1
|
Milnes MR, Robinson CD, Foley AP, Stepp C, Hale MD, John-Alder HB, Cox RM. Effects of testosterone on urogenital tract morphology and androgen receptor expression in immature Eastern Fence lizards (Sceloporus undulatus). Gen Comp Endocrinol 2024; 346:114418. [PMID: 38036014 DOI: 10.1016/j.ygcen.2023.114418] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/13/2023] [Revised: 11/14/2023] [Accepted: 11/26/2023] [Indexed: 12/02/2023]
Abstract
In non-avian reptiles, the onset of sexual dimorphism of the major structures of the urogenital tract varies temporally relative to gonadal differentiation, more so than in other amniote lineages. In the current study, we used tonic-release implants to investigate the effects of exogenous testosterone (T) on postnatal development of the urogenital tract in juvenile Eastern Fence Lizards (Sceloporus undulatus) to better understand the mechanisms underlying the ontogeny of sexual differentiation in reptiles. We examined gonads, mesonephric kidneys and ducts (male reproductive tract primordia), paramesonephric ducts (oviduct primordia), sexual segments of the kidneys (SSKs), and hemiphalluses to determine which structures were sexually dimorphic independent of T treatment and which structures exhibited sexually dimorphic responses to T. To better understand tissue-level responsiveness to T treatment, we also characterized androgen receptor (AR) expression by immunohistochemistry. At approximately 4 months after hatching in control animals, gonads were well differentiated but quiescent; paramesonephric ducts had fully degenerated in males; mesonephric kidneys, mesonephric ducts, and SSKs remained sexually undifferentiated; and hemiphalluses could not be everted in either sex. Exogenous T caused enlargement, regionalization, and secretory activity of the mesonephric ducts and SSKs in both sexes; enlargement and regionalization of the oviducts in females; and enlargement of male hemipenes. The most responsive tissues exhibited moderate but diffuse staining for AR in control lizards and intense nuclear staining in T-treated lizards, suggestive of autoregulation of AR. The similarity between sexes in the responsiveness of the mesonephric ducts and SSK to T indicates an absence of sexually dimorphic organizational effects in these structures prior to treatment, which was initiated approximately 2 months after hatching. In contrast, the sex-specific responses in oviducts and hemipenes indicate that significant organization and/or differentiation had taken place prior to treatment.
Collapse
Affiliation(s)
- Matthew R Milnes
- Department of Biological and Environmental Sciences, Georgia College and State University, Milledgeville, GA 31061, USA.
| | | | - Alexis P Foley
- Department of Biological and Environmental Sciences, Georgia College and State University, Milledgeville, GA 31061, USA.
| | - Charleigh Stepp
- Department of Biological and Environmental Sciences, Georgia College and State University, Milledgeville, GA 31061, USA.
| | - Matthew D Hale
- Department of Biology, University of Virginia, Charlottesville, VA 22904, USA.
| | - Henry B John-Alder
- Department of Ecology, Evolution, and Natural Resources, Rutgers University, New Brunswick, NJ 08901, USA.
| | - Robert M Cox
- Department of Biology, University of Virginia, Charlottesville, VA 22904, USA.
| |
Collapse
|
2
|
Suárez-Varón G, Mendoza-Cruz E, Acosta A, Villagrán-Santa Cruz M, Cortez D, Hernández-Gallegos O. Genetic determination and JARID2 over-expression in a thermal incubation experiment in Casque-Headed Lizard. PLoS One 2022; 17:e0263804. [PMID: 35797377 PMCID: PMC9262179 DOI: 10.1371/journal.pone.0263804] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2022] [Accepted: 06/16/2022] [Indexed: 11/19/2022] Open
Abstract
Non-avian reptiles, unlike mammals and birds, have undergone numerous sex determination changes. Casque-Headed Lizards have replaced the ancestral XY system shared across pleurodonts with a new pair of XY chromosomes. However, the evolutionary forces that triggered this transition have remained unclear. An interesting hypothesis suggests that species with intermediate states, with sex chromosomes but also thermal-induced sex reversal at specific incubation temperatures, could be more susceptible to sex determination turnovers. We contrasted genotypic data (presence/absence of the Y chromosome) against the histology of gonads of embryos from stages 35–37 incubated at various temperatures, including typical male-producing (26°C) and female-producing (32°C) temperatures. Our work apparently reports for the first time the histology of gonads, including morphological changes, from stages 35–37 of development in the family Corytophanidae. We also observed that all embryos developed hemipenes, suggesting sex-linked developmental heterochrony. We observed perfect concordance between genotype and phenotype at all temperatures. However, analysis of transcriptomic data from embryos incubated at 26°C and 32°C identified transcript variants of the chromatin modifiers JARID2 and KDM6B that have been linked to temperature-dependent sex determination in other reptiles. Our work tested the validity of a mixed sex determination system in the family Corytophanidae. We found that XY chromosomes are dominant; however, our work supports the hypothesis of a conserved transcriptional response to incubation temperatures across non-avian reptiles that could be a reminiscence of an ancestral sex determination system.
