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Kircher BK, McCown MA, Scully DM, Behringer RR, Larina IV. Structural analysis of the female reptile reproductive system by micro-computed tomography and optical coherence tomography†. Biol Reprod 2024; 110:1077-1085. [PMID: 38641547 PMCID: PMC11180613 DOI: 10.1093/biolre/ioae039] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2024] [Revised: 03/05/2024] [Accepted: 03/07/2024] [Indexed: 04/21/2024] Open
Abstract
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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Affiliation(s)
- Bonnie K Kircher
- Department of Genetics, University of Texas MD Anderson Cancer Center, Houston, TX USA
| | - Michaela A McCown
- Department of Integrative Physiology, Baylor College of Medicine, Houston, TX, USA
| | - Deirdre M Scully
- Department of Integrative Physiology, Baylor College of Medicine, Houston, TX, USA
| | - Richard R Behringer
- Department of Genetics, University of Texas MD Anderson Cancer Center, Houston, TX USA
| | - Irina V Larina
- Department of Integrative Physiology, Baylor College of Medicine, Houston, TX, USA
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2
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Clear E, Grant R, Gardiner J, Brassey C. Baculum shape complexity correlates to metrics of post-copulatory sexual selection in Musteloidea. J Morphol 2023; 284:e21572. [PMID: 36806148 PMCID: PMC10952176 DOI: 10.1002/jmor.21572] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2022] [Revised: 02/14/2023] [Accepted: 02/18/2023] [Indexed: 02/22/2023]
Abstract
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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Affiliation(s)
- Emma Clear
- Faculty of Science and EngineeringManchester Metropolitan UniversityManchesterUK
| | - Robyn Grant
- Faculty of Science and EngineeringManchester Metropolitan UniversityManchesterUK
| | - James Gardiner
- Institute of Life Course and Medical SciencesThe University of LiverpoolLiverpoolUK
| | - Charlotte Brassey
- Faculty of Science and EngineeringManchester Metropolitan UniversityManchesterUK
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3
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Shil SK, Zahangir MM, Das BC, Rahman MM, Yadav SK, Kibria MM, Zonaed Siddiki A. Macro and microanatomy of some organs of a juvenile male Ganges River dolphin (Platanista gangetica spp. gangetica). Anat Histol Embryol 2023; 52:180-189. [PMID: 36197312 DOI: 10.1111/ahe.12869] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2022] [Revised: 09/12/2022] [Accepted: 09/18/2022] [Indexed: 11/30/2022]
Abstract
Ganges River dolphins (Platanista gangetica spp. gangetica) are air-breathing, warm-blooded mammals endemic to the Ganges and Karnaphuli rivers of the Indian subcontinent. Nevertheless, very little basic histomorphological research has been conducted on this endangered species. Therefore, this study aimed to describe the morphological features of different organs of P. gangetica. Despite becoming aquatic animals, they showed similarities with terrestrial mammals, such as the pair of lungs and an apical bronchus in the respiratory system, which are pretty standard in ruminants and pigs. However, unlike the terrestrial animal, the tracheobronchial tree was stiffer due to circularly arranged anastomosing plates of the hyaline cartilaginous ring in the trachea, cartilaginous plates in the bronchiole, and thick alveolar septa. The digestive system showed a three-chambered mechanical and glandular stomach similar to the artiodactyles. However, the intestine showed smaller caecum like the monogastric mammal. The urogenital system showed lobulated kidneys, a urinary bladder, a fibroelastic penis with sigmoid flexure, and a long urethral process similar to some terrestrial ruminants. Considering the aquatic environment, all those modifications, unlike terrestrial mammals, are necessary for their adaptation. Thus, this research will broadly help our clinicians and conservationist to take further steps toward disease diagnosis and monitoring of marine health of this endangered species.
