Scanning electron microscopy (SEM) and 3D visualization
For documentation of morphology using SEM, three radulae were carefully extracted and cleaned by a short ultrasonic bath in 70% EtOH. Subsequently they were mounted on SEM specimen holders by double-sided adhesive carbon tape and sputter-coated with platinum (5 nm layer). For visualization, we used a SEM Zeiss LEO 1525 (One Zeiss Drive, Thornwood, NY, USA). Only mature teeth from the working zone, which can be identified by lack of covering epithelia, were studied. To document the wear on the teeth, radulae were rewetted by 70% EtOH afterwards, cleaned by a short ultrasonic bath, rearranged on SEM sample holders and visualized again in the SEM. Nomenclature of teeth was adapted from (Ong et al., 2017).
For the 3D visualization, mature radular teeth of the working zone of two radulae were extracted manually with foreceps. Each tooth was mounted on SEM specimen holders by double-sided adhesive carbon tape, sputter-coated with platinum (5 nm layer), and visualized under the SEM from all sides. Using the 3D software Blender v2.83 (Blender Foundation), the teeth were then modelled by hand always comparing the 3D visualization with the SEM images taken from different sides (see also protocol in Krings et al., 2020, 2021e). In the same manner, the position and embedment of the teeth within the membrane were reconstructed.