1
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Debruyn G, Geltmeyer J, Schoolaert E, Nicolaï MPJ, Xie W, Wynant M, Shawkey MD, De Clerck K, D'Alba L. Hydric Environment and Chemical Composition Shape Non-avian Reptile Eggshell Absorption. Integr Comp Biol 2024; 64:107-119. [PMID: 38755009 DOI: 10.1093/icb/icae040] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2023] [Revised: 04/19/2024] [Accepted: 05/06/2024] [Indexed: 05/18/2024] Open
Abstract
The amniotic egg fulfils a critical role in reproduction by serving as an interface between the external environment and the embryo. Because non-avian reptiles are rarely incubated, they must be heated by, and absorb water from, the oviposition site for the developing embryo. The mechanisms by which they absorb sufficient, but not excess, water and how these mechanisms vary with local habitat is largely unknown, despite its significance to their evolution. Here, we first performed histology, Fourier-transform infrared spectroscopy and dynamic vapor sorption experiments to elucidate the mechanisms of eggshell absorption for 56 reptile species. Then, we used phylogenetic comparative analysis to test the hypothesis that the absorptive capacity of reptile eggshells increases with aridity of the environment. We found that water absorption increases in the presence of a superficial mucopolysaccharide layer and decreases with increased calcium content. We found that eggs from arid environments have highly absorbent eggshells, but only in species with weakly calcified shells. Our results suggest that reptile eggshells have over evolutionary time tuned absorptive capacity to environmental moisture level. Since these eggs often must sustain conflicting constraints, they may serve as inspirations for new biomimetic materials, such as water filtering membranes or humidity sensors.
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Affiliation(s)
- Gerben Debruyn
- Department of Biology, Evolution and Optics of Nanostructures Group, University of Ghent, Ledeganckstraat 35, 9000 Ghent, Belgium
| | - Jozefien Geltmeyer
- Center for Textile Science and Engineering, Faculty of Engineering and Architecture, University of Ghent, Tech Lane Science Park 701, B-9052 Ghent, Belgium
| | - Ella Schoolaert
- Center for Textile Science and Engineering, Faculty of Engineering and Architecture, University of Ghent, Tech Lane Science Park 701, B-9052 Ghent, Belgium
| | - Michaël P J Nicolaï
- Department of Biology, Evolution and Optics of Nanostructures Group, University of Ghent, Ledeganckstraat 35, 9000 Ghent, Belgium
| | - Wanjie Xie
- Department of Biology, Evolution and Optics of Nanostructures Group, University of Ghent, Ledeganckstraat 35, 9000 Ghent, Belgium
| | - Maarten Wynant
- Center for Textile Science and Engineering, Faculty of Engineering and Architecture, University of Ghent, Tech Lane Science Park 701, B-9052 Ghent, Belgium
| | - Matthew D Shawkey
- Department of Biology, Evolution and Optics of Nanostructures Group, University of Ghent, Ledeganckstraat 35, 9000 Ghent, Belgium
| | - Karen De Clerck
- Center for Textile Science and Engineering, Faculty of Engineering and Architecture, University of Ghent, Tech Lane Science Park 701, B-9052 Ghent, Belgium
| | - Liliana D'Alba
- Department of Biology, Evolution and Optics of Nanostructures Group, University of Ghent, Ledeganckstraat 35, 9000 Ghent, Belgium
- Naturalis Biodiversity Center, Darwinweg 2, 2333 CR Leiden, The Netherlands
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2
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Han F, Yu Y, Zhang S, Zeng R, Wang X, Cai H, Wu T, Wen Y, Cai S, Li C, Wu R, Zhao Q, Xu X. Exceptional Early Jurassic fossils with leathery eggs shed light on dinosaur reproductive biology. Natl Sci Rev 2024; 11:nwad258. [PMID: 38707200 PMCID: PMC11067957 DOI: 10.1093/nsr/nwad258] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2023] [Revised: 09/25/2023] [Accepted: 09/27/2023] [Indexed: 05/07/2024] Open
Abstract
Our understanding of pre-Cretaceous dinosaur reproduction is hindered by a scarcity of evidence within fossil records. Here we report three adult skeletons and five clutches of embryo-containing eggs of a new sauropodomorph from the Lower Jurassic of southwestern China, displaying several significant reproductive features that are either unknown or unlike other early-diverging sauropodomorphs, such as relatively large eggs with a relatively thick calcareous shell formed by prominent mammillary cones, synchronous hatching and a transitional prehatching posture between the crocodilians and living birds. Most significantly, these Early Jurassic fossils provide strong evidence for the earliest known leathery eggs. Our comprehensive quantitative analyses demonstrate that the first dinosaur eggs were probably leathery, elliptical and relatively small, but with relatively long eggshell units, and that along the line to living birds, the most significant change in reptilian egg morphology occurred early in theropod evolution rather than near the origin of Aves.
