Correlative XRF, ptychography and light microscopy on shielding pigments of Clunio larval ocelli

Abstract

The nature of retinal shielding pigment in the larval eyes of the midge Clunio marinus was studied by high resolution scanning X-ray fluorescence (XRF) analysis correlated with light microscopy (LM) and scanning coherent X-ray diffractive imaging (ptychography). Clunio is known as a unique model system to decipher mechanisms underlying the complex moon-related rhythms. Shielding pigment granules within the photoreceptor cells of their primitive eyes (ocelli) have been shown to change appearance in the same rhythm. We compared the relative amount of trace metals (Ca, Ni, Zn, Cu), obtained by XRF, within single melanosomes (diameter about 500 nm) and the surrounding photoreceptor cells with their optical density in the light microscope and -for the first time -the electron density derived from ptychography images. Though individual pigment granules can be identified and correlated in images of all three techniques the optical density, electron density and especially element concentrations within individual granules seem to vary independently. We discuss that the state of melanogenesis is not synchronized inside the ocellus. K: Analysis and statistical methods; Multi-modality systems; X-ray fluorescence (XRF) systems 1Corresponding author.

PtyNAMi: ptychographic nano-analytical microscope

“…A main strength of scanning hard X-ray microscopy is that different X-ray analytical contrasts can be accessed all at once (Schropp et al, 2011;Kahnt et al, 2018;Falkenberg et al, 2018;Stachnik et al, 2020). This multi-modal approach allows one to investigate functional materials such as thin-film solar cells under different scientific perspectives and correlate, for example, their function with their elemental composition or structural properties (Stuckelberger et al, 2017).…”