Collapse
Affiliation(s)
- Gabriel Suárez-Varón
- Laboratorio de Herpetología, Facultad de Ciencias, Universidad Autónoma del Estado de México, Instituto Literario # 100 Centro, Toluca, Estado de México, México
| | - Eva Mendoza-Cruz
- Laboratorio de Biología Tisular y Reproductora, Departamento de Biología Comparada, Facultad de Ciencias, Universidad Nacional Autónoma de México, Ciudad de México, México
| | | | - Maricela Villagrán-Santa Cruz
- Laboratorio de Biología Tisular y Reproductora, Departamento de Biología Comparada, Facultad de Ciencias, Universidad Nacional Autónoma de México, Ciudad de México, México
| | - Diego Cortez
- Centro de Ciencias Genómicas, UNAM, Cuernavaca, México
- * E-mail:
| | - Oswaldo Hernández-Gallegos
- Laboratorio de Herpetología, Facultad de Ciencias, Universidad Autónoma del Estado de México, Instituto Literario # 100 Centro, Toluca, Estado de México, México
| |
Collapse
|
3
|
Folwell M, Sanders K, Crowe-Riddell J. The Squamate Clitoris: A Review and Directions for Future Research. Integr Comp Biol 2022; 62:icac056. [PMID: 35662336 DOI: 10.1093/icb/icac056] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The clitoris is a part of the genitalia of female amniotes that typically functions to stimulate sensory arousal. It usually consists of a small organ that is dimorphic and homologous to the penis. The developing amniote embryo forms a genital tubule, then sex hormones initiate a developmental cascade to form either a penis or clitoris. In squamates (lizards and snakes) the genital tubule develops into a paired hemiphallus structure called the "hemiclitores" in the female and the "hemipenes" in the male. The complex evolution of squamate hemipenes has been extensively researched since early discoveries in the 1800's, and this has uncovered huge diversity in hemipenis size, shape, and ornamentation (e.g., protrusions of spines, hooks, chalices, cups). In contrast, the squamate hemiclitoris has been conspicuously under investigated, and the studies that describe this anatomy are fraught with inconsistences. This paper aims to clarify the current state of knowledge of the squamate hemiclitoris, providing a foundation for further research on its morphology and functional role. We show that while several studies have described the gross anatomy of hemiclitores in lizards, comparative information is entirely lacking for snakes. Several papers cite earlier authors as having reported discoveries of the snake hemiclitores in vipers and colubrid snakes. However, our examination of this reveals only erroneous reports of hemiclitores in snakes and shows that these stem from misinterpretations of the true anatomy or species involved. An especially problematic source of confusion is the presence of intersex individuals in some snake populations; these form reproductively functional ovaries and a single hemipenis, with the latter sometimes mistaken for a hemiclitoris (the intersex hemipenis is usually smaller and less spinous than the male hemipenis). Further research is recommended to identify the defining anatomical features of the squamate hemiclitores. Such studies will form a vital basis of future comparative analyses of variation in female genitalia in squamates and other amniotes.
