FYFD

Tag: biology

  • The Livers of Our Rivers

    The Livers of Our Rivers

    To the naked eye, mussels and other bivalves don’t appear to be doing much. But these filter feeders are hard at work. The mussel takes in water through its incurrent siphon (on the right side in this image), and tiny cilia move the water through its gills, which filter out plankton and other edibles. Wastewater flows out the exacurrent siphon, seen here as the plume coming out the top of the mussel.

    Mussel species are important indicators of the health of both fresh and marine water bodies. Because they’re stationary and they are constantly processing the water, the health of these bivalves is indicative of the ecosystem’s overall health. (Image credit: S. Allen, source)

  • How Mantas Filter But Never Clog

    How Mantas Filter But Never Clog

    Manta rays spend much of their time leisurely cruising through the water with their meter-wide mouths open. As they swim, they filter plankton, which makes up most of their diet, from the water. And they do so without ever clogging. 

    The inside of the manta’s mouth is lined with gill rakers (upper right), a series of comb-like teeth. When flow hits the leading edge of these (bottom), it creates a vortex that accelerates any particles caught in the flow. They essentially ricochet along the top of the gill rakers, getting led straight into the manta’s digestive system – while excess water gets deflected between the gill rakers and back out the manta’s gills. To drive this, all the manta has to do is swim; with the right flow speed, the shape of the gill rakers handles all the filtration with no additional effort. (Image credit: manta ray – G. Flood; gill rakers – M. Paig-Tran; flow vis – R. Divi et al., source; research credit: M. Paig-Tran et al.; via The Atlantic; submitted by Kam-Yung Soh)

  • Featured Video Play Icon

    Bioinspiration, Underwater Sniffing, and Mixing Toothpaste

    In this month’s FYFD/JFM video, we explore some intersections between the animal kingdom and our own lives. Learn about designing better buildings with inspiration from termites; see the fascinating superpower of the star-nosed mole; and learn what goes into products like the toothpaste you (hopefully) use daily. All this and more in the latest video! Missed one of our previous ones? Good news: we’ve got you covered. (Image and video credit: N. Sharp and T. Crawford)

  • Featured Video Play Icon

    Flying Beetles, Stinging Nettles, and Jellyfish

    In the latest JFM/FYFD video, we tackle some of the less pleasant aspects of summer weather: stopping invasive insects, understanding how plants dispense poison, and looking at the physics behind jellyfish stings. And if you’ve missed any of our previous videos, we’ve got you covered. (Image and video credit: T. Crawford and N. Sharp)

  • The Flutter of Kelp

    The Flutter of Kelp

    Many species of kelp change their blade shape depending on the current they experience. In fast-moving waters, the kelp grows flat blades, but when the water around them is slower, the same plant will grow ruffled edges on its blades. In a slow current, the ruffled version’s extra drag causes it to flutter up and down with a large amplitude. That helps spread the blades out to catch more sunlight and increase photosynthesis, but it comes at the cost of higher drag, which could tear the plant from its holdfast.

    In contrast, the flat-bladed kelp collapses into a more hydrodynamic shape. This clumps the flat blades together, making photosynthesis harder, but it streamlines the kelp, making it easier to resist getting ripped out by fast-moving tides. (Image credit: J. Hildering; research credit: M. Koehl et al.; submission by Marc A.)

  • Featured Video Play Icon

    Why Fish Don’t Freeze

    Have you ever wondered why it is that fish in a pond or lake don’t freeze during the winter? The secret is due to a peculiarity of water that’s vital for life here on Earth. In general, cold things are denser than warmer ones. This is why, for the most part, cold fluids tend to sink and warmer ones rise here on Earth. So as fall moves into winter and water near the surface of a pond cools, it sinks. But only to a point.

