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. 2023 Apr 18;26(5):106678.
doi: 10.1016/j.isci.2023.106678. eCollection 2023 May 19.

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

Kai Wang  1   2 , Hong-He Xu  1 , Bing-Cai Liu  1   2 , Jiao Bai  1   2 , Yao Wang  3 , Peng Tang  1 , Jian-Feng Lu  1 , Yi Wang  1
Affiliations

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

Kai Wang et al. iScience. .

Abstract

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.

Keywords: Ecology; Microorganism; Paleontology.

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Conflict of interest statement

The authors declare no competing interests.

Figures

None
Graphical abstract
Figure 1
Figure 1
Geographic and geologic map of the fossil locality (A) Geographic map of Guangxi Zhuang Autonomous Region, southwestern China. Black rectangle shows the general location of the studied area. (B) Geologic map of the southern part of the Shiqiao Town, showing the outcrops of Lower Devonian and the sampling locality.
Figure 2
Figure 2
Scanning electron microscopy photographs of Cangwuella ampulliformis gen. nov., sp. nov. from the Cangwu Formation in Guangxi, southwestern China (A) Two attached tests with a laceration on the shell of the right one, NIGP 179653. (B) Close-up of the yellow in Figure 2A, showing the acetabuliform structures preserved inside the shell. (C) A test covered with filaments, NIGP 179648. (D) A test with a well-preserved aperture, holotype, NIGP 179657. (E) Close-up of the yellow box in Figure 2D, highlighting the undulating margin of the aperture. (F) Close-up of the yellow box in Figure 2C, showing that the filaments are hollow. (G) Close-up of the yellow box in Figure 2J, showing the ‘pores’ on the shell wall surface. (H) A test with a broken chamber, paratype, NIGP 179644. (I) Close-up of the yellow box in Figure 2H, showing the honeycomb structure, which is composed of three layers. (J) A test with an individual acetabuliform structure falling out of the chamber, near the aperture, NIGP 179658. (K) Close-up of the white box in Figure 2J, showing the acetabuliform structure. Scale bar is 50 μm for Figures 2A, 2C, 2D, 2H and 2J; 20 μm for Figures 2B and 2E; 10 μm for Figures 2F, 2G, 2I and 2K.
Figure 3
Figure 3
Three-dimensional reconstruction of Cangwuella ampulliformis gen. nov., sp. nov., based on synchrotron radiation X-ray tomography (A) Lateral view, with S1 and S2 marking the location of slice views in Figures 3C and 3F respectively, paratype, NIGP 179659. (B) Transparent view of Figure 3A, showing the acetabuliform structures preserved inside the shell. (C) View from S1 in Figure 3A. (D) Proximal (vertical) view of the yellow structure in Figure 3C, showing the oval shape. (E) Equatorial (lateral) view of the yellow structure in Figure 3C, showing the round-bottomed acetabuliform shape. (F) View from S2 in Figure 3A. Scale bar is 50 μm for Figures 3A, 3B, 3C and 3F; 20 μm for Figures 3D and 3E.
Figure 4
Figure 4
Palaeoecosystem reconstruction of the Lower Devonian Cangwu Formation in southwestern China This figure shows the paleoecosystem with a coast setting. Testate amoeba Cangwuella ampulliformis gen. nov., sp. nov. lived in a nearshore environment with algae and the euchelicerate Houia. Tall to diminutive plants on land belong to Zosterophyllopsida and rhyniophytoids respectively.
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