Collapse
Affiliation(s)
- Megan Folwell
- The University of Adelaide, Faculty of Biological Science
| | - Kate Sanders
- University of Adelaide, Faculty of Biological Science
| | | |
Collapse
|
4
|
Whiteley SL, Georges A, Weisbecker V, Schwanz LE, Holleley CE. Ovotestes suggest cryptic genetic influence in a reptile model for temperature-dependent sex determination. Proc Biol Sci 2021; 288:20202819. [PMID: 33467998 DOI: 10.1098/rspb.2020.2819] [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: 01/02/2023] Open
Abstract
Sex determination and differentiation in reptiles is complex. Temperature-dependent sex determination (TSD), genetic sex determination (GSD) and the interaction of both environmental and genetic cues (sex reversal) can drive the development of sexual phenotypes. The jacky dragon (Amphibolurus muricatus) is an attractive model species for the study of gene-environment interactions because it displays a form of Type II TSD, where female-biased sex ratios are observed at extreme incubation temperatures and approximately 50 : 50 sex ratios occur at intermediate temperatures. This response to temperature has been proposed to occur due to underlying sex determining loci, the influence of which is overridden at extreme temperatures. Thus, sex reversal at extreme temperatures is predicted to produce the female-biased sex ratios observed in A. muricatus. The occurrence of ovotestes during development is a cellular marker of temperature sex reversal in a closely related species Pogona vitticeps. Here, we present the first developmental data for A. muricatus, and show that ovotestes occur at frequencies consistent with a mode of sex determination that is intermediate between GSD and TSD. This is the first evidence suggestive of underlying unidentified sex determining loci in a species that has long been used as a model for TSD.
Collapse
Affiliation(s)
- Sarah L Whiteley
- Institute for Applied Ecology, University of Canberra, Canberra, Australia.,Australian National Wildlife Collection, CSIRO, Canberra, Australia
| | - Arthur Georges
- Institute for Applied Ecology, University of Canberra, Canberra, Australia
| | - Vera Weisbecker
- College of Science and Engineering, Flinders University, Adelaide, Australia
| | - Lisa E Schwanz
- Evolution and Ecology Research Centre, School of Biological, Earth and Environmental Sciences, UNSW, Sydney, Australia
| | - Clare E Holleley
- Australian National Wildlife Collection, CSIRO, Canberra, Australia
| |
Collapse
|
5
|
Van Dyke JU, Thompson MB, Burridge CP, Castelli MA, Clulow S, Dissanayake DSB, Dong CM, Doody JS, Edwards DL, Ezaz T, Friesen CR, Gardner MG, Georges A, Higgie M, Hill PL, Holleley CE, Hoops D, Hoskin CJ, Merry DL, Riley JL, Wapstra E, While GM, Whiteley SL, Whiting MJ, Zozaya SM, Whittington CM. Australian lizards are outstanding models for reproductive biology research. AUST J ZOOL 2020. [DOI: 10.1071/zo21017] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Australian lizards are a diverse group distributed across the continent and inhabiting a wide range of environments. Together, they exhibit a remarkable diversity of reproductive morphologies, physiologies, and behaviours that is broadly representative of vertebrates in general. Many reproductive traits exhibited by Australian lizards have evolved independently in multiple lizard lineages, including sociality, complex signalling and mating systems, viviparity, and temperature-dependent sex determination. Australian lizards are thus outstanding model organisms for testing hypotheses about how reproductive traits function and evolve, and they provide an important basis of comparison with other animals that exhibit similar traits. We review how research on Australian lizard reproduction has contributed to answering broader evolutionary and ecological questions that apply to animals in general. We focus on reproductive traits, processes, and strategies that are important areas of current research, including behaviours and signalling involved in courtship; mechanisms involved in mating, egg production, and sperm competition; nesting and gestation; sex determination; and finally, birth in viviparous species. We use our review to identify important questions that emerge from an understanding of this body of research when considered holistically. Finally, we identify additional research questions within each topic that Australian lizards are well suited for reproductive biologists to address.