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Affiliation(s)
- Fenglu Han
- School of Earth Sciences, China University of Geosciences (Wuhan), Wuhan 430074, China
| | - Yilun Yu
- Key Laboratory of Vertebrate Evolution and Human Origins, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, Beijing 100044, China
- University of Chinese Academy of Sciences, Beijing 101408, China
| | - Shukang Zhang
- Key Laboratory of Vertebrate Evolution and Human Origins, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, Beijing 100044, China
| | - Rong Zeng
- Guizhou Provincial Museum, Guiyang 550081, China
| | - Xinjin Wang
- Guizhou Provincial Institute of Cultural Relics and Archaeology, Guiyang 550001, China
| | - Huiyang Cai
- Guizhou Provincial Museum, Guiyang 550081, China
| | | | - Yingfeng Wen
- Pingba Institute of Cultural Relics Administration, Anshun 550820, China
| | - Sifu Cai
- Guizhou Provincial Museum, Guiyang 550081, China
| | - Chun Li
- Key Laboratory of Vertebrate Evolution and Human Origins, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, Beijing 100044, China
| | - Rui Wu
- School of Earth Sciences, China University of Geosciences (Wuhan), Wuhan 430074, China
| | - Qi Zhao
- Key Laboratory of Vertebrate Evolution and Human Origins, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, Beijing 100044, China
| | - Xing Xu
- Centre for Vertebrate Evolutionary Biology, Yunnan University, Kunming 650091, China
- Key Laboratory of Vertebrate Evolution and Human Origins, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, Beijing 100044, China
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3
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Wu HJ, Tseng YC, Tsao SH, Chiang PL, Tai WY, Hsieh HI, Yu HT, Juang JY. A Comparative Study on the Microstructures, Mineral Content, and Mechanical Properties of Non-Avian Reptilian Eggshells. BIOLOGY 2023; 12:688. [PMID: 37237502 PMCID: PMC10215611 DOI: 10.3390/biology12050688] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/15/2023] [Revised: 04/25/2023] [Accepted: 05/05/2023] [Indexed: 05/28/2023]
Abstract
We analyze 214 freshly laid eggs belonging to 16 species across three orders of Class Reptilia. Using mechanical compression tests, we measure each egg's absolute stiffness (K, unit: N m-1) and relative stiffness (C number). The effective Young's modulus, E, was obtained by combining experimental and numerical methods. The mineral (CaCO3) content was measured by acid-base titration, the microstructures by scanning electron microscopy (SEM), and the crystallography by electron backscatter diffraction (EBSD). We find that the C number of reptilian eggs is, on average, higher than that of bird eggs, indicating that reptilian eggs are stiffer with respect to the egg mass than birds. However, Young's moduli of the reptilian eggshells (32.85 ± 3.48 GPa) are similar to those of avian eggshells (32.07 ± 5.95 GPa), even though those eggshells have different crystal forms, microstructures, and crystallography. Titration measurement shows that the reptilian eggshells are highly mineralized (>89% for nine Testudines species and 96% for Caiman crocodilus). Comparing the species with aragonite and calcite crystals, we find that calcite shells, including those of the Kwangsi gecko (inner part) and spectacled caiman (outer part), generally have larger grains than the aragonite ones. However, the grain size is not correlated to the effective Young's modulus. Also, as measured by the C number, the aragonite shells are, on average, stiffer than the calcite ones (except for the Kwangsi gecko), primarily due to their thicker shells.
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Affiliation(s)
- Hsio-Jou Wu
- Department of Mechanical Engineering, National Taiwan University, Taipei 10617, Taiwan; (H.-J.W.); (Y.-C.T.); (S.-H.T.); (P.-L.C.)