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Affiliation(s)
- Subrata Kumar Shil
- Department of Anatomy and Histology, Faculty of Veterinary Medicine, Chittagong Veterinary and Animal Sciences University, Chattogram, Bangladesh
| | - Md Mahiuddin Zahangir
- Department of Fish Biology and Biotechnology, Faculty of Fisheries, Chittagong Veterinary and Animal Sciences University, Chattogram, Bangladesh
| | - Bhajan Chandra Das
- Department of Medicine and Surgery, Faculty of Veterinary Medicine, Chittagong Veterinary and Animal Sciences University, Chattogram, Bangladesh
| | - Mohammad Mahbubur Rahman
- Department of Pathology and Parasitology, Faculty of Veterinary Medicine, Chittagong Veterinary and Animal Sciences University, Chattogram, Bangladesh
| | - Saroj Kumar Yadav
- Department of Medicine and Surgery, Faculty of Veterinary Medicine, Chittagong Veterinary and Animal Sciences University, Chattogram, Bangladesh
| | - Md Manzoorul Kibria
- Halda River Research Laboratory, Department of Zoology, Faculty of Biological Sciences, University of Chittagong, Chattogram, Bangladesh
| | - Amam Zonaed Siddiki
- Department of Pathology and Parasitology, Faculty of Veterinary Medicine, Chittagong Veterinary and Animal Sciences University, Chattogram, Bangladesh
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4
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Abstract
Despite their evolutionary and biomedical importance, studies of the morphology and function of female genitalia have continued to lag behind those of male genitalia. While studying female genitalia can be difficult because of their soft, deformable and internal nature, recent advances in imaging, geometric analyses of shape and mechanical testing have been made, allowing for a much greater understanding of the incredible diversity of form and function of female genitalia. Here we summarize some of these methods, as well as discuss some big questions in the field that are beginning to be examined now, and will continue to benefit from further work, especially a comparative approach. Topics of further research include examination of the morphology of female genitalia in situ, in-depth anatomical work in many more species, studies of the interplay between natural and sexual selection in influencing features of vaginal morphology, how these diverse functions influence the mechanical properties of tissues, and studies of clitoris morphology and function across amniotes. Many other research topics related to female genitalia remain largely unexplored, and we hope that the papers in this issue will continue to inspire further research on female genitalia.
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Affiliation(s)
- Patricia L R Brennan
- Department of Biological Sciences, Mount Holyoke College, South Hadley, MA 01075, USA
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5
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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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6
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Moore BC, Kelly DA, Piva M, Does M, Kim DK, Simoncini M, Leiva PML, Pina CI. Genital anatomy and copulatory interactions in the broad snouted Caiman (Caiman latirostris). Anat Rec (Hoboken) 2021; 305:3075-3087. [PMID: 34236769 DOI: 10.1002/ar.24699] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2021] [Accepted: 03/29/2021] [Indexed: 11/09/2022]
Abstract
The broad snouted caiman is a crocodylian native to South America that is subject to extensive conservation management in both wild and farming environments. Although reproductive behaviors like egg laying and clutch care have been examined in this species, little else is known about their copulatory system. We examined the anatomy of male and female cloacal and genital tissues ex vivo to build hypotheses of their interactions during copulation and the effects of that interaction on insemination. Male phallic glans tissues were artificially inflated to expand into their copulatory state, allowing the examination and quantification of structural changes at the gross and tissue levels. Digital reconstruction of MRI stacks yielded three-dimensional tissue compartment specific glans models of the inflated state. Silicone molds of female cloacae and oviducts in conjunction with dissection and diceCT analysis allowed us to assess internal geometry and infer how male and female features interact in copulo. We observed glans expansion within the female proctodeum would result in a copulatory lock limiting deeper intromission or retraction. Intromission and subsequent creation of the copulatory lock produces extensive clitoral compression, providing a possible mechanism for female assessment of male copulatory performance. Further, glans expansion forms a distal lumen that positions the glans tip in or near the vaginal openings. A coiled, muscular vagina provides a possible mechanism for postcopulatory sexual selection by excluding semen. Together, the complex male-female interaction supports evidence for cryptic selection by female choice, which can act as a driver of genital coevolution.