Collapse
|
6
|
Griffing AH, Sanger TJ, Daza JD, Nielsen SV, Pinto BJ, Stanley EL, Gamble T. Embryonic development of a parthenogenetic vertebrate, the mourning gecko (
Lepidodactylus lugubris
). Dev Dyn 2019; 248:1070-1090. [DOI: 10.1002/dvdy.72] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2019] [Revised: 06/10/2019] [Accepted: 06/11/2019] [Indexed: 12/11/2022] Open
Affiliation(s)
- Aaron H. Griffing
- Department of Biological SciencesMarquette University Milwaukee Wisconsin
| | - Thomas J. Sanger
- Department of BiologyLoyola University in Chicago Chicago Illinois
| | - Juan D. Daza
- Department of Biological SciencesSam Houston State University Huntsville Texas
| | - Stuart V. Nielsen
- Department of HerpetologyFlorida Museum of Natural History Gainesville Florida
| | - Brendan J. Pinto
- Department of Biological SciencesMarquette University Milwaukee Wisconsin
| | - Edward L. Stanley
- Department of HerpetologyFlorida Museum of Natural History Gainesville Florida
| | - Tony Gamble
- Department of Biological SciencesMarquette University Milwaukee Wisconsin
- Milwaukee Public Museum Milwaukee Wisconsin
- Bell Museum of Natural HistoryUniversity of Minnesota Saint Paul Minnesota
| |
Collapse
|
7
|
Delssin AR, Sandoval MT, Ortiz MA, Alvarez BB. Development and differentiation of the reproductive system of Tropidurus catalanensis (Squamata: Tropiduridae). J Morphol 2019; 280:244-258. [PMID: 30653714 DOI: 10.1002/jmor.20940] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2018] [Revised: 11/06/2018] [Accepted: 12/10/2018] [Indexed: 01/13/2023]
Abstract
Development and differentiation of the reproductive system in lizards begin in the embryonic period, although the stage and time of their occurrence vary according to populations and species. In this study, the events of the development and differentiation of the reproductive system of males and females of Tropidurus catalanensis were characterized during the embryonic, neonatal, and juvenile periods. Embryos at Stages 27, 34, 37, 40, and 41, neonates and juveniles, from Corrientes, Argentina, were analyzed. At Stage 27, the genital ridge was not observed but primordial germ cells were recorded in the yolk sac as well as the mesenteric mesenchyme, indicating the beginning of germ cell migration. Gonadal differentiation commenced at Stage 34. In males from Stage 37, the testes possessed seminiferous cords with Sertoli cells and spermatogonia, while in hatchlings seminiferous tubules and interstitial tissue with mature Leydig cells were present. Spermatogenesis was observed in a specimen of 51.9 mm snout-vent length, corresponding to the minimum reproductive size. In females, from Stage 37 until hatching, the ovaries had a cavernous medulla and a cortex with somatic cells and abundant oogonia. The onset of meiosis and folliculogenesis occurred in the juvenile period.
Collapse
Affiliation(s)
- Andrea Raquel Delssin
- Departamento de Biología, Facultad de Ciencias Exactas y Naturales y Agrimensura, Universidad Nacional del Nordeste, Embriología Animal. Av. Libertad 5470, CP 3400, Corrientes, Argentina.,Universidad Nacional del Nordeste-Consejo Nacional de Investigaciones Científicas y Tecnológicas (UNNE-CONICET), FaCENA (CP 3400), Corrientes, Argentina
| | - María Teresa Sandoval
- Departamento de Biología, Facultad de Ciencias Exactas y Naturales y Agrimensura, Universidad Nacional del Nordeste, Embriología Animal. Av. Libertad 5470, CP 3400, Corrientes, Argentina
| | - Martin Alejandro Ortiz
- Departamento de Biología, Facultad de Ciencias Exactas y Naturales y Agrimensura, Universidad Nacional del Nordeste, Embriología Animal. Av. Libertad 5470, CP 3400, Corrientes, Argentina.,Universidad Nacional del Nordeste-Consejo Nacional de Investigaciones Científicas y Tecnológicas (UNNE-CONICET), FaCENA (CP 3400), Corrientes, Argentina
| | - Blanca Beatriz Alvarez
- Departamento de Biología, Facultad de Ciencias Exactas y Naturales y Agrimensura, Universidad Nacional del Nordeste, Embriología Animal. Av. Libertad 5470, CP 3400, Corrientes, Argentina
| |
Collapse
|
8
|
Developmental asynchrony and antagonism of sex determination pathways in a lizard with temperature-induced sex reversal. Sci Rep 2018; 8:14892. [PMID: 30291276 PMCID: PMC6173690 DOI: 10.1038/s41598-018-33170-y] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2018] [Accepted: 09/19/2018] [Indexed: 12/22/2022] Open
Abstract
