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Clear E, Grant RA, Carroll M, Brassey CA. A Review and Case Study of 3D Imaging Modalities for Female Amniote Reproductive Anatomy. Integr Comp Biol 2022; 62:icac027. [PMID: 35536568 PMCID: PMC10570564 DOI: 10.1093/icb/icac027] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2022] [Revised: 04/20/2022] [Indexed: 11/13/2022] Open
Abstract
Recent advances in non-invasive imaging methods have revitalised the field of comparative anatomy, and reproductive anatomy has been no exception. The reproductive systems of female amniotes present specific challenges, namely their often internal "hidden" anatomy. Quantifying female reproductive systems is crucial to recognising reproductive pathologies, monitoring menstrual cycles, and understanding copulatory mechanics. Here we conduct a review of the application of non-invasive imaging techniques to female amniote reproductive anatomy. We introduce the commonly used imaging modalities of computed tomography (CT) and magnetic resonance imaging (MRI), highlighting their advantages and limitations when applied to female reproductive tissues, and make suggestions for future advances. We also include a case study of micro CT and MRI, along with their associated staining protocols, applied to cadavers of female adult stoats (Mustela erminea). In doing so, we will progress the discussion surrounding the imaging of female reproductive anatomy, whilst also impacting the fields of sexual selection research and comparative anatomy more broadly.
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Affiliation(s)
- Emma Clear
- Department of Natural Sciences, Manchester Metropolitan University, Chester St, Manchester M1 5GD, UK
- Williamson Park Zoo, Quernmore Road, Lancaster, Lancashire LA1 1UX, UK
| | - Robyn A Grant
- Department of Natural Sciences, Manchester Metropolitan University, Chester St, Manchester M1 5GD, UK
| | - Michael Carroll
- Department of Life Sciences, Manchester Metropolitan University, Chester St, Manchester M1 5GD, UK
| | - Charlotte A Brassey
- Department of Natural Sciences, Manchester Metropolitan University, Chester St, Manchester M1 5GD, UK
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Orbach DN, Brassey CA, Gardiner JD, Brennan PLR. 3D genital shape complexity in female marine mammals. Ecol Evol 2021; 11:3210-3218. [PMID: 33841778 PMCID: PMC8019040 DOI: 10.1002/ece3.7269] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2020] [Revised: 12/17/2020] [Accepted: 01/12/2021] [Indexed: 11/06/2022] Open
Abstract
Comparisons of 3D shapes have recently been applied to diverse anatomical structures using landmarking techniques. However, discerning evolutionary patterns can be challenging for structures lacking homologous landmarks. We used alpha shape analyses to quantify vaginal shape complexity in 40 marine mammal specimens including cetaceans, pinnipeds, and sirenians. We explored phylogenetic signal and the potential roles of natural and sexual selection on vaginal shape evolution. Complexity scores were consistent with qualitative observations. Cetaceans had a broad range of alpha complexities, while pinnipeds were comparatively simple and sirenians were complex. Intraspecific variation was found. Three-dimensional surface heat maps revealed that shape complexity was driven by invaginations and protrusions of the vaginal wall. Phylogenetic signal was weak and metrics of natural selection (relative neonate size) and sexual selection (relative testes size, sexual size dimorphism, and penis morphology) did not explain vaginal complexity patterns. Additional metrics, such as penile shape complexity, may yield interesting insights into marine mammal genital coevolution. We advocate for the use of alpha shapes to discern patterns of evolution that would otherwise not be possible in 3D anatomical structures lacking homologous landmarks.
