In common tests on survival, the reaction to overwhelming intoxication 

 is identical in all species, i.e., death. The percentage of mortality, 

 for a given time may, however, vary significantly depending on the sensi- 

 tivity of organisms, their anerobiotic ability, their lipid content, the 

 degree of oxygen saturation of the medium, and many other factors. In 

 addition to studies of mortality, visual behavioral reactions are also 

 quite indicative. At present, experience in analysis of behavioral reac- 

 tions in organisms is limited to two classes of toxicants, pesticides and 

 heavy metals. It is possible that the reactions described are not univer- 

 sal, and the action of other toxicants is manifested in a different way. 

 For example, the well known peculiarities of behavior of aquatic organisms 

 in the presence of phenol (Alekseev, 1970) differs essentially from those 

 described below for a number of species. 



Cladocerans in a non-toxic medium move by leaps, rarely settling onto 

 the bottom. The movements of the antennae are even. The heart rhythm in 

 different species varies from 200 to 300 (occasionally up to 500) beats 

 per minute, the eyes are brightly pigmented, and the body is multicolored. 

 In a toxic medium the movements are predominantly rotatory and revolving 

 around the body axis or along a spiral. The latter is especially 

 characteristic reaction to toxic pesticides. As intoxication progresses, 

 the crustaceans lie immobile, the body contracts convulsively, the 

 antennae jerks, the heart beat diminishes to a single uneven contraction 

 per minute, and the eyes become depigmented. The body may acquire a red 

 coloration. The females abort immediately after transfer into the toxic 

 medium, shedding both eggs and embryos. After prolonged exposures to low 

 concentrations of toxicant, embryonic abnormalities may arise. These 

 anomolies may include twisted antennae, underdeveloped eyes, and the like. 



The copepods do not usually manifest symptoms of disturbed behavior 

 in toxic media. The rotifers, however, pass into a state of anabiosis, 

 change in body length, and cease to feed (observable microscopically by 

 decoloration of the intestine). Counts of living, anabiotic, and dead 

 rotifers in a Fuks-Rozental Counting Chamber or other hemocytometer esta- 

 blish the toxic effect quantitatively in comparison with the control. 



In toxic media, the usually quick moving gammarids (Gammcvuu, pulux, 

 G. lacuAtxii.) become sluggish and nearly immobile. Under the influence 

 of heavy metals, their bodies may acquire a red tint. Aquatic sowbugs 

 react similiarly. 



Chironomid larvae in water move in a spiral fashion. On a suitable 

 substrate, they begin case construction. Under the influence of toxic 

 substances, their body is convulsively stretched and straightened, they 

 lie immovable on the bottom and fail to construct cases. In hemoglobin 

 containing species {ChJjionomvu> plumoAiu , C. i>2min<icLlcJDJ>) the red color 

 may assume a greenish blue, or disappear altogether. 



The image forms of chironomids appear to be rather sensitive to the 

 presence of DDT residues in storage organs and tissues of fishes (Bereza, 

 1972). In contact with tissues of predatory fishes (fat, brain) con- 

 taining considerable quantities of accumulated DDT, chironomids are para- 



107 



