Micro-CT imaging allows researchers to visualize both the internal and external features of an object without destroying the specimen, which makes this technique ideal for digitizing chemically-dried insect specimens. With micro-CT, valuable natural history collections can now be digitized while preserving the original objects. Micro-CT allows for high resolution examination of insect samples and supports research focused on studying the insects themselves. Additionally, those exploring biomimicry and other evolutionary type work often choose micro-CT as a useful technique for the 3D visualizations and high resolution imaging it provides.

X-Ray Microscopy Imaging of Chemically-Dried Insects

Through chemical drying of the samples, many features of the insect are preserved without the changes to tissue samples that typically occur upon standard air drying¹. For this work, samples were collected fresh and stored in an alcohol solution. The alcohol was replaced through soaking in hexamethyldisilazine (HMDS). Finally, the HMDS was evaporated in air within a glove box, fully drying the sample and leaving a thin silane layer throughout the sample.  As can be seen in Figure 1 above, both the carpenter bee and the firefly were captured with high detail using the SkyScan 1272 with an isotropic voxel size of 4µm.

Figure 2: Clipped volumetric renderings of carpenter bee (top) and firefly (bottom)

One primary function of X-ray microscopy is the nondestructive visualization of internal features within samples. As shown in Figure 2, the internal organs and muscles of both samples are evident in the results and the chemical drying process reduced damage to the soft tissue and organs during dehydration.

Figure 3: Clipped volumetric renderings focused on the heads of carpenter bee (top) and firefly (bottom)

Likewise, many researchers focus on the internal connections and organs within the insect’s head (Figure 3). The heads of both insects were captured with fine detail, even showing the structures within the eyes of both insects along with the mouth parts. 

Figure 4: Volumetric renderings of Carpenter Bee (top) and Firefly (bottom) samples with flight muscles segmented

Using Synopsys Simpleware software, the flight muscles of both insects were manually segmented. Anatomical differences in the flight muscles between the insects are shown in Figure 4. The segmented flight muscles were overlaid upon the remainder of the volumetric data to highlight their relative position within the anatomy of each insect.

Figure 5: Volumetric renderings of Carpenter Bee (top) and Firefly (bottom) flight muscles

Isolating the flight muscles from the remainder of the sample allows a closer examination of the differences and similarities between the samples (Figure 5). Both samples have tight bundles of muscles arranged into columns. The carpenter bee bundles are more regularly spaced with open space between the bundles. In contrast, the firefly has less space between muscles and is more compact.

Conclusion

The high-resolution micro-CT imaging with the SkyScan 1272 is well suited for smaller, low density samples like insects. We hope you found this Image of the Month informative and encourage you to subscribe to our newsletter and social media channels in preparation for the continuation of our image of the month series next month.

Scan Specifications

These scans were completed on our desktop SkyScan 1272 system at the Micro Photonics Imaging Laboratory in Allentown, PA. Reconstructions were completed using NRecon and visualization of 2D and 3D results were completed using Dataviewer, CTVox, and Simpleware software.

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References

1. B. D. Metscher, “MicroCT for comparative morphology: simple staining methods allow high-contrast 3D imaging of diverse non-mineralized animal tissues.,” BMC Physiol., vol. 9, no. 1, p. 11, Jan. 2009.