“Bats exhibit an outstanding diversity of cranial morphologies and diets. However, comparative studies of jaw muscle architecture have been difficult due the small size of most bats. This study used diceCT to provide, for the first time, a detailed characterization of the gross and internal anatomy of the jaw muscles across an ecologically diverse sample of bats. DiceCT allowed me to evaluate interspecific differences in muscle attachments, compartments, and scaling in the context of dietary specialization, and to provide novel anatomical descriptions within the feeding apparatus of bats. By doing so, this study revealed unexplored anatomical diversity that can inform future work in functional and evolutionary morphology.”
“Manual dissection is both inherently destructive to specimens, and reliant upon the use of sampling sites to assess muscle fascicle properties and their distribution. We present the results of a digital technique using diceCT to identify and map whole-muscle fascicle distributions within the jaw-adductor musculature of a primate specimen. Comparing these data to dissection results of the contralateral muscles, we demonstrate an ability to determine architectural variables non-invasively through the use of diceCT. Though muscle complexity may impact the convergence between traditional and digital methods, we conclude that this technique offers great potential for future work of whole-muscle mapping, whilst circumventing specimen loss.”
“Is iodine perfusable?”
This is one of the most frequently asked questions by the diceCT community, and the Witmer Lab at Ohio University has answered: “Absolutely!”
SpiceCT (selectively perfusable iodine-based contrast-enhanced CT) is particularly good at staining large specimens very rapidly. Iodine is perfused through the arterial system and across capillary beds, staining soft tissues nearly instantaneously and allowing for targeting regions of interest based on blood supply.
The Witmer lab recently presented their new protocol at the Society for Integrative and Comparative Biology meeting in San Francisco on 4 January 2018 and are now sharing that poster widely on FigShare. Download the poster, and add a new tool to your arsenal!
“Does dramatic functional change depend on dramatic morphological change? Kaji et al. used contrast-enhanced micro-CT and confocal imaging, high-speed video, and kinematic experiments with select 3D-printed models, to reconstruct the evolutionary changes in form and function that yielded spectacular snapping claws from simple pinching claws in two shrimp families. They discovered that two novel claw-joint types — a slip joint and a torque-reversal joint — preceded the evolution of snapping. They also found that the evolutionary transitions slip joint ➔ torque-reversal joint ➔ snapping occurred in both shrimp families studied. These results show how subtle changes in joint-form yielded dramatic changes in claw function (e.g., closing speed) during the evolution of snapping claws.”
– Lead author, Tomonari Kaji (@)
“We applied the diceCT technique to image, in three dimensions, a mammalian tooth development pattern, using embryos and pouch young of the tammar wallaby (Macropus eugenii). This enabled individual tissue layers within developing teeth to be clearly distinguishable and even allowed us to image single-cell layer tissues with higher magnification sub-volume scans. Within the same scan we could 3D-visualise both the soft and hard tissues present at various stages through tooth development, including the primary and secondary dental laminae, as well as first and second generations of teeth. With these contrast-enhanced scans, we produced 3D models of in-situ tooth development, demonstrating the enormous potential to visualise this and other organogenetic patterns using this technique.”
“We investigated the mechanics of copulatory interactions in marine mammals to determine how morphological diversity of genitalia correlates with function during simulated copulation. The excised penises of deceased male cetaceans and pinnipeds were distended, positioned inside the vaginas of females from the same species, and CT-scanned in situ using diceCT techniques. We found evidence of both congruent and antagonistic genital coevolution between the sexes, depending on the species. Sexual selection forces contribute to the extensive genital morphological variation observed in male and female marine mammals.”
–Lead author, Dara Orbach (@)
“We tested the controversial hypothesis that mammalian brain parts scale conservatively with brain size because of developmental constraints on size-dependent, neurogenetic patterns. Early cell-level constraint should be reflected in conserved patterns of mammalian brain partition growth, but the data required to test this expectation have been unavailable. The hydrogel/DiceCT technique, however, represents a fast way of measuring growth in minute brains, allowing us to provide the first quantification of mammalian brain partition growth. Across three marsupial species, we found no evidence of partition growth regularities with brain size or age although intraspecific growth patterns were very regular. This suggests that species-specific brain growth patterns do exist, albeit not as part of a global pattern of evolutionary developmental constraint.”
– Project Leader, Vera Weisbecker
“The African clawed frog Xenopus laevis is one of the world’s most widely used model organisms – yet existing anatomical descriptions are nearly a century old, incomplete and use outdated nomenclature. Moreover, Xenopus exhibits many unusual skeletal and soft-tissue characters compared to well-described “typical” frogs such as Rana. We used diceCT to create a 3D digital dissection of Xenopus, including the skeleton, muscles, nervous, respiratory digestive and reproductive systems. The method was particularly useful in this instance as it preserves 3D topological relationships and permitted dissection of a very small, fragile specimen.”
– Lead Author, Laura Porro
Download the dissectable 3D model from the Journal of Anatomy!