Ediacaran biota: The dawn of animal life in the shadow of giant protists

Seilacher, Adolf; Grazhdankin, Dmitri; Legouta, Anton

doi:10.2517/prpsj.7.43

Cited by 242 publications

(209 citation statements)

References 30 publications

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“…However, many three-dimensionally preserved erniettomorph and rangeomorph modules are filled with sediment but show no evidence of opening or damaging. Thus, it is possible that they incorporated sediments during growth, similarly to modern xenophyophores, which uptake sediments and organic waste within their body to increase mechanical strength and SA/V ratios (32)(33)(34). Similar conclusions about sand ingestion were reached concerning Ernietta ( Fig.…”

Section: Resultsmentioning

confidence: 67%

Osmotrophy in modular Ediacara organisms

Laflamme

Xiao

Kowalewski

2009

Proc. Natl. Acad. Sci. U.S.A.

140

130

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The Ediacara biota include macroscopic, morphologically complex soft-bodied organisms that appear globally in the late Ediacaran Period (575-542 Ma). The physiology, feeding strategies, and functional morphology of the modular Ediacara organisms (rangeomorphs and erniettomorphs) remain debated but are critical for understanding their ecology and phylogeny. Their modular construction triggered numerous hypotheses concerning their likely feeding strategies, ranging from micro-to-macrophagus feeding to photoautotrophy to osmotrophy. Macrophagus feeding in rangeomorphs and erniettomorphs is inconsistent with their lack of oral openings, and photoautotrophy in rangeomorphs is contradicted by their habitats below the photic zone. Here, we combine theoretical models and empirical data to evaluate the feasibility of osmotrophy, which requires high surface area to volume (SA/V) ratios, as a primary feeding strategy of rangeomorphs and erniettomorphs. Although exclusively osmotrophic feeding in modern ecosystems is restricted to microscopic bacteria, this study suggests that (i) fractal branching of rangeomorph modules resulted in SA/V ratios comparable to those observed in modern osmotrophic bacteria, and (ii) rangeomorphs, and particularly erniettomorphs, could have achieved osmotrophic SA/V ratios similar to bacteria, provided their bodies included metabolically inert material. Thus, specific morphological adaptations observed in rangeomorphs and erniettomorphs may have represented strategies for overcoming physiological constraints that typically make osmotrophy prohibitive for macroscopic life forms. These results support the viability of osmotrophic feeding in rangeomorphs and erniettomorphs, help explain their taphonomic peculiarities, and point to the possible importance of earliest macroorganisms for cycling dissolved organic carbon that may have been present in abundance during Ediacaran times.erniettomorphs ͉ rangeomorphs ͉ Fractofusus ͉ Pteridinium

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Section: Resultsmentioning

confidence: 67%

Osmotrophy in modular Ediacara organisms

Laflamme

Xiao

Kowalewski

2009

Proc. Natl. Acad. Sci. U.S.A.

140

130

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“…Interpretations of the fossils range from members of the modern animal phyla (e.g. Glaessner, 1984), to members of an extinct group (the Vendobionta; Seilacher, 1992), or unicellular protists (Seilacher et al, 2003), or even fungi (Peterson et al, 2003) or lichens (Retallack, 1994). Our interpretations of the evolutionary relationships of these fossils lead us to use the taxonomic grouping Petalonamae Pflug (see Pflug 1972) to describe the various fossils of the Ediacaran Period, such as Charnia, Pteridinium and even, in our view, Dickinsonia (Fig.…”

Section: Implications For Macrofossil Preservationmentioning

confidence: 99%

Remarkable preservation of microbial mats in Neoproterozoic siliciclastic settings: Implications for Ediacaran taphonomic models

Callow

Brasier

2009

Earth-Science Reviews

123

101

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It is beyond doubt that the appearance of infaunal bioturbation and metazoan biomineralization across the Ediacaran-Cambrian transition irreversibly affected the nature of marine sediment architecture and biogeochemistry. Here we review those changes in relation to their likely effect upon the processes of fossil preservation, especially within siliciclastic sediments. Processes of soft-tissue preservation in siliciclastic settings from the Ediacaran Period, including microbes and microbial mats as well as Ediacaran macrofossils, are here reviewed within this context. Highlighted examples include the exceptional preservation of microbes found in association with wrinkle structures and Ediacaran macrofossils in England and Newfoundland (replicated by silicate minerals) and in the White Sea region of Russia (replicated by iron sulphide). These occurrences show that soft-tissue preservation in siliciclastic settings went well beyond that typical for Ediacaran macrofossils alone and also extended to similar modes of preservation in associated microbes. Using these new observations it can be argued that several existing explanations for Ediacaran fossil preservation can be united within a biogeochemical model that involves evolution of the sediment Mixed Layer across this transition.

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“…Extant microbial populations collectively are estimated to number at least 4,000,000,000,000,000,000,000,000,000,000 (4 quintillion or 4 × 10 30 ) cells [7], making them the most abundant life form on Earth. The current fossil records suggest that the dawn of Animalia occurred much more recently during the Ediacaran period, an epoch occurring 635-541 million years ago (Mya) [8,9]. Bilaterian animals subsequently flourished and diversified during the Cambrian (542-488 Mya) in an event referred to as the Cambrian Explosion.…”

Section: Introductionmentioning

confidence: 99%

Towards an Evolutionary Model of Animal-Associated Microbiomes

Yeoman

Chia

Yıldırım

et al. 2011

Entropy

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Second-generation sequencing technologies have granted us greater access to the diversity and genetics of microbial communities that naturally reside endo-and ecto-symbiotically with animal hosts. Substantial research has emerged describing the diversity and broader trends that exist within and between host species and their associated microbial ecosystems, yet the application of these data to our evolutionary understanding of microbiomes appears fragmented. For the most part biological perspectives are based on limited observations of oversimplified communities, while mathematical and/or computational modeling of these concepts often lack biological precedence. In recognition of this disconnect, both fields have attempted to incorporate ecological theories, although their applicability is currently a subject of debate because most ecological theories were developed based on observations of macro-organisms and their ecosystems. For the OPEN ACCESSEntropy 2011, 13 571 purposes of this review, we attempt to transcend the biological, ecological and computational realms, drawing on extensive literature, to forge a useful framework that can, at a minimum be built upon, but ideally will shape the hypotheses of each field as they move forward. In evaluating the top-down selection pressures that are exerted on a microbiome we find cause to warrant reconsideration of the much-maligned theory of multi-level selection and reason that complexity must be underscored by modularity.

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Ediacaran biota: The dawn of animal life in the shadow of giant protists

Cited by 242 publications

References 30 publications

Osmotrophy in modular Ediacara organisms

Osmotrophy in modular Ediacara organisms

Remarkable preservation of microbial mats in Neoproterozoic siliciclastic settings: Implications for Ediacaran taphonomic models

Towards an Evolutionary Model of Animal-Associated Microbiomes

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