scholarly journals Miniaturization during a Silurian environmental crisis generated the modern brittle star body plan

2022 ◽  
Vol 5 (1) ◽  
Author(s):  
Ben Thuy ◽  
Mats E. Eriksson ◽  
Manfred Kutscher ◽  
Johan Lindgren ◽  
Lea D. Numberger-Thuy ◽  
...  
Keyword(s):  
Fossil Record ◽  
Driving Forces ◽  
Brittle Star ◽  
Environmental Crisis ◽  
Star Body ◽  
Animal Group ◽  
Environmental Perturbation ◽  
Speciation Event ◽  
Global Extinction ◽  
Structural Simplification

AbstractPivotal anatomical innovations often seem to appear by chance when viewed through the lens of the fossil record. As a consequence, specific driving forces behind the origination of major organismal clades generally remain speculative. Here, we present a rare exception to this axiom by constraining the appearance of a diverse animal group (the living Ophiuroidea) to a single speciation event rather than hypothetical ancestors. Fossils belonging to a new pair of temporally consecutive species of brittle stars (Ophiopetagno paicei gen. et sp. nov. and Muldaster haakei gen. et sp. nov.) from the Silurian (444–419 Mya) of Sweden reveal a process of miniaturization that temporally coincides with a global extinction and environmental perturbation known as the Mulde Event. The reduction in size from O. paicei to M. haakei forced a structural simplification of the ophiuroid skeleton through ontogenetic retention of juvenile traits, thereby generating the modern brittle star bauplan.

scholarly journals Enduring evolutionary embellishment of cloudinids in the Cambrian

2021 ◽  
Vol 8 (12) ◽  
Author(s):  
Tae-Yoon S. Park ◽  
Jikhan Jung ◽  
Mirinae Lee ◽  
Sangmin Lee ◽  
Yong Yi Zhen ◽  
...  
Keyword(s):  
Asexual Reproduction ◽  
Fossil Record ◽  
Evolutionary History ◽  
Structural Complexity ◽  
Cambrian Explosion ◽  
Animal Group ◽  
Reproduction Mode ◽  
First Case ◽  
History Of ◽  
Mode Tracking

The Ediacaran–Cambrian transition and the following Cambrian Explosion are among the most fundamental events in the evolutionary history of animals. Understanding these events is enhanced when phylogenetic linkages can be established among animal fossils across this interval and their trait evolution monitored. Doing this is challenging because the fossil record of animal lineages that span this transition is sparse, preserved morphologies generally simple and lifestyles in the Ediacaran and Cambrian commonly quite different. Here, we identify derived characters linking some members of an enigmatic animal group, the cloudinids, which first appeared in the Late Ediacaran, to animals with cnidarian affinity from the Cambrian Series 2 and the Miaolingian. Accordingly, we present the first case of an animal lineage represented in the Ediacaran that endured and diversified successfully throughout the Cambrian Explosion by embellishing its overall robustness and structural complexity. Among other features, dichotomous branching, present in some early cloudinids, compares closely with a cnidarian asexual reproduction mode. Tracking this morphological change from Late Ediacaran to the Miaolingian provides a unique glimpse into how a primeval animal group responded during the Cambrian Explosion.

scholarly journals Towards a socially sustainable city concept in Vietnam - international experience, local policy making and preparatory steps

2018 ◽  
Vol 12 (5) ◽  
pp. 73-87
Author(s):  
Nguyen Quang Minh
Keyword(s):  
Driving Forces ◽  
Global Climate ◽  
Local Level ◽  
Social Sustainability ◽  
International Experience ◽  
Environmental Crisis ◽  
Local Policy ◽  
Sustainable City ◽  
Holistic Concept ◽  
Good Individual

Sustainability is a holistic concept in development studies, including urban studies, encompassing natural, technical and social aspects, and has been regarded as an ultimate goal for every nation to strive for as well as for every community to achieve in the context of global climate change, environmental crisis and social instability caused by various socio-economic factors. In addition to theoretical investigation, going for social sustainability in practice requires a well prepared action programme which should begin with learning from international experience (especially when it comes to such a new and superior development concept as social sustainability), understanding both the strengths and the weaknesses, and finding new driving forces. Given that a neighbourhood is a miniature (and a complete unit) of a city, social sustainability may be considered and experimented at the local level first. This proves to be a simpler task to fulfil, a more practical approach to a rather complex issue and a wise option to make. The author aims to analyse some of the world’s best examples before reviewing the current potentials and then comes up with a number of suggestions for the first cornerstones of the future society that will be mainly established on the basis of humanity with core social values and good individual opportunities offered to all citizens. Keywords: social sustainability; sustainable city; neighbourhood.

