Development of the limpet Testudinalia testudinalis (O.F. Müller, 1776) (Patellogastropoda, Mollusca) from the White Sea, with special reference to the radula

ABSTRACT Development of the limpet Testudinalia testudinalis collected from the White Sea was studied using light and scanning electron microscopy. Cleavage and early development of T. testudinalis were consistent with the general pattern of patellogastropod development, differing in only minor details, such as temperature-dependent developmental rates. A pre-torsional veliger radula was detected by calcofluor white staining of unpolymerized chitin. The veliger radula consisted of nine transverse rows with three teeth per row, which transformed into the radula of newly settled juveniles with five teeth per row (one central and two pairs of lateral teeth). The juvenile radula, with two pairs of lateral and one pair of hook-like marginal teeth, resembled the adult radula in terms of teeth form and co-localization. Radula formation differs between the larva and adult in that each tooth is formed by several odontoblasts and microvillar secretion in the former, whereas it is formed by numerous cells and apocrine secretion in the latter.