A Review and Case Study of 3D Imaging Modalities for Female Amniote Reproductive Anatomy

Clear, Emma; Grant, Robyn A.; Carroll, Michael A.; Brassey, Charlotte A.

doi:10.1093/icb/icac027

Cited by 4 publications

(1 citation statement)

References 143 publications

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“…Additionally, a quantitative analysis of the corresponding female anatomy in these species would prove extremely informative. Historically overlooked due to difficulties in collection and imaging of soft tissue (Orbach, 2022 ), modern techniques (including silicone casting, computed tomography and magnetic resonance imaging) offer the opportunity for shape complexity analysis at the same standard as those techniques used here (Clear et al, 2022 ). A comprehensive understanding of both male and female genital anatomy, covariance of genital morphology (André et al, 2020 ) and analysis of copulatory fit, as conducted in other species (cetaceans: Orbach et al, 2017 ; caiman: Moore et al, 2021 ), will provide the opportunity to explore how variation in form might influence copulatory function in Musteloidea.…”

Section: Discussionmentioning

confidence: 99%

Baculum shape complexity correlates to metrics of post‐copulatory sexual selection in Musteloidea

Clear

Grant

Gardiner

et al. 2023

Journal of Morphology

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The penis bone, or baculum, is present in many orders of mammals, although its function is still relatively unknown, mainly due to the challenges with studying the baculum in vivo. Suggested functions include increasing vaginal friction, prolonging intromission and inducing ovulation. Since it is difficult to study baculum function directly, functional morphology can give important insights. Shape complexity techniques, in particular, are likely to offer a useful metric of baculum morphology, especially since finding homologous landmarks on such a structure is challenging.This study focuses on measuring baculum shape complexity in the Musteloidea-a large superfamily spanning a range of body sizes with well-developed, qualitatively diverse bacula. We compared two shape complexity metrics-alpha shapes and ariaDNE and conducted analyses over a range of six different coefficients, or bandwidths, in 32 species of Musteloidea. Overall, we found that shape complexity, especially at the baculum distal tip, is associated with intromission duration using both metrics. These complexities can include hooks, bifurcations and other additional projections. In addition, alpha shapes complexity was also associated with relative testes mass. These results suggest that post-copulatory mechanisms of sexual selection are probably driving the evolution of more complex-shaped bacula tips in Musteloidea and are likely to be especially involved in increasing intromission duration during copulation.

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Section: Discussionmentioning

confidence: 99%

Baculum shape complexity correlates to metrics of post‐copulatory sexual selection in Musteloidea

Clear

Grant

Gardiner

et al. 2023

Journal of Morphology

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Tracking gonadal development in fish: An in vivo MRI study on polar cod, Boreogadus saida (Lepechin, 1774)

Vogt,

Wermter,

Nahrgang

et al. 2024

NMR in Biomedicine

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Magnetic resonance imaging (MRI) was applied to determine the sex of polar cod (Boreogadus saida Lepechin, 1774) (Actinopterygii: Gadidae) and to follow the gonadal development in individual animals over time. Individual unanaesthetised fish were transferred to a measurement chamber inside a preclinical 9.4 T MRI scanner and continuously perfused with aerated seawater. A screening procedure at an average of 3.5 h, consisting of a set of MRI scans of different orientations, was repeated every 4 weeks on the same set of reproducing B. saida (n = 10) with a body length of about 20 cm. Adapted multi‐slice flow‐compensated fast low‐angle shot (FcFLASH) and rapid acquisition with relaxation enhancement (RARE) protocols with an in‐plane resolution of 313 μm and an acquisition time of 2.5 min were used to visualise the morphology of various organs, including the gonads within the field of view (FOV). The MR images provided high resolution, enabling specific sex determination, calculation of gonad volumes, and determination of oocyte sizes. Gonad maturation was followed over 4 months from November 2021 until shortly before spawning in February 2022. The gonad volume increased by 2.3–25.5% for males and by 11.5–760.7% for females during the observation period. From October to February, the oocyte diameter increased from 427 μm (n = 1) to 1346 ± 27 μm (n = 4). Interestingly, individual oocytes showed changes in MR contrast over time that can be attributed to the morphological development of the oocytes. The results fit well with previous literature data from classical invasive studies. The presented approach has great potential for various ecophysiological applications such as monitoring natural or delayed development of internal organs or sex determination under different environmental conditions.

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Structural analysis of the female reptile reproductive system by micro-computed tomography and optical coherence tomography

Kircher,

McCown,

Scully

et al. 2024

Biology of Reproduction

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Volumetric data provide unprecedented structural insight to the reproductive tract and add vital anatomical context to the relationships between organs. The morphology of the female reproductive tract in non-avian reptiles varies between species, corresponding to a broad range of reproductive modes and providing valuable insight to comparative investigations of reproductive anatomy. However, reproductive studies in reptilian models, such as the brown anole studied here, have historically relied on histological methods to understand the anatomy. While these methods are highly effective for characterizing the cell types present in each organ, histological methods lose the 3D relationships between images and leave the architecture of the organ system poorly understood. We present the first comprehensive volumetric analyses of the female brown anole reproductive tract using two non-invasive, non-destructive imaging modalities: micro-computed tomography (microCT) and optical coherence tomography (OCT). Both are specialized imaging technologies that facilitate high-throughput imaging and preserve three-dimensional information. This study represents the first time that microCT has been used to study all reproductive organs in this species and the very first time that OCT has been applied to this species. We show how the non-destructive volumetric imaging provided by each modality reveals anatomical context including orientation and relationships between reproductive organs of the anole lizard. In addition to broad patterns of morphology, both imaging modalities provide the high resolution necessary to capture details and key anatomical features of each organ. We demonstrate that classic histological features can be appreciated within whole-organ architecture in volumetric imaging using microCT and OCT, providing the complementary information necessary to understand the relationships between tissues and organs in the reproductive system. This side-by-side imaging analysis using microCT and OCT allows us to evaluate the specific advantages and limitations of these two methods for the female reptile reproductive system.

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A Review and Case Study of 3D Imaging Modalities for Female Amniote Reproductive Anatomy

Cited by 4 publications

References 143 publications

Baculum shape complexity correlates to metrics of post‐copulatory sexual selection in Musteloidea

Baculum shape complexity correlates to metrics of post‐copulatory sexual selection in Musteloidea

Tracking gonadal development in fish: An in vivo MRI study on polar cod, Boreogadus saida (Lepechin, 1774)

Structural analysis of the female reptile reproductive system by micro-computed tomography and optical coherence tomography

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