Hedrick Brandon P, Yohe Laurel, Vander Linden Abby, Dávalos Liliana M, Sears Karen, Sadier Alexa, Rossiter Stephen J, Davies Kalina T J, Dumont Elizabeth
1Department of Organismic and Evolutionary Biology,Harvard University,Cambridge,MA 02138,USA.
2Department of Ecology and Evolution,Stony Brook University,650 Life Sciences Building,Stony Brook,NY 11794,USA.
Microsc Microanal. 2018 Jun;24(3):284-291. doi: 10.1017/S1431927618000399. Epub 2018 Jun 19.
The increased accessibility of soft-tissue data through diffusible iodine-based contrast-enhanced computed tomography (diceCT) enables comparative biologists to increase the taxonomic breadth of their studies with museum specimens. However, it is still unclear how soft-tissue measurements from preserved specimens reflect values from freshly collected specimens and whether diceCT preparation may affect these measurements. Here, we document and evaluate the accuracy of diceCT in museum specimens based on the soft-tissue reconstructions of brains and eyes of five bats. Based on proxies, both brains and eyes were roughly 60% of the estimated original sizes when first imaged. However, these structures did not further shrink significantly over a 4-week staining interval, and 1 week in 2.5% iodine-based solution yielded sufficient contrast for differentiating among soft-tissues. Compared to six "fresh" bat specimens imaged shortly after field collection (not fixed in ethanol), the museum specimens had significantly lower relative volumes of the eyes and brains. Variation in field preparation techniques and conditions, and long-term storage in ethanol may be the primary causes of shrinkage in museum specimens rather than diceCT staining methodology. Identifying reliable tissue-specific correction factors to adjust for the shrinkage now documented in museum specimens requires future work with larger samples.
通过基于可扩散碘的对比增强计算机断层扫描（diceCT）获取软组织数据的便利性提高，使得比较生物学家能够利用博物馆标本扩大其研究的分类学广度。然而，目前仍不清楚从保存标本中获得的软组织测量值如何反映新鲜采集标本的值，以及diceCT制备过程是否会影响这些测量值。在此，我们基于对五只蝙蝠的大脑和眼睛的软组织重建，记录并评估diceCT在博物馆标本中的准确性。基于代理数据，首次成像时，大脑和眼睛的大小大致为估计原始大小的60%。然而，在4周的染色间隔内，这些结构并未进一步显著缩小，在2.5%的碘基溶液中浸泡1周就产生了足以区分软组织的对比度。与野外采集后不久成像的六个“新鲜”蝙蝠标本（未用乙醇固定）相比，博物馆标本的眼睛和大脑相对体积明显较小。野外制备技术和条件的差异以及在乙醇中的长期保存可能是博物馆标本收缩的主要原因，而非diceCT染色方法。确定可靠的组织特异性校正因子以调整目前在博物馆标本中记录到的收缩情况，需要未来使用更大样本进行研究。
