Most captured spiders that are preserved in ethanol do not keep their bright colors for long. Over time scientists have observed their color gradually leach away. However, a spider species from Madagascar caught the attention of one researcher when she noticed that even after decades of being preserved in ethanol the bright colors remained as brilliant as when they were first preserved. She decided that this was too interesting to simply leave unanswered, so a study was launched to discover exactly why these little spiders stay so colorful.


The Phoroncidia rubroargentea, a spider that comes from Madagascar, is striking in a number of ways. They are extremely tiny, three millimeters to be exact, which is isn’t much bigger than a few grains of salt. However, it was their brilliant colors that were able to remain just as bright as when they were alive, even decade after being preserved in ethanol that really captivated Sarah Kariko.  To solve this problem, Kariko and a team of other researchers decided to find out just what made this little spider so durable. What they found was rather interesting.


The spider uses a combination of strategies to create the brilliant colors. These include actual structural colors, pigment, and fluorescent material to create these colors, which are then completely covered in a layer of tough cuticle. They performed spectroscopy measurements, a wide array of imaging techniques, including optical microscopy and fluorescence to electron microscopy, in order to examine the colors, and detailed fluorescent imaging. They found that part of the spider’s coloring , specifically the silver color, was created by a material similar to reflective fish scales. Highly reflective plates are stacked on top of each other, with each plate reflecting light at a slightly different wavelength. These wavelengths both created and cancel out other colors to produce their bright coloring. Because it is structural, the color doesn’t fade away in ethanol, like most other spiders.


Why do you think this spider evolved to have these kinds of indestructible colored plates?   



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