Tag Archives: Scanning Electron Microscope

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Turkey Feathers: Intricate Structures

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Here, we’re featuring the structures of turkey feathers. More specifically, some optical and electron microscope images of the intricate structure of a portion of a tail feather donated by a wild turkey (Meleagris gallopavo) from a large flock living on the Danvers-Wenham, MA town line.

 

Wild Turkey tail feather 10x
Wild Turkey tail feather 20x
Tail Feather Zstack, Extended Focus Mode, 60x

The large central shaft (rachis) is visible near the top of the lowest magnification optical (above) and electron microscopic (below) images, with the array of barbs branching off it. The barbs form the two vanes of the feather, one on each side of the rachis. Branching off the barbs are the barbules. The tiny hooks that hold the barbules together are called barbicels, and are clearly visible in the SEM images below.

61x
100x
500x

At low magnification (original magnifications are shown), optical images were taken using a stereo zoom microscope. At higher magnification however, the 3-dimensional nature of the feather structures make it difficult to capture a fully “in-focus” image. One way to solve that problem is to acquire a composite (in this case, approximately 100) images at different focal planes (Extended Focus Mode). The resulting image is in focus throughout the entire depth of the features present in the sample. The same portion of the feather was then mounted for viewing in the Scanning Electron Microscope (SEM), and a thin (approximately 2 nm) of gold-palladium metal was sputtered onto the sample to provide a conductive sample surface to minimize charge buildup from the incident electron  beam. Because the wavelength of electrons is considerably shorter than that of visible light, the electron microscope provides significantly greater depth of field and depth of focus than the optical microscope.

Blog Post, Methodologies

Ticks: The More You Know

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The image of the month is a false-colored secondary electron (SE) image of the mouth parts of a tick, taken using a Scanning Electron Microscope (SEM). The subject is most likely a male deer tick (shown below in the black-and-white SE image), commonly found in Massachusetts and across the northeast – and a prime carrier of the bacteria that causes Lyme disease, Borrelia burgdorferi (B. burgdorferi).

In February of 2016, the Centers for Disease Control announced that a new species of this bacteria, B. mayonii also causes Lyme in people. And now a new tick-borne virus that is on the rise – Pawassan – was a recent topic of discussion on National Public Radio’s On Point program. Pawassan can cause paralysis and death in humans, representing a new threat in what has been described as the worst year for ticks in recent history – largely because of the wet conditions nationwide over the winter and spring.

The false-coloring was collected by acquiring multiple images using a solid state backscatter detector that allows the user to select specific parts of the detector for image acquisition. Using an image processing program, colors can be assigned to specific images that are then combined to produce a natural-looking color scheme. Both the false-color and ‘normal’ images were collected using special lower-vacuum conditions to avoid drying and other artifacts that occur under the normal high-vacuum environment of the SEM.