- Department of Life Science, National Taiwan University, Taipei 10617, Taiwan;
| | - Yu-Chien Tseng
- Department of Mechanical Engineering, National Taiwan University, Taipei 10617, Taiwan; (H.-J.W.); (Y.-C.T.); (S.-H.T.); (P.-L.C.)
| | - Shu-Han Tsao
- Department of Mechanical Engineering, National Taiwan University, Taipei 10617, Taiwan; (H.-J.W.); (Y.-C.T.); (S.-H.T.); (P.-L.C.)
| | - Pei-Lin Chiang
- Department of Mechanical Engineering, National Taiwan University, Taipei 10617, Taiwan; (H.-J.W.); (Y.-C.T.); (S.-H.T.); (P.-L.C.)
| | - Wei-Yu Tai
- Taipei Zoo, Taipei 11656, Taiwan; (W.-Y.T.); (H.-I.H.)
| | - Hsin-I Hsieh
- Taipei Zoo, Taipei 11656, Taiwan; (W.-Y.T.); (H.-I.H.)
| | - Hon-Tsen Yu
- Department of Life Science, National Taiwan University, Taipei 10617, Taiwan;
- Degree Program of Genome and Systems Biology, National Taiwan University, Taipei 10617, Taiwan
| | - Jia-Yang Juang
- Department of Mechanical Engineering, National Taiwan University, Taipei 10617, Taiwan; (H.-J.W.); (Y.-C.T.); (S.-H.T.); (P.-L.C.)
- Program in Nanoengineering and Nanoscience, Graduate School of Advanced Technology, National Taiwan University, Taipei 10617, Taiwan
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4
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Triassic sauropodomorph eggshell might not be soft. Nature 2022; 610:E8-E10. [PMID: 36261569 DOI: 10.1038/s41586-022-05151-9] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2020] [Accepted: 07/27/2022] [Indexed: 11/08/2022]
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5
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Legendre LJ, Choi S, Clarke JA. The diverse terminology of reptile eggshell microstructure and its effect on phylogenetic comparative analyses. J Anat 2022; 241:641-666. [PMID: 35758681 DOI: 10.1111/joa.13723] [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: 02/24/2022] [Revised: 05/05/2022] [Accepted: 06/16/2022] [Indexed: 11/29/2022] Open
Abstract
Reptile eggshell ensures water and gas exchange during incubation and plays a key role in reproductive success. The diversity of reptilian incubation and life history strategies has led to many clade-specific structural adaptations of their eggshell, which have been studied in extant taxa (i.e. birds, crocodilians, turtles, and lepidosaurs). Most studies on non-avian eggshells were performed over 30 years ago and categorized reptile eggshells into two main types: "hard" and "soft" - sometimes with a third intermediate category, "semi-rigid." In recent years, however, debate over the evolution of eggshell structure of major reptile clades has revealed how definitions of hard and soft eggshells influence inferred deep-time evolutionary patterns. Here, we review the diversity of extant and fossil eggshell with a focus on major reptile clades, and the criteria that have been used to define hard, soft, and semi-rigid eggshells. We show that all scoring approaches that retain these categories discretize continuous quantitative traits (e.g. eggshell thickness) and do not consider independent variation of other functionally important microstructural traits (e.g. degree of calcification, shell unit inner structure). We demonstrate the effect of three published approaches to discretizing eggshell type into hard, semi-rigid, and soft on ancestral state reconstructions using 200+ species representing all major extant and extinct reptile clades. These approaches result in different ancestral states for all major clades including Archosauria and Dinosauria, despite a difference in scoring for only 1-4% of the sample. Proposed scenarios of reptile eggshell evolution are highly conditioned by sampling, tree calibration, and lack of congruence between definitions of eggshell type. We conclude that the traditional "soft/hard/semi-rigid" classification of reptilian eggshells should be abandoned and provide guidelines for future descriptions focusing on specific functionally relevant characteristics (e.g. inner structures of shell units, pores, and membrane elements), analyses of these traits in a phylogenetic context, and sampling of previously undescribed taxa, including fossil eggs.
