Real-time phase-contrast x-ray imaging: a new technique for the study of animal form and function
1 Advanced Photon Source, Argonne National Laboratory, 9700 S. Cass Ave., Argonne, IL 60439, USA
2 Department of Zoology, Field Museum of Natural History, 1400 S. Lake Shore Dr., Chicago, IL, 60605, USA
3 Section of Organismal, Integrative, and Systems Biology, School of Life Sciences, Arizona State University, PO Box 874501, Tempe, AZ, 85287-4501, USA
BMC Biology 2007, 5:6 doi:10.1186/1741-7007-5-6Published: 1 March 2007
Rhythmic compressive movements in the tracheal system in the carabid beetle Platynus decentis, demonstrating the utility of phase-contrast synchrotron imaging for studies of respiratory dynamics in small animals. View (1.3 × 1.0 mm) is a dorsoventral projection through prothorax of a beetle (mass ~ 45 mg) using monochromatic x-rays (25 keV). The midline of the beetle lies on the right side of the video between the two coxae (large circular structures, bottom right). Collapse and reinflation of the air-filled tracheal tubes can be seen in the majority of the tubes in view. The smallest tracheal tubes that can be seen are about 10 μm in diameter; tracheoles (<1 μm diameter) are too small to be resolved. The circle and dark opaque spots the upper right are an air bubble and particles in the esophagus, respectively; note that they move anteriorly and posteriorly during the compression of the tracheal tubes. The white and dark spots that do not move with the beetle movement are artifacts due to the incident beam and detector system.
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Passage of food bolus through the esophagus of the butterfly Pieris rapae. View (1.3 × 1.0 mm) is a lateral projection through the thorax of the butterfly (mass ~50 mg), with food moving from anterior (upper right) to posterior (lower left). The butterfly was feeding on a mixture of sugar water and iodine compound (Isovue). X-ray energy (33.2 keV) was tuned just above the K-edge for iodine, making the food bolus appear dark. This clip demonstrates how synchrotron imaging can be used to visualize internal food transport during feeding in small animals. Note that the esophagus is collapsed until the bolus passes through; the light structure running along the same diagonal axis is a tracheal tube. From this clip, it can be seen that the bolus is tapered at both ends and is transported at a speed of ~1.5 mm/s.
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Movements of the foregut and gut contents of the carabid beetle Pterostichus stygicus. View (3.3 × 2.5 mm) is a dorsoventral projection through the pterothorax, posterior to the mesocoxae (circular structures seen at top of image). The beetle (mass ~210 mg) was fed macerated larva sprinkled with cadmium powder to increase x-ray (25 keV) absorption contrast; the gut boundaries and food movement can only be seen in places with cadmium powder. In this sequence, the crop (bag-like structure, center left) is squeezed anteriorly and then slowly settles back into its initial orientation. Mixing movements and peristalsis of the proventriculus (cylindrical structure, right side) can also be seen. Note that the proventriculus is closed, preventing food from moving posteriorly into the midgut. Dark bands on the left side of the video are artifacts from the incident beam.
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