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Affiliation(s)
- Dara N. Orbach
- Department of Life SciencesTexas A&M University‐ Corpus ChristiCorpus ChristiTXUSA
- Department of Biological SciencesMount Holyoke CollegeSouth HadleyMAUSA
| | - Charlotte A. Brassey
- School of Science and the EnvironmentManchester Metropolitan UniversityManchesterUK
| | - James D. Gardiner
- Department of Musculoskeletal and Ageing ScienceInstitute of Lifecourse and Medical SciencesUniversity of LiverpoolLiverpoolUK
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Orbach DN, Brennan PLR, Hedrick BP, Keener W, Webber MA, Mesnick SL. Asymmetric and Spiraled Genitalia Coevolve with Unique Lateralized Mating Behavior. Sci Rep 2020; 10:3257. [PMID: 32094449 PMCID: PMC7039966 DOI: 10.1038/s41598-020-60287-w] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2019] [Accepted: 02/10/2020] [Indexed: 02/04/2023] Open
Abstract
Asymmetric genitalia and lateralized mating behaviors occur in several taxa, yet whether asymmetric morphology in one sex correlates or coevolves with lateralized mating behavior in the other sex remains largely unexplored. While lateralized mating behaviors are taxonomically widespread, among mammals they are only known in the harbor porpoise (Phocoena phocoena). Males attempt copulation by approaching a female exclusively on her left side. To understand if this unusual lateralized behavior may have coevolved with genital morphology, we quantified the shape of female and male harbor porpoise reproductive tracts using 2D geometric morphometrics and 3D models of the vaginal lumen and inflated distal penis. We found that the vaginas varied individually in shape and that the vaginas demonstrated both significant directional and fluctuating asymmetry. This asymmetry resulted from complex 3D spirals and vaginal folds with deep recesses, which may curtail the depth or direction of penile penetration and/or semen movement. The asymmetric shapes of the vaginal lumen and penis tip were both left-canted with similar angular bends that mirrored one another and correspond with the left lateral mating approach. We suggest that the reproductive anatomy of both sexes and their lateral mating behavior coevolved.
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Affiliation(s)
- Dara N Orbach
- Texas A&M University- Corpus Christi, Department of Life Sciences, 6300 Ocean Dr., Corpus Christi, Texas, 78412, USA. .,Mount Holyoke College, Department of Biological Sciences, 50 College Street, South Hadley, Massachusetts, 01075, USA.
| | - Patricia L R Brennan
- Mount Holyoke College, Department of Biological Sciences, 50 College Street, South Hadley, Massachusetts, 01075, USA
| | - Brandon P Hedrick
- Louisiana State University Health Sciences Center, Department of Cell Biology and Anatomy, 1901 Perdido Street, New Orleans, LA, 70112, USA.,University of Oxford, Department of Earth Sciences, South Parks Road, Oxford, OX1 3AN, UK
| | - William Keener
- The Marine Mammal Center, 2000 Bunker Road, Sausalito, California, 94965, USA
| | - Marc A Webber
- The Marine Mammal Center, 2000 Bunker Road, Sausalito, California, 94965, USA
| | - Sarah L Mesnick
- Marine Mammal and Turtle Division, Southwest Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, 8901 La Jolla Shores Drive, La Jolla, California, 92037, USA
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Brennan PL, Orbach DN. Copulatory behavior and its relationship to genital morphology. ADVANCES IN THE STUDY OF BEHAVIOR 2020. [DOI: 10.1016/bs.asb.2020.01.001] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
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Orbach D, Rattan S, Hogan M, Crosby A, Brennan P. Biomechanical properties of female dolphin reproductive tissue. Acta Biomater 2019; 86:117-124. [PMID: 30641290 DOI: 10.1016/j.actbio.2019.01.012] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2018] [Revised: 01/02/2019] [Accepted: 01/10/2019] [Indexed: 01/08/2023]
Abstract
Whales, dolphins, and porpoises have unusual vaginal folds of unknown function(s) that are hypothesized to play an important role in sexual selection. The potential function of vaginal folds was assessed by testing the mechanical properties of common bottlenose dolphin (Tursiops truncatus) reproductive tract tissues in 6 different regions and across age classes in post-mortem specimens. We assessed the regional (local) and overall effective elastic modulus of tissues using indentation and tensile tests, respectively. We explore the non-linear mechanical response of biological tissues, which are not often quantified. Indentation tests demonstrated that sexual maturity state, tissue region, force history, and force magnitude values significantly affected the measured effective elastic modulus. Tissue was stiffest in the vaginal fold region and overall stiffer in sexually immature compared to mature animals, likely reflecting biomechanical adaptations associated with copulation and parturition. Tensile tests showed that only tissue region significantly affected the effective modulus. Our data support the hypothesis that vaginal folds function as mechanical barriers to the penis and may provide females with mechanisms to reduce copulatory forces on other reproductive tissue. STATEMENT OF SIGNIFICANCE: Cetaceans have unusual folds of vaginal wall tissue that appear to evolve under sexual selection mechanisms and present physical barriers to the penis during copulation. We explore the biomaterial properties of vaginal fold tissue, how it varies from other reproductive tract tissues, and ontogenetic patterns. We demonstrate that vaginal folds can withstand higher mechanical forces and respond in a manner conducive to dissipating copulatory forces to other reproductive tissues. This study yields exciting insights on how female genital tissue may function during copulation, and is the first to do so in any vertebrate species. Additionally, we provide an example for testing biological tissues, non-linear properties, and materials with uneven surface structure and uneven thickness.