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Affiliation(s)
- Lucas J Legendre
- Department of Geological Sciences, University of Texas at Austin, Austin, Texas, USA
| | - Seung Choi
- Department of Earth Sciences, Montana State University, Bozeman, Montana, USA.,Key Laboratory of Vertebrate Evolution and Human Origins of Chinese Academy of Sciences, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, Beijing, China
| | - Julia A Clarke
- Department of Geological Sciences, University of Texas at Austin, Austin, Texas, USA
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6
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Kulshreshtha G, D’Alba L, Dunn IC, Rehault-Godbert S, Rodriguez-Navarro AB, Hincke MT. Properties, Genetics and Innate Immune Function of the Cuticle in Egg-Laying Species. Front Immunol 2022; 13:838525. [PMID: 35281050 PMCID: PMC8914949 DOI: 10.3389/fimmu.2022.838525] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2021] [Accepted: 01/31/2022] [Indexed: 01/13/2023] Open
Abstract
Cleidoic eggs possess very efficient and orchestrated systems to protect the embryo from external microbes until hatch. The cuticle is a proteinaceous layer on the shell surface in many bird and some reptile species. An intact cuticle forms a pore plug to occlude respiratory pores and is an effective physical and chemical barrier against microbial penetration. The interior of the egg is assumed to be normally sterile, while the outer eggshell cuticle hosts microbes. The diversity of the eggshell microbiome is derived from both maternal microbiota and those of the nesting environment. The surface characteristics of the egg, outer moisture layer and the presence of antimicrobial molecules composing the cuticle dictate constituents of the microbial communities on the eggshell surface. The avian cuticle affects eggshell wettability, water vapor conductance and regulates ultraviolet reflectance in various ground-nesting species; moreover, its composition, thickness and degree of coverage are dependent on species, hen age, and physiological stressors. Studies in domestic avian species have demonstrated that changes in the cuticle affect the food safety of eggs with respect to the risk of contamination by bacterial pathogens such as Salmonella and Escherichia coli. Moreover, preventing contamination of internal egg components is crucial to optimize hatching success in bird species. In chickens there is moderate heritability (38%) of cuticle deposition with a potential for genetic improvement. However, much less is known about other bird or reptile cuticles. This review synthesizes current knowledge of eggshell cuticle and provides insight into its evolution in the clade reptilia. The origin, composition and regulation of the eggshell microbiome and the potential function of the cuticle as the first barrier of egg defense are discussed in detail. We evaluate how changes in the cuticle affect the food safety of table eggs and vertical transmission of pathogens in the production chain with respect to the risk of contamination. Thus, this review provides insight into the physiological and microbiological characteristics of eggshell cuticle in relation to its protective function (innate immunity) in egg-laying birds and reptiles.
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Affiliation(s)
- Garima Kulshreshtha
- Department of Cellular and Molecular Medicine, Faculty of Medicine, University of Ottawa, Ottawa, ON, Canada
| | - Liliana D’Alba
- Evolutionary Ecology, Naturalis Biodiversity Center, Leiden, Netherlands
| | - Ian C. Dunn
- The Roslin Institute and Royal (Dick) School of Veterinary Studies, University of Edinburgh, Edinburgh, United Kingdom
| | | | | | - Maxwell T. Hincke
- Department of Cellular and Molecular Medicine, Faculty of Medicine, University of Ottawa, Ottawa, ON, Canada
- Department of Innovation in Medical Education, Faculty of Medicine, University of Ottawa, Ottawa, ON, Canada
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7
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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: 9] [Impact Index Per Article: 3.0] [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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8
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Oser SE, Chin K, Sertich JJW, Varricchio DJ, Choi S, Rifkin J. Tiny, ornamented eggs and eggshell from the Upper Cretaceous of Utah represent a new ootaxon with theropod affinities. Sci Rep 2021; 11:10021. [PMID: 33976315 PMCID: PMC8113451 DOI: 10.1038/s41598-021-89472-1] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2020] [Accepted: 04/21/2021] [Indexed: 11/09/2022] Open
Abstract
A new Cretaceous ootaxon (eggshell type) from the Kaiparowits Formation of Grand Staircase-Escalante National Monument is among a growing number of very small eggs described from the Mesozoic. Analyses of two partial eggs (~ 17.7 mm in diameter) and 29 eggshell fragments reveal that this new ootaxon exhibits nodose ornamentation with distinctive branching pore canals that open atop the nodes. Its two-layered microstructure consists of a mammillary layer and a continuous layer with rugged grain boundaries between calcite grains. Although the exact identity of the egg producer is unknown, the eggshell microstructure and small size is consistent with a small-bodied avian or non-avian theropod. The specific combination of small egg size, branching pores, two-layered microstructure, and dispersituberculate ornamentation preserved in this new ootaxon is unique among theropod eggs. This underscores that both eggshell and skeletal fossils of Cretaceous theropods can display a mosaic of transitional morphological and behavioural features characteristic of both avian and non-avian taxa. As such, this new ootaxon increases the diversity of Cretaceous eggs and informs our understanding of the evolution of theropod eggshell microstructure and morphology.
