Snakes are elongated, limbless, carnivorous reptiles that first appeared in the fossil record during the Cretaceous period, between 145.5 and 65.5 million years ago. The study of snakes has been greatly advanced by the use of micro-CT scanning, which has allowed comprehensive study of internal structures and skeletal elements that would otherwise be inaccessible or possibly be seen only in a single view. Because of its non-invasive and non-destructive methodology, micro-CT can facilitate morphometric studies, phylogenetics analysis, and biomechanics modeling.
X-Ray Microscopic Imaging of a Rattlesnake
This month we imaged a rattlesnake at three scales using the SkyScan 1273 micro-CT. The large sample volume of the SkyScan 1273 allowed us to examine the snake at a full body overview scale and two higher resolution captures of regions of high interest – the head and tail.
The sample was first imaged as a general overview at an isotropic voxel size of 80 µm. Following this capture, the sample was trimmed and mounted in sections to image the head at a 20 µm voxel size and the tail at a 10 µm voxel size to generate higher resolution datasets of both regions.
As shown in Figure 2, the SkyScan 1273 micro-CT captured the fine bones and thin rattle components using an isotropic voxel size of 10 µm. To better visualize the lower density, organic shells which comprise the rattle, the signal from the bone was saturated in this image.
When looking through the 3D view of the rattlesnake, we can clearly see the interlocking organic shells that comprise the distinctive rattlesnake tail (Figure 3). When agitated, the snake will shake its tail, causing the organic shells to strike one another and produce the distinctive sound associated with rattlesnakes.
In examining the head, the bone structure shows great detail in the jaws and teeth with multiple rows of teeth visible within the head (Figure 4). The unique feature of many snakes, where the bottom jaw halves are only connected by soft tissue allowing for the consumption of large prey, is also evident.
Conclusion
The large sample volume (~10×10 inches) of the SkyScan 1273 micro-CT was helpful in allowing us to explore the rattlesnake sample at several scales. The full body of the snake fit within the instrument for overview imaging and then specific regions of interest were extracted from the larger sample and imaged at improved resolution.
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Scan Specifications
| Sample | Full Snake | Snake Head | Snake Tail |
| Voltage (kV) | 110 | 80 | 35 |
| Current (µA) | 300 | 300 | 180 |
| Filter | 0.3 mm Copper | 0.5 mm Aluminum | None |
| Pixel Size (µm) | 80 | 20 | 10 |
| Rotation Step | 0.3 | 0.25 | 0.25 |
| Exposure Time (ms) | 94 | 64 | 300 |
| Rotation Extent (deg.) | 360 | 180 | 180 |
| Scan Time (HH:MM:SS) | 02:07:56 | 01:34:38 | 02:59:24 |
These scans were completed on our SkyScan 1273 micro-CT system at the Micro Photonics Imaging Laboratory in Allentown, PA. Reconstructions were completed using NRecon 2.0 while visualization and volumetric inspection of the 2D and 3D results were completed using DataViewer and CTVox. CTAn was utilized to isolate the bones from the soft tissue and mounting material signal.
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