Within 30 days after the beginning of the 

 second extended test series, a total of 8 broods 

 was born in the experimental tanks and the con- 

 trol (table 3). Out of 44 born in the DDT, 21 

 were bom dead or died within several hours. 

 Those born in .0185 and .010 ppm DDT (a total 

 of 14) had abnormally large yolk sacs which 

 were resorbed within several days if the fish 

 survived. Six guppies of a brood born dead in 

 .001 ppm DDT also had slightly distended yolk 

 sacs. The twenty born later in this concentra- 

 tion were apparently normal . 



^ Distended yolk sac present; A=aliTe j D=dead 



Preliminary observations were made on 

 relative survival and growth rates of the DDT- 

 exposed and control newborn. By placing the 

 young guppies bom in .010 and .001 ppm and in 

 the control on days 23 and 24 of the above ex- 

 periment into untreated well water, it was 

 possible to obtain a tentative idea of the com- 

 parative survival and growth rates . The 

 survival rate of the fish born in DDT was lower 

 than that of those from the control . Of the & 

 fish removed from .0010 ppm, the 6 from .010, 

 and the 5 from the control, there were 4 survi- 

 vors from each at the end of 40 days . The 

 average total length of the guppies from the DDT 

 test solutions was 10 mm while that of the guppies 

 bom in untreated water was 11 mm . The obser- 

 vations were made on limited numbers of animals 

 however, and definite conclusions are unwar- 

 ranted. 



One to 14 -day TL/m determinations for 

 14-21 day guppy fry: --The sensitivity of 2- to 

 3 -week guppies was considerably greater than 

 that of the adults. While the 14-day TL/m for 

 the adults was .018 ppm, it was as low as .0024 

 ppm for the young, almost a ten -fold difference 

 (table 4). The TL/m values for the shorter per- 

 iods of time were also consistently lower for the 

 young than those for the adults. Stress symptoms 

 were similar to those of adult guppies. 



Trout 



2 weeks /•3.2» K.2* 2.U ■'.18 



10 weeks .0057 .00195 .00056 



no. one .018 .0175 .Olit .Ollj 

 flngerlings 



(11 weeks) 



» Concentrations above 3.2 precipitated out of solution 

 so values above 3.2 ppm could not be determined under 

 present condtions of exposure. 



Bloassays with young brown trout 



One to 14 -day TL/m determinations for 

 14-day trout fry with yolk sacs: --As the TL/m 

 values in table 4 for 14-day trout fry suggest, 

 sensitivity to DDT increased markedly during 

 the second week of exposure. From the seventh 

 to fourteenth day, the fry became increasingly 

 sensitive to the DDT and the survival dropped 

 from 80 percent in the concentrations of 3.2 

 and .32 ppm and from 100 percent in . 18 ppm 

 on the seventh day to percent in all three tanks 

 by the fourteenth day. It was not possible to 

 determine the precise TL/m value for the 96 

 hour period as the DDT precipitated out of solu- 

 tion in the concentration tested above 3-2 ppm 

 (10 ppm). 



The typical signs of stress in the DDT 

 solutions were first a loss of balance, evidenced 

 by the fish remaining on their sides rather than 

 upright, and then almost complete loss of muscu - 

 lar control. When the fry were stimulated with 

 a glass rod, they seemed unable to swim away 

 and responded only by weak contortions of the 

 body, such as Lifting the head and tail away from 

 the bottom of the aquarium . There was wide 

 individual variation in the time lapse before these 

 signs of stress appeared in the fry, and there 

 seemed to be little correlation between concen- 

 ttation of DDT and the time by which all the 

 fish in a tank appeared affected. Within 7 days, 

 all survivors exhibited the uncontrolled muscular 

 movements. At the end of 14 days, the control 

 fry had resorbed their yolk sacs almost entirely 

 and had become pigmented, while the fry in DDT 

 remained pale and still retained the large yolk 

 sacs- -an indication that little development had 

 occurred in the 2 -week exposure to DDT. 



