Physiological versus Biological Control in Bivalve Calcite Prisms: Comparison of Euheterodonts and Pteriomorphs.

Harper, E. M. and Checa, A (2017) Physiological versus Biological Control in Bivalve Calcite Prisms: Comparison of Euheterodonts and Pteriomorphs. The Biological Bulletin, 232. pp. 19-29. ISSN 1464-7931 DOI https://doi.org/10.1086/691382

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Abstract

Multiple groups of bivalve molluscs produce calcitic shell layers, many of these broadly classified as "prismatic." Various pteriomorphian bivalves (such as oysters, pterioids, and mussels) secrete prismatic microstructures with high organic content and clear, strong biological control. However, we present the results of a detailed analysis by scanning electron microscopy (SEM), thermogravimetric analysis, and electron backscatter diffraction to characterize the calcitic prisms in two different clades within the euheterodont bivalves: the extant Chama arcana and the extinct rudists. These results show that the form of prisms constructed is both closely similar between the two taxa and significantly different from those of the pteriomorph bivalves. Most notably, C. arcana and the extinct rudists lack the clear organic outer envelopes and uniform polygonal, cross-sectional appearance. Instead, they form interdigitating crystals of very varied diameters, with some crystals encapsulating others. We advocate retaining the term "fibrillar prisms" to classify these euheterodont microstructures. These fibrillar prisms are more closely similar to abiotic speleothem deposits than to the calcitic prisms of pteriomorph bivalves. We argue that calcite prism growth in euheterodonts is dominated by abiotic constraints whereas, in pteriomorphs (such as oysters, pterioids, and mussels), it is under strong biological control.

Item Type:	Article
Uncontrolled Keywords:	2016AREP; IA71
Subjects:	04 - Palaeobiology
Divisions:	04 - Palaeobiology
Journal or Publication Title:	The Biological Bulletin
Volume:	232
Page Range:	pp. 19-29
Identification Number:	https://doi.org/10.1086/691382
Depositing User:	Sarah Humbert
Date Deposited:	15 Feb 2018 18:01
Last Modified:	15 Feb 2018 18:01
URI:	http://eprints.esc.cam.ac.uk/id/eprint/4105

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