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Makanya AN, Jimoh SA, Maina JN. Methods of In Ovo and Ex Ovo Ostrich Embryo Culture with Observations on the Development and Maturation of the Chorioallantoic Membrane. MICROSCOPY AND MICROANALYSIS : THE OFFICIAL JOURNAL OF MICROSCOPY SOCIETY OF AMERICA, MICROBEAM ANALYSIS SOCIETY, MICROSCOPICAL SOCIETY OF CANADA 2023; 29:1523-1530. [PMID: 37488818 DOI: 10.1093/micmic/ozad060] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/13/2022] [Revised: 03/07/2023] [Accepted: 05/08/2023] [Indexed: 07/26/2023]
Abstract
Culture of shell-free and windowed eggs for drug testing and other experiments has been perfected for smaller eggs such as those of chickens, where the developing blood vessels of the chorioallantoic membrane (CAM) become accessible for manipulative studies. However, due to the thickness and hardness of the ostrich egg shell, such techniques are not applicable. Using a tork craft mini rotary and a drill bit, we established windowed egg, in-shell-membrane windowed egg, and in-shell-membrane shell-free methods in the ostrich egg, depending on whether the shell membranes were retained or not. Concomitant study of the developing CAM revealed that at embryonic day 16 (E16), the three layers of the CAM were clearly delineated and at E25, the chorionic capillaries had fused with the epithelium while the CAM at E37 had reached maturity and the chorion and the allantois were both 3-4 times thicker and villous cavity (VC) and capillary-covering cells were well delineated. Both intussusceptive and sprouting angiogenesis were found to be the predominant modes of vascular growth in the ostrich CAM. Development and maturation of the ostrich CAM are similar to those of the well-studied chicken egg, albeit its incubation time being twice in duration.
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Affiliation(s)
- Andrew N Makanya
- Department of Vet Anatomy & Physiology, University of Nairobi, Riverside Drive, Chiromo Campus, Box 30197-00100, Nairobi, Kenya
- Department of Zoology, University of Johannesburg, P.O. Box 524, Auckland Park 2006, Johannesburg, South Africa
| | - Sikiru A Jimoh
- Department of Human Biology, Walter Sisulu University, Nelson Mandela Drive, Private Bag X1, UNITRA 5117, Mthatha, Eastern Cape, South Africa
| | - John N Maina
- Department of Zoology, University of Johannesburg, P.O. Box 524, Auckland Park 2006, Johannesburg, South Africa
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Hechenleitner EM, Fernandez Blanco MV, Núñez-Campero SR, Fiorelli LE, Bona P. Unexpected morphological variability in the eggshells of the South American caimans Caiman latirostris and Caiman yacare. Sci Rep 2023; 13:4894. [PMID: 36966165 PMCID: PMC10039913 DOI: 10.1038/s41598-023-31837-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2023] [Accepted: 03/17/2023] [Indexed: 03/27/2023] Open
Abstract
Eggshell morphology is a valuable indicator of the local conditions within the nests of modern crocodilians and birds. In contrast to these latter, the anatomical structure of the eggshells of most crocodilian species is practically unknown. Here, we provide the first characterization of crocodilian eggshells, using x-ray micro-CT scans. We studied eggshells of Caiman latirostris and Caiman yacare from various developmental stages that coincide with the beginning of embryonic ossification. The new 3D renderings revealed complex ornamentation, unique among crocodilians, and amphora-shaped pore canals, some of which converge in single pore openings. We also documented a high density of pore canals with a gas diffusion capacity 45 times higher than the average predicted for modern avian eggshells. The external ornamentation and the thickness of the compact layer of the eggshells (i.e. excluding ornamentation) showed ontogenetic and interspecific differences that could be related to nesting materials and nesting areas selected by each species. The shell features described here evidence a greater structural complexity than previously recognized in phylogenetically close, sympatric crocodilian species. Further comprehensive morphological analyses on other modern and fossil crocodilian eggshells using micro-CT technology will shed new light on the evolution of reproductive strategies in this intriguing archosaur clade.
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Affiliation(s)
- E Martín Hechenleitner
- Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Godoy Cruz 2290, C1425FQB, CABA, Argentina.
- Centro Regional de Investigaciones Científicas y Transferencia Tecnológica de La Rioja (CRILAR), Provincia de La Rioja, UNLaR, SEGEMAR, UNCa, CONICET, Entre Ríos y Mendoza S/N, 5301, Anillaco, La Rioja, Argentina.
