight, directed by Gillian Jacobs, we learned about Grace Hopper from several biographers, archival photographs, and footage of her speaking in her later years. If you've never heard of Grace Hopper, or you're even vaguely interested in the history of computing or women in computing, this is a must-watch:

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Why Are Glaciers Blue?
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The bright azure blue sported by many glaciers is one of nature's most stunning hues. But how does it happen, when the snow we see is usually white? As Joe Hanson of It's Okay to Be Smart explains in the video below, the snow and ice we see mostly looks white, cloudy, or clear because all of the visible light striking its surface is reflected back to us. But glaciers have a totally different structure—their many layers of tightly compressed snow means light has to travel much further, and is scattered many times throughout the depths. As the light bounces around, the light at the red and yellow end of the spectrum gets absorbed thanks to the vibrations of the water molecules inside the ice, leaving only blue and green light behind. For the details of exactly why that happens, check out Hanson's trip to Alaska's beautiful (and endangered) Mendenhall Glacier below.

[h/t The Kid Should See This]

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