scholarly journals Early Cambrian record of failed durophagy and shell repair in an epibenthic mollusc

2007 ◽  
Vol 3 (3) ◽  
pp. 314-317 ◽  
Author(s):  
Christian B Skovsted ◽  
Glenn A Brock ◽  
Anna Lindström ◽  
John S Peel ◽  
John R Paterson ◽  
...  
Keyword(s):  
Fossil Record ◽  
Direct Evidence ◽  
Driving Forces ◽  
South Australia ◽  
Early Cambrian ◽  
Metazoan Evolution ◽  
Flinders Ranges ◽  
Shell Repair ◽  
Early Metazoan

Predation is arguably one of the main driving forces of early metazoan evolution, yet the fossil record of predation during the Ediacaran–Early Cambrian transition is relatively poor. Here, we present direct evidence of failed durophagous (shell-breaking) predation and subsequent shell repair in the Early Cambrian (Botoman) epibenthic mollusc Marocella from the Mernmerna Formation and Oraparinna Shale in the Flinders Ranges, South Australia. This record pushes back the first appearance of durophagy on molluscs by approximately 40 Myr.

Diversification and extinction patterns among Neogene perimediterranean mammals

1989 ◽  
Vol 325 (1228) ◽  
pp. 401-420 ◽  
Keyword(s):  
Late Miocene ◽  
Fossil Record ◽  
Driving Forces ◽  
High Rate ◽  
Eastern Africa ◽  
European Continent ◽  
Southern France ◽  
Early Pliocene ◽  
Faunal Turnover ◽  
Extinction Event

The best mammalian fossil record during the Neogene of Western Europe is that of the rodents, the most successful and diversified mammal order. The study of origination and extinction during the Neogene (24-3 Ma BP) in one of the best documented areas, Spain and southern France, gives an insight into the dynamics of these communities and indicates the possible nature of the driving forces. Three main periods of time show a high rate of origination: the late Burdigalian (17.5 Ma BP), the early Vallesian (11.5-11 Ma BP) and the early Pliocene (4.2- 3.8 Ma BP). Two of these high origination-rate periods are immediately followed by important extinction events during which all cohorts are deeply affected (11.5-11 Ma BP and 4.2- 3.8 Ma BP). The most important extinction event seems to occur during the early Vallesian (11.5-11 Ma BP), which probably includes the middle/late Miocene boundary. At the Miocene/Pliocene boundary, and during the early Pliocene, the faunal turnover seems to become faster, inducing a strong decrease of the mean species duration. Whereas the main immigration event, which occurs at 17.5 Ma BP, can be related to other faunal migrations in terms of the closure of the Tethys, as it occurs also in eastern Africa and in southwest Asia, the middle/late Miocene boundary event may have been related to a period of ice growth in the Southern Hemisphere. The extinction event that affects the planktonic foraminifera at 12 Ma BP cannot be chronologically correlated to this southwestern European land-mammal extinction event, because the calibration of the marine fossil record during that time-span has to be precise. Some limited terrestrial faunal exchanges that occur during the Messinian between southwestern Europe and northwestern Africa do not deeply affect the general faunal dynamics. Both allochthonous cohorts of immigrants become rapidly extinct. Several endemic rodent faunas, indicating insular conditions, have been reported from the southern edge of the western European continent from the middle Miocene up to the Pliocene. All show low taxonomic diversity, strong endemism and short survival. Some of them, like those of the Gargano Islands during the late Miocene, underwent peculiar morphological changes and also speciation. The large number of rodent genera coevolving in the Gargano Islands is indicative of the large surface areas of these islands. The general geographic pattern of southwestern Europe during the Neogene may therefore correspond to a large continental province including Spain and southern France with some kind of fast-modifying archipelago on its southern rim.