- Instituto de Biología de La Conservación y Paleobiología (IBICOPA) DACEFyN-UNLaR, Av. Gob. Vernet y Apóstol Felipe, 5300, La Rioja, Argentina.
| | - María V Fernandez Blanco
- Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Godoy Cruz 2290, C1425FQB, CABA, Argentina.
- División Paleontología Vertebrados, Anexo II Laboratorios del Museo de La Plata, Facultad de Ciencias Naturales y Museo, Universidad Nacional de La Plata, Calles 122 y 60, B1900FWA, La Plata, Buenos Aires, Argentina.
| | - Segundo R Núñez-Campero
- Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Godoy Cruz 2290, C1425FQB, CABA, Argentina
- Centro Regional de Investigaciones Científicas y Transferencia Tecnológica de La Rioja (CRILAR), Provincia de La Rioja, UNLaR, SEGEMAR, UNCa, CONICET, Entre Ríos y Mendoza S/N, 5301, Anillaco, La Rioja, Argentina
- Instituto de Biología de La Conservación y Paleobiología (IBICOPA) DACEFyN-UNLaR, Av. Gob. Vernet y Apóstol Felipe, 5300, La Rioja, Argentina
| | - Lucas E Fiorelli
- Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Godoy Cruz 2290, C1425FQB, CABA, Argentina
- Centro Regional de Investigaciones Científicas y Transferencia Tecnológica de La Rioja (CRILAR), Provincia de La Rioja, UNLaR, SEGEMAR, UNCa, CONICET, Entre Ríos y Mendoza S/N, 5301, Anillaco, La Rioja, Argentina
| | - Paula Bona
- Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Godoy Cruz 2290, C1425FQB, CABA, Argentina
- División Paleontología Vertebrados, Anexo II Laboratorios del Museo de La Plata, Facultad de Ciencias Naturales y Museo, Universidad Nacional de La Plata, Calles 122 y 60, B1900FWA, La Plata, Buenos Aires, Argentina
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Starck JM, Stewart JR, Blackburn DG. Phylogeny and evolutionary history of the amniote egg. J Morphol 2021; 282:1080-1122. [PMID: 33991358 DOI: 10.1002/jmor.21380] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2020] [Revised: 05/07/2021] [Accepted: 05/12/2021] [Indexed: 01/02/2023]
Abstract
We review morphological features of the amniote egg and embryos in a comparative phylogenetic framework, including all major clades of extant vertebrates. We discuss 40 characters that are relevant for an analysis of the evolutionary history of the vertebrate egg. Special attention is given to the morphology of the cellular yolk sac, the eggshell, and extraembryonic membranes. Many features that are typically assigned to amniotes, such as a large yolk sac, delayed egg deposition, and terrestrial reproduction have evolved independently and convergently in numerous clades of vertebrates. We use phylogenetic character mapping and ancestral character state reconstruction as tools to recognize sequence, order, and patterns of morphological evolution and deduce a hypothesis of the evolutionary history of the amniote egg. Besides amnion and chorioallantois, amniotes ancestrally possess copulatory organs (secondarily reduced in most birds), internal fertilization, and delayed deposition of eggs that contain an embryo in the primitive streak or early somite stage. Except for the amnion, chorioallantois, and amniote type of eggshell, these features evolved convergently in almost all major clades of aquatic vertebrates possibly in response to selective factors such as egg predation, hostile environmental conditions for egg development, or to adjust hatching of young to favorable season. A functionally important feature of the amnion membrane is its myogenic contractility that moves the (early) embryo and prevents adhering of the growing embryo to extraembryonic materials. This function of the amnion membrane and the liquid-filled amnion cavity may have evolved under the requirements of delayed deposition of eggs that contain developing embryos. The chorioallantois is a temporary embryonic exchange organ that supports embryonic development. A possible evolutionary scenario is that the amniote egg presents an exaptation that paved the evolutionary pathway for reproduction on land. As shown by numerous examples from anamniotes, reproduction on land has occurred multiple times among vertebrates-the amniote egg presenting one "solution" that enabled the conquest of land for reproduction.
