Shallow-marine testate amoebae with internal structures from the Lower Devonian of China

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Summary

Testate amoebae, a polyphyletic protist group inhabiting a wide variety of extant ecosystems, have evolved as far back as early Neoproterozoic. However, their fossil record is discontinuous and biased toward empty shells. Here, we report an arcellinid testate amoeba species, Cangwuella ampulliformis gen. nov., sp. nov., from a shallow-marine community in the Early Devonian of Guangxi, southwestern China. With the aid of scanning electron microscopy and X-ray micro-tomography, we find that the shell of our testate amoeba contains some acetabuliform structures. Although such configuration does not match exactly with the known internal structures in extant testate amoebae, our fossils highlight the potential of exploring the ecological relationships between fossil testate amoebae and their associated organisms, and increase our knowledge on the diversity of testate amoebae in Early Devonian environments.

Graphical abstract

Highlights

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A fossil species of Arcellinida is described from the Lower Devonian of China
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Smooth-walled acetabuliform structures are shown in the shell of this testate amoeba
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Shallow-marine arcellinid testate amoebae occurred during the Early Devonian

Abstract

Paleontology; Ecology; Microorganism

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Most cited references 74

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Revisions to the Classification, Nomenclature, and Diversity of Eukaryotes

Sina M Adl, David Bass, Christopher E Lane … (2019)

Abstract This revision of the classification of eukaryotes follows that of Adl et al., 2012 [J. Euk. Microbiol. 59(5)] and retains an emphasis on protists. Changes since have improved the resolution of many nodes in phylogenetic analyses. For some clades even families are being clearly resolved. As we had predicted, environmental sampling in the intervening years has massively increased the genetic information at hand. Consequently, we have discovered novel clades, exciting new genera and uncovered a massive species level diversity beyond the morphological species descriptions. Several clades known from environmental samples only have now found their home. Sampling soils, deeper marine waters and the deep sea will continue to fill us with surprises. The main changes in this revision are the confirmation that eukaryotes form at least two domains, the loss of monophyly in the Excavata, robust support for the Haptista and Cryptista. We provide suggested primer sets for DNA sequences from environmental samples that are effective for each clade. We have provided a guide to trophic functional guilds in an appendix, to facilitate the interpretation of environmental samples, and a standardized taxonomic guide for East Asian users.

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Endosymbiotic associations within protists.

Eva Nowack, Michael Melkonian (2010)

The establishment of an endosymbiotic relationship typically seems to be driven through complementation of the host's limited metabolic capabilities by the biochemical versatility of the endosymbiont. The most significant examples of endosymbiosis are represented by the endosymbiotic acquisition of plastids and mitochondria, introducing photosynthesis and respiration to eukaryotes. However, there are numerous other endosymbioses that evolved more recently and repeatedly across the tree of life. Recent advances in genome sequencing technology have led to a better understanding of the physiological basis of many endosymbiotic associations. This review focuses on endosymbionts in protists (unicellular eukaryotes). Selected examples illustrate the incorporation of various new biochemical functions, such as photosynthesis, nitrogen fixation and recycling, and methanogenesis, into protist hosts by prokaryotic endosymbionts. Furthermore, photosynthetic eukaryotic endosymbionts display a great diversity of modes of integration into different protist hosts. In conclusion, endosymbiosis seems to represent a general evolutionary strategy of protists to acquire novel biochemical functions and is thus an important source of genetic innovation.

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Sporopollenin in the cell wall of Chlorella and other algae: Ultrastructure, chemistry, and incorporation of (14)C-acetate, studied in synchronous cultures.

A W Atkinson, B. Gunning, P John (1972)

Cells of Chlorella fusca var. vacuolata (Cambridge 211/8p) resisted efforts aimed at producing naked protoplasts by enzymatic degradation of the cell wall, and a study of the development and composition of the wall was therefore undertaken. 1. After cytokinesis has produced naked autospores within the mother cell wall, cell wall formation commences outside the autospore plasma membrane with the appearance of small trilaminar plaques. These enlarge while inter-autospore granular material diminishes in quantity, and they eventually fuse to produce a complete trilaminar sheath around each autospore. 2. A microfibrillar, cellulase digestible, layer is deposited between the trilaminar component and the plasma membrane. Meanwhile the corresponding microfibrillar component of the mother cell wall is digested leaving only its resistant trilaminar component. 3. The trilaminar component includes a substance considered to be the polymerized carotenoid, sporopollenin, on the basis of its resistance to extreme extraction procedures including acetolysis, and its infra red absorption spectrum. 4. Two phases of sporopollenin biosynthesis were detected by means of pulse and pulse-chase treatments with (14)C-acetate at intervals during the cell cycle in synchronous cultures. One coincides with the formation of the sporopollenin-containing trilaminar wall component, and the other is 6-8 hours earlier while the cells are in karyokinesis. The former yields labelled sporopollenin directly and the latter probably represents formation of a precursor. 5. Of five other strains of Chlorella tested, only one possesses sporopollenin, and so does one Scenedesmus and two out of three strains of Prototheca. 6. Examination of the wall structure of the above algae suggest a relationship between the presence of sporopollenin and the development of an outer, trilaminar wall component. 7. A survey of the literature gives support to this hypothesis and further suggests that the ability to synthesise sporopollenin is related to the ability to produce secondary carotenoids. 8. The significance of the findings is discussed.

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Author and article information

Contributors

Hong-He Xu

Journal

Journal ID (nlm-ta): iScience

Journal ID (iso-abbrev): iScience

Title: iScience

Publisher: Elsevier

ISSN (Electronic): 2589-0042

Publication date PMC-release: 18 April 2023

Publication date Collection: 19 May 2023

Publication date (Electronic): 18 April 2023

Volume: 26

Issue: 5

Electronic Location Identifier: 106678

Affiliations

[1 ]State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology and Center for Excellence in Life and Paleoenvironment, Chinese Academy of Sciences, Nanjing 210008, China

[2 ]University of Chinese Academy of Sciences, Beijing 100049, China

[3 ]School of Geography and Tourism, Qufu Normal University, Rizhao 276826, China

Author notes

[∗ ]Corresponding author hhxu@ 123456nigpas.ac.cn

[4]

Lead contact

Article

Publisher Item ID: S2589-0042(23)00755-1 Publisher ID: 106678

DOI: 10.1016/j.isci.2023.106678

PMC ID: 10173733

PubMed ID: 37182111

SO-VID: 884cadca-eecd-4d03-907f-5ae3bfd011e7

License:

This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

History

Date received : 7 February 2023

Date revision received : 8 March 2023

Date accepted : 12 April 2023

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