scholarly journals A new bathyal ophiacanthid brittle star (Ophiuroidea: Ophiacanthidae) with Caribbean affinities from the Plio-Pleistocene of the Mediterranean

Zootaxa ◽  
2020 ◽  
Vol 4820 (1) ◽  
pp. 19-30
Author(s):  
LEA D. NUMBERGER-THUY ◽  
BEN THUY
Keyword(s):  
Deep Sea ◽  
Fossil Record ◽  
Brittle Star ◽  
Morphological Comparison ◽  
Western Atlantic ◽  
Faunal Turnover ◽  
Unknown Species ◽  
Recent Species ◽  
The Mediterranean ◽  
New Discovery

Identifiable remains of large deep-sea invertebrates are exceedingly rare in the fossil record. Thus, every new discovery adds to a better understanding of ancient deep-sea environments based on direct fossil evidence. Here we describe a collection of dissociated skeletal parts of ophiuroids (brittle stars) from the latest Pliocene to earliest Pleistocene of Sicily, Italy, preserved as microfossils in sediments deposited at shallow bathyal depths. The material belongs to a previously unknown species of ophiacanthid brittle star, Ophiacantha oceani sp. nov. On the basis of morphological comparison of skeletal microstructures, in particular spine articulations and vertebral articular structures of the lateral arm plates, we conclude that the new species shares closest ties with Ophiacantha stellata, a recent species living in the present-day Caribbean at bathyal depths. Since colonization of the deep Mediterranean following the Messinian crisis at the end of the Miocene was only possibly via the Gibraltar Sill, the presence of tropical western Atlantic clades in the Plio-Pleistocene of the Mediterranean suggests a major deep-sea faunal turnover yet to be explored.

scholarly journals Towards a socially sustainable city concept in Vietnam - international experience, local policy making and preparatory steps

2018 ◽  
Vol 12 (5) ◽  
pp. 73-87
Author(s):  
Nguyen Quang Minh
Keyword(s):  
Driving Forces ◽  
Global Climate ◽  
Local Level ◽  
Social Sustainability ◽  
International Experience ◽  
Environmental Crisis ◽  
Local Policy ◽  
Sustainable City ◽  
Holistic Concept ◽  
Good Individual

Sustainability is a holistic concept in development studies, including urban studies, encompassing natural, technical and social aspects, and has been regarded as an ultimate goal for every nation to strive for as well as for every community to achieve in the context of global climate change, environmental crisis and social instability caused by various socio-economic factors. In addition to theoretical investigation, going for social sustainability in practice requires a well prepared action programme which should begin with learning from international experience (especially when it comes to such a new and superior development concept as social sustainability), understanding both the strengths and the weaknesses, and finding new driving forces. Given that a neighbourhood is a miniature (and a complete unit) of a city, social sustainability may be considered and experimented at the local level first. This proves to be a simpler task to fulfil, a more practical approach to a rather complex issue and a wise option to make. The author aims to analyse some of the world’s best examples before reviewing the current potentials and then comes up with a number of suggestions for the first cornerstones of the future society that will be mainly established on the basis of humanity with core social values and good individual opportunities offered to all citizens. Keywords: social sustainability; sustainable city; neighbourhood.

scholarly journals Molecular Evolutionary Characteristics of the 2019 Novel Coronavirus (SARS-CoV-2) Contracted by Tunisian Citizens: Comparison and Relationship to Other Human and Animal Coronaviruses Based on Spike Glycoprotein-Coding Gene Sequences Analysis

2021 ◽  
Vol 2 (4) ◽  
pp. 9-44
Author(s):  
Moncef Boulila
Keyword(s):  
Driving Forces ◽  
Purifying Selection ◽  
Dromedary Camel ◽  
Spike Glycoprotein ◽  
Animal Group ◽  
Depth Analysis ◽  
Tunisian Patients ◽  
Sequences Analysis ◽  
Human Coronaviruses ◽  
Novel Coronavirus

