scholarly journals High Magnesium Calcite and Disordered Dolomite Growth on Leaf-cutting Ants: Challenges and Implications

2020 ◽  
Vol 26 (S2) ◽  
pp. 92-94
Author(s):  
Yihang Fang ◽  
Hongjie Li ◽  
Huifang Xu
Keyword(s):  
Magnesium Calcite ◽  
Leaf Cutting ◽  
High Magnesium Calcite

scholarly journals Biomineral armor in leaf-cutter ants

2020 ◽  
Vol 11 (1) ◽  
Author(s):  
Hongjie Li ◽  
Chang-Yu Sun ◽  
Yihang Fang ◽  
Caitlin M. Carlson ◽  
Huifang Xu ◽  
...  
Keyword(s):  
Protective Role ◽  
In Vitro Synthesis ◽  
Anatomical Structures ◽  
Magnesium Calcite ◽  
Leaf Cutting ◽  
High Magnesium Calcite ◽  
Acromyrmex Echinatior

AbstractAlthough calcareous anatomical structures have evolved in diverse animal groups, such structures have been unknown in insects. Here, we report the discovery of high-magnesium calcite [CaMg(CO3)2] armor overlaying the exoskeletons of major workers of the leaf-cutter ant Acromyrmex echinatior. Live-rearing and in vitro synthesis experiments indicate that the biomineral layer accumulates rapidly as ant workers mature, that the layer is continuously distributed, covering nearly the entire integument, and that the ant epicuticle catalyzes biomineral nucleation and growth. In situ nanoindentation demonstrates that the biomineral layer significantly hardens the exoskeleton. Increased survival of ant workers with biomineralized exoskeletons during aggressive encounters with other ants and reduced infection by entomopathogenic fungi demonstrate the protective role of the biomineral layer. The discovery of biogenic high-magnesium calcite in the relatively well-studied leaf-cutting ants suggests that calcareous biominerals enriched in magnesium may be more common in metazoans than previously recognized.

scholarly journals Biomineral armor in leaf-cutter ants

2020 ◽  
Author(s):  
Hongjie Li ◽  
Chang-Yu Sun ◽  
Yihang Fang ◽  
Caitlin M. Carlson ◽  
Huifang Xu ◽  
...  
Keyword(s):  
Protective Role ◽  
Nucleation And Growth ◽  
Anatomical Structures ◽  
Magnesium Calcite ◽  
Leaf Cutting ◽  
High Magnesium Calcite ◽  
Acromyrmex Echinatior

AbstractAlthough calcareous anatomical structures have evolved in diverse animal groups, such structures have been unknown in insects. Here, we report the discovery of high-magnesium calcite [CaMg(CO3)2] armor overlaying the exoskeletons of major workers of the leaf-cutter ant Acromyrmex echinatior. Live-rearing and in vitro synthesis experiments indicate that the biomineral layer accumulates rapidly as ant workers mature, that the layer is continuously distributed, covering nearly the entire integument, and that the ant epicuticle catalyzes biomineral nucleation and growth. In situ nanoindentation demonstrates that the biomineral layer significantly hardens the exoskeleton. Increased survival of ant workers with biomineralized exoskeletons during aggressive encounters with other ants and reduced infection by entomopathogenic fungi demonstrate the protective role of the biomineral layer. The discovery of biosynthesized high-magnesium calcite in the relatively well-studied leaf-cutting ants suggests that calcareous biominerals enriched in magnesium may be more common in metazoans than previously recognized.

High-Magnesium Calcite Mesocrystals: Formation in Aqueous Solution under Ambient Conditions

2017 ◽  
Vol 56 (51) ◽  
pp. 16202-16206 ◽  
Author(s):  
Pao-Tao Yu ◽  
Chieh Tsao ◽  
Chun-Chieh Wang ◽  
Chun-Yu Chang ◽  
Chia-Hsin Wang ◽  
...  
Keyword(s):  
Aqueous Solution ◽  
Ambient Conditions ◽  
Magnesium Calcite ◽  
High Magnesium Calcite

scholarly journals THE HIGH-MAGNESIUM CALCITE ORIGIN OF NUMMULITID FORAMINIFERA AND IMPLICATIONS FOR THE IDENTIFICATION OF CALCITE DIAGENESIS

Palaios ◽  
2020 ◽  
Vol 35 (10) ◽  
pp. 421-431
Author(s):  
LAURA J. COTTON ◽  
DAVID EVANS ◽  
SIMON J. BEAVINGTON-PENNEY
Keyword(s):  
Magnesium Content ◽  
Carbonate Diagenesis ◽  
X Ray Diffraction ◽  
Larger Benthic Foraminifera ◽  
X Ray ◽  
Low Magnesium ◽  
Fossil Material ◽  
Magnesium Calcite ◽  
High Magnesium Calcite ◽  
Geochemical Studies

ABSTRACT Nummulites were one of the most abundant and widespread larger benthic foraminifera of the Paleogene, however, confusion remains within the literature as to whether their original test mineralogy was high or low magnesium calcite. As the number of studies using proxies based on Nummulites and related nummulitid geochemistry increase, it is essential to have a firm understanding of test composition to assess preservation within potential samples, and to interpret results. Here we employ a combination of X-ray diffraction, Fourier transform infra-red spectroscopy, and laser ablation ICPMS to determine magnesium content across exceptionally preserved and poorly preserved fossil material as well as modern examples of nummulitids—showing conclusively a primary intermediate to high magnesium calcite composition. This composition appears to be closely related to fluctuating ocean chemistry through the Paleogene. Using these results as an indicator of preservation we examine variation in trace element data across a suite of samples, and introduce the concept of the preservagram, a method of quickly visualizing different styles of carbonate diagenesis. Understanding the original mineralogy of nummulitids and, therefore, the extent to which specimens have been diagenetically altered, is essential as larger foraminifera are increasingly used in geochemical studies.

A precise and accurate method for the quantitative determination of carbonate minerals by X-Ray diffraction using a spiking technique

1971 ◽  
Vol 38 (296) ◽  
pp. 481-487 ◽  
Author(s):  
H. A. Gunatilaka ◽  
Roger Till
Keyword(s):  
Diffraction Method ◽  
Accurate Method ◽  
X Ray Diffraction ◽  
Carbonate Minerals ◽  
X Ray ◽  
Low Magnesium ◽  
Coefficients Of Variation ◽  
Magnesium Calcite ◽  
Peak Areas ◽  
High Magnesium Calcite

SummaryA precise and accurate X-ray diffraction method has been developed whereby the weight percentages of aragonite and low- and high-magnesium calcite are determined from the integrated peak areas of spiked and unspiked samples. The spike mixture was prepared from organisms extracted from the samples to be analysed. Use of a spiking method also avoided the preparation of working curves from artificial mixtures of carbonate minerals, which may not have the same diffraction behaviour as the unknowns. A test of the precision of the method indicates the following coefficients of variation: aragonite, 1·4 %; low-magnesium calcite, 1·5 %; high-magnesium calcite, 7·8 %. A test of the accuracy of the method indicates no significant bias in any of the carbonate results, except in samples where high-magnesium calcite values are below 10 %. Quartz may also be determined by this method (coefficient of variation 23·9 %; positive bias in values greater than 10 %).

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