Snowflakes still hold mystery

This post contributed by Nadine Lymn, ESA Director of Public Affairs Their silent, shimmery beauty has long stirred human aesthetic appreciation and for centuries individuals have sought to unravel the secrets of snowflakes.  Why are there so many varieties?  Why do all snowflakes have six “arms”?  And why does each flake appear unique, no matter how many fall from the sky? We know the answers to these questions as described on the National Oceanic and Atmospheric Administration’s website: temperature and humidity determine their shape, their six “arms” are the result of the internal order of an ice crystal’s water molecules, and, because each crystal encounters slightly different atmospheric conditions, each snowflake appears unique. But enough mystery about the particulars remains that some scientists continue to try to unravel it.  One such scientist is Caltech physicist Kenneth Libbrecht, who is looking into the physics of exactly how water vapor molecules are incorporated into a growing ice crystal.  He has also created a webpage, SnowCrystals.com which is a true treasure-trove of information for anyone interested in snowflakes.  It includes not only magnificent photographs taken by Libbrecht, such as the one below, but also showcases the science of snowflakes and the historical figures who sought to understand these ephemeral beauties. For example, as long ago as 1611, German mathematician Johannes Kepler, put together a “treatise” for the king which he entitled, A New Year’s Gift or On the Six-Cornered Snowflake. Libbrecht notes that this was the first scientific reference to snow crystals and that Kepler was especially intrigued by the six arms of snowflakes, speculating that it must have something to do with the morphology of the crystals. The website includes other individuals, such as “Snowflake Man” Wilson Bentley, a self-educated Vermont farmer, who became so enraptured with snowflakes he saw under his microscope that he persuaded his parents to purchase a special bellows camera to try to capture them before they melted.  After years of trial and error, Bentley became the first person to take a photomicrograph of an ice crystal and went on to capture 5,000 images of snowflakes.  According to Duncan Blanchard, who wrote a biography about him, Bentley’s first article appeared in Popular Scientific Monthly in 1898 and included this vivid description of an ice crystal: “A careful study of this internal structure not only reveals new and far greater elegance of form than the simple outlines exhibit, but by means of these wonderfully delicate and exquisite figures much may be learned of the history of each crystal, and the changes through which it has passed in its journey through cloudland.  Was ever life history written in more...

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Pollination from the plant’s perspective

If plants had a perspective, they would probably think of pollinators as more than just extra-friendly house guests. That is, plants would be more likely to view pollinators as the mutual friend who likes to set up blind dates. Bees might limit pollen to its use as a protein source for the hive, and birds might devour the flesh of a fruit and eliminate the seed as waste. However, many flowering plants, as Bug Girl pointed out in a post in honor of National Pollinator Week, have evolved alongside these pollinators for only one purpose: reproduction. “Sure, you can toss your pollen out on the wind and hope it lands in the right place. And for a lot of plants, evergreens in particular, this works just fine,” she wrote. “That methodology results in a lot of wasted gametes (plant sperm) though, so for nearly all flowering plants, insects or other pollinators are needed for plant nookie.” Sometimes the pollinator-plant relationship is mutualistic, and in many cases, one species or another is dependent upon the other for its survival. Take the agave plant. Probably the most well-known species is the blue agave plant (Agave tequilana), the nectar of which is used as a granular sugar substitute and to make tequila (one of the “finer” products of pollination, along with chocolate and coffee, mentioned by Bug Girl ). Leptonycteris nivalis, known as the greater long-nosed bat or Mexican long-nosed bat, and the lesser long-nosed bat (Leptonycteris curasoae), are the primary pollinators of this economically and ecologically valuable plant. This agave-bat relationship is mutually beneficial. The bats, hovering in place like a hummingbird, use their long muzzles to feed on the high-fructose nectar of the agave. At the same time, the plants’ pollen collects on the bats’ fur. The bats then travel from plant to plant, spreading pollen as they drink from the nectar-filled stalks that bloom each night across the southwestern U.S. and Mexico. The bats also migrate based on the blooming time of these plants. They arrive in Texas—particularly in Big Bend National Park, where a single colony resides in the Chisos Mountains—shortly after agave plants, such as the century plant (Agave havardiana), begin to bloom. Unfortunately, the lesser long-nosed bat and the Mexican long-nosed bat are endangered—and as their numbers decline, agave plant reproduction becomes more limited. A little farther north, however, some species of agave plants—those that are not harvested for tequila— have evolved to attract both bats and moths to serve as pollinators. Agave plants have several ways of advertising their nectar: the scent, the color of the flower and the shape, or morphology, of the structure...

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How fence lizards got their shimmy

Eastern Fence Lizards are rampant across the American southeast but, in recent years, they’ve begun to coexist with invasive red fire ants from South America. Because the lizards and the ants have similar requirements (terrestrial areas with abundant sunlight), they often find themselves occupying the same space. And the ants don’t like it. Tracy Langkilde of Penn State University studies the interactions of these territorial animals in Arkansas, Louisiana and Alabama. She’s found that fire ants will attack lizards not just when they’re near the ants’ territory or their mound, but also when they’re simply wandering by. The opportunistic ants will swarm a lizard, roaming its body and stinging it by pulling up the lizard’s spiny scales and stinging the soft skin underneath. Twelve ants can kill a three-inch lizard in under a minute. So how do the lizards defend themselves against such ambushes? “Lizards do pretty much what we would do. They shake the ants off using this big body shimmy, and then they run away from the mound. “ Langkilde also found that the longer a population has coexisted with the introduced ants, the more common is this behavior. Further, these lizard populations have longer legs than populations that don’t coexist with fire ants, which may improve their shimmy shake and allow them to live another day. Langkilde talks about how this adaptation is indicative of rapid evolution in this month’s edition of ESA’s podcast series Field Talk, titled “Lizard Evolution and the Ants In Your Pants Dance.” Listen above or on ESA’s podcast...

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