World of Intricate Muscles Revealed Inside Velvet Worm's Wee Leg

For decades, X-ray computer tomography (CT) scanning has enabled scientists to noninvasively examine the insides of organisms and objects, and model them in 3D. But the technology only worked on subjects that were larger than 500 nanometers (a nanometer is 1-billionth of a meter, or 400-billionths of an inch).

Recently, scientists developed a tabletop Nano-CT system capable of capturing images in 3D at an unprecedentedly small scale — 100 nanometers. Its limits were recently tested on a velvet worm’s minuscule legs, which measure a mere 0.02 inches (0.4 millimeters) long, and this novel technology successfully visualized individual muscle fibers inside the worm's leg, the researchers reported in a new study. [Images: Tiny Life Revealed in Stunning Microscope Photos]

Nano-CT uses nanotubes to tightly focus X-rays and visualize much smaller objects at higher resolution than had been possible with CT scans until now. As the process creates a digital 3D model of the object from a single scan, it is cheaper and less time-consuming to use than other high-resolution imaging methods that can only capture 2D images on a single plane, such as scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM), the researchers explained in the study.

The scientists tested the system by looking inside the legs of the tiny velvet worms —soft-bodied animals that resemble worms with multiple sets of limbs. They are part of the group panarthropoda, which includes arthropods and tardigrades. The scans revealed that the worms' feet contained circular muscles, which had been hinted at in prior studies but were not meticulously described, the scientists reported.

Velvet worms are an ancient lineage that has changed little in 500 million years, and their closest relationships on the tree of life are still being debated, the scientists wrote in the study. Internal examination of their delicate limb structures could offer scientists new insights into the animals' locomotion, and may help researchers puzzle out how segmented limbs in arthropods evolved, study co-author Georg Mayer, head of the Department of Zoology at the University of Kassel, said in a statement.

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Mindy Weisberger is a science journalist and author of "Rise of the Zombie Bugs: The Surprising Science of Parasitic Mind-Control" (Hopkins Press). She formerly edited for Scholastic and was a channel editor and senior writer for Live Science. She has reported on general science, covering climate change, paleontology, biology and space. Mindy studied film at Columbia University; prior to LS, she produced, wrote and directed media for the American Museum of Natural History in NYC. Her videos about dinosaurs, astrophysics, biodiversity and evolution appear in museums and science centers worldwide, earning awards such as the CINE Golden Eagle and the Communicator Award of Excellence. Her writing has also appeared in Scientific American, The Washington Post, How It Works Magazine and CNN.