testate amoebae
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2021 ◽  
pp. jgs2021-061
Author(s):  
Zongjun Yin ◽  
Weichen Sun ◽  
Joachim Reitner ◽  
Maoyan Zhu

The embryo-like fossils from the early Ediacaran Weng'an Biota (Southwest China, 609 million years ago), widely interpreted as members of holozoans, potentially provide insights to understanding the early evolution of development of metazoans and the rise of the animal kingdom. However, the biodiversity of the embryo-like fossil assemblage is largely underestimated, and its more precise phylogenetic affinities within the holozoan tree are still under debate. Here we describe a new species of embryo-like fossil Ostiosphaera rara n. gen. n. sp. from the Ediacaran Weng'an Biota. These three-dimensional, phosphatized specimens exhibit a spherical morphology, an ornamented thick envelope with a circular opening and a membrane-bounded, multicellular inner body. In terms of biological characteristics, Ostiosphaera rara show similarities to a number of extant and fossil analogues including testate amoebae, unicellular green algae, cellular slime mold Fonticuida and co-occurring Weng'an embryo-like fossils. Although the phylogenetic affinity of Ostiosphaera rara is difficult to constrain very precisely based on the available evidence, it is reasonable to follow the holozoan interpretation for them, since that they share the same grade complexity with the co-occurring embryo-like fossils such as Megasphaera and Helicoforamina in terms of the combination of biological features. It is worth mentioning that the new holozoans resemble asexual reproductive gemmules of fossil and living demosponges in size, morphology, circular opening, and cellular anatomy. If the similarity between them reflects biological affinity rather than convergent evolution, this discovery would force us to rethink the evolutionary history of Precambrian sponges.Thematic collection: This article is part of the Advances in the Cambrian Explosion collection available at: https://www.lyellcollection.org/cc/advances-cambrian-explosion


The Holocene ◽  
2021 ◽  
pp. 095968362110604
Author(s):  
Mauro Caffau ◽  
Emanuele Lodolo ◽  
Federica Donda ◽  
Massimo Zecchin ◽  
Jorge G Lozano ◽  
...  

The spectacular water outburst occurring semi-periodically when the ice-dam formed by the external front of the Perito Moreno glacier collapses, is one of the most attracting events in the UNESCO ‘Parque Nacional Los Glaciares’ of southern Patagonia. These occurrences have been documented since 1936. Instead, evidence of previous events has been only indirectly provided by dendrochronology analysis. Here we show for the first time radiocarbon-dated sediment cores collected within a small inlet of Brazo Sur, that is, the southern arm of Lago Argentino that record ice-dammings in the Little Ice Age, at 324–266 cal yrs BP, as measured on a vegetal fragment sampled at ca. 14 cm from the top of a core. A common characteristic of the three sediment cores is the abrupt change in the stratigraphic record found at variable depths of 14–18 cm from the top of the cores. This change is marked by a hiatus spanning ca. 3200 years, separating planar-laminated sediments below from an alternation of erosional and depositional events above it, indicating recurring high-energy conditions generated by the emptying of the lake basin. In addition, we observed significant changes in the abundance of environmental indicators as testate amoebae below and above the hiatus. These well-preserved stratigraphic records highlight the key role of glaciolacustine deposits in reconstructing the glacial dynamics and palaeoclimate evolution of a glaciated region.


2021 ◽  
Vol 131 ◽  
pp. 108122
Author(s):  
Thomas G. Sim ◽  
Graeme T. Swindles ◽  
Paul J. Morris ◽  
Andy J. Baird ◽  
Dan J. Charman ◽  
...  

Check List ◽  
2021 ◽  
Vol 17 (5) ◽  
pp. 1205-1219
Author(s):  
Cínthya Viana Souza Rocha ◽  
Matheus Santos dos Anjos ◽  
Deivson Araújo Brandão ◽  
Caio Ceza da Silva Nunes ◽  
Mariane Amorim Rocha ◽  
...  

