scholarly journals Micro- and Macroscale Patterns of Petal Morphogenesis in Nigella damascena (Ranunculaceae) Revealed by Geometric Morphometrics and Cellular Analyses

2021 ◽  
Vol 12 ◽  
Author(s):  
Pierre Galipot ◽  
Sylvain Gerber ◽  
Martine Le Guilloux ◽  
Florian Jabbour ◽  
Catherine Damerval
Keyword(s):  
Geometric Morphometrics ◽  
Shape Change ◽  
Morphological Diversity ◽  
Pollinator Attraction ◽  
Petal Development ◽  
Inner Organs ◽  
Quantitative Basis ◽  
Petal Shape ◽  
Evo Devo ◽  
Nigella Damascena

Petals, the inner organs in a differentiated perianth, generally play an important role in pollinator attraction. As such they exhibit an extraordinary diversity of shapes, sizes, and colors. Being involved in pollinator attraction and reward, they are privileged targets of evolution. The corolla of the Ranunculaceae species Nigella damascena consists of elaborate nectariferous petals, made of a stalk, upper, and lower lips forming a nectar pouch, shiny pseudonectaries, and pilose ears. While the main events of petal development are properly described, a few is known about the pattern of organ size and shape covariation and the cellular dynamics during development. In this study, we investigated the relationships between morphogenesis and growth of N. damascena petals using geometric morphometrics coupled with the study of cell characteristics. First, we found that petal shape and size dynamics are allometric during development and that their covariation suggests that petal shape change dynamics are exponentially slower than growth. We then found that cell proliferation is the major driver of shape patterning during development, while petal size dynamics are mostly driven by cell expansion. Our analyses provide a quantitative basis to characterize the relationships between shape, size, and cell characteristics during the development of an elaborate floral structure. Such studies lay the ground for future evo-devo investigations of the large morphological diversity observed in nectariferous structures, in Ranunculaceae and beyond.

scholarly journals Origin of animal multicellularity: precursors, causes, consequences—the choanoflagellate/sponge transition, neurogenesis and the Cambrian explosion

2017 ◽  
Vol 372 (1713) ◽  
pp. 20150476 ◽  
Author(s):  
Thomas Cavalier-Smith
Keyword(s):  
Connective Tissue ◽  
Photosynthetic Bacteria ◽  
Cell Structure ◽  
Morphological Diversity ◽  
Cambrian Explosion ◽  
Feeding Modes ◽  
Selection For ◽  
Evo Devo ◽  
Gastraea Theory ◽  
Bacterial Food

Evolving multicellularity is easy, especially in phototrophs and osmotrophs whose multicells feed like unicells. Evolving animals was much harder and unique; probably only one pathway via benthic ‘zoophytes’ with pelagic ciliated larvae allowed trophic continuity from phagocytic protozoa to gut-endowed animals. Choanoflagellate protozoa produced sponges. Converting sponge flask cells mediating larval settling to synaptically controlled nematocysts arguably made Cnidaria. I replace Haeckel's gastraea theory by a sponge/coelenterate/bilaterian pathway: Placozoa, hydrozoan diploblasty and ctenophores were secondary; stem anthozoan developmental mutations arguably independently generated coelomate bilateria and ctenophores. I emphasize animal origin's conceptual aspects (selective, developmental) related to feeding modes, cell structure, phylogeny of related protozoa, sequence evidence, ecology and palaeontology. Epithelia and connective tissue could evolve only by compensating for dramatically lower feeding efficiency that differentiation into non-choanocytes entails. Consequentially, larger bodies enabled filtering more water for bacterial food and harbouring photosynthetic bacteria, together adding more food than cell differentiation sacrificed. A hypothetical presponge of sessile triploblastic sheets (connective tissue sandwiched between two choanocyte epithelia) evolved oogamy through selection for larger dispersive ciliated larvae to accelerate benthic trophic competence and overgrowing protozoan competitors. Extinct Vendozoa might be elaborations of this organismal grade with choanocyte-bearing epithelia, before poriferan water channels and cnidarian gut/nematocysts/synapses evolved. This article is part of the themed issue ‘Evo-devo in the genomics era, and the origins of morphological diversity’.