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Affiliation(s)
- Brandon C Moore
- Department of Biomedical Science, College of Veterinary Medicine, University of Missouri, Columbia, Missouri, USA.,Deartment of Biology, School of Health Sciences, Stephens College, Columbia, Missouri, USA
| | - Diane A Kelly
- Department of Psychological and Brain Sciences, University of Massachusetts, Amherst, Massachusetts, USA
| | - Milan Piva
- Department of Biomedical Science, College of Veterinary Medicine, University of Missouri, Columbia, Missouri, USA
| | - Mark Does
- Department of Biomedical Engineering, Vanderbilt University School of Medicine, Nashville, Tennessee, USA
| | - Dong Kyu Kim
- Department of Biomedical Engineering, Vanderbilt University School of Medicine, Nashville, Tennessee, USA
| | - Melina Simoncini
- CICyTTP (CONICET-Prov. ER-UADER), Proyecto Yacare, FCYT/UADER, Diamante, Entre Ríos, Argentina
| | - Pamela M L Leiva
- CICyTTP (CONICET-Prov. ER-UADER), Proyecto Yacare, FCYT/UADER, Diamante, Entre Ríos, Argentina
| | - Carlos I Pina
- CICyTTP (CONICET-Prov. ER-UADER), Proyecto Yacare, FCYT/UADER, Diamante, Entre Ríos, Argentina
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7
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Matsumura Y, Kovalev A, Gorb SN. Mechanical properties of a female reproductive tract of a beetle and implications for penile penetration. Proc Biol Sci 2021; 288:20211125. [PMID: 34229492 DOI: 10.1098/rspb.2021.1125] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
Coevolution of male and female genitalia is widespread in animals. Nevertheless, few studies have examined the mechanics of genital interactions during mating. We characterized the mechanical properties of the elongated female genitalia, the spermathecal duct, of the small cassidine beetle, Cassida rubiginosa. The data were compared with the mechanical properties of the elongated male genitalia, the flagellum. We analysed the material distributions of the spermathecal duct using a microscopy technique, established a tensile test setup under a light microscope and conducted tensile tests. Diameter and tensile stiffness gradients were present along the spermathecal duct, but its Young's modulus and material distribution were more or less homogeneous. The results confirmed the hypothesis based on numerical simulations that the spermathecal duct is more rigid than the flagellum. In the study species, the penile penetration force is simply applied to the base of the hyper-elongated flagellum and conveyed along the flagellum to its tip. Considering this simple penetration mechanism, the relatively low flexibility of the spermathecal duct, compared to the flagellum, is likely to be essential for effective penetration of the flagellum.
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Affiliation(s)
- Yoko Matsumura
- Department of Functional Morphology and Biomechanics, Zoological Institute, University of Kiel, Am Botanischen Garten 1-9, 24118 Kiel, Germany
| | - Alexander Kovalev
- Department of Functional Morphology and Biomechanics, Zoological Institute, University of Kiel, Am Botanischen Garten 1-9, 24118 Kiel, Germany
| | - Stanislav N Gorb
- Department of Functional Morphology and Biomechanics, Zoological Institute, University of Kiel, Am Botanischen Garten 1-9, 24118 Kiel, Germany
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8
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Brennan PLR, Sterett M, DiBuono M, Lara Granados G, Klo K, Marsden R, Schleinig P, Tanner L, Purdy S. Intra-horn Penile Intromission in the Alpaca Vicugna pacos and Consequences to Genital Morphology. Integr Comp Biol 2021; 61:624-633. [PMID: 33970265 DOI: 10.1093/icb/icab050] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Copulatory behavior and genital morphology interact to deliver sperm more effectively during mating, but the nature of this interaction has not been explored in depth in most vertebrates. Alpacas have unusually long copulations lasting 15-20 min, and a unique copulatory behavior, where the penis intromits all the way past the cervix, into the uterine horns. Here we describe the morphology of male and female genitalia and report unique morphological characteristics that may be associated with this unusual insemination mode. Vaginal shape is highly variable, and seemingly not associated with age or parity. The cranial vagina varies between bulbous and cylindrical, while the caudal vagina is typically narrower and always cylindrical. The cervix consists of a series of two to three spirals or rings, and it is often found in a relaxed state that may prevent damage caused by the cartilaginous penis tip as it pushes through the cervix to reach the uterine horns. The uterus and uterine horns have a complex shape with multiple constrictions. The cartilaginous penis tip has a sharp urethral process that may help to push against these constrictions. The diameter of the vaginal lumen is much greater than the diameter of the penis suggesting that there is little direct interaction between them, and that female vaginal shape is not under strong copulatory selection. In effect, the entire female reproductive tract of the female is interacting with the penis during copulation.
