Renewal mechanisms of buccal armature in Flabellina verrucosa (Nudibranchia: Aeolidida: Flabellinidae)

General morphology and ultrastructure of the radula of Testudinalia testudinalis (O. F. Müller, 1776) (Patellogastropoda, Gastropoda)

“…The correlation between the number of mature teeth and the speed of shedding old teeth were not previously documented (Isarankura & Runham, ; Padilla, Dittman, Franz, & Sladek, ), but the correlation between the diet, length of the radula and the speed of shedding have been presumed by Underwood (). The same set of radular zones, except maturation zone were teeth increase in size, have also been recognized in other gastropods, including Flabellina verrucosa (Sars, 1829), Helix pomatia , and Limax flavus , Linnaeus, 1758 (Kerth, ; Mikhlina et al, ).…”

“…As far as known and in contrast to our findings, newly formed teeth of other gastropods (e.g., Helix pomatia Linnaeus, 1758) have the same size as mature teeth (Kerth, ; Kerth, ; Wiesel & Peters, ). The increasing size of the teeth in T. testudinalis can be explained by the extraordinary long radula, having more than 120 rows in contrast to 20–30 rows in Heterobranchia (Kerth, ; Mikhlina et al, ). This increase in length has a corresponding increase in the maturation zone where the teeth are enlarged and thickened by the supraradular epithelial secretion activity.…”

“…This is when the polymerization of the vesicle material occurs. Teeth are synthesized by microvillar secretion in the single studied patellid species Patella pellucida Linnaeus, 1758 (Peters, ) and several species of Heterobranchia (Hughes, ; Kerth, ; Mackenstedt & Märkel, ; Mikhlina et al, ; Wiesel & Peters, ). Two studied species of Caenogastropoda (Mischor & Märkel, ; Vortsepneva et al, ; see Table ) combine the apocrine and microvillar secretion during tooth formation. The tooth shape in T. testudinalis is not determined by microvilli as it was suggested for other gastropods (Runham, ; Wiesel & Peters, ), but by the localization of odontoblasts in the cushions.…”

“…The general morphology of the gastropod radula is well studied and is used as an important character for taxonomy on different levels (Lindberg, ; Moskalev, ; Powell, ; Sasaki, ), yet, there are only a few studies dedicated to the morphogenesis of the radula and its ultrastructure (Table ; Kerth, ; Mackenstedt & Märkel, ; Mikhlina et al, ; Mischor & Märkel, ; Peters, ; Vortsepneva et al, ; Wiesel & Peters, ).…”

“…Based on these studies we defined three main trends in radular formation at an ultrastructural level: (a) a single tooth could be synthesized by a varying number of cells, including a single odontoblast, as in Opisthobranchia, to many hundreds of odontoblasts in Patellogastropoda; (b) shape and size of the odontoblasts differ in different groups and probably depend on the quantity of the odontoblasts; and (c) new teeth are formed by apocrine secretion (Patelogastropoda), microvillar growth (Patelogastropoda and Heteronranchia), or the secretion of a mixed type (Caenogastropoda; Table ; Hughes, ; Kerth, ; Mackenstedt & Märkel, ; Mikhlina et al, ; Mischor & Märkel, ; Peters, ; Rinkevich, ; Wiesel & Peters, ). Nevertheless, we still need more information in order to delineate the boundaries of morphological variability before we can answer questions on functional significance of tooth formation.…”