One to 14 -day TL/m determinations for 

 lO-week trout fry: --After the fry had resorbed 

 their yolk sacs, they became sensitive to exceed- 

 ingly small dosages. The 14-day TL/m value 

 for the 10-week fry was approximately 1/300 

 as great as the value for the 2 -week fry. The 

 appearance and duration of stress symptoms 

 before death appeared later and lasted longer 

 in the lower concentrations of DDT. A change 

 in pigmentation was the first indication of 

 stress. The fry became much lighter except 

 for the tail tip, which was very dark. Disturb- 

 ances of nervous and muscular control were 

 indicated first by quick jerky movements, fol- 

 lowed by complete loss of balance. Just before 

 death, the fry were found lying on their backs, 

 the mouths operated with apparent difficulty, and 

 there was no response to probing with a glass 

 rod. 



One to 14 -day TL/m determinations for 

 number one fingerlings: --After the trout had 

 grown to the fingerling stage, they were more 

 resistant to DDT than the 10 -week fry which 

 had recently lost the yolk sacs. None of the 

 fish in .032 ppm survived more than 2 days, 

 but of the fish in .010 ppm, 70 percent survived 

 14 days of exposure and 100 percent of the fish 

 in the lower concentrations of .0032, .0010, and 

 .00032 survived the 2 -week test. On the basis 

 of the data, the 7- and 14-day TL/m was deter- 

 mined to be .014 ppm DDT (table 4). The 14- 

 day TL/m for these fish was found to be 25 times 

 more than for the 10 -week fry. 



Histopatho logical condition of trout fry and adult 

 guppy tissues following exposure to DDT 



In general, histopathological conditions 

 were similar in the tissues of both the trout and 

 guppies despite the differences in age, DDT 

 concentration, and exposure periods. Conse- 

 quently, the description of tissue changes caused 

 directly or indirectly by DDT is presented as 

 that which is typical either of the experimentals 

 or of the controls. 



Brain: --No histopathological condition 

 was observed in the mid- or hindbrain of the 

 guppy or trout. A few very small areas of 

 vacuolation, perhaps indicative of irregularly 

 swollen myelin sheaths or degenerating and 

 swelling oUgodendroglia, were present in the 

 outer portion of the cerebral lobes of one trout 

 fry. 



Intestine: --Marked abnormalities were 

 present along the intestinal tract of both fish. 

 In the guppy both the connective tissue and colum- 

 nar epithelium were necrotic and highly disorgan- 

 ized (figs . 3 and 4) . In most villi it was not 

 possible to distinguish whether the cells of the 

 epithelial layer had disappeared or dispersed. 

 The changes in the trout intestine were even more 

 marked. The connective tissue between the villi 

 and the smooth muscle was either necrotic or 

 entirely absent (figs . 5 and 6) . The columnar 

 cells were irregular as in the gut of the guppy. 

 There was also severe vacuolation of the 

 epithelium (fig. 7). This necrotic layer was 

 occasionally observed sloughing off into the 

 lumen . 



Liver: -- Degeneration of varying degrees 

 was noted in the liver tissue. In the extreme 

 cases in the guppy Uver, necrosis gave the 

 entire organ a foamy appearance (figs . 8 and 9) . 

 Both the normal and the experimental trout livers 

 were full of small vacuoles (figs. 10 and 11), per- 

 haps fat vacuoles resulting from the resorption of 

 the fatty yolk . Mounts also found fatty vacuolation 

 in the livers of normal and experimental guppies 

 in endrin and attributed it to a high content of fat 

 in the diet. There was some enlargement of the 

 vacuoles in the livers of the experimental fish, 

 and swollen nuclei were scattered in the liver of 

 the DDT-exposed trout. 



Kidney: --There was no visible change in 

 the guppy kidney tubules by the first or second day, 

 but the tubules of the trout were generally occluded 

 or congested with debris. There was some slough- 

 ing of the epithelial cells of the tubules (fig. 12). 



4/ Mount, D. Personal communication of October 31, 1960, to Susan King 



from Taft Sanitary Engineering Center. (Thesis -1960. A study of the chronic 

 effects of endrin, an insecticide, on the guppy / Lebistes reticulatus /, and on 

 the bluntnose minnow /Pimephales notatus/, Ohio State University. 