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Affiliation(s)
- Patricia L R Brennan
- Department of Biological Sciences, Mount Holyoke College, South Hadley, MA 01075, USA
| | - Maya Sterett
- Department of Biological Sciences, Mount Holyoke College, South Hadley, MA 01075, USA
| | - Mary DiBuono
- Department of Biological Sciences, Mount Holyoke College, South Hadley, MA 01075, USA
| | - Genesis Lara Granados
- Department of Biological Sciences, Mount Holyoke College, South Hadley, MA 01075, USA
| | - Kay Klo
- Department of Biological Sciences, Mount Holyoke College, South Hadley, MA 01075, USA
| | - Rebecca Marsden
- Department of Biological Sciences, Mount Holyoke College, South Hadley, MA 01075, USA
| | - Pearl Schleinig
- Department of Biological Sciences, Mount Holyoke College, South Hadley, MA 01075, USA
| | - Louise Tanner
- Department of Biological Sciences, Mount Holyoke College, South Hadley, MA 01075, USA
| | - Stephen Purdy
- North American Camelid Studies Program, Nunoa Project, Belchertown, MA 01007, USA
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9
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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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10
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André GI, Firman RC, Simmons LW. Baculum shape and paternity success in house mice: evidence for genital coevolution. Philos Trans R Soc Lond B Biol Sci 2020; 375:20200150. [PMID: 33070728 DOI: 10.1098/rstb.2020.0150] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Sexual selection is believed to be responsible for the rapid divergence of male genitalia, which is a widely observed phenomenon across different taxa. Among mammals, the stimulatory role of male genitalia and female 'sensory perception' has been suggested to explain these evolutionary patterns. Recent research on house mice has shown that baculum (penis bone) shape can respond to experimentally imposed sexual selection. Here, we explore the adaptive value of baculum shape by performing two experiments that examine the effects of male and female genitalia on male reproductive success. Thus, we selected house mice (Mus musculus domesticus) from families characterized by extremes in baculum shape (relative width) and examined paternity success in both non-competitive (monogamous) and competitive (polyandrous) contexts. Our analyses revealed that the relative baculum shape of competing males influenced competitive paternity success, but that this effect was dependent on the breeding value for baculum shape of the family from which females were derived. Our data provide novel insight into the potential mechanisms underlying the evolution of the house mouse baculum and lend support to the stimulatory hypothesis for the coevolution of male and female genitalia. This article is part of the theme issue 'Fifty years of sperm competition'.
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Affiliation(s)
- Goncalo I André
- Centre for Evolutionary Biology, School of Biological Sciences (M092), The University of Western Australia, Crawley, 6009 Western Australia, Australia
| | - Renée C Firman
- Centre for Evolutionary Biology, School of Biological Sciences (M092), The University of Western Australia, Crawley, 6009 Western Australia, Australia
| | - Leigh W Simmons
- Centre for Evolutionary Biology, School of Biological Sciences (M092), The University of Western Australia, Crawley, 6009 Western Australia, Australia
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11
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Brassey CA, Behnsen J, Gardiner JD. Postcopulatory sexual selection and the evolution of shape complexity in the carnivoran baculum. Proc Biol Sci 2020; 287:20201883. [PMID: 33049172 PMCID: PMC7657853 DOI: 10.1098/rspb.2020.1883] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
The baculum is an enigmatic bone within the mammalian glans penis, and the driving forces behind its often bizarre shape have captivated evolutionary biologists for over a century. Hypotheses for the function of the baculum include aiding in intromission, stimulating females and assisting with prolonged mating. Previous attempts to test these hypotheses have focused on the gross size of the baculum and have failed to reach a consensus. We conducted three-dimensional imaging and apply a new method to quantify three-dimensional shape complexity in the carnivoran baculum. We show that socially monogamous species are evolving towards complex-shaped bacula, whereas group-living species are evolving towards simple bacula. Overall three-dimensional baculum shape complexity is not related to relative testes mass, but tip complexity is higher in induced ovulators and species engaging in prolonged copulation. Our study provides evidence of postcopulatory sexual selection pressures driving three-dimensional shape complexity in the carnivore baculum.
