Comparison of the global crystallographic texture of minerals in the shells of Bathymodiolus thermophilus Kenk et B.R. Wilson, 1985 and species of the genus Mytilus Linnaeus, 1758

The global crystallographic texture of calcite and aragonite in the shells of the bivalves Bathymodiolus thermophilus, Mytilus galloprovincialis, M. edulis and M. trossulus was studied by means of neutron diffraction. It was revealed that the general appearance of pole figures isolines of both minerals coincides for the studied species. The crystallographic texture sharpness evaluated by means of pole density on the calcite pole figures ((0006), $\left(10\overline{1}4\right)$) and aragonite pole figures ((012)/(121), (040)/(221)) coincides or has close values for deep-sea hydrothermal species B. thermophilus and the studied shallow-water species of the genus Mytilus. The calcite pole figures (0006) and $\left(10\overline{1}4\right)$ of B. thermophilus show a shift in the position of texture maximum values compared to corresponding pole figures of other mussels. The shell microstructure of all studied mollusks is similar, only the shape of the fibers of B. thermophilus differs. Global crystallographic texture is a stable feature of the family Mytilidae. The extreme habitat conditions of the hydrothermal biotope do not significantly affect the crystallographic texture of B. thermophilus.