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Affiliation(s)
- Sara E Oser
- Museum of Natural History, University of Colorado, Boulder, CO, 80309, USA.
| | - Karen Chin
- Museum of Natural History, University of Colorado, Boulder, CO, 80309, USA.,Department of Geological Sciences, University of Colorado, Boulder, CO, 80309, USA
| | - Joseph J W Sertich
- Department of Earth Sciences, Denver Museum of Nature & Science, Denver, CO, 80205, USA
| | - David J Varricchio
- Department of Earth Sciences, Montana State University, Bozeman, MT, 59717, USA
| | - Seung Choi
- Department of Earth Sciences, Montana State University, Bozeman, MT, 59717, USA
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9
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Le Roy N, Stapane L, Gautron J, Hincke MT. Evolution of the Avian Eggshell Biomineralization Protein Toolkit - New Insights From Multi-Omics. Front Genet 2021; 12:672433. [PMID: 34046059 PMCID: PMC8144736 DOI: 10.3389/fgene.2021.672433] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2021] [Accepted: 04/08/2021] [Indexed: 11/13/2022] Open
Abstract
The avian eggshell is a remarkable biomineral, which is essential for avian reproduction; its properties permit embryonic development in the desiccating terrestrial environment, and moreover, are critically important to preserve unfertilized egg quality for human consumption. This calcium carbonate (CaCO3) bioceramic is made of 95% calcite and 3.5% organic matrix; it protects the egg contents against microbial penetration and mechanical damage, allows gaseous exchange, and provides calcium for development of the embryonic skeleton. In vertebrates, eggshell occurs in the Sauropsida and in a lesser extent in Mammalia taxa; avian eggshell calcification is one of the fastest known CaCO3 biomineralization processes, and results in a material with excellent mechanical properties. Thus, its study has triggered a strong interest from the researcher community. The investigation of eggshell biomineralization in birds over the past decades has led to detailed characterization of its protein and mineral constituents. Recently, our understanding of this process has been significantly improved using high-throughput technologies (i.e., proteomics, transcriptomics, genomics, and bioinformatics). Presently, more or less complete eggshell proteomes are available for nine birds, and therefore, key proteins that comprise the eggshell biomineralization toolkit are beginning to be identified. In this article, we review current knowledge on organic matrix components from calcified eggshell. We use these data to analyze the evolution of selected matrix proteins and underline their role in the biological toolkit required for eggshell calcification in avian species. Amongst the panel of eggshell-associated proteins, key functional domains are present such as calcium-binding, vesicle-binding and protein-binding. These technical advances, combined with progress in mineral ultrastructure analyses, have opened the way for new hypotheses of mineral nucleation and crystal growth in formation of the avian eggshell, including transfer of amorphous CaCO3 in vesicles from uterine cells to the eggshell mineralization site. The enrichment of multi-omics datasets for bird species is critical to understand the evolutionary context for development of CaCO3 biomineralization in metazoans, leading to the acquisition of the robust eggshell in birds (and formerly dinosaurs).
