title: SEM observation of structural (non-mineralogical) alteration inside the previously crystallized nacreous layer of Crenomytilus grayanus (Bivalvia: Mytilidae).
abstract: A microstructural and mineralogical study shows the transition of aragonitic nacreous tablets to aragonitic prisms inside previously secreted nacre, i.e. without contact with the mantle or extrapallial fluid, in a field-collected mytilid bivalve Crenomytilus grayanus (D.). The intermediate zone between nacre and new prisms is represented by nacre tablets "stuck together" or by disordered calcium carbonate material. The modified nacre forms aragonitic lenses of prisms (ALPs). These lenses may reach 500 μm in thickness below the tunnels excavated by the shell borers. ALPs are similar to myostracal prisms in mineralogy, morphology, and orientation, but differ from those in the outer shell layer. The process of ALPs formation is different to that of normal shell formation (e.g. nacre-prisms transition between prismatic and nacreous layers), remote biomineralization, extra shell thickening, as well as, shell repair, erosion, deformation or disease. Response to shell excavation by boring organisms is discussed as the reason for the appearance of ALPs.
authors.affiliation: Institut des sciences de la mer de Rimouski (ISMER), Université du Québec à Rimouski, 310, allée des Ursulines, Rimouski QC G5L 3A1, Canada. m.zuykov@mail.ru
authors.forename: Michael
authors.initials: M
authors.lastname: Zuykov
authors.forename: Emilien
authors.initials: E
authors.lastname: Pelletier
authors.forename: Galina
authors.initials: G
authors.lastname: Kolyuchkina
mesh_terms: D060105:Animal Shells / Q000737:chemistry*; D000818:Animals; D002119:Calcium Carbonate / Q000737:chemistry; D008855:Microscopy, Electron, Scanning / Q000662:veterinary; D049879:Mytilidae / Q000378:metabolism*; D060734:Nacre / Q000737:chemistry*
chemical_list: D060734:Nacre; D002119:Calcium Carbonate