In contributing to the initiative to address the COVID-19 pandemic and in order to enhance the knowledge on driving forces shaping the evolution of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) (isolated from Tunisian patients), a comparison in relation to other coronaviruses infecting humans (SARS-CoV-1, MERS-CoV, HCoV/229E, HCoV/NL63, HCoV/OC43, and HCoV/HKU1) as well as animals (SARS-CoVs in tiger, bats, civet, pangolin, bovine, and MERS-CoV in dromedary/camel), was conducted. In-depth analysis was carried out involving 115 sequences of spike glycoprotein-coding gene extracted from the international databases. Phylogeny inference allowed the reconstruction of a bifurcating tree where four distinct groups were delineated and at the same time, three animal accessions (SARS-CoV-2/tiger, MERS-CoV/camel, and SARS-CoV/bovine) shifted from the animal group and integrated the human coronaviruses clades. Nonetheless, in the presence of reticulate events such as recombination, networks described better the phylogenetic relationships rather than the classic dendrogram. Thus, networks were produced and identified four clusters containing sharply demarcated subgroups (eight subdivisions). Except networked phylogenies of SARS-CoV-1, SARS-CoV-2, and HCoV/HKU1, all the others showed edges and boxes illustrating the occurrence of incompatibilities related to the sequences of spike glycoprotein-coding gene. Thereby and consolidating this result, three methods (RDP package, GARD, and RECCO) were used to detect breakpoints in aligned sequences. Except the clades SARS-CoV-1 and SARS-CoV-2, all the remaining phylogenetic subdivisions were subject to recombination. Furthermore, the screening of selection pressure in all studied sequences by various statistics-based models of the HyPhy package, showed that, similarly, the lineages belonging to the clades SARS-CoV-1 and SARS-CoV-2 were not under selection. In contrast, all members of the remaining clades underwent, to different extents, adaptive selection as well as purifying selection.

Solute redistribution during in-situ irradiation of alloys in the high voltage electron microscope

1978 ◽  
Vol 36 (1) ◽  
pp. 370-371
Author(s):  
P. R. Okamoto ◽  
N.Q. Lam ◽  
R. L. Lyles
Keyword(s):  
Electron Microscope ◽  
High Voltage ◽  
Driving Forces ◽  
Solute Diffusion ◽  
Solute Redistribution ◽  
Voltage Electron ◽  
High Voltage Electron Microscope ◽  
High Voltage Electron ◽  
Thin Foils ◽  
Solute Atoms

During irradiation of thin foils in a high voltage electron microscope (HVEM) defect gradients will be set up between the foil surfaces and interior. In alloys defect gradients provide additional driving forces for solute diffusion since any preferential binding and/or exchange between solute atoms and mobile defects will couple a net flux of solute atoms to the defect fluxes. Thus, during irradiation large nonequilibrium compositional gradients can be produced near the foil surfaces in initially homogeneous alloys. A system of coupled reaction-rate and diffusion equations describing the build up of mobile defects and solute redistribution in thin foils and in a semi-infinite medium under charged-particle irradiation has been formulated. Spatially uniform and nonuniform damage production rates have been used to model solute segregation under electron and ion irradiation conditions.An example calculation showing the time evolution of the solute concentration in a 2000 Å thick foil during electron irradiation is shown in Fig. 1.

Early ossicle growth in the regenerating disc of a brittle star

1994 ◽  
Vol 52 ◽  
pp. 364-365
Author(s):  
M. Shlepr ◽  
R. L. Turner
Keyword(s):  
Cell Membrane ◽  
Light Microscopy ◽  
De Novo ◽  
Current Model ◽  
Syncytium Formation ◽  
Brittle Star ◽  
Intracellular Location ◽  
Limited Volume ◽  
Tissue Calcification

Calcification in the echinoderms occurs within a limited-volume cavity enclosed by cytoplasmic extensions of the mineral depositing cells, the sclerocytes. The current model of this process maintains that the sheath formed from these cytoplasmic extensions is syncytial. Prior studies indicate that syncytium formation might be dependent on sclerocyte density and not required for calcification. This model further envisions that ossicles formed de novo nucleate and grow intracellularly until the ossicle effectively outgrows the vacuole. Continued ossicle growth occurs within the sheath but external to the cell membrane. The initial intracellular location has been confirmed only for elements of the echinoid tooth.The regenerating aboral disc integument of ophiophragmus filograneus was used to test the current echinoderm calcification model. This tissue is free of calcite fragments, thus avoiding questions of cellular engulfment, and ossicles are formed de novo. The tissue calcification pattern was followed by light microscopy in both living and fixed preparations.

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