Effect of weak and ultraweak combined magnetic fields and low-intensity microwaves on regeneration in the planarian <Emphasis Type="Italic">Dugesia tigrina</Emphasis>

Regeneration (blastema growth) in Dugesia tigrina was accelerated if prior to transection the planarians were exposed to a weak constant magnetic field (42 μT) combined with an ultraweak alternating magnetic field (40 nT, 3.7 Hz); lesser stimulation was obtained with weak microwaves (100 μW/cm² at 36 GHz). Field exposure after transection produced only half of the effect (magnetic field) or none at all (microwaves).     

Specific features of eye regeneration in multiocular planarians <Emphasis Type="Italic">Polycelis tenuis</Emphasis>

Regeneration and negative phototaxis were studied in planarians Polycelis tenuis, in which the anterior body end is fringed with many eyes. Comparative data for the same indices are given for binocular planarians Girardia tigrina. Multiple eyes regenerated gradually with a decrease in the rate of regeneration and independently from the rate of restoration of the anterior body end, where they are located. Negative phototaxis was restored independently from the total amount of regenerated eyes. It was unstable in both planarian species.     

Weak influences of physical and chemical factors on the morphogenetic process (in Invertebrates)

Analysis is presented of long-term data obtained in investigation of the effects of weak influences on morphogenetic processes in invertebrates (regeneration of planarians Dugesia (Girardia) tigrina and postembryonic development of insects, the grain beetle Tenebrio molitor). Weak physical and chemical factors were used: electromagnetic radiation, constant, alternating, and combined magnetic fields, and low concentrations of solutions of neuropeptides. It is shown that these influences are characterized by instability and opposite directions (from stimulatory to inhibitory). The dependence of the effects on external factors and the course of internal processes was established.     

Morphogenesis in Planarians Dugesia tigrina

We carried out computer morphometry in regenerates of planarians Dugesia tigrina. The blastema growth was analyzed in fragments of planarians after their fission and after transverse transection at different body levels. The blastema was growing at a higher rate on tail fragments than on the head fragments and the growth rate was the higher, the closer the transection was to the head end. After fission, the blastema was growing at a slower rate than after transection in the fission zone. The growth of adjacent blastemas formed on both sides after fission or transection proceeded at different rates as a function of new body polarity.     

Regeneration processes in various species of planarians

Blastema growth and functional maturation of the pharynx during regeneration in various planarian species were compared. The intensity of blastema growth was highest in Polycelis tenuis; the lowest, in Schmidtea mediterranea. In the sexual and asexual races of Girardia tigrina blastema growth differed inconsiderably. The function of the pharynx during the regeneration of caudal fragments lacking pharynx was manifested in G. tigrina in the usual amount of time, while in the regeneration of head fragments lacking pharynx, this function occured earlier. In other planarian species of the other two typed, the times of pharynx regeneration had no regular character and took longer compared to the same process in G. tigrina.     

Regulation of the Feeding Behavior of the Planarian Dugesia (Girardia) tigrina

In planarians, individual components of the feeding behavior are identified. The reaction of approaching the food object is a motor response of the body to chemical or physical signals coming from the object. As a continuation of the first response, the motor reaction of the pharynx appears aimed at capturing the food. Both reactions can occur independently, but an interdependence between them is also revealed. After ablation of the pharynx, the food cannot be captured, but the reaction of approaching it also is inhibited. After removal of the ganglion, the reaction of approaching the food object is inhibited, but the food capture also is partially suppressed. The food digestion occurring at the last stage affects the food-procuring reactions. The described reactions together with the process of digestion are integrated into the single complex forming the planarian feeding behavior.     

Studies on the Effect of a Weak Electromagnetic Field on Pharynx Regeneration in Dugesia tigrina Planarians

We have studied the effect of a weak electromagnetic field on the morphogenesis of the planarian Dugesia tigrina. The regeneration of the pharynx was examined after its amputation. We have determined the rate of the appearance of the food response of a new pharynx. Experimental conditions were varied, such as dose and duration of irradiation, season, and time of irradiation after surgery. The results of experiments conducted with 2966 planarians have shown that weak electromagnetic field has various effects, which appear either as stimulation of regeneration or as its inhibition. In some experiments, there was no effect at all. These differences depend on numerous factors and may be modulated.