Pistol Shrimp Pack Some Serious Heat

When I’m not blogging for mental_floss, I can usually be found wearing bright orangerubber pants and gutting, cutting and selling fish at my local Whole Foods (and winning awards for it). Sometimes, my two worlds collide and I find some fascinating stuff involving my ocean-dwelling friends that begs for a blog post. This is one of those times.

The 500+ species of pistol shrimp around the world have one “normal-sized” claw (that is, proportional to their body, the way most shrimp do) and one claw that is about half the size of their bodies. This oversized claw stays open until the shrimp, while defending itself from a predator or hunting for a meal, snaps it closed.

Closing the claw results in the creation of a powerful a powerful, 60mph jet of water and, in its low-pressure wake, a cavitation bubble. When this bubble collapses, it produces 1) a bright flash of light that lasts for a fraction of a second, 2) sound pressures of up to 11.74 psi at a distance of 4 cm from the claw, 3) interior temperatures reaching over 4,000 degrees Fahrenheit, and 4) a loud “pop” that can register at 218 decibels (Here’s a little chart to put that in perspective for you).

A “shot” from a pistol shrimp claw can stun or even kill small marine animals at close proximity, allowing the shrimp to escape danger or consume its prey.

The resulting shock wave easily stuns and kills small fish. Researchers who study—and have been shot at by—pistol shrimp say the pain is not unlike the effect of getting hit by a rubber band gun.

More fascinating than the shrimp’s defenses are the way some of them work with goby fish. The goby has better eyesight than the shrimp, so the shrimp keep in constant physical contact with the fish by resting their antennae on the fish’s tail. The shrimp takes any sudden movement on the part of the goby as a sign of danger, and both fish and shrimp head for the shrimps burrow. With the fish having played watchman, the shrimp then holds up its end of the bargain by acting as an armed guard until the danger has passed.

You can see the pistol shrimp in action here (with over the top sound and video editing)…

...and here (without any sonic embellishment)…

College Board Wants to Erase Thousands of Years From AP World History, and Teachers Aren't Happy

One would be forgiven for thinking that the Ides of March are upon us, because Julius Caesar is being taken out once again—this time from the Advanced Placement World History exam. The College Board in charge of the AP program is planning to remove the Roman leader, and every other historical figure who lived and died prior to 1450, from high school students’ tests, The New York Times reports.

The nonprofit board recently announced that it would revise the test, beginning in 2019, to make it more manageable for teachers and students alike. The current exam covers over 10,000 years of world history, and according to the board, “no other AP course requires such an expanse of content to be covered over a single school year.”

As an alternative, the board suggested that schools offer two separate year-long courses to cover the entirety of world history, including a Pre-AP World History and Geography class focusing on the Ancient Period (before 600 BCE) up through the Postclassical Period (ending around 1450). However, as Politico points out, a pre-course for which the College Board would charge a fee "isn’t likely to be picked up by cash-strapped public schools," and high school students wouldn't be as inclined to take the pre-AP course since there would be no exam or college credit for it.

Many teachers and historians are pushing back against the proposed changes and asking the board to leave the course untouched. Much of the controversy surrounds the 1450 start date and the fact that no pre-colonial history would be tested.

“They couldn’t have picked a more Eurocentric date,” Merry E. Wiesner-Hanks, who previously helped develop AP History exams and courses, told The New York Times. “If you start in 1450, the first thing you’ll talk about in terms of Africa is the slave trade. The first thing you’ll talk about in terms of the Americas is people dying from smallpox and other things. It’s not a start date that encourages looking at the agency and creativity of people outside Europe.”

A group of teachers who attended an AP open forum in Salt Lake City also protested the changes. One Michigan educator, Tyler George, told Politico, “Students need to understand that there was a beautiful, vast, and engaging world before Europeans ‘discovered’ it.”

The board is now reportedly reconsidering its decision and may push the start date of the course back some several hundred years. Their decision will be announced in July.

[h/t The New York Times]

North America: East or West Coast?


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