Testate amoebae are single-celled protists whose protoplasm is contained within a carapace composed of gelatinous to imbricated chitinous plates having variable chemical compositions. We inventoried the testate amoebae community present in the plankton and periphyton of the Pantanal dos Marimbus swamp in Bahia state, Brazil. Sixty-five samples of plankton and periphyton were analyzed during May and September/2014 and April/2015. We identified 65 taxa of testate amoebae distributed in eight families, 15 genera, 45 species, and 16 varieties. The most representative families were Arcellidae, Centropyxidae, and Difflugiidae, corresponding to 24.6%, 19.7% and 14.8% of the taxa respectively. The periphyton had greater richness (59 taxa) than the plankton (39 taxa). Of the taxa found, 15 represent new records for Bahia and 14 for northeastern Brazil. The Marimbus Pantanal swamp showed an expressive richness of testate amoebae, and our data increases the number of species of these organisms known to Bahia and northeastern Brazil, where work with those organisms is still scarce.


2021 ◽  
Vol 784 ◽  
pp. 147026
Author(s):  
Jean Claude Ndayishimiye ◽  
Tian Lin ◽  
Pascaline Nyirabuhoro ◽  
Gan Zhang ◽  
Wenjing Zhang ◽  
...  

The Holocene ◽  
2021 ◽  
pp. 095968362110332
Author(s):  
Agnieszka Mroczkowska ◽  
Piotr Kittel ◽  
Katarzyna Marcisz ◽  
Ekaterina Dolbunova ◽  
Emilie Gauthier ◽  
...  

Peatlands are important records of past environmental changes. Based on a multiproxy analysis, the main factors influencing the evolution of a peatland can be divided into autogenic and allogenic. Among the important allogenic factors, apart from climate change, are deforestation and drainage, which are directly associated with human impact. Numerous consequences arise from these processes, the most important of which are physical and chemical denudation in the catchment and the related hydrological disturbances in the catchment and peatland. The present study determined how human activities and the past climatic variability mutually influenced the development of a small peatland ecosystem. The main goals of the study were: (1) to trace the local changes of the peatland history over the past 600 years, (2) to investigate their relationship with changes in regional hydroclimate patterns, and (3) to estimate the sensitivity of a small peatland to natural and human impact. Our reconstructions were based on a multiproxy analysis, including the analysis of pollen, macrofossils, Chironomidae, Cladocera, and testate amoebae. Our results showed that, depending on the changes in water level, the history of peatland can be divided into three phases as follows: 1/the phase of stable natural conditions, 2/phase of weak changes, and 3/phase of significant changes in the catchment. Additionally, to better understand the importance of the size of catchment and the size of the depositional basin in the evolution of the studied peatland ecosystem, we compared data from two peatlands – large and small – located close to each other. The results of our study indicated that “size matters,” and that larger peatlands are much more resilient and resistant to rapid changes occurring in the direct catchment due to human activities, whereas small peatlands are more sensitive and perfect as archives of environmental changes.


2021 ◽  
pp. 125828
Author(s):  
Carmen Soler-Zamora ◽  
Rubén González-Miguéns ◽  
Antonio Guillén-Oterino ◽  
Enrique Lara

Diversity ◽  
2021 ◽  
Vol 13 (6) ◽  
pp. 269
Author(s):  
Rafael Carballeira ◽  
Xabier Pontevedra-Pombal

Testate amoebae are one of the most studied groups of microorganisms in Sphagnum peatland ecosystems and, therefore, one of the most reliable bioindicators of their ecological status. Peatland ecosystems are supported by a delicate biogeochemical balance that leads to the formation of peat, one of the main sinks of C, as a result of soil–atmosphere interaction, but currently they are one of the most threatened wetland types at their southern distribution limit. In the European continent, where climatic conditions limit peat formation, they have endured significant anthropic pressure for centuries, and the risk of loss of biodiversity linked to these ecosystems is critical. In addition, peatlands are poorly known ecosystems in the Iberian Peninsula compared with other wetlands; therefore, we have studied the chemical parameters of water and the diversity patterns of testate amoebae in the western Iberian Peninsula to better understand the current status of these ecosystems. The analysis of testate amoeba communities showed an inverse relationship between the diversity and conservation status of these peatlands, both in relation to chemical parameters (i.e., pH, electrical conductivity, phosphates) and to the proportion of anthropized area, with a marked geographical pattern in the degree of anthropogenic disturbance.


Pedobiologia ◽  
2021 ◽  
pp. 150732
Author(s):  
Manfred Wanner ◽  
Yoichiro Sogame ◽  
Miki Shimizu

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