Structural and functional changes in the visual system of insects in cases of miniaturization

Despite the numerous studies on insect compound eyes within the last 100 years, the number of investigations specifically dealing with the eyes of species of the smallest body size is relatively low. Based on theoretical optical examinations and considerations concerning spatial constraints, an unlimited reduction in the size of a compound eye and the visual neuropiles is predicted not to be possible, a suggestion that begs the question as to how the tiniest of insects might deal with the postulated restrictions. Using various descriptive morpho-analytical methods (light microscopy (LM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM)), we focus on functional and structural changes that occur in insects because of the evolution of their small body size within a lineage (miniaturization). We are interested in size-dependent morphological adaptations, evolutionary novelties and their evolvability and the consequences of miniaturization with respect to the ecology and behaviour of the investigated species.The addition of serial-sectioning transmission electron microscopy (ssTEM) to the previously mentioned methodologies allows us to include, for the first time, three-dimensional ultrastructural work on compound eyes, stemmata and visual neuropiles, in order to analyse volumetric spatial constraints and limits of miniaturization at the cellular level.

Key publications from this project

Fischer S., Lu Z., Meinertzhagen I.A. (2019) Three-dimensional ultrastructural organization of the ommatidium of the minute parasitoid wasp Trichogramma evanescens. Arthropod Structure and Development (in print). doi.org/10.1016/j.asd.2018.12.003

Fischer S., Lu Z., Meinertzhagen I.A. (2017) From two to three dimensions: The importance of the third dimension for evaluating the limits to neuronal miniaturization in insects. J Comp Neurol. (526 (4):653-662). doi.org/10.1002/cne.24358

Makarova A., Polilov A., Fischer S. (2015) Comparative morphological analysis of compound eye miniaturization in minute Hymenoptera. Arthropod Structure & Development 44(1):21-32. doi.org/10.1016/j.asd.2014.11.001