scholarly journals Major evolutionary transitions and innovations: the tympanic middle ear

2017 ◽  
Vol 372 (1713) ◽  
pp. 20150483 ◽  
Author(s):  
Abigail S. Tucker
Keyword(s):  
Middle Ear ◽  
Morphological Diversity ◽  
The Novel ◽  
Evolutionary Transitions ◽  
Jaw Joint ◽  
Evolution Of Mammals ◽  
Key Steps ◽  
Evo Devo ◽  
Relationship Of ◽  
The Relationship

One of the most amazing transitions and innovations during the evolution of mammals was the formation of a novel jaw joint and the incorporation of the original jaw joint into the middle ear to create the unique mammalian three bone/ossicle ear. In this review, we look at the key steps that led to this change and other unusual features of the middle ear and how developmental biology has been providing an understanding of the mechanisms involved. This starts with an overview of the tympanic (air-filled) middle ear, and how the ear drum (tympanic membrane) and the cavity itself form during development in amniotes. This is followed by an investigation of how the ear is connected to the pharynx and the relationship of the ear to the bony bulla in which it sits. Finally, the novel mammalian jaw joint and versatile dentary bone will be discussed with respect to evolution of the mammalian middle ear. This article is part of the themed issue ‘Evo-devo in the genomics era, and the origins of morphological diversity’.

scholarly journals Phylogenetic evidence for the modular evolution of metazoan signalling pathways

2017 ◽  
Vol 372 (1713) ◽  
pp. 20150477 ◽  
Author(s):  
Leslie S. Babonis ◽  
Mark Q. Martindale
Keyword(s):  
Cell Signalling ◽  
Large Body ◽  
Morphological Diversity ◽  
Signalling Pathway ◽  
Signalling Pathways ◽  
Special Focus ◽  
Tissue Interactions ◽  
Modular Evolution ◽  
Membrane Bound ◽  
Evo Devo

Communication among cells was paramount to the evolutionary increase in cell type diversity and, ultimately, the origin of large body size. Across the diversity of Metazoa, there are only few conserved cell signalling pathways known to orchestrate the complex cell and tissue interactions regulating development; thus, modification to these few pathways has been responsible for generating diversity during the evolution of animals. Here, we summarize evidence for the origin and putative function of the intracellular, membrane-bound and secreted components of seven metazoan cell signalling pathways with a special focus on early branching metazoans (ctenophores, poriferans, placozoans and cnidarians) and basal unikonts (amoebozoans, fungi, filastereans and choanoflagellates). We highlight the modular incorporation of intra- and extracellular components in each signalling pathway and suggest that increases in the complexity of the extracellular matrix may have further promoted the modulation of cell signalling during metazoan evolution. Most importantly, this updated view of metazoan signalling pathways highlights the need for explicit study of canonical signalling pathway components in taxa that do not operate a complete signalling pathway. Studies like these are critical for developing a deeper understanding of the evolution of cell signalling. This article is part of the themed issue ‘Evo-devo in the genomics era, and the origins of morphological diversity’.

scholarly journals Evolutionary versatility of the avian neck

2021 ◽  
Vol 288 (1946) ◽  
pp. 20203150
Author(s):  
Ryan D. Marek ◽  
Peter L. Falkingham ◽  
Roger B. J. Benson ◽  
James D. Gardiner ◽  
Thomas W. Maddox ◽  
...  
Keyword(s):  
Cervical Spine ◽  
Geometric Morphometrics ◽  
Multivariate Statistics ◽  
Three Dimensional ◽  
Morphological Diversity ◽  
Ecological Niches ◽  
Neck Length ◽  
Ecological Functions ◽  
Length Scales