Vertebrate sex differentiation follows a conserved suite of developmental events: the bipotential gonads differentiate and shortly thereafter sex specific traits become dimorphic. However, this may not apply to squamates, a diverse vertebrate lineage comprising of many species with thermosensitive sexual development. Of the three species with data on the relative timing of gonad differentiation and genital dimorphism, the females of two (Niveoscincus ocellatus and Barisia imbricata) exhibit a phase of temporary pseudohermaphroditism or TPH (gonads have differentiated well before genital dimorphism). We report a third example of TPH in Pogona vitticeps, an agamid with temperature-induced male to female sex reversal. These findings suggest that for female squamates, genital and gonad development may not be closely synchronised, so that TPH may be common. We further observed a high frequency of ovotestes, a usually rare gonadal phenotype characterised by a mix of male and female structures, exclusively associated with temperature-induced sex reversal. We propose that ovotestes are evidence of a period of antagonism between male and female sex-determining pathways during sex reversal. Female sexual development in squamates is considerably more complex than has been appreciated, providing numerous avenues for future exploration of the genetic and hormonal cues that govern sexual development.
Collapse
|
9
|
Ollonen J, Da Silva FO, Mahlow K, Di-Poï N. Skull Development, Ossification Pattern, and Adult Shape in the Emerging Lizard Model Organism Pogona vitticeps: A Comparative Analysis With Other Squamates. Front Physiol 2018; 9:278. [PMID: 29643813 PMCID: PMC5882870 DOI: 10.3389/fphys.2018.00278] [Citation(s) in RCA: 47] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2018] [Accepted: 03/08/2018] [Indexed: 12/02/2022] Open
Abstract
The rise of the Evo-Devo field and the development of multidisciplinary research tools at various levels of biological organization have led to a growing interest in researching for new non-model organisms. Squamates (lizards and snakes) are particularly important for understanding fundamental questions about the evolution of vertebrates because of their high diversity and evolutionary innovations and adaptations that portrait a striking body plan change that reached its extreme in snakes. Yet, little is known about the intricate connection between phenotype and genotype in squamates, partly due to limited developmental knowledge and incomplete characterization of embryonic development. Surprisingly, squamate models have received limited attention in comparative developmental studies, and only a few species examined so far can be considered as representative and appropriate model organism for mechanistic Evo-Devo studies. Fortunately, the agamid lizard Pogona vitticeps (central bearded dragon) is one of the most popular, domesticated reptile species with both a well-established history in captivity and key advantages for research, thus forming an ideal laboratory model system and justifying his recent use in reptile biology research. We first report here the complete post-oviposition embryonic development for P. vitticeps based on standardized staging systems and external morphological characters previously defined for squamates. Whereas the overall morphological development follows the general trends observed in other squamates, our comparisons indicate major differences in the developmental sequence of several tissues, including early craniofacial characters. Detailed analysis of both embryonic skull development and adult skull shape, using a comparative approach integrating CT-scans and gene expression studies in P. vitticeps as well as comparative embryology and 3D geometric morphometrics in a large dataset of lizards and snakes, highlights the extreme adult skull shape of P. vitticeps and further indicates that heterochrony has played a key role in the early development and ossification of squamate skull bones. Such detailed studies of embryonic character development, craniofacial patterning, and bone formation are essential for the establishment of well-selected squamate species as Evo-Devo model organisms. We expect that P. vitticeps will continue to emerge as a new attractive model organism for understanding developmental and molecular processes underlying tissue formation, morphology, and evolution.
