Functional mapping of the ommatidia based on a complete reconstruction of the compound eye of Megaphragma (Hymenoptera: Trichogrammatidae)тезисы доклада
Аннотация:Compound eyes are among the most complex and important sense organs. The structure andmorphofunctional specializations of the ommatidia in insect compound eyes have been described for years using light and electron microscopy. The current understanding of the cellular organization is based mostly on 2D data collected on single retinotopic sections. The new age of 3D electron microscopy gives access to the precise cellular and subcellular reconstructions of whole eyes as well as synaptic configurations of the insect’s visual system. That helps us better understand the analyzer–neuron interactions in visual processing modeling. The whole head of Megaphragma amalphitanum was scanned on a double-beam microscope (FIB-SEM) with a resolution of 8 nm per pixel for all xyz measurements. As a result, we provide the first detailed complete 3D reconstruction of the compound eye at the cellular and subcellular levels. Our complex morphological analysis of eachphotoreceptor position, diameters and shapes of the rhabdoms, volumes of cell bodies and rhabdomeres, orientation angles of microvilli along the rhabdom axis, diameters and curvature of each of the lenses and general optic parameters calculations gives us unique data and constitute the first steps of functional mapping of the eye. The shapes and lengths of cones, degrees of lenses curvature, and shapes of the rhabdom are markedly different in the dorsal rim ommatidia and in the regular ones. Specialized microvilli orientation angle along the rhabdom in ommatidia of the dorsal rim area (DRA) most likely indicates an increased sensitivity to polarized light. Our findings show the strict morphological difference between the morphology of seven facets of DRA ommatidia and is consistent with cartridge connectivity trends reconstructed in collaboration with Dmitry Chklovskii team (Flatiron Institute). The organization of compound eyes and possible functional mapping in minute wasps are of particular interest and show that even the smallest eyes retain functional specialization areas. Due to its small body size and unique adaptations of its miniaturized nervous system, Megaphragma can be used as a model for the study of brain neuroarchitecture. This study was supported by the Russian Science Foundation (project no. 22-14-00028).