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Affiliation(s)
- Charlotte A Brassey
- Department of Natural Sciences, Manchester Metropolitan University, M1 5GD, UK
| | - Julia Behnsen
- Manchester X-ray Imaging Facility, University of Manchester, M13 9PL, UK
| | - James D Gardiner
- Institute of Ageing and Chronic Disease, University of Liverpool, L7 8TX, UK
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12
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André GI, Firman RC, Simmons LW. The coevolution of male and female genitalia in a mammal: A quantitative genetic insight. Evolution 2020; 74:1558-1567. [PMID: 32490547 DOI: 10.1111/evo.14031] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2019] [Revised: 04/10/2020] [Accepted: 05/30/2020] [Indexed: 12/28/2022]
Abstract
Male genitalia are among the most phenotypically diverse morphological traits, and sexual selection is widely accepted as being responsible for their evolutionary divergence. Studies of house mice suggest that the shape of the baculum (penis bone) affects male reproductive fitness and experimentally imposed postmating sexual selection has been shown to drive divergence in baculum shape across generations. Much less is known of the morphology of female genitalia and its coevolution with male genitalia. In light of this, we used a paternal half-sibling design to explore patterns of additive genetic variation and covariation underlying baculum shape and female vaginal tract size in house mice (Mus musculus domesticus). We applied a landmark-based morphometrics approach to measure baculum size and shape in males and the length of the vaginal tract and width of the cervix in females. Our results reveal significant additive genetic variation in house mouse baculum morphology and cervix width, as well as evidence for genetic covariation between male and female genital measures. Our data thereby provide novel insight into the potential for the coevolutionary divergence of male and female genital traits in a mammal.
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Affiliation(s)
- Gonçalo I André
- Centre for Evolutionary Biology, School of Biological Sciences (M092), The University of Western Australia, Crawley, 6009, Australia
| | - Renée C Firman
- Centre for Evolutionary Biology, School of Biological Sciences (M092), The University of Western Australia, Crawley, 6009, Australia
| | - Leigh W Simmons
- Centre for Evolutionary Biology, School of Biological Sciences (M092), The University of Western Australia, Crawley, 6009, Australia
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13
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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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14
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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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15
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Sloan NS, Simmons LW. The evolution of female genitalia. J Evol Biol 2019; 32:882-899. [PMID: 31267594 DOI: 10.1111/jeb.13503] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2019] [Revised: 06/14/2019] [Accepted: 06/21/2019] [Indexed: 02/07/2023]
Abstract
Female genitalia have been largely neglected in studies of genital evolution, perhaps due to the long-standing belief that they are relatively invariable and therefore taxonomically and evolutionarily uninformative in comparison with male genitalia. Contemporary studies of genital evolution have begun to dispute this view, and to demonstrate that female genitalia can be highly diverse and covary with the genitalia of males. Here, we examine evidence for three mechanisms of genital evolution in females: species isolating 'lock-and-key' evolution, cryptic female choice and sexual conflict. Lock-and-key genital evolution has been thought to be relatively unimportant; however, we present cases that show how species isolation may well play a role in the evolution of female genitalia. Much support for female genital evolution via sexual conflict comes from studies of both invertebrate and vertebrate species; however, the effects of sexual conflict can be difficult to distinguish from models of cryptic female choice that focus on putative benefits of choice for females. We offer potential solutions to alleviate this issue. Finally, we offer directions for future studies in order to expand and refine our knowledge surrounding female genital evolution.
