already 5 times as resistant as the initial generation. The selection is 

 of a nonspecific character. After the selection for resistance to phenol, 

 the fish were simultaneously more resistant to another toxicant, polychlor- 

 pinene (Figure 1 ) . 



We have also investigated the effect of sublethal concentrations on dif- 

 ferent vital biological characteristics of fish: Behavior (general moto ac- 

 tivity, feeding, defense, sexual behavior, conditioned responses) growth 

 rate, and reproduction. Physiological functions such as bioelectric ac- 

 tivity of nerve and muscle systems, neurosecretion in the hyothalamo-hypo- 

 physial system, immunological reactions, and blood analysis have been 

 included as indices of intoxication. Pathologic changes in the structure 

 of fish organs have been studied under lethal concentrations. 



Chronic phenol influence causes considerable changes in behavior, and 

 first of all in conditioned reflexes and then in other functions of the or- 

 ganism (Figure 1). Conditioned reflex method may be recommended as a 

 highly sensitive test for determining water toxicity. Under a prolonged 

 toxicant influence, inhibition of feeding, sexual behavior, defense func- 

 tions, and growth rate takes place. 



After Kuba's (1969) investigations, it has been established, on the 

 basis of electrophysiological data, that phenol acts primarily on neuromus- 

 cular synapses, increasing the frequency in formation of miniature terminal 

 disc potentials (Figure 2). Concentrations of phenol lethal for the whole 

 organism do not produce a noticeable effect on the total action potential 

 of peripheral nerves nor on the evoked responses of the fish brain (olfac- 

 tory bulb) . 



Pathomorphological changes in fish organs and hypothalamo-hypophysial 

 system reactions under phenol intoxication are of general and nonspecific 

 character. Thus, they are unlikely to be of any significance for post- 

 mortem diagnosis to toxicosis. 



The principal results of the second part of the investigation are pre- 

 sented below. 



DESTRUCTION OF PHENOL IN MODEL COMMUNITIES 



The destruction of phenol was studied in 28 aquaria, 3-15 liter in vol- 

 ume, filled with river water and sand. Several components (aquatic organ- 

 isms, mineral fertilizers, ultraviolet radiation) were introduced into the 

 aquaria. 



One series of experiments performed in 6 aquaria may be cited as an ex- 

 ample. 



Aquarium 1 - without aquatic organisms 



187 