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Orbach DN, Kelly DA, Solano M, Brennan PLR. Genital interactions during simulated copulation among marine mammals. Proc Biol Sci 2018; 284:rspb.2017.1265. [PMID: 29021172 DOI: 10.1098/rspb.2017.1265] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2017] [Accepted: 09/04/2017] [Indexed: 11/12/2022] Open
Abstract
Genitalia are morphologically variable across many taxa and in physical contact during intromission, but little is known about how variation in form correlates with function during copulation. Marine mammals offer important insights into the evolutionary forces that act on genital morphology because they have diverse genitalia and are adapted to aquatic living and mating. Cetaceans have a fibroelastic penis and muscular vaginal folds, while pinnipeds have a baculum and lack vaginal folds. We examined copulatory fit in naturally deceased marine mammals to identify anatomical landmarks in contact during copulation and the potential depth of penile penetration into the vagina. Excised penises were artificially inflated to erection with pressurized saline and compared with silicone vaginal endocasts and within excised vaginas in simulated copulation using high-resolution, diffusible iodine-based, contrast-enhanced computed tomography. We found evidence suggestive of both congruent and antagonistic genital coevolution, depending on the species. We suggest that sexual selection influences morphological shape. This study improves our understanding of how mechanical interactions during copulation influence the shape of genitalia and affect fertility, and has broad applications to other taxa and species conservation.
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Affiliation(s)
- Dara N Orbach
- Department of Biology, Life Science Center, Dalhousie University, 1355 Oxford Street, Halifax, Nova Scotia, B3H 4R2, Canada .,Department of Biological Sciences, Mount Holyoke College, 50 College Street, South Hadley, MA 01075, USA
| | - Diane A Kelly
- Department of Psychological and Brain Sciences, University of Massachusetts, 135 Hicks Way, Amherst, MA 01003, USA
| | - Mauricio Solano
- Clinical Sciences Department, Tufts University Cummings School of Veterinary Medicine, 200 Westboro Road, North Grafton, MA 01536, USA
| | - Patricia L R Brennan
- Department of Biological Sciences, Mount Holyoke College, 50 College Street, South Hadley, MA 01075, USA
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Orbach DN, Hedrick B, Würsig B, Mesnick SL, Brennan PLR. The evolution of genital shape variation in female cetaceans. Evolution 2017; 72:261-273. [PMID: 29134627 DOI: 10.1111/evo.13395] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2017] [Accepted: 11/05/2017] [Indexed: 12/31/2022]
Abstract
Male genital diversification is likely the result of sexual selection. Female genital diversification may also result from sexual selection, although it is less well studied and understood. Female genitalia are complex among whales, dolphins, and porpoises, especially compared to other vertebrates. The evolutionary factors affecting the diversity of vaginal complexity could include ontogeny, allometry, phylogeny, sexual selection, and natural selection. We quantified shape variation in female genitalia using 2D geometric morphometric analysis, and validated the application of this method to study soft tissues. We explored patterns of variation in the shape of the cervix and vagina of 24 cetacean species (n = 61 specimens), and found that genital shape varies primarily in the relative vaginal length and overall aspect ratio of the reproductive tract. Extensive genital shape variation was partly explained by ontogenetic changes and evolutionary allometry among sexually mature cetaceans, whereas phylogenetic signal, relative testis size, and neonate size were not significantly associated with genital shape. Female genital shape is diverse and evolves rapidly even among closely related species, consistent with predictions of sexual selection models and with findings in invertebrate and vertebrate taxa. Future research exploring genital shape variation in 3D will offer new insights into evolutionary mechanisms because internal vaginal structures are variable and can form complex spirals.
