Morphological peculiarities statoconia in statocysts of terrestrial pulmonary snail Helix lucorum.

Vast majority of statoconia in statocysts of Helix lucorum are of oval shape and have smooth surface. Each statoconium in its central part has a nucleus, a spherical mass of 1.5 μ in diameter, surrounded by concentric structures. Minority of statoconia are of subcircular, elongated, rectangular, triangular, irregular, and sometimes fanciful shape and are structured around several nuclei or around small statoconia consolidated by shared growth layers. Apart from statoconia, spherical formations lacking mineral composition of 0.3-2.5 μ in diameter were also found in the statocyst cavity. Similar formations were found in vacuoles of sensory cells of statocyst epithelial lining. It is hypothesized that statoconium nuclei and growth layers around them are of different origin: the nuclei are formed by statocyst sensory cells, while the mineral component is a result of activity of supporting cells.