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Affiliation(s)
- J Matthias Starck
- Department of Biology, Ludwig-Maximilians-University Munich, Planegg-Martinsried, Germany
| | - James R Stewart
- Department of Biology, Ludwig-Maximilians-University Munich, Planegg-Martinsried, Germany.,Department of Biological Sciences, East Tennessee State University, Johnson City, Tennessee, USA
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Legendre LJ, Clarke JA. Shifts in eggshell thickness are related to changes in locomotor ecology in dinosaurs. Evolution 2021; 75:1415-1430. [PMID: 33913155 DOI: 10.1111/evo.14245] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2020] [Revised: 03/13/2021] [Accepted: 04/21/2021] [Indexed: 12/16/2022]
Abstract
Birds share an array of unique characteristics among extant land vertebrates. Among these, external and microstructural characteristics of extant bird eggs have been linked to changes in reproductive strategy that arose among non-avian theropod dinosaurs. More recently, differences in egg proportions recovered in crown birds relative to other dinosaurs were suggested as possibly linked to avian flight, but dense sampling close to its proposed origin was lacking. Here we assess the evolution of eggshell thickness in a targeted sample of 114 dinosaurs including birds, and test the relationship of eggshell thickness with potential life history correlates and locomotor mode using phylogenetic comparative methods. Only egg mass and flight are identified as significant predictors of eggshell thickness. While a high correlation between egg mass and eggshell thickness is expected, that relationship is much stronger in flying taxa, which show a significantly higher slope and lower residual variance than flightless species. This suggests stabilizing selection of eggshell thickness among theropods, as recovered for other traits in extant birds (e.g. genome size, metabolic rate). Within living birds, Eufalconimorphae present an apomorphic increase in relative eggshell thickness which remains unexplained, as few morphological synapomorphies of this clade have been identified.
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Affiliation(s)
- Lucas J Legendre
- Department of Geological Sciences, University of Texas at Austin, Austin, TX, USA
| | - Julia A Clarke
- Department of Geological Sciences, University of Texas at Austin, Austin, TX, USA
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Vieco‐Galvez D, Castro I, Morel PCH, Chua WH, Loh M. The eggshell structure in apteryx; form, function, and adaptation. Ecol Evol 2021; 11:3184-3202. [PMID: 33841776 PMCID: PMC8019059 DOI: 10.1002/ece3.7266] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2020] [Revised: 01/09/2021] [Accepted: 01/15/2021] [Indexed: 11/22/2022] Open
Abstract
Apteryx is a genus of flightless birds endemic to New Zealand known to lay very large eggs in proportion to body weight. The eggshell of Apteryx is unusually thin and less porous than allometrically expected possibly as a compensation for a very long incubation period. Past studies have been carried out on Apteryx australis, a species which once comprised all kiwi with brown plumage, now separated into three distinct species. These species use different habitats and live at different latitudes and altitudes, therefore generating a need to revise our knowledge of the attributes of their eggshells. In this study, we measured the physical characteristics and water conductance on eggshell fragments of these three species and Great-spotted Kiwi and relate them to the environmental conditions of their respective environments; we also measured the water vapor conductance of Brown Kiwi eggs of late stages of incubation. We found that several trade-offs exist between incubation behavior, environmental conditions, and eggshell structure. We found differences between species in eggshell water vapor conductance seemingly related to altitude; Brown Kiwi and Rowi generally inhabiting lower altitudes had the highest conductance and Tokoeka, generally living in montane environments, the lowest. This is achieved by an increased eggshell thickness rather than a pore area reduction. Finally, the water vapor conductance late in incubation was 58% higher than infertile unincubated eggs, suggesting a drastic increase in conductance throughout the long incubation period. Using the values previously reported, we calculated the embryonic eggshell thinning to be 32.5% at the equatorial region of the eggshell. We describe several new features, such as triangular mineral particles in the cuticle, reported for the extinct Trigonoolithus amoei, and confirmed the existence of plugged pores. We suggest that these structures provide microbial protection needed by a burrow nesting species with a long incubation period.
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Affiliation(s)
- David Vieco‐Galvez
- School of Agriculture and EnvironmentMassey UniversityPalmerston NorthNew Zealand
| | - Isabel Castro
- School of Agriculture and EnvironmentMassey UniversityPalmerston NorthNew Zealand
| | - Patrick C. H. Morel
- School of Agriculture and EnvironmentMassey UniversityPalmerston NorthNew Zealand
| | - Wei Hang Chua
- School of Health SciencesMassey UniversityPalmerston NorthNew Zealand
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