S. I. Plotnikova

On structural-functional organization of dragonfly mushroom bodies and some general considerations about purpose of these formations

Anatomy as well as (for the first time) the fine structure have been studied of the mushroom bodies located in protocerebrum of the supraesophageal ganglion of dragonflies—the most ancient flying insects on Earth. Used in the work are larvae of the last age (prior to winging), in which the mushroom body structure has already been completely formed and corresponds to that in imago. The total organization of the dragonfly mushroom bodies has been established to be more primitive than that of other insects studied so far. This involves both the number of interneurons (Kenyon cells) present in the mushroom bodies and the character of anaptic connections formed by these cells. There is confirmed the absence in dragonflies of the mushroom body calyces that in opinion of some authors are obligatory “input gates” into these structures. Peculiarities of the neuropil structure in the area of the absent calyces are studied in detail. For the first time in insects there are revealed the direct (without additional synaptic switching) pathways forming the “afferent input” from optic lobes into the mushroom body calyx area. Also detected are the direct pathways going from the mushroom bodies to the abdominal chain (“efferent output”). A possible functional significance of these findings as well as the general role of mushroom bodied in control of some forms of insect behavior are discussed.

Localization of Glutamate in the Nervous System of the Fly Drosophila melanogaster: An Immunocytochemical Study

Localization of glutamate in the central nervous system of the fly Drosophila melanogaster was studied using highly specific polyclonal rabbit antibody to glutamate conjugated to the bovine serum albumin. Glutamate was revealed in the mushroom body Canyon cells, whose processes were traced in the stem of the mushroom bodies, then entered their α- and β-blades. A group of four glutamate-containing cells (vln) is located ventrally on the border of the lateral procerebrum and medulla. The main process of each cell formed glutamate-containing varicose branchings in the dorsal part of the mushroom body cup. It has been established that lateral neurons of the central body of the F1- and Fml-types were immunostained positively for glutamate. The obtained data on distribution of glutamate-containing cells in the brain centers studied in Drosophila indicate participation of glutamate in integration of the sensory information and locomotor coordination.

Data in favor of possible olfactory function of the antennal nerve and lateral lobe of protocerebrum of larva of the dragonfly Aeschna grandis

Using staining with methylene blue of larvae of dragonflies of the genus Aeschna sp. (2000 animals) the antennal nerve was shown to be connected with the lateral lobe of protocerebrum with a septum, through which sensory fibers enter the lobe. Near the lateral lobe of the antennal nerve, two enlargements are found, which contain motor neurons of antennal muscle as well as the incoming sensory fibers of antennal receptors and descending lateral bundles of fibers of lobes of mushroom bodies. In the lateral lobe of protocerebrum there is revealed arborization of neurons with terminal apparatuses similar to endings of the descending neuron of the glomerular antennal tract of the domestic fly.

Structural-functional peculiarities of the wing apparatus of insects that do not have and do have the maneuvering flight

The work considers character of behavior in flight and discusses peculiarities of structural-functional organization of the wing apparatus of two representatives of insects—the migratory Asian locust Locusta migratoria (a low-maneuvering insect) and the dragonfly-darner Aeshna sp. (an insect able to perform complex maneuvers in air). The main principles underlying the insect wing apparatus activity are considered and the mechanisms allowing the dragonflies to perform complex maneuvers in the flight are analyzed in detail.

Insects and Vertebrates: Analogous Structures in Higher Integrative Centers of the Brain

This work deals with studies on anatomical relationships, neuronal composition, and some synaptic connections that exist in the central complex (CC) in the supraesophageal ganglion in larva of dragonfly g. Aeschna. It has been shown that CC contains protocerebral bridge of an elongated and slightly curved cylindrical shape, fan-shaped and ellipsoid bodies of a bean-like shape and two small roundish noduli. There were revealed (stained) neurons providing both internal connections of CC and its connections with other CNS regions. Connections with tritocerebrum, the higher center of the autonomic nervous system, and subesophageal ganglion, an intermediate “relay” between supraesophageal ganglion and truncal brain, have been established. The existence of connections of CC with nuclei of abdominal nervous chain is suggested. Connection of ocelli with the CC has been traced. Unipolar neurons of the same type have been revealed, each of them giving collaterals to protocerebral bridge and ending as bushy terminals that form the main part of glomerule in the fan-shaped and ellipsoid bodies. Glomeruli are arranged in rows, in which cross connections have been found. It has been established that the structure of neuropils of the fan-shaped and ellipsoid bodies represent a shielding structure described in the cerebral cortex, midbrain cortex, and cerebellar cortex of vertebrates. Thus, in insects, like in vertebrates, the shielding structures developed not only in optic centers, but also in structures performing higher integrative functions. A possible functional role of the central complex is discussed.