    Water is at its densest at 4 degrees Celsius. Any colder and the water will actually expand and become less dense. This is why you can’t fill ice cube trays to the very top before putting them in the freezer. In the pond it means that buoyant convection shuts down at 4 degrees Celsius. When the water at the top keeps cooling down to the freezing point, it doesn’t sink. Instead, the fish and other pond life get to spend the winter at a chill – but not freezing – 4 degrees. (Video credit: A. Fillo)

  • The Sensitivity of a Seal’s Whiskers

    The Sensitivity of a Seal’s Whiskers

    Harbor seals and their brethren have a superpower that lets them track their prey even without sight or sound. It’s their whiskers, which are sensitive enough to follow the trail left by a single fish thirty seconds earlier. The secret to the whisker’s sensitivity lies in its shape. Instead of a uniform, circular cross-section, the seal’s whisker is oval-shaped and its width varies along the length in a wavy pattern. So unlike a straight cylinder, which vibrates when towed through water, the seal’s whiskers are unperturbed by their own movement. They shed only weak vortices and do not vibrate as a result.

    But, if you expose the whiskers to any external turbulence, like the vortices trailing a fish, the whisker ‘slaloms’ back-and-forth in time with the wake. That motion gets transmitted to the nerves in the seal’s cheek, carrying potential information about both the size and speed of the wake’s originator. Researchers hope similar bio-inspired whiskers could help underwater vehicles track schools of fish or locate underwater drilling leaks. (Image credit: M. Richter; video credit: MIT; research credit: H. Beem and M. Triantafyllou; via the Economist; submitted by Russ A. and Kam-Yung Soh)

  • Reducing Viscosity With Bacteria

    Reducing Viscosity With Bacteria

    Conventional wisdom – and the Second Law of Thermodynamics – require all fluids to have viscosity, with the noted and bizarre exception of superfluids, which can flow with zero viscosity. In essence, you cannot have work (i.e. flow) for free. Some effort has to be lost to resistance.

    But scientists have discovered, bizarrely, that adding bacteria to water can result in zero or even negative viscosities – meaning that effort is required to keep the flow from accelerating. Before you ask, no, this is not a recipe for a perpetual motion machine. What happens when the bacteria-filled fluid is sheared is that the bacteria align and start collectively swimming. The local effects of each bacteria combine en masse to create a fluid that seemingly flows on its own. In the end, though, it’s the bacteria that are supplying that work. It certainly raises interesting prospects, though, for harnessing the power of bacterial superfluids. See the links below for more. (Image credit: M. Copeland, source; research credit: S. Guo et al., A. Loisy et al.; via Quanta; submitted by Kam-Yung Soh)

  • Swirling Blooms

    Swirling Blooms

    Every summer, as the ice melts, the waters of the Chukchi Sea off the Alaskan coast come alive with phytoplankton blooms. In satellite images like this one, they can look like abstract paintings formed from swirling colors. In the Chukchi Sea, two main currents collide. One, water from the Bering Sea, is cold, salty, and nutrient-rich. This is the preferred home to phytoplankton known as diatoms, which are responsible for some of the greenish hues seen here.

    Coccolithophores, another variety of phytoplankton, prefer the warmer, less salty Alaskan coastal waters. Despite a relative lack of nutrients, the  coccolithophores thrive, creating the milky turquoise color seen in the image. Knowing these characteristics of the phytoplankton, observing the growth of blooms over time may tell scientists about how the flows in these areas shift and change from year to year. (Image credit: NASA; via NASA Earth Observatory)

  • When Sound Makes You Vertiginous

    When Sound Makes You Vertiginous

    For some people, a musical tone is enough to induce vertigo and feelings of being drunk. These individuals often have a small hole or defect in the bone that surrounds the canals of the inner ear. Normally, the fluid inside these canals reacts when we rotate our heads, triggering a counterrotation of our eyes that helps stabilize the image on our retinas. But when there’s a defect in the bone surrounding the canal, certain acoustic tones may pump that fluid directly. The patient’s eyes then try to correct for a rotation that’s not occurring, thereby inducing dizziness and vertigo. (Image credit: M. Moiner; research credit: M. Iversen et al.; submitted by Marc A.)