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Affiliation(s)
| | | | | | - Maxwell T Hincke
- Department of Innovation in Medical Education, University of Ottawa, Ottawa, ON, Canada.,Department of Cellular and Molecular Medicine, University of Ottawa, Ottawa, ON, Canada
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10
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D'Alba L, Goldenberg J, Nallapaneni A, Parkinson DY, Zhu C, Vanthournout B, Shawkey MD. Evolution of eggshell structure in relation to nesting ecology in non-avian reptiles. J Morphol 2021; 282:1066-1079. [PMID: 33713039 DOI: 10.1002/jmor.21347] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2020] [Revised: 02/01/2021] [Accepted: 02/21/2021] [Indexed: 12/14/2022]
Abstract
Amniotic eggs are multifunctional structures that enabled early tetrapods to colonize the land millions of years ago, and are now the reproductive mode of over 70% of all terrestrial amniotes. Eggshell morphology is at the core of animal survival, mediating the interactions between embryos and their environment, and has evolved into a massive diversity of forms and functions in modern reptiles. These functions are critical to embryonic survival and may serve as models for new antimicrobial and/or breathable membranes. However, we still lack critical data on the basic structural and functional properties of eggs, particularly of reptiles. Here, we first characterized egg shape, shell thickness, porosity, and mineralization of eggs from 91 reptile species using optical images, scanning electron microscopy, and micro computed tomography, and collected data on nesting ecology from the literature. We then used comparative analyses to test hypotheses on the selective pressures driving their evolution. We hypothesized that eggshell morphology has evolved to protect shells from physical damage and desiccation, and, in support, found a positive relationship between thickness and precipitation, and a negative relationship between porosity and temperature. Although mineralization varied extensively, it was not correlated with nesting ecology variables. Ancestral state reconstructions show thinning and increased porosity over evolutionary time in squamates, but the opposite in turtles and crocodilians. Egg shape, size, porosity and calcification were correlated, suggesting potential structural or developmental tradeoffs. This study provides new data and insights into the morphology and evolution of reptile eggs, and raises numerous questions for additional research.
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Affiliation(s)
- Liliana D'Alba
- Department of Biology, EON-Unit, Universiteit Gent, Ghent, Belgium
| | | | - Asritha Nallapaneni
- Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California, USA
| | - Dilworth Y Parkinson
- Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California, USA
| | - Chenhui Zhu
- Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California, USA
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11
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Blackburn DG, Stewart JR. Morphological research on amniote eggs and embryos: An introduction and historical retrospective. J Morphol 2021; 282:1024-1046. [PMID: 33393149 DOI: 10.1002/jmor.21320] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2020] [Revised: 12/31/2020] [Accepted: 01/01/2021] [Indexed: 12/21/2022]
Abstract
Evolution of the terrestrial egg of amniotes (reptiles, birds, and mammals) is often considered to be one of the most significant events in vertebrate history. Presence of an eggshell, fetal membranes, and a sizeable yolk allowed this egg to develop on land and hatch out well-developed, terrestrial offspring. For centuries, morphologically-based studies have provided valuable information about the eggs of amniotes and the embryos that develop from them. This review explores the history of such investigations, as a contribution to this special issue of Journal of Morphology, titled Developmental Morphology and Evolution of Amniote Eggs and Embryos. Anatomically-based investigations are surveyed from the ancient Greeks through the Scientific Revolution, followed by the 19th and early 20th centuries, with a focus on major findings of historical figures who have contributed significantly to our knowledge. Recent research on various aspects of amniote eggs is summarized, including gastrulation, egg shape and eggshell morphology, eggs of Mesozoic dinosaurs, sauropsid yolk sacs, squamate placentation, embryogenesis, and the phylotypic phase of embryonic development. As documented in this review, studies on amniote eggs and embryos have relied heavily on morphological approaches in order to answer functional and evolutionary questions.
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Affiliation(s)
- Daniel G Blackburn
- Department of Biology and Electron Microscopy Center, Trinity College, Hartford, Connecticut, USA
| | - James R Stewart
- Department of Biological Sciences, East Tennessee State University, Johnson City, Tennessee, USA
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12
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Hermyt M, Metscher B, Rupik W. Do all geckos hatch in the same way? Histological and
3D
studies of egg tooth morphogenesis in the geckos
Eublepharis macularius
Blyth 1854 and
Lepidodactylus lugubris
Duméril & Bibron 1836. J Morphol 2020; 281:1313-1327. [DOI: 10.1002/jmor.21249] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2020] [Revised: 07/08/2020] [Accepted: 07/22/2020] [Indexed: 02/06/2023]
Affiliation(s)
- Mateusz Hermyt
- Faculty of Natural Sciences, Institute of Biology, Biotechnology and Environmental Protection University of Silesia in Katowice Katowice Poland
| | - Brian Metscher
- Department of Evolutionary Biology University of Vienna Vienna Austria
| | - Weronika Rupik
- Faculty of Natural Sciences, Institute of Biology, Biotechnology and Environmental Protection University of Silesia in Katowice Katowice Poland
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