ИСТИНА

The structure and function of the brain are one of the most thrilling unresolved enigmas of modern science. One of the most promising ways to shed light on this subject are connectomics - a rapidly developing field of biology concerning the research on brain connections. Significant results were obtained in this field in recent years; however, it was yet considered to be impossible to create an adequate connectome of an animal with a relatively complex behavior. Here we present a project designed to achieve this goal. Megaphragma (Hymenoptera: Trichogrammatidae) is the smallest flying insect on Earth, being only 200 mkm in length. This insect demonstrates highly specific and sophisticated behavior (i.e. flying and finding a host for oviposition). Moreover, Megaphragma is the unique animal, for only in its nervous system neural cells lacking nuclei were discovered. Its brain consists only of approximately 7000 cells, of which only about 350 contain nuclei (in an adult individual). Small size and small amount of cells allows creating a 3D model of the brain, including mapping the connections within it. SEM high-definition photographs were obtained, and 3D neuron models and connections between them are being reconstructed on their base. On this step of the project 3D model of Megaphragma eye is being created on cellular and subcellular levels. Retinal cells in each of 29 ommatidium of the eye are being reconstructed in full volume, and their projections in the occipital lobes are being constructed with special attention to synapses. Moreover, in the mean time ways of conducting an immunohistochemical research on Megaphragma neuronal cells are being designed in our laboratory. Using confocal microscopy, labelling cells with fluorescent-marked antibodies would allow to distinguish between neural and glial cells, and, potentially, between different functional types of the latter, and map them in Megaphragma brain. Now, different fixation protocols and target antibodies are being tested to identify the most suitable and applicable of them. Joining the results of immunohisochemical research with 3D model of the brain may allow to characterise neurons from morphological and functional points of view at the same time and, eventually, discover peculiarities of unique Megaphragma brain.