Bird necks display unparalleled levels of morphological diversity compared to other vertebrates, yet it is unclear what factors have structured this variation. Using three-dimensional geometric morphometrics and multivariate statistics, we show that the avian cervical column is a hierarchical morpho-functional appendage, with varying magnitudes of ecologically driven osteological variation at different scales of organization. Contrary to expectations given the widely varying ecological functions of necks in different species, we find that regional modularity of the avian neck is highly conserved, with an overall structural blueprint that is significantly altered only by the most mechanically demanding ecological functions. Nevertheless, the morphologies of vertebrae within subregions of the neck show more prominent signals of adaptation to ecological pressures. We also find that both neck length allometry and the nature of neck elongation in birds are different from other vertebrates. In contrast with mammals, neck length scales isometrically with head mass and, contrary to previous work, we show that neck elongation in birds is achieved predominantly by increasing vertebral lengths rather than counts. Birds therefore possess a cervical spine that may be unique in its versatility among extant vertebrates, one that, since the origin of flight, has adapted to function as a surrogate forelimb in varied ecological niches.

scholarly journals Unexpected Morphological Diversity in New Zealand’s Large Diplodactylidae Geckos

2021 ◽  
Author(s):  
Lachie Scarsbrook ◽  
Emma Sherratt ◽  
Rod Hitchmough ◽  
R. Ewan Fordyce ◽  
Nicolas J. Rawlence
Keyword(s):  
New Zealand ◽  
Geometric Morphometrics ◽  
Relative Size ◽  
Three Dimensional ◽  
Morphological Diversity ◽  
Anthropogenic Disturbances ◽  
Species Level ◽  
Global Biodiversity ◽  
The Impact ◽  
Shape And Size

Abstract Prehistoric anthropogenically-mediated extinctions have impacted global biodiversity; however effects on herpetofauna are poorly-documented. New Zealand’s Diplodactylidae geckos exhibit high species-level diversity, largely independent of discernible osteological changes (cryptic). Consequently, taxonomic affinities of isolated skeletal elements (fossils) are primarily determined by relative size, particularly in the identification of Hoplodactylus duvaucelii; New Zealand’s largest extant gecko species. Here, three-dimensional geometric morphometrics of maxillae (a common fossilized element) was used to determine whether consistent shape and size differences exist between genera, and if cryptic extinctions have occurred in ‘Hoplodactylus cf. duvaucelii’. Sampling included 13 Diplodactylidae species from five genera, and 11 Holocene ‘H. cf. duvaucelii’ subfossil individuals. We found phylogenetic history was the most important predictor of maxilla morphology among extant Diplodactylidae genera. Relative size comparisons could only differentiate Hoplodactylus from other genera, with the remaining genera exhibiting variable degrees of overlap. Six subfossils were positively identified as H. duvaucelii, confirming their proposed Holocene distribution throughout New Zealand. Conversely, five subfossils showed no affinities towards any modern Diplodactylidae genera, implying either increased morphological diversity in mainland ‘H. cf. duvaucelii’ or the presence of at least one extinct, large, broad-toed Diplodactylidae species. These results highlight the impact of anthropogenic disturbances on insular reptile diversity.

Landmark-Based Shape Analysis on Middle Cerebral Intracranial Aneurysms: A Geometric Morphometrics Approach to Infer Natural History

2020 ◽  
Vol 17 ◽  
Author(s):  
Vincent M. Tutino ◽  
Anthony J. Yan ◽  
Sricharan S. Veeturi ◽  
Tatsat R. Patel ◽  
Hamidreza Rajabzadeh-Oghaz ◽  
...  
Keyword(s):  
Principal Component Analysis ◽  
Natural History ◽  
Geometric Morphometrics ◽  
Hierarchical Clustering ◽  
Intracranial Aneurysms ◽  
Shape Change ◽  
Principal Component ◽  
Component Analysis ◽  
Maximum Height ◽  
Cross Sectional

