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Please use this identifier to cite or link to this item: http://hdl.handle.net/10481/31084

Title: Early Stage Biomineralization in the Periostracum of the ‘Living Fossil’ Bivalve Neotrigonia
Authors: Checa González, Antonio
Salas, Carmen
Harper, Elizabeth M.
Bueno-Pérez, Juan de Dios
Issue Date: 2014
Abstract: A detailed investigation of the shell formation of the palaeoheterodont ‘living fossil’ Neotrigonia concentrated on the timing and manufacture of the calcified ‘bosses’ which stud the outside of all trigonioid bivalves (extant and fossil) has been conducted. Electron microscopy and optical microscopy revealed that Neotrigonia spp. have a spiral-shaped periostracal groove. The periostracum itself is secreted by the basal cell, as a thin dark pellicle, becoming progressively transformed into a thin dark layer by additions of secretions from the internal outer mantle fold. Later, intense secretion of the internal surface of the outer mantle fold forms a translucent layer, which becomes transformed by tanning into a dark layer. The initiation of calcified bosses occurred at a very early stage of periostracum formation, deep within the periostracal groove immediately below the initialmost dark layer. At this stage, they consist of a series of polycyclically twinned crystals. The bosses grow as the periostracum traverse through the periostracal groove, in coordination with the thickening of the dark periostracal layer and until, upon reaching the mantle edge, they impinge upon each other and become transformed into large prisms separated by dark periostracal walls. In conclusion, the initial bosses and the external part of the prismatic layer are fully intraperiostracal. With later growth, the prisms transform into fibrous aggregates, although the details of the process are unknown. This reinforces the relationships with other groups that have the ability to form intraperiostracal calcifications, for example the unionoids with which the trigonioids form the clade Paleoheterodonta. The presence of similar structures in anomalodesmatans and other euheterodonts raises the question of whether this indicates a relationship or represents a convergence. The identification of very early calcification within an organic sheet has interesting implications for our understanding of how shells may have evolved.
Sponsorship: Coordinated Research Projects CGL2010-20748-C02-01 (AGC, EMH) and 02 (CS) (DGI, Spanish MICINN); the Research Group RNM363 (Consejería de Economía, Investigación, Ciencia y Empleo, Junta de Andalucía); and the FP7 COST Action TD0903 of the European Community.
Publisher: Public Library of Science (PLOS)
Keywords: Basal cells
Bivalves
Calcification
Crystals
Microvilli
Prisms
Secretion
Vesicles
URI: http://hdl.handle.net/10481/31084
ISSN: 1932-6203
Rights : Creative Commons Attribution-NonCommercial-NoDerivs 3.0 License
Citation: Checa, A.; Salas, C.; Harper, E.M.; Bueno-Pérez, J.D. Early Stage Biomineralization in the Periostracum of the ‘Living Fossil’ Bivalve Neotrigonia. Plos One, 9(2): e90033 (2014). [http://hdl.handle.net/10481/31084]
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