Collapse
Affiliation(s)
- Joni Ollonen
- Program in Developmental Biology, Institute of Biotechnology, University of Helsinki, Helsinki, Finland
| | - Filipe O. Da Silva
- Program in Developmental Biology, Institute of Biotechnology, University of Helsinki, Helsinki, Finland
| | - Kristin Mahlow
- Museum für Naturkunde, Leibniz Institute for Evolution and Biodiversity Science, Berlin, Germany
| | - Nicolas Di-Poï
- Program in Developmental Biology, Institute of Biotechnology, University of Helsinki, Helsinki, Finland
| |
Collapse
|
10
|
Whiteley SL, Holleley CE, Ruscoe WA, Castelli M, Whitehead DL, Lei J, Georges A, Weisbecker V. Sex determination mode does not affect body or genital development of the central bearded dragon ( Pogona vitticeps). EvoDevo 2017; 8:25. [PMID: 29225770 PMCID: PMC5716226 DOI: 10.1186/s13227-017-0087-5] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2017] [Accepted: 11/21/2017] [Indexed: 11/10/2022] Open
Abstract
Background The development of male- or female-specific phenotypes in squamates is typically controlled by either temperature-dependent sex determination (TSD) or chromosome-based genetic sex determination (GSD). However, while sex determination is a major switch in individual phenotypic development, it is unknownhow evolutionary transitions between GSD and TSD might impact on the evolution of squamate phenotypes, particularly the fast-evolving and diverse genitalia. Here, we take the unique opportunity of studying the impact of both sex determination mechanisms on the embryological development of the central bearded dragon (Pogona vitticeps). This is possible because of the transitional sex determination system of this species, in which genetically male individuals reverse sex at high incubation temperatures. This can trigger the evolutionary transition of GSD to TSD in a single generation, making P. vitticeps an ideal model organism for comparing the effects of both sex determination processes in the same species. Results We conducted four incubation experiments on 265 P. vitticeps eggs, covering two temperature regimes ("normal" at 28 °C and "sex reversing" at 36 °C) and the two maternal sexual genotypes (concordant ZW females or sex-reversed ZZ females). From this, we provide the first detailed staging system for the species, with a focus on genital and limb development. This was augmented by a new sex chromosome identification methodology for P. vitticeps that is non-destructive to the embryo. We found a strong correlation between embryo age and embryo stage. Aside from faster growth in 36 °C treatments, body and external genital development was entirely unperturbed by temperature, sex reversal or maternal sexual genotype. Unexpectedly, all females developed hemipenes (the genital phenotype of adult male P. vitticeps), which regress close to hatching. Conclusions The tight correlation between embryo age and embryo stage allows the precise targeting of specific developmental periods in the emerging field of molecular research on P. vitticeps. The stability of genital development in all treatments suggests that the two sex-determining mechanisms have little impact on genital evolution, despite their known role in triggering genital development. Hemipenis retention in developing female P. vitticeps, together with frequent occurrences of hemipenis-like structures during development in other squamate species, raises the possibility of a bias towards hemipenis formation in the ancestral developmental programme for squamate genitalia.
Collapse
Affiliation(s)
- Sarah L Whiteley
- School of Biological Sciences, University of Queensland, Brisbane, QLD Australia.,Australian National Wildlife Collection, National Research Collections Australia, CSIRO, Canberra, ACT Australia.,Institute for Applied Ecology, University of Canberra, Canberra, ACT Australia
| | - Clare E Holleley
- Australian National Wildlife Collection, National Research Collections Australia, CSIRO, Canberra, ACT Australia.,Institute for Applied Ecology, University of Canberra, Canberra, ACT Australia
| | - Wendy A Ruscoe
- Institute for Applied Ecology, University of Canberra, Canberra, ACT Australia
| | - Meghan Castelli
- Australian National Wildlife Collection, National Research Collections Australia, CSIRO, Canberra, ACT Australia.,Institute for Applied Ecology, University of Canberra, Canberra, ACT Australia
| | - Darryl L Whitehead
- School of Biomedical Science, University of Queensland, Brisbane, QLD Australia
| | - Juan Lei
- School of Biological Sciences, University of Queensland, Brisbane, QLD Australia
| | - Arthur Georges
- Institute for Applied Ecology, University of Canberra, Canberra, ACT Australia
| | - Vera Weisbecker
- School of Biological Sciences, University of Queensland, Brisbane, QLD Australia
| |
Collapse
|