Abstract Scolecophidian snakes have long posed challenges for scholars interested in elucidating their anatomy. The importance, and relative paucity, of high‐quality anatomical data pertaining to scolecophidians was brought into sharp focus in the late 20 th century as part of a controversy over the phylogeny and ecological origin of snakes. The basal position of scolecophidians in the phylogeny of snakes makes their anatomy, behavior, ecology, and evolution especially important for such considerations. The depauperate fossil record for the group meant that advances in understanding their evolutionary history were necessarily tied to biogeographic distributions and anatomical interpretations of extant taxa. Osteological data, especially data pertaining to the skull and mandible, assumed a dominant role in shaping historical and modern perspectives of the evolution of scolecophidians. Traditional approaches to the exploration of the anatomy of these snakes relied heavily upon serial‐sectioned specimens and cleared‐and‐stained specimens. The application of X‐ray computed tomography (CT) to the study of scolecophidians revolutionized our understanding of the osteology of the group, and now, via diffusible iodine‐based contrast‐enhanced computed tomography (diceCT), is yielding data sets on internal soft anatomical features as well. CT data sets replicate many aspects of traditional anatomical preparations, are readily shared with a global community of scholars, and now are available for unique holotype and other rare specimens. The increasing prevalence and relevance of CT data sets is a strong incentive for the establishment and maintenance of permanent repositories for digital data.
more »
« less
This content will become publicly available on July 6, 2024
The first full body diffusible iodine‐based contrast‐enhanced computed tomography dataset and teaching materials for a member of the Testudines
Diffusible iodine‐based contrast‐enhanced Computed Tomography (diceCT) is now a widely used technique for imaging metazoan soft anatomy. Turtles present a particular challenge for anatomists; gross dissection is inherently destructive and irreversible, whereas their near complete shell of bony plates, covered with keratinous scutes, presents a barrier for iodine diffusion and significantly increases contrast‐enhanced CT preparation time. Consequently, a complete dataset visualizing the internal soft anatomy of turtles at high resolution and in three dimensions has not yet been successfully achieved. Here we outline a novel method that augments traditional diceCT preparation with an iodine injection technique to acquire the first full body contrast‐enhanced dataset for the Testudines. We show this approach to be an effective method of staining the soft tissues inside the shell. The resulting datasets were processed to produce anatomical 3D models that can be used in teaching and research. As diceCT becomes a widely employed method for nondestructively documenting the internal soft anatomy of alcohol preserved museum specimens, we hope that methods applicable to the more challenging of these, such as turtles, will contribute toward the growing stock of digital anatomy in online repositories.
more » « less- NSF-PAR ID:
- 10441872
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- The Anatomical Record
- Volume:
- 307
- Issue:
- 3
- ISSN:
- 1932-8486
- Format(s):
- Medium: X Size: p. 535-548
- Size(s):
- ["p. 535-548"]
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
null (Ed.)Abstract 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.more » « less
-
Diffusible iodine-based contrast-enhanced computed tomography (diceCT) has emerged as a viable tool for discriminating soft tissues in serial CT slices, which can then be used for three-dimensional analysis. This technique has some potential to supplant histology as a tool for identification of body tissues. Here, we studied the head of an adult fruit bat ( Cynopterus sphinx ) and a late fetal vampire bat ( Desmodus rotundus ) using diceCT and µCT. Subsequently, we decalcified, serially sectioned and stained the same heads. The two CT volumes were rotated so that the sectional plane of the slice series closely matched that of histological sections, yielding the ideal opportunity to relate CT observations to corresponding histology. Olfactory epithelium is typically thicker, on average, than respiratory epithelium in both bats. Thus, one investigator (SK), blind to the histological sections, examined the diceCT slice series for both bats and annotated changes in thickness of epithelium on the first ethmoturbinal (ET I), the roof of the nasal fossa, and the nasal septum. A second trial was conducted with an added criterion: radioopacity of the lamina propria as an indicator of Bowman’s glands. Then, a second investigator (TS) annotated images of matching histological sections based on microscopic observation of epithelial type, and transferred these annotations to matching CT slices. Measurements of slices annotated according to changes in epithelial thickness alone closely track measurements of slices based on histologically-informed annotations; matching histological sections confirm blind annotations were effective based on epithelial thickness alone, except for a patch of unusually thick non-OE, mistaken for OE in one of the specimens. When characteristics of the lamina propria were added in the second trial, the blind annotations excluded the thick non-OE. Moreover, in the fetal bat the use of evidence for Bowman’s glands improved detection of olfactory mucosa, perhaps because the epithelium itself was thin enough at its margins to escape detection. We conclude that diceCT can by itself be highly effective in identifying distribution of OE, especially where observations are confirmed by histology from at least one specimen of the species. Our findings also establish that iodine staining, followed by stain removal, does not interfere with subsequent histological staining of the same specimen.more » « less
-
more » « less
ABSTRACT The organization and length of a muscle's fascicles imparts its contractile properties. Longer fascicles permit increased muscle excursion, whereas changes in fascicle orientation relate to the overall vector of contractile force. Collecting data on fascicle architecture has traditionally involved destructive and irreversible gross dissection. In recent years, however, new imaging modalities have permitted muscles and their fascicles to be visualized nondestructively. Here, we present data from a primate (
Callithrix jacchus ), in which, for the first time, individual muscle fascicles are digitally “dissected” (segmented and reconstructed) using nondestructive, high‐resolution diffusible iodine‐based contrast‐enhanced computed tomography (DiceCT) techniques. We also present quantitative data on the length and orientation of these fascicles within 10 muscle divisions of the jaw adductor and abductor musculature (superficial, deep, and zygomatic portions of temporalis and masseter; medial and lateral pterygoid; anterior and posterior digastric) and compare these digitally measured lengths to fascicular lengths measured using traditional gross and chemical dissection. Digitally derived fascicle lengths correspond well to their dissection‐derived counterparts. Moreover, our analyses of changes in fascicle orientation across the adductor complex enable us to visualize previously uncharacterized levels of detail and highlight significant variation between adjacent muscle layers within muscle groups (e.g., between superficial, deep, and zygomatic portions of masseter and temporalis). We conclude that this technique offers great potential to future research, particularly for questions centered around the visualization and quantification of obscured and often‐overlooked muscles such as the pterygoid and digastric muscles, and for deriving more accurate models of the masticatory system as a whole. Anat Rec, 302:1891–1900, 2019. © 2019 American Association for Anatomy -
more » « less
Synopsis Contrast enhanced computed-tomography imaging like diffusible iodine-based contrast-enhanced computed tomography (diceCT) can provide detailed information on muscle architecture important to comparative analyses of functional morphology, using non-destructive approaches. However, manual segmentation of muscle fascicles/fibers is time-consuming, and automated approaches are at times inaccessible and unaffordable. Here, we introduce GoodFibes, an R package for reconstructing muscle architecture in 3D from diceCT image stacks. GoodFibes uses textural analysis of image grayscale values to track straight or curved fiber paths through a muscle image stack. Accessory functions provide quality checking, fiber merging, and 3D visualization and export capabilities. We demonstrate the utility and effectiveness of GoodFibes using two datasets, from an ant and bat diceCT scans. In both cases, GoodFibes provides reliable measurements of mean fiber length compared to traditional approaches, and is as effective as currently available software packages. This open-source, free to use software package will help to improve access to tools in the analysis of muscle fiber anatomy using diceCT scans. The flexible and transparent R-language environment allows other users to build on the functions described here and permits direct statistical analysis of the resulting fiber metrics. We hope that this will increase the number of comparative and evolutionary studies incorporating these rich and functionally important datasets.