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Affiliation(s)
- Nadia S Sloan
- Centre for Evolutionary Biology, School of Biological Sciences (M092), The University of Western Australia, Crawley, Western Australia, Australia
| | - Leigh W Simmons
- Centre for Evolutionary Biology, School of Biological Sciences (M092), The University of Western Australia, Crawley, Western Australia, Australia
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16
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Are hemipenial traits under sexual selection in Tropidurus lizards? Hemipenial development, male and female genital morphology, allometry and coevolution in Tropidurus torquatus (Squamata: Tropiduridae). PLoS One 2019; 14:e0219053. [PMID: 31291313 PMCID: PMC6619691 DOI: 10.1371/journal.pone.0219053] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2018] [Accepted: 06/14/2019] [Indexed: 11/19/2022] Open
Abstract
Male genitalia show considerable morphological variation among animals with internal fertilization and exhibit a high level of evolvability in lizards. Studies have suggested that sexual selection may be driving hemipenial evolution against natural selection and pleiotropy. Given the direct interaction of male and female genitals, coevolution of the aforementioned is posited by several hypotheses of genital evolution. However, there are only a few studies on female genitalia morphology, resulting in a lack of coevolution description and understanding. Studies of allometric patterns have filled some gaps by answering questions about male genital evolution and could prove a powerful tool in clarifying coevolution between male and female genitals. Here, we studied the genital morphology of Tropidurus torquatus. This Tropidurus lizard species is an emerging Neotropical lizard model organism notable for having enlarged hemipenial lobes in contrast with other tropidurid species. In this study, we analyzed hemipenial development in early and late stages, describing both morphological variation and ontogenetic allometric pattern. We used quantitative traits to describe male and female genital morphology, examining their static allometric patterns and correspondence. Our study provides a quantitative discussion on the evolution of lizard genitals, suggesting that sexual selection plays an important role in genital evolution in Tropidurus lizards.
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17
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Simmons LW, Fitzpatrick JL. Female genitalia can evolve more rapidly and divergently than male genitalia. Nat Commun 2019; 10:1312. [PMID: 30899023 PMCID: PMC6428859 DOI: 10.1038/s41467-019-09353-0] [Citation(s) in RCA: 40] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2018] [Accepted: 03/07/2019] [Indexed: 01/02/2023] Open
Abstract
Male genitalia exhibit patterns of divergent evolution driven by sexual selection. In contrast, for many taxonomic groups, female genitalia are relatively uniform and their patterns of evolution remain largely unexplored. Here we quantify variation in the shape of female genitalia across onthophagine dung beetles, and use new comparative methods to contrast their rates of divergence with those of male genitalia. As expected, male genital shape has diverged more rapidly than a naturally selected trait, the foretibia. Remarkably, female genital shape has diverged nearly three times as fast as male genital shape. Our results dispel the notion that female genitalia do not show the same patterns of divergent evolution as male genitalia, and suggest that female genitalia are under sexual selection through their role in female choice. Although male genital shape is known to evolve rapidly in response to sexual selection, relatively little is known about the evolution of female genital shape. Here, the authors show that across onthophagine dung beetles, female genital shape has diverged much more rapidly than male genital shape.
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Affiliation(s)
- Leigh W Simmons
- Centre for Evolutionary Biology, School of Biological Sciences (M092), The University of Western Australia, Crawley, WA, 6009, Australia.
| | - John L Fitzpatrick
- Department of Zoology/Ethology, Stockholm University, Svante Arrhenius väg 18B, SE-10691, Stockholm, Sweden
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18
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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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19
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Wang JY, Liao WB. Digest: Ontogenesis and evolutionary allometry shape divergent evolution of genitalia in female cetaceans. Evolution 2017; 72:404-405. [PMID: 29287128 DOI: 10.1111/evo.13414] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2017] [Accepted: 12/05/2017] [Indexed: 01/03/2023]
Affiliation(s)
- Jia Yu Wang
- Key Laboratory of Southwest China Wildlife Resources Conservation (Ministry of Education), China West Normal University, Nanchong, 637009 Sichuan, China.,Institute of Eco-adaptation in Amphibians and Reptiles, China West Normal University, Nanchong, 637009 Sichuan, China
| | - Wen Bo Liao
- Key Laboratory of Southwest China Wildlife Resources Conservation (Ministry of Education), China West Normal University, Nanchong, 637009 Sichuan, China.,Institute of Eco-adaptation in Amphibians and Reptiles, China West Normal University, Nanchong, 637009 Sichuan, China
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