Background:: Due to scarcity of longitudinal data, the morphologic development of intracranial aneurysms (IAs) during their natural history remains poorly understood. However, longitudinal information can often be inferred from cross-sectional datasets as demonstrated by anatomists’ use of geometric morphometrics to build evolutionary trees, reconstructing species inter-relationships based on morphologic landmarks. Objective:: We adopted these tools to analyze cross-sectional image data and infer relationships between IA morphologies. Methods:: On 3D reconstructions of 52 middle cerebral artery (MCA) IAs (9 ruptured) and 10 IA-free MCAs (baseline geometries), 7 semi-automated landmarks were placed at the proximal parent artery and maximum height. From these, 64 additional landmarks were computationally generated to create a 71-landmark point cloud of 213 xyz coordinates. This data was normalized by Procrustes transformation and used in principal component analysis, hierarchical clustering, and phylogenetic analyses. Results:: Principal component analysis showed separation of IA-free MCA geometries and grouping of ruptured IAs from unruptured IAs. Hierarchical clustering delineated a cluster of only unruptured IAs that were significantly smaller and more spherical than clusters that had ruptured IAs. Phylogenetic classification placed ruptured IAs more distally in the tree than unruptured IAs, indicating greater shape derivation. Groups of unruptured IAs were observed, but ruptured IAs were invariably found in mixed lineages with unruptured IAs, suggesting that some pathways of shape change may be benign while other are more associated with rupture. Conclusion:: Geometric morphometric analyses of larger datasets may indicate particular pathways of shape change leading toward aneurysm rupture versus stabilization.

scholarly journals Cavefish and the basis for eye loss

2017 ◽  
Vol 372 (1713) ◽  
pp. 20150487 ◽  
Author(s):  
Jaya Krishnan ◽  
Nicolas Rohner
Keyword(s):  
Embryonic Development ◽  
Convergent Evolution ◽  
Current Knowledge ◽  
Morphological Diversity ◽  
Astyanax Mexicanus ◽  
Genomic Resources ◽  
Evolutionary Forces ◽  
Different Populations ◽  
Entire World ◽  
Evo Devo

Animals have colonized the entire world from rather moderate to the harshest environments, some of these so extreme that only few animals are able to survive. Cave environments present such a challenge and obligate cave animals have adapted to perpetual darkness by evolving a multitude of traits. The most common and most studied cave characteristics are the regression of eyes and the overall reduction in pigmentation. Studying these traits can provide important insights into how evolutionary forces drive convergent and regressive adaptation. The blind Mexican cavefish ( Astyanax mexicanus ) has emerged as a useful model to study cave evolution owing to the availability of genetic and genomic resources, and the amenability of embryonic development as the different populations remain fertile with each other. In this review, we give an overview of our current knowledge underlying the process of regressive and convergent evolution using eye degeneration in cavefish as an example. This article is part of the themed issue ‘Evo-devo in the genomics era, and the origins of morphological diversity’.

scholarly journals The origins, scaling and loss of tetrapod digits

2017 ◽  
Vol 372 (1713) ◽  
pp. 20150482 ◽  
Author(s):  
Aditya Saxena ◽  
Matthew Towers ◽  
Kimberly L. Cooper
Keyword(s):  
Limb Development ◽  
Genome Engineering ◽  
Charles Darwin ◽  
Morphological Diversity ◽  
Supporting Evidence ◽  
Developmental Potential ◽  
Current State ◽  
Evolutionary Variation ◽  
Hands And Feet ◽  
Evo Devo

Many of the great morphologists of the nineteenth century marvelled at similarities between the limbs of diverse species, and Charles Darwin noted these homologies as significant supporting evidence for descent with modification from a common ancestor. Sir Richard Owen also took great care to highlight each of the elements of the forelimb and hindlimb in a multitude of species with focused attention on the homology between the hoof of the horse and the middle digit of man. The ensuing decades brought about a convergence of palaeontology, experimental embryology and molecular biology to lend further support to the homologies of tetrapod limbs and their developmental origins. However, for all that we now understand about the conserved mechanisms of limb development and the development of gross morphological disturbances, little of what is presented in the experimental or medical literature reflects the remarkable diversity resulting from the 450 million year experiment of natural selection. An understanding of conserved and divergent limb morphologies in this new age of genomics and genome engineering promises to reveal more of the developmental potential residing in all limbs and to unravel the mechanisms of evolutionary variation in limb size and shape. In this review, we present the current state of our rapidly advancing understanding of the evolutionary origin of hands and feet and highlight what is known about the mechanisms that shape diverse limbs. This article is part of the themed issue ‘Evo-devo in the genomics era, and the origins of morphological diversity’.

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