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Affiliation(s)
- Dara N Orbach
- Department of Biology, Dalhousie University, Life Science Center, 1355 Oxford Street, Halifax, NS B3H 4R2, Canada.,Department of Biological Sciences, Mount Holyoke College, Amherst, Massachusetts
| | - Brandon Hedrick
- Department of Biological Sciences, University of Massachusetts-Amherst, Amherst, Massachusetts
| | - Bernd Würsig
- Department of Marine Biology, Texas A&M University at Galveston, Galveston, Texas
| | - Sarah L Mesnick
- Southwest Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, La Jolla, California
| | - Patricia L R Brennan
- Department of Biological Sciences, Mount Holyoke College, Amherst, Massachusetts.,Department of Biological Sciences, University of Massachusetts-Amherst, Amherst, Massachusetts
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Orbach DN, Marshall CD, Mesnick SL, Würsig B. Patterns of cetacean vaginal folds yield insights into functionality. PLoS One 2017; 12:e0175037. [PMID: 28362830 PMCID: PMC5376333 DOI: 10.1371/journal.pone.0175037] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2016] [Accepted: 03/20/2017] [Indexed: 11/18/2022] Open
Abstract
Complex foldings of the vaginal wall are unique to some cetaceans and artiodactyls and are of unknown function(s). The patterns of vaginal length and cumulative vaginal fold length were assessed in relation to body length and to each other in a phylogenetic context to derive insights into functionality. The reproductive tracts of 59 female cetaceans (20 species, 6 families) were dissected. Phylogenetically-controlled reduced major axis regressions were used to establish a scaling trend for the female genitalia of cetaceans. An unparalleled level of vaginal diversity within a mammalian order was found. Vaginal folds varied in number and size across species, and vaginal fold length was positively allometric with body length. Vaginal length was not a significant predictor of vaginal fold length. Functional hypotheses regarding the role of vaginal folds and the potential selection pressures that could lead to evolution of these structures are discussed. Vaginal folds may present physical barriers, which obscure the pathway of seawater and/or sperm travelling through the vagina. This study contributes broad insights to the evolution of reproductive morphology and aquatic adaptations and lays the foundation for future functional morphology analyses.
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Affiliation(s)
- Dara N. Orbach
- Department of Biology, Dalhousie University, Halifax, Nova Scotia, Canada
- Department of Marine Biology, Texas A&M University at Galveston, Galveston, Texas, United States of America
- * E-mail:
| | - Christopher D. Marshall
- Department of Marine Biology, Texas A&M University at Galveston, Galveston, Texas, United States of America
- Department of Wildlife and Fisheries Sciences, Texas A&M University, College Station, Texas, United States of America
| | - Sarah L. Mesnick
- Southwest Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, La Jolla, California, United States of America
| | - Bernd Würsig
- Department of Marine Biology, Texas A&M University at Galveston, Galveston, Texas, United States of America
- Department of Wildlife and Fisheries Sciences, Texas A&M University, College Station, Texas, United States of America
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Katz H, Johansson O. Reproductive Tract Histology in South American Fur Seal Pups ( Arctophoca australis). Anat Rec (Hoboken) 2017; 300:600-613. [DOI: 10.1002/ar.23533] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2016] [Revised: 07/07/2016] [Accepted: 08/03/2016] [Indexed: 11/11/2022]
Affiliation(s)
- Helena Katz
- Facultad de Veterinaria, Área de Histología y Embriología, Universidad de la República; Alberto Lasplaces 1550 Montevideo CP 11600 Uruguay
| | - Olle Johansson
- The Experimental Dermatology Unit, Department of Neuroscience; Karolinska Institute; Stockholm 171 77 Sweden
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