The brachiopods of the orders Lingulida, Craniida, Orthida, Pentamerida, Rhynchonellida, Chonetida, Spiriferida, Spiriferinida, and Athyridida from the Middle–Upper Devonian and Lower...

A both wild and farmed mussels in natural conditions, anthropogenic inputs are usually reflected in the increase of the content of specific elements. To determine the possible effect of the elemental patterns of farmed and wild mussels (Mytilus galloprovincialis) collected in the Saldanha Bay area (South Africa) on the crystallographic texture of the shells, the content of 20 elements in shells and 24 in the soft tissue of mussels was determined by neutron activation analysis. The crystallographic texture of mussel shells was analyzed using time-of-flight neutron diffraction. The wild mussels from open ocean site live in stressful natural conditions and contain higher amounts of the majority of determined elements in comparison with mussels farmed in closed water areas with anthropogenic loadings. The changes between the maximums of the same pole figures of the three samples are in the range of variability identified for the genus Mytilus. The content of Cl, Sr, and I was the highest in mussels from the open ocean site, which is reflected by the lowest mass/length ratio. The determined crystallographic textures of mussels are relatively stable as shown in the analyzed pole figures despite the concentrations of Na, Mg, Cl, Br, Sr, and I in shells, which significantly differ for wild and farmed mussels. The stability of the crystallographic texture that we observed suggests that it can be used as a reference model, where if a very different texture is determined, increased attention to the ecological situation should be paid.

The crystallographic texture of modern, subfossil and fossils (Upper Pleistocene) shells of the bivalves Mytilus galloprovincialis, modern and subfossil Mytilus trossulus, as well as modern and fossil (Upper Pleistocene) Ostrea edulis are studied using neutron diffraction. It is revealed that shells of mussel species of different ages are characterized by a high ordering of calcite crystals—a sharp texture. Aragonite crystals are poorly distributed, depending on the shape of the valves. In a warm, dry climate, shells of M. galloprovincialis undergo stratification of the shell matter, which violates the crystallographic texture. Under land conditions, the ordering of calcite crystals in M. galloprovincialis shells decreases. In the subfossil M. trossulus and fossil M. galloprovincialis and O. edulis, the crystallographic texture intensity of the calcite and aragonite changes over hundreds and thousands of years.

It is assumed that the crystallographic texture of minerals in the shells of recent and fossil mollusks is very stable. To check this, it is necessary to examine the shells of animals that had lain in sediments for millions of years and lived in different conditions. It is revealed that the crystallographic texture of calcite in the shells of Gryphaea dilatata from deposits from the Middle Callovian–Lower Oxfordian (Jurassic), which lived in different water areas, is not affected by habitat conditions and the fossilization process. The crystallographic texture was studied using pole figures measured by neutron diffraction. The neutron diffraction method makes it possible to study the crystallographic texture in large samples—up to 100 cm³ in volume without destroying them. The recrystallization features of the G. dilatata valve, which affect the crystallographic texture, were discovered for the first time. This is determined from the isolines appearance of pole figures. The crystallographic texture of the G. dilatata mollusks’ different valves vary depending on their shape. The pole figures of calcite in the thick-walled valves of G. dilatata, Pycnodonte mirabilis, and Ostrea edulis are close to axial and display weak crystallographic texture.