Functional Role of Dragonfly Legs before and after Wing Formation: Rearrangement of Coordinatory Relationships

We report here our studies of the characteristics of the structural-functional organization of the leg apparatus of the dragonfly Aeshna grandis, in larvae of the final instar, whose legs have a locomotor function, and in adult winged individuals (imagoes), whose legs have lost their locomotor function and are used mainly as traps to catch prey in the air. Neither the shape nor the proportions of individual leg segments in imagoes were significantly different from those in larvae, and all changes in the functional role of the legs in imagoes occur as a result of changes in the mechanisms controlling the functioning of the leg muscles and the corresponding rearrangements in coordinatory relationships. These rearrangements, as evidenced by the data reported here, affect the mechanisms generating motor commands, the appearance of a tight correlation in the operation of the wing muscles and the leg apparatus, and various others. These mechanisms are discussed.

Peculiarities of structural-functional organization of the motor neuropil in the dragonfly thoracic ganglia

The study considers structural-functional relations in motor neuropil of the thoracic ganglia in dragonflies-insects capable of performing very complex and fast maneuvering in flight. The motor neuropil in dragonflies was shown to be more differentiated than in less mobile insects, while its motor nuclei are more outlined and approached to each other. There were revealed dendrites of the leg muscle motoneurons (intermediate nucleus), running to the anterior and posterior nuclei that contain dendrites of the wing muscle motoneurons. A possible role of such a dendrite approaching is discussed for close functional cooperation of wing and leg muscles essential for dragonflies to catch a large prey in flight by using their legs. Peculiarities of structural organization of the wing muscle motoneurons in dragonflies and locusts are considered to suggest the greater functional capabilities of motoneurons in the dragonfly motor apparatus.

Some Connections of Optic Lobes with Supraesophageal Ganglion of the Dragonfly Aeschna grandis

Optic centers of insects were the object whose study provided A.A. Zavarzin with the idea of par� allelism of histological structures. In Zavarzin’s point of view, the nervous apparatus of vision or� gans of the dragonfly of the genus Aeschna can be ascribed to the part of the nervous system that cephalizes the trunkate brain and the visceral ner� vous system [1]. Zavarzin studied neuronal relations of all three optic ganglia of each animal side [2, 3]. Connec� tions of these structures between each other have remained unstudied. The last instar larvae of the dragonfly Aeschna grandis, before alating, were injected with a syringe with 0.06% methylene blue in 0.75% NaCl through the extremity of the second leg pair. To prevent leak of the methylene blue solution, a ligature was placed on the leg. After 1 h the animals were dis� sected, the CNS was rapidly removed and fixed in 16% ammonium molybdate for 16 h. The material was washed out, dehydrated with absolute ethanol, and cleared in xylene. The total preparations were

Motor activity of infusoria: Theoretical and applied aspects

The article considers morpho-functional organization of cilia—the infusorian locomotion organs—and shows a great complexity of motor behavior of these unicellulars. The problem of control of locomotor activity of infusorian as the single organism is discussed, and the conclusion is made that the system of control of movements is to be multilevel and to include receptor, afferent, central, efferent, and effector links. The role of central integrator and coordinator of motor behavior can be played by the cell nucleus (macronucleus) closely connected with periphery by cytoskeleton dynamic elements. The problem of fight with infusoria parasitizing in the human and animal bodies by impairing motor activity of these unicellulars is also discussed.

Descending Neurons of the Epipharyngeal Ganglion in the Dragonfly Aeschna Larva

Using staining with methylene blue, several descending neurons were revealed in the epipharyngeal ganglion of the dragonfly Aeschna larva. Among them there is a neuron that has extensive arborization and unites a significant part of the epipharyngeal ganglion. The contacts of this neuron with the bundle of optic fibers from the lobule are found, which allows suggesting its participation in the descending visual pathway. A neuron of the central complex of the descending tract is revealed.