Confocal laser scanning microscope (CLSM)
To document the autofluorescence of the tooth material, two clean radulae and some individual mature teeth were arranged on object glass slides, following the procedure of Michels & Gorb (2012). Each radula was surrounded by a stack of reinforcement rings. The rings were filled with glycerin (greater than or equal to 99.5%, free of water, Carl Roth GmbH & Co. KG, Karlsruhe, Germany) and subsequently covered by a glass cover slip. Following the protocol of Krings et al. (2022d, 2023), samples were visualized employing a Zeiss LSM 700 confocal laser scanning microscope (Carl Zeiss Microscopy GmbH, Jena, Germany). Four stable solid-state lasers with wavelengths of 405 nm, 488 nm, 555 nm, and 639 nm were used. Bandpass or longpass emission filters (420–480 nm, greater than or equal to 490 nm, greater than or equal to 560 nm, or greater than or equal to 640 nm) were applied. After scanning, images of autofluorescence were superimposed (with maximum intensity projection) using the software Zeiss Efficient Navigation (Zen) (Carl Zeiss MicroImaging GmbH). Finally, the color blue was assigned to the autofluorescence signal received from the laser with wavelength 405 nm, green to 488 nm, red (50% saturation) to 555 